Toby G. Rossman, Ph.D.

Genetic and epigenetic effects of environmental arsenicals
Rossman, Toby G; Klein, Catherine B
2011 Nov 1;3(11):1135-1141, Metallomics : integrated biometal science
Environmental arsenic compounds and their methylated metabolites do not form adducts with DNA, but do cause oxidative DNA damage. Chromosome aberrations are seen at toxic concentrations. Genetic effects that occur at non-toxic concentrations include aneuploidy, comutagenesis (resulting from indirect effects on DNA repair), and delayed mutagenesis (probably secondary to aneuploidy and/or epigenetic effects). Effects of trivalent arsenicals on poly(ADP ribose) polymerase and P53 activation may mediate effects on DNA repair and aneuploidy. A growing literature points to the epigenetic effects of arsenic compounds in cells and in vivo. A review of the current literature on DNA methylation, histone modifications and microRNA effects is presented
— id: 140528, year: 2011, vol: 3, page: 1135, stat: Journal Article,

Arsenite induced poly(ADP-ribosyl)ation of tumor suppressor P53 in human skin keratinocytes as a possible mechanism for carcinogenesis associated with arsenic exposure
Komissarova, Elena V; Rossman, Toby G
2010 Mar 15;243(3):399-404, Toxicology & applied pharmacology
Arsenite is an environmental pollutant. Exposure to inorganic arsenic in drinking water is associated with elevated cancer risk, especially in skin. Arsenite alone does not cause skin cancer in animals, but arsenite can enhance the carcinogenicity of solar UV. Arsenite is not a significant mutagen at non-toxic concentrations, but it enhances the mutagenicity of other carcinogens. The tumor suppressor protein P53 and nuclear enzyme PARP-1 are both key players in DNA damage response. This laboratory demonstrated earlier that in cells treated with arsenite, the P53-dependent increase in p21(WAF1/CIP1) expression, normally a block to cell cycle progression after DNA damage, is deficient. Here we show that although long-term exposure of human keratinocytes (HaCaT) to a nontoxic concentration (0.1 microM) of arsenite decreases the level of global protein poly(ADP-ribosyl)ation, it increases poly(ADP-ribosyl)ation of P53 protein and PARP-1 protein abundance. We also demonstrate that exposure to 0.1 microM arsenite depresses the constitutive expression of p21 mRNA and P21 protein in HaCaT cells. Poly(ADP-ribosyl)ation of P53 is reported to block its activation, DNA binding and its functioning as a transcription factor. Our results suggest that arsenite's interference with activation of P53 via poly(ADP-ribosyl)ation may play a role in the comutagenic and cocarcinogenic effects of arsenite
— id: 107924, year: 2010, vol: 243, page: 399, stat: Journal Article,

Inappropriate cytotoxicity measurements
Rossman, Toby G
2009 Mar;50(2):81-81, Environmental & molecular mutagenesis
— id: 94524, year: 2009, vol: 50, page: 81, stat: Journal Article,

Mechanism of selenium-induced inhibition of arsenic-enhanced UVR carcinogenesis in mice
Burns, Fredric J; Rossman, Toby; Vega, Katherine; Uddin, Ahmed; Vogt, Stefan; Lai, Barry; Reeder, Richard J
2008 Jun;116(6):703-708, Environmental health perspectives
BACKGROUND: Hairless mice that ingested arsenite in drinking water exhibited more than a 5-fold enhancement of ultraviolet radiation (UVR) carcinogenesis, whereas arsenite alone was carcinogenically inactive. Dietary organoselenium blocked the cancer enhancement effect of arsenic but not cancer induction by UVR. OBJECTIVE: In this study we sought to explain selenium blockage of As enhancement by establishing the extent that As and Se tissue distributions are coincident or divergent. METHODS: We used the X-ray fluorescence microprobe at the Advanced Photon Source (Argonne National Laboratory) to probe sections of skin and liver from hairless mice exposed to a) UVR, b) UVR + As, c) UVR + organoselenium, or d) UVR + As + organoselenium. RESULTS: We found elevated levels of As in the skin epithelium (hair follicles and epidermis) and diffusely in the liver of mice exposed to UVR + As. Arsenic was entirely absent in skin in mice exposed to UVR + As + organoselenium, but a diffuse low level was seen in the liver. As and Se locations were consistently divergent in skin; As was more diffusely distributed, whereas Se was strongly associated with membranes. X-ray absorption near-edge spectra are consistent with the presence of the seleno-bis(S-glutathionyl) arsinium ion in the liver. CONCLUSIONS: Supplemental Se was uncommonly effective at preventing even a trace of As in skin at 14 or 196 days of continuous exposure to As in drinking water. Traces of the seleno-bis(S-glutathionyl) arsinium ion in the liver suggested that formation of this compound was more likely to be responsible for the As-blocking effect of Se than was a mechanism based on antioxidation
— id: 93323, year: 2008, vol: 116, page: 703, stat: Journal Article,

Gene expression levels in normal human lymphoblasts with variable sensitivities to arsenite: identification of GGT1 and NFKBIE expression levels as possible biomarkers of susceptibility
Komissarova, Elena V; Li, Ping; Uddin, Ahmed N; Chen, Xuyan; Nadas, Arthur; Rossman, Toby G
2008 Jan 15;226(2):199-205, Toxicology & applied pharmacology
Drinking arsenic-contaminated water is associated with increased risk of neoplasias of the skin, lung, bladder and possibly other sites, as well as other diseases. Earlier, we showed that human lymphoblast lines from different normal unexposed donors showed variable sensitivities to the toxic effects of arsenite. In the present study, we used microarray analysis to compare the basal gene expression profiles between two arsenite-resistant (GM02707, GM00893) and two arsenite-sensitive lymphoblast lines (GM00546, GM00607). A number of genes were differentially expressed in arsenite-sensitive and arsenite-resistant cells. Among these, gamma-glutamyltranspeptidase 1 (GGT1) and NF kappa B inhibitor-epsilon (NFKBIE) showed higher expression levels in arsenite-resistant cells. RT-PCR analysis with gene-specific primers confirmed these results. Reduction of GGT1 expression level in arsenite-resistant lymphoblasts with GGT1-specific siRNA resulted in increased cell sensitivity to arsenite. In conclusion, we have demonstrated for the first time that expression levels of GGT1 and possibly NFKBIE might be useful as biomarkers of genetic susceptibility to arsenite. Expression microarrays can thus be exploited for identifying additional biomarkers of susceptibility to arsenite and to other toxicants
— id: 76110, year: 2008, vol: 226, page: 199, stat: Journal Article,

Long-term exposure to submicromolar arsenite induces chromosome instability via bypass of the spindle assembly checkpoint in mammalian cells
Mauro, M; Leszczynska, J; Barbata, G; Caradonna, F; Sciandrello, G; Rossman, TG; Klein, CB
2008 AUG ;49(7):548-548, Environmental & molecular mutagenesis
— id: 86808, year: 2008, vol: 49, page: 548, stat: Journal Article,

Mechanism of inhibition of arsenite co-carcinogenesis by supplemental selenium
Rossman, TG; Uddin, AN; Burns, FJ; Vega, K
2008 AUG ;49(7):557-557, Environmental & molecular mutagenesis
— id: 86809, year: 2008, vol: 49, page: 557, stat: Journal Article,

Further evidence against a direct genotoxic mode of action for arsenic-induced cancer
Klein, Catherine B; Leszczynska, Joanna; Hickey, Christina; Rossman, Toby G
2007 Aug 1;222(3):289-297, Toxicology & applied pharmacology
Arsenic in drinking water, a mixture of arsenite and arsenate, is associated with increased skin and other cancers in Asia and Latin America, but not the United States. Arsenite alone in drinking water does not cause skin cancers in experimental animals; therefore, it is not a complete carcinogen in skin. We recently showed that low concentrations of arsenite enhanced the tumorigenicity of solar UV irradiation in hairless mice, suggesting arsenic cocarcinogenesis with sunlight in skin cancer and perhaps with different carcinogenic partners for lung and bladder tumors. Cocarcinogenic mechanisms could include blocking DNA repair, stimulating angiogenesis, altering DNA methylation patterns, dysregulating cell cycle control, induction of aneuploidy and blocking apoptosis. Arsenicals are documented clastogens but not strong mutagens, with weak mutagenic activity reported at highly toxic concentrations of inorganic arsenic. Previously, we showed that arsenite, but not monomethylarsonous acid (MMA[III]), induced delayed mutagenesis in HOS cells. Here, we report new data on the mutagenicity of the trivalent methylated arsenic metabolites MMA(III) and dimethylarsinous acid [DMA(III)] at the gpt locus in Chinese hamster G12 cells. Both methylated arsenicals seemed mutagenic with apparent sublinear dose responses. However, significant mutagenesis occurred only at highly toxic concentrations of MMA(III). Most mutants induced by MMA(III) and DMA(III) exhibited transgene deletions. Some non-deletion mutants exhibited altered DNA methylation. A critical discussion of cell survival leads us to conclude that clastogenesis occurs primarily at highly cytotoxic arsenic concentrations, casting further doubt as to whether a genotoxic mode of action (MOA) for arsenicals is supportable
— id: 72150, year: 2007, vol: 222, page: 289, stat: Journal Article,

Pro-angiogenesis action of arsenic and its reversal by selenium-derived compounds
Mousa, Shaker A; O'Connor, Laura; Rossman, Toby G; Block, Eric
2007 May;28(5):962-967, Carcinogenesis
Inorganic arsenic (arsenite and arsenate) in drinking water has been associated with skin cancers and increased incidence of cardiovascular diseases. Additionally, studies have demonstrated the pro-angiogenic effect of arsenite and its potential promotion of tumor angiogenesis and tumor progression. Furthermore, recent reports demonstrated reversal of skin co-carcinogenesis by an organoselenium compound. The present study was undertaken to determine the effect and mechanism on angiogenesis of arsenite at low level and its potential reversal by various selenium-derived compounds. The pro-angiogenesis effects and mechanisms of sodium arsenite were determined using the chick chorioallantoic membrane (CAM) model over 3 days and compared with standard pro-angiogenesis factors, such as basic fibroblast growth factor (b-FGF). Additionally, the potential effect of various selenium-derived compounds-such as dimethyl selenone, diphenyl selenone, sodium selenite or Se-methyl selenocysteine-in reversing the pro-angiogenesis effect of arsenite or b-FGF was also determined in the CAM model. The pro-angiogenesis effect of arsenite or b-FGF was significantly (P < 0.01) blocked by dimethyl selenone, diphenyl selenone, sodium selenite or Se-methyl selenocysteine. The pro-angiogenesis effect of either sodium arsenite at 33 nM or b-FGF was blocked (P < 0.01) by the extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation inhibitor, PD 98059. Additionally, the pro-angiogenic effect of arsenic or b-FGF was blocked as well (P < 0.01) by the alphavbeta3 antagonist, XT199. These data suggest that the pro-angiogenesis effect of arsenic is initiated at the plasma membrane integrin alphavbeta3, involves activation of the ERK1/2 pathway and is effectively reversed by various selenium-derived compounds
— id: 72151, year: 2007, vol: 28, page: 962, stat: Journal Article,

Arsenic
Rossman TG
Environmental and occupational medicine Philadelphia : Wolters Kluwer/Lippincott Williams & Wilkins, 2007,
— id: 4388, year: 2007, vol: , page: 1006, stat: Chapter,

Expression microarray analysis identified gamma-glutamyl transferase expression level as a possible biomarker for arsenic sensitivity
Rossman, TG; Komissarova, EV; Uddin, AN
2007 AUG ;48(7):559-559, Environmental & molecular mutagenesis
— id: 74190, year: 2007, vol: 48, page: 559, stat: Journal Article,

Dietary chromium and nickel enhance UV-carcinogenesis in skin of hairless mice
Uddin, Ahmed N; Burns, Fredric J; Rossman, Toby G; Chen, Haobin; Kluz, Thomas; Costa, Max
2007 Jun 15;221(3):329-338, Toxicology & applied pharmacology
The skin cancer enhancing effect of chromium (in male mice) and nickel in UVR-irradiated female Skh1 mice was investigated. The dietary vitamin E and selenomethionine were tested for prevention of chromium-enhanced skin carcinogenesis. The mice were exposed to UVR (1.0 kJ/m(2) 3x weekly) for 26 weeks either alone, or combined with 2.5 or 5.0 ppm potassium chromate, or with 20, 100 or 500 ppm nickel chloride in drinking water. Vitamin E or selenomethionine was added to the lab chow for 29 weeks beginning 3 weeks before the start of UVR exposure. Both chromium and nickel significantly increased the UVR-induced skin cancer yield in mice. In male Skh1 mice, UVR alone induced 1.9+/-0.4 cancers/mouse, and 2.5 or 5.0 ppm potassium chromate added to drinking water increased the yields to 5.9+/-0.8 and 8.6+/-0.9 cancers/mouse, respectively. In female Skh1 mice, UVR alone induced 1.7+/-0.4 cancers/mouse, and the addition of 20, 100 or 500 ppm nickel chloride increased the yields to 2.8+/-0.9, 5.6+/-0.7 and 4.2+/-1.0 cancers/mouse, respectively. Neither vitamin E nor selenomethionine reduced the cancer yield enhancement by chromium. These results confirm that chromium and nickel, while not good skin carcinogens per se, are enhancers of UVR-induced skin cancers in Skh1 mice. Data also suggest that the enhancement of UVR-induced skin cancers by chromate may not be oxidatively mediated since the antioxidant vitamin E as well as selenomethionine, found to prevent arsenite-enhanced skin carcinogenesis, failed to suppress enhancement by chromate
— id: 72149, year: 2007, vol: 221, page: 329, stat: Journal Article,

The genotoxic and epigenetic profile of arsenite and methylated metabolites in mammalian cells
Leszczynska, J; Hickey, C; Rossman, T; Klein, CB
2006 JUL ;47(6):470-470, Environmental & molecular mutagenesis
— id: 69546, year: 2006, vol: 47, page: 470, stat: Journal Article,

Analysis of the ability of individual isoflavones in soybean-processing by-product mixtures to reduce spontaneous mutation in mismatch-repair deficient cells
Mure, K; Plewa, MJ; Takeshita, T; Rossman, TG; Klein, CB
2006 JUL ;47(6):461-461, Environmental & molecular mutagenesis
— id: 69544, year: 2006, vol: 47, page: 461, stat: Journal Article,

Arsenic as a co-carcinogen
Rossman, TG; Uddin, AN; Burns, FJ
2006 DEC ;19(12):1700-1700, Chemical research in toxicology
— id: 71052, year: 2006, vol: 19, page: 1700, stat: Journal Article,

Letter to the editor
Rossman, Toby G
2006 Jan 18;231(2):339-340, Cancer letters
— id: 72152, year: 2006, vol: 231, page: 339, stat: Journal Article,

Selenium prevents spontaneous and arsenite-induced mutagenesis
Rossman, TG; Uddin, AN
2005 ;1275(1):173-179, International congress series
Selenium (Se) and arsenic are next-door neighbors on the periodic table and have similar chemical properties as metalloids. Arsenic antagonizes selenium toxicity in a number of organisms. Inorganic arsenic in drinking water is a human carcinogen while selenium compounds are anticarcinogenic in animals and humans. Our previous work showed that arsenite enhanced solar UV-induced skin cancer in the hairless mouse and caused delayed mutagenesis in human HOS cells. Here, we assess the abilities of three selenium compounds to antagonize arsenite. Sodium selenite is far more toxic to HOS cells than selenomethionine and Se-(methyl)selenocysteine in a 10-day clonality assay. When concentrations subtoxic in the clonality assay were assessed for long-term effects on growth, selenite, but not the organic compounds, caused a delayed inhibitory effect after 3 weeks. None of the Se compounds effectively blocked arsenite toxicity. Both organoselenium compounds blocked spontaneous and arsenite-induced delayed mutagenesis. The mechanism of delayed mutagenesis by arsenite is not known, but reactive oxygen species may play a role. We suggest that the antimutagenic action of organoselenium might result from up-regulation of the selenoproteins GSH peroxidase and thioredoxin reductase, which would protect against spontaneous and arsenite-induced oxidative DNA damage. (c) 2004 Elsevier B.V. All rights reserved
— id: 104617, year: 2005, vol: 1275, page: 173, stat: Journal Article,

Vitamin E and organoselenium prevent the cocarcinogenic activity of arsenite with solar UVR in mouse skin
Uddin, Ahmed N; Burns, Fredric J; Rossman, Toby G
2005 Dec;26(12):2179-2186, Carcinogenesis
Arsenic-induced carcinogenesis is a worldwide problem for which there is currently limited means for control. Recently, we showed that arsenite in drinking water greatly potentiates solar ultraviolet radiation (UVR) induced skin cancer in mice, at concentrations as low as 1.25 mg/l. In this study, we examined the protective efficacy of vitamin E and 1,4-phenylenebis(methylene)selenocyanate (p-XSC) against tumors induced by UVR and UVR + arsenite. Hairless mice were exposed to UVR alone (1.0 kJ/m(2) x 3 times weekly) or UVR + sodium arsenite (5 mg/l in drinking water) and fed lab chow supplemented or not with vitamin E (RRR-alpha-tocopheryl acetate, 62.5 IU/kg diet) or p-XSC (10 mg/kg) for 26 weeks. The tumor yield for mice receiving UVR alone was 3.6 tumors/mouse and the addition of arsenite to the drinking water increased the yield to 7.0 tumors/mouse (P < 0.005). Vitamin E and p-XSC reduced the tumor yield in mice given UVR + arsenite by 2.1-fold (P < 0.001) and 2-fold (P < 0.002), respectively. Vitamin E, but not p-XSC, reduced the tumor yield induced by UVR alone by 30% (P < 0.05). No significant difference in tumor types or grade of malignancy was observed in mice treated with or without chemopreventives. Immunostaining of mouse skin for 8-oxo-2'-deoxyguanosine (8-oxo-dG) revealed a significant reduction of 8-oxo-dG formation in mice treated with vitamin E or p-XSC compared with those treated with UVR + arsenite. These results show that vitamin E and p-XSC protect strongly against arsenite-induced enhancement of UVR carcinogenesis
— id: 61332, year: 2005, vol: 26, page: 2179, stat: Journal Article,

Arsenite-induced alterations of DNA photodamage repair and apoptosis after solar-simulation UVR in mouse keratinocytes in vitro
Wu, Feng; Burns, Fredric J; Zhang, Ronghe; Uddin, Ahmed N; Rossman, Toby G
2005 Aug;113(8):983-986, Environmental health perspectives
Our laboratory has shown that arsenite markedly increased the cancer rate caused by solar-simulation ultraviolet radiation (UVR) in the hairless mouse skin model. In the present study, we investigated how arsenite affected DNA photodamage repair and apoptosis after solar-simulation UVR in the mouse keratinocyte cell line 291.03C. The keratinocytes were treated with different concentrations of sodium arsenite (0.0, 2.5, 5.0 microM) for 24 hr and then were immediately irradiated with a single dose of 0.30 kJ/m2 UVR. At 24 hr after UVR, DNA photoproducts [cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs)] and apoptosis were measured using the enzyme-linked immunosorbent assay and the two-color TUNEL (terminal deoxynucleotide transferase dUTP nick end labeling) assay, respectively. The results showed that arsenite reduced the repair rate of 6-4PPs by about a factor of 2 at 5.0 microM and had no effect at 2.5 microM. UVR-induced apoptosis at 24 hr was decreased by 22.64% at 2.5 microM arsenite and by 61.90% at 5.0 microM arsenite. Arsenite decreased the UVR-induced caspase-3/7 activity in parallel with the inhibition of apoptosis. Colony survival assays of the 291.03C cells demonstrate a median lethal concentration (LC50) of arsenite of 0.9 microM and a median lethal dose (LD50) of UVR of 0.05 kJ/m2. If the present results are applicable in vivo, inhibition of UVR-induced apoptosis may contribute to arsenite's enhancement of UVR-induced skin carcinogenesis
— id: 62598, year: 2005, vol: 113, page: 983, stat: Journal Article,

Caffeic acid phenethyl ester (CAPE) prevents transformation of human cells by arsenite (As) and suppresses growth of As-transformed cells
Yang, Chengfeng; Wu, Jing; Zhang, Ronghe; Zhang, Ping; Eckard, Jonathan; Yusuf, Rita; Huang, Xi; Rossman, Toby G; Frenkel, Krystyna
2005 Sep 15;213(1-2):81-96, Toxicology
Recent evidence suggests that inflammatory cytokines and growth factors contribute to arsenite (As)-induced human carcinogenesis. We investigated the expression of inflammatory cytokine mRNAs during the transformation process induced by chronic As exposure in non-tumorigenic human osteogenic sarcoma (N-HOS) cells using gene arrays, and results were confirmed by RT-PCR and protein arrays. Caffeic acid phenethyl ester (CAPE), a naturally occurring immunomodulating agent, was used to evaluate the role of inflammatory factors in the process of As-mediated N-HOS cell transformation and in As-transformed HOS (AsT-HOS) cells. We found that an 8-week continuous exposure of N-HOS to 0.3 microM arsenite resulted in HOS cell transformation. That exposure also caused substantial decreases in inflammatory cytokine mRNAs, such as interleukin (IL) IL-1alpha, IL-2, IL-8, IL-18, MCP-1, TGF-beta2, and TNF-alpha, while it increased c-jun mRNA in a time-dependent manner. Co-incubation of N-HOS with As and CAPE (0.5-2.5 microM) prevented As-mediated declines in cytokine mRNAs in the co-treated cells, as well as their transformation to anchorage independence, while it caused decreases in c-jun mRNA. CAPE (up to 10 microM) had no effect on growth of N-HOS cells. However, CAPE (1-10 microM) treatment of AsT-HOS cells inhibited cell growth, induced cell cycle G2/M arrest, and triggered apoptosis, accompanied by changes in cytokine gene expression, as well as decreases in cyclin B1 and cdc2 abundance. Resveratrol (RV) and (-)(.) epigallocatechin gallate (EGCG), preventive agents present in grapes and green tea, respectively, induced similar changes in AsT-HOS cell growth but required much higher doses than CAPE to cause 50% growth arrest (<2.5 microM CAPE versus 25 microM RV or 50 microM EGCG). Overall, our findings suggest that inflammatory cytokines play an important role in the suppressive effects of CAPE on As-induced cell transformation and in the selective cytotoxicity of CAPE to As-transformed HOS cells
— id: 58743, year: 2005, vol: 213, page: 81, stat: Journal Article,

Arsenic-induced enhancement of ultraviolet radiation carcinogenesis in mouse skin: a dose-response study
Burns, Fredric J; Uddin, Ahmed N; Wu, Feng; Nadas, Arthur; Rossman, Toby G
2004 Apr;112(5):599-603, Environmental health perspectives
The present study was designed to establish the form of the dose-response relationship for dietary sodium arsenite as a co-carcinogen with ultraviolet radiation (UVR) in a mouse skin model. Hairless mice (strain Skh1) were fed sodium arsenite continuously in drinking water starting at 21 days of age at concentrations of 0.0, 1.25, 2.5, 5.0, and 10 mg/L. At 42 days of age, solar spectrum UVR exposures were applied three times weekly to the dorsal skin at 1.0 kJ/m2 per exposure until the experiment ended at 182 days. Untreated mice and mice fed only arsenite developed no tumors. In the remaining groups a total of 322 locally invasive squamous carcinomas occurred. The carcinoma yield in mice exposed only to UVR was 2.4 +/- 0.5 cancers/mouse at 182 days. Dietary arsenite markedly enhanced the UVR-induced cancer yield in a pattern consistent with linearity up to a peak of 11.1 +/- 1.0 cancers/mouse at 5.0 mg/L arsenite, representing a peak enhancement ratio of 4.63 +/- 1.05. A decline occurred to 6.8 +/- 0.8 cancers/mouse at 10.0 mg/L arsenite. New cancer rates exhibited a consistent-with-linear dependence on time beginning after initial cancer-free intervals ranging between 88 and 95 days. Epidermal hyperplasia was elevated by arsenite alone and UVR alone and was greater than additive for the combined exposures as were growth rates of the cancers. These results demonstrate the usefulness of a new animal model for studying the carcinogenic action of dietary arsenite on skin exposed to UVR and should contribute to understanding how to make use of animal data for assessment of human cancer risks in tissues exposed to mixtures of carcinogens and cancer-enhancing agents. Key words: arsenic, arsenite, cancer, hairless, mouse, radiation, skin, ultraviolet, UV
— id: 43217, year: 2004, vol: 112, page: 599, stat: Journal Article,

Exposure to chromium (VI) in the drinking water increases susceptibility to UV-induced skin tumors in hairless mice
Davidson, Todd; Kluz, Thomas; Burns, Fredric; Rossman, Toby; Zhang, Qunwei; Uddin, Ahmed; Nadas, Arthur; Costa, Max
2004 May 1;196(3):431-437, Toxicology & applied pharmacology
Hexavalent chromium (Cr (VI)) is a well known-human carcinogen with exposures occurring in both occupational and environmental settings. Although lung carcinogenicity has been well documented for occupational exposure via inhalation, the carcinogenic hazard of drinking water exposure to Cr (VI) has yet to be established. We used a hairless mouse model to study the effects of K(2)CrO(4) in the drinking water on ultraviolet radiation (UVR)-induced skin tumors. Hairless mice were unexposed or exposed to UVR alone (1.2 kJ/m(2)), K(2)CrO(4) alone at 2.5 and 5.0 ppm, or the combination of UVR and K(2)CrO(4) at 0.5, 2.5, and 5.0 ppm. Mice were observed on a weekly basis for the appearance of skin tumors larger than 2 mm. All the mice were euthanized on day 182. The skin tumors were excised and subsequently analyzed microscopically for malignancy by histopathology. There was a total absence of observable skin tumors in untreated mice and in mice exposed to chromate alone. However, there was a dose-dependent increase in the number of skin tumors greater than 2 mm in mice exposed to K(2)CrO(4) and UV compared with mice exposed to UV alone. The increase in tumors larger than 2 mm was statistically significant (P < 0.05) for UV and K(2)CrO(4) at the two highest K(2)CrO(4) doses (2.5 and 5.0 ppm), and there was a statistically significant increase in the numbers of malignant tumors per mouse in the UVR plus K(2)CrO(4) (5 ppm) group compared with UV alone. The data presented here indicate that K(2)CrO(4) increases the number of UV-induced skin tumors in a dose-dependent manner, and these results support the concern that regulatory agencies have relative to the carcinogenic health hazards of widespread human exposure to Cr (VI) in drinking water
— id: 43216, year: 2004, vol: 196, page: 431, stat: Journal Article,

Arsenite induces delayed mutagenesis and transformation in human osteosarcoma cells at extremely low concentrations
Mure, Kanae; Uddin, Ahmed N; Lopez, Laura C; Styblo, Miroslav; Rossman, Toby G
2003 ;41(5):322-331, Environmental & molecular mutagenesis
Arsenite is a human multisite carcinogen, but its mechanism of action is not known. We recently found that extremely low concentrations (</=0.1 microM) of arsenite transform human osteosarcoma TE85 (HOS) cells to anchorage-independence. In contrast to other carcinogens which transform these cells within days of exposure, almost 8 weeks of arsenite exposure are required for transformation. We decided to reexamine the question of arsenite mutagenicity using chronic exposure in a spontaneous mutagenesis assay we previously developed. Arsenite was able to cause a delayed increase in mutagenesis at extremely low concentrations (</=0.1 microM) in a dose-dependent manner. The increase in mutant frequency occurred after almost 20 generations of growth in arsenite. Transformation required more than 30 generations of continuous exposure. We also found that arsenite induced gene amplification of the dihydrofolate reductase (DHFR) gene in a dose-dependent manner. Since HOS cells are able to methylate arsenite at a very low rate, it was possible that active metabolites such as monomethylarsonous acid (MMA(III)) contributed to the delayed mutagenesis and transformation in these cells. However, when the assay was repeated with MMA(III), we found no significant increase in mutagenesis or transformation, suggesting that arsenite-induced delayed mutagenesis and transformation are not caused by arsenite's metabolites, but by arsenite itself. Our results suggest that long-term exposure to low concentrations of arsenite may affect signaling pathways that result in a progressive genomic instability
— id: 39198, year: 2003, vol: 41, page: 322, stat: Journal Article,

fau and its ubiquitin-like domain (FUBI) transforms human osteogenic sarcoma (HOS) cells to anchorage-independence
Rossman, Toby G; Visalli, Melissa A; Komissarova, Elena V
2003 Mar 27;22(12):1817-1821, Oncogene
Arsenite is the most likely carcinogenic form of arsenic in the environment. Previously, expression cloning for cDNAs whose overexpression confers arsenite-resistance in Chinese hamster V79 cells identified two genes: fau and a novel gene, asr2. The fau gene encodes a ubiquitin-like protein (here called FUBI) fused to the ribosomal S30 protein. Since the expression of the fox sequence (antisense to fau) increased the tumorigenicity of a mouse sarcoma virus, it was proposed that fau might be a tumor suppressor gene. We intended to test its ability to block arsenite-induced transformation of human osteogenic sarcoma (HOS) cells to anchorage-independence. Instead, we found that overexpressing fau itself was able to transform HOS cells. When the two domains were expressed separately, only FUBI was transforming and only the S30 domain conferred arsenite resistance. An incidental finding was the transforming activity of the selectable marker, hyg. FUBI belongs to the ubiquitin-like protein group that is capable of forming conjugates to other proteins, although none have so far been identified. Alternatively, FUBI may act as a substitute or inhibitor of ubiquitin, to which it is most closely related, or to close ubiquitin-like relatives UCRP, FAT10, and/or Nedd8
— id: 39261, year: 2003, vol: 22, page: 1817, stat: Journal Article,

In vitro bioavailability of heavy metals in pressure-treated wood dust
Gordon, Terry; Spanier, Jonathan; Butala, John H; Li, Ping; Rossman, Toby G
2002 May;67(1):32-37, Toxicological sciences
Pressure treatment with chromium, copper, and arsenic (CCA) is the most prevalent method for protecting wood used in outdoor construction projects. Although these metals are tightly bound to the wood fibers and are not released under most conditions of use, we examined the bioavailability of metals in CCA pressure-treated wood dust in vitro. Cytotoxicity and metallothionein (MT) mRNA expression were examined in V79 Chinese hamster lung fibroblast cells incubated with respirable-size wood dust generated by sanding CCA-treated and untreated (control) Southern yellow pine. In colony survival studies, increased cytotoxicity (p < 0.05) occurred in V79 cells treated with CCA wood dust (351 +/- 77 microg/ml, mean +/- SE) compared with control wood dust (883 +/- 91 microg/ml). Increased cytotoxicity with CCA wood dust also occurred in an arsenic resistant subline of V79 cells, thus suggesting that arsenic was not responsible for the increased cytotoxicity. Metallothionein mRNA was significantly increased after 48 h of treatment with CCA wood dust compared with control wood dust. Incubation of CCA wood dust in cell culture media resulted in the transfer of copper, but not chromium or arsenic, into the media. Moreover, the treatment of cells with this filtered extract resulted in significantly increased metallothionein mRNA, suggesting that bioavailable copper is responsible for inducing metallothionein mRNA in V79 cells. Thus, these bioassays suggest that metals become bioavailable during in vitro culture of phagocytic V79 cells with CCA wood dust
— id: 39673, year: 2002, vol: 67, page: 32, stat: Journal Article,

Arsenite cocarcinogenesis: an animal model derived from genetic toxicology studies
Rossman, Toby G; Uddin, Ahmed N; Burns, Fredric J; Bosland, Maarten C
2002 Oct;110 Suppl 5(4):749-752, Environmental health perspectives
Although epidemiologic evidence shows an association between inorganic arsenic in drinking water and increased risk of skin, lung, and bladder cancers, no animal model for arsenic carcinogenesis has been successful. This lack has hindered mechanistic studies of arsenic carcinogenesis. Previously, we and others found that low concentrations (< or =5 microm) of arsenite (the likely environmental carcinogen), which are not mutagenic, can enhance the mutagenicity of other agents, including ultraviolet radiation (UVR) and alkylating agents. This enhancing effect appears to result from inhibition of DNA repair by arsenite, but not via inhibition of DNA repair enzymes. Rather, low concentrations of arsenite disrupt p53 function and upregulate cyclin D1. Failure to find an animal model for arsenic carcinogenesis might be because arsenite is not a carcinogen per se but acts as an enhancing agent (cocarcinogen) with a genotoxic partner. We tested this hypothesis with solar UVR in hairless but immunocompetent Skh1 mice. Mice were given 10 mg/L sodium arsenite in drinking water (or not) and irradiated with 1.7 KJ/m(2) solar UVR 3 times weekly. As expected, no tumors appeared in any organs in control mice or in mice given arsenite alone. After 26 weeks irradiated mice given arsenite had a 2.4-fold increase in skin tumor yield compared with mice given UVR alone. The tumors were mostly squamous cell carcinomas, and those occurring in mice given UVR plus arsenite were much larger and more invasive. These results are consistent with the hypothesis that arsenic acts as a cocarcinogen with a second (genotoxic) agent by inhibiting DNA repair and/or enhancing positive growth signaling. Skin cancers in populations drinking water containing arsenic may be caused by the enhancement by arsenic compounds of carcinogenesis induced by UVR (or other environmental agents). It is possible that lung and bladder cancers associated with arsenic in drinking water may also require a carcinogenic partner
— id: 34894, year: 2002, vol: 110 Suppl 5, page: 749, stat: Journal Article,

Genes upregulated in lead-resistant glioma cells reveal possible targets for lead-induced developmental neurotoxicity
Li P; Rossman TG
2001 Nov;64(1):90-99, Toxicological sciences
Identifying genes upregulated in lead-resistant cells should give insight into lead toxicity and cellular protective mechanisms and may also result in identification of proteins that may be useful as biomarkers. Glial cells are thought to protect neurons against heavy metals. Rat glioma C6 cells share many properties of normal glial cells. To identify and analyze genes upregulated in a lead-resistant variant, PbR11, suppression subtractive hybridization (SSH) between mRNAs of wild-type and PbR11 cells was performed. Sequencing and database searches identified three genes, thrombospondin-1, heparin sulfate 6-sulfotransferase, and neuropilin-1, which play important roles in angiogenesis and axon growth during development. Two genes, HSP90 and UBA3, are involved in the ubiquitin-proteosome system. One gene was identified as that of a rat endogenous retrovirus and another, 2C9, is a transcript expressed in fos-transformed cells. PbR11 also overexpresses c-fos. Expression of these genes and effects of short-term lead exposure (24 h, up to 600 microM) on their expression in C6 cells was examined. The rat endogenous retrovirus and 2C9 are expressed only in PbR11 cells, and show no expression, either constitutive or lead-induced, in wild-type C6 cells. HSP90 is expressed at low level constitutively in C6 cells, but can be induced in a dose-dependent manner by lead. In contrast, thrombospondin-1 is repressed in a dose-dependent manner by lead. The other genes (HS6ST, neuropilin, and UBA3) show low constitutive expression and are neither upregulated nor downregulated by exposure to lead. We suggest that neuropilin-1, heparin sulfate 6-sulfotransferase, and thrombospondin-1 may be important targets for lead-induced developmental neurotoxicity
— id: 39473, year: 2001, vol: 64, page: 90, stat: Journal Article,

Reduction of spontaneous mutagenesis in mismatch repair-deficient and proficient cells by dietary antioxidants
Mure K; Rossman TG
2001 Sep 1;480-481(1):85-95, Mutation research
Cells lacking mismatch repair (MMR) exhibit elevated levels of spontaneous mutagenesis. Evidence exists that MMR is involved in repair of some DNA lesions besides mismatches. If some oxidative DNA lesions are substrates for MMR, then the excess mutagenesis in MMR(-) cells might be blocked by dietary antioxidants. Effects of the dietary antioxidants ascorbate, alpha-tocopherol, (-)-epigallocatechin gallate (EGCG) and lycopene on spontaneous mutagenesis were studied using mismatch repair-deficient (hMLH1(-)) human colon carcinoma HCT116 cells and HCT116/ch3 cells, in which normal human chromosome 3 has been added to restore mismatch repair. HCT116 cells have a 22-fold higher spontaneous mutation rate compared with HCT116/ch3 cells. HCT116 cells cultured in 1% fetal bovine serum (FBS) have twice the spontaneous mutation rate of those cultured in 10% FBS, most likely due to reduction in serum antioxidants in the low serum medium. As expected, alpha-tocopherol (50 microM) and ascorbate (284 microM) reduced spontaneous mutagenesis in HCT116 cells growing in 1% serum more dramatically than in cells cultured in 10% serum. The strongest antimutagenic compound was lycopene (5 microM), which reduced spontaneous mutagenesis equally (about 70%) in HCT116 cells growing in 10 and 1% FBS and in HCT116/ch3 cells. Since lycopene was equally antimutagenic in cells growing in low and high serum, it may have another antimutagenic mechanism in addition to its antioxidant effect. Surprisingly, EGCG (10 microM) was toxic to cells growing in low serum. It also reduced spontaneous mutagenesis equally (nearly 40%) in HCT116 and HCT116/ch3 cells.The large proportion of spontaneous mutagenesis that can be blocked by antioxidants in mismatch repair-deficient cells support the hypothesis that a major cause of their excess mutagenesis is endogenous oxidants. Blocking spontaneous mutagenesis, perhaps with a cocktail of antioxidants, should reduce the risk of cancer in people with a genetic defect in mismatch repair as well as other individuals
— id: 26697, year: 2001, vol: 480-481, page: 85, stat: Journal Article,

Arsenite is a cocarcinogen with solar ultraviolet radiation for mouse skin: an animal model for arsenic carcinogenesis
Rossman TG; Uddin AN; Burns FJ; Bosland MC
2001 Oct 1;176(1):64-71, Toxicology & applied pharmacology
Although epidemiological evidence shows an association between arsenic in drinking water and increased risk of skin, lung, and bladder cancers, arsenic compounds are not animal carcinogens. The lack of animal models has hindered mechanistic studies of arsenic carcinogenesis. Previously, this laboratory found that low concentrations of arsenite (the likely environmental carcinogen) which are not mutagenic can enhance the mutagenicity of other agents, including ultraviolet radiation (UVR). This enhancing effect appears to result from inhibition of DNA repair by arsenite. Recently we found that low concentrations of arsenite disrupted p53 function and upregulated cyclin D1. These results suggest that the failure to find an animal model for arsenic carcinogenesis is because arsenite is not a carcinogen per se, but rather acts as an enhancing agent (cocarcinogen) with a genotoxic partner. We tested this hypothesis with solar UVR as carcinogenic stimulus in hairless Skh1 mice. Mice given 10 mg/l sodium arsenite in drinking water for 26 weeks had a 2.4-fold increase in yield of tumors after 1.7 KJ/m(2) UVR three times weekly compared with mice given UVR alone. No tumors appeared in mice given arsenite alone. The tumors were mostly squamous cell carcinomas, and those occurring in mice given UVR plus arsenite appeared earlier and were much larger and more invasive than in mice given UVR alone. These results are consistent with the hypothesis that arsenic acts as a cocarcinogen with a second (genotoxic) agent by inhibiting DNA repair and/or enhancing positive growth signaling
— id: 32229, year: 2001, vol: 176, page: 64, stat: Journal Article,

Human cell models for arsenic carcinogenicity and toxicity : transformation and genetic susceptbility
Rossman TG; Visalli MA; Uddin An; Hu Y
Arsenic exposure and health effects New York : Elsevier, 2001,
— id: 4389, year: 2001, vol: , page: 285, stat: Chapter,

Effects of arsenite on p53, p21 and cyclin D expression in normal human fibroblasts - a possible mechanism for arsenite's comutagenicity
Vogt BL; Rossman TG
2001 Jul 1;478(1-2):159-168, Mutation research
Arsenite, the most likely environmental carcinogenic form of arsenic, is not significantly mutagenic at non-toxic concentrations, but is able to enhance the mutagenicity of other agents. Evidence suggests that this comutagenic effect of arsenite is due to inhibition of DNA repair, but no specific repair enzyme has been found to be sensitive to low (<1&mgr;M) concentrations of arsenite. To determine whether arsenite affects signaling which might alter DNA repair, this study assesses the effect of arsenite on p53-related signal transduction pathways after ionizing radiation. Long-term (14 day) low dose (0.1&mgr;M) arsenite caused a modest increase in p53 expression in WI38 normal human fibroblasts, while only toxic (50&mgr;M) concentrations increased p53 levels after short-term (18h) exposure. When cells were irradiated (6Gy), p53 and p21 protein concentrations were increased after 4h, as expected. Both long-term, low dose and short-term, high dose exposure to arsenite greatly suppressed the radiation-induced increase in p21 abundance. In addition, long-term, low dose (but not short-term, high dose) exposure to arsenite resulted in increased expression of cyclin D1. These results show that in cells treated with arsenite, p53-dependent increase in p21 expression, normally a block to cell cycle progression after DNA damage, is deficient. At the same time, low (non-toxic) exposure to arsenite enhances positive growth signaling. We suggest that the absence of normal p53 functioning, along with increased positive growth signaling in the presence of DNA damage may result in defective DNA repair and account for the comutagenic effects of arsenite
— id: 21185, year: 2001, vol: 478, page: 159, stat: Journal Article,

Reduction of spontaneous mutation in mismatch repair deficient human colon cancer cell lines by dietary antioxidants
Mure, K; Rossman, T
2000 Apr 08-13;35(Suppl. 31):44-44, Environmental & molecular mutagenesis
— id: 15832, year: 2000, vol: 35, page: 44, stat: Journal Article,

Cloning genes whose levels of expression are altered by metals: implications for human health research [In Process Citation]
Rossman TG
2000 Sep;38(3):335-339, American journal of industrial medicine
When cells are exposed to toxicants, changes in gene expression ensue. To date, there is little information on gene expression changes induced by metals in mammalian cells. The basic methods for identifying altered gene expression of both a temporary and a permanent nature are outlined, with examples drawn mostly from what is known about metal-induced changes in gene expression. The application of this information in the development of new biomarkers of exposure and effect, in identifying individuals with altered susceptibility to metal compounds, and in the choice of genes for microarrays is discussed.
— id: 10344, year: 2000, vol: 38, page: 335, stat: Journal Article,

Genes overexpressed in lead-resistant rat glioma cells
Rossman TG; Li P
2000 ;6:107-109, Metal ions in biology & medicine = Les ions metalliques en biologie et en medicine
— id: 72780, year: 2000, vol: 6, page: 107, stat: Journal Article,

Arsenite genotoxicity may be mediated by interference with DNA damage-inducible signalling
Rossman TG
Arsenic exposure and health effects New York : Chapman & Hall, 1999,
— id: 4391, year: 1999, vol: , page: 233, stat: Chapter,

Effects of metallothionein expression on development of drug resistance
Rossman TG; Goncharova EI
Metallothionein IV Basel : Birkhauser Verlag, 1999,
— id: 4390, year: 1999, vol: , page: 573, stat: Chapter,

Expression cloning for arsenite-resistance resulted in isolation of tumor-suppressor fau cDNA: possible involvement of the ubiquitin system in arsenic carcinogenesis
Rossman TG; Wang Z
1999 Feb;20(2):311-316, Carcinogenesis
Arsenic is a human carcinogen whose mechanism of action is unknown. Previously, this laboratory demonstrated that arsenite acts as a comutagen by interfering with DNA repair, although a specific DNA repair enzyme sensitive to arsenite has not been identified. A number of stable arsenite-sensitive and arsenite-resistant sublines of Chinese hamster V79 cells have now been isolated. In order to gain understanding of possible targets for arsenite's action, one arsenite-resistant subline, As/R28A, was chosen as a donor for a cDNA expression library. The library from arsenite-induced As/R28A cells was transfected into arsenite-sensitive As/S5 cells, and transfectants were selected for arsenite-resistance. Two cDNAs, asr1 and asr2, which confer arsenite resistance to arsenite-hypersensitive As/S5 cells as well as to wild-type cells, were isolated. asr1 shows almost complete homology with the rat fau gene, a tumor suppressor gene which contains a ubiquitin-like region fused to S30 ribosomal protein. Arsenite was previously shown to inhibit ubiquitin-dependent proteolysis. These results suggest that the tumor suppressor fau gene product or some other aspect of the ubiquitin system may be a target for arsenic toxicity and that disruption of the ubiquitin system may contribute to the genotoxicity and carcinogenicity of arsenite
— id: 7437, year: 1999, vol: 20, page: 311, stat: Journal Article,

Isolation and properties of lead-resistant variants of rat glioma cells
Dolzhanskaya N; Goncharova E; Rossman TG
1998 Oct;65(1):31-43, Biological trace element research
Glial cells are thought to protect neurons from heavy-metal toxicity. To gain a better understanding of mechanisms of protection against lead compounds, a number of lead-resistant C6 rat glioma cell sublines have been isolated. After 8 mo of growth in the absence of lead nitrate, three sublines still maintain their lead-resistant phenotype. None of the lead-resistant sublines are cross-resistant to Cd(II) or Ni(II), but all are cross-resistant (in varying degrees) to Hg(II), As(III), Sb(III), and Sn(II), and one is resistant to trimethyl tin. No inducible lead resistance is seen in any glioma line. One subline has been used to create cell-cell hybrids with wild-type cells. The hybrids exhibit dominance of the lead-resistant phenotype. To identify and analyze altered gene expression at the mRNA level in the lead-resistant sublines, the differential display technique was used. Numerous differences are seen between amplified fragments from wild-type and lead-resistant cells. Candidate clones are now being analyzed to confirm the differential expression and to isolate cDNAs that confer lead resistance
— id: 7324, year: 1998, vol: 65, page: 31, stat: Journal Article,

Arsenic
Rossman TG
Environmental & occupational medicine Philadelphia : Lippincott-Raven, 1998,
— id: 4392, year: 1998, vol: , page: 1007, stat: Chapter,

Molecular and genetic toxicology of arsenic
Rossman TG
Environmental toxicology : current developments Amsterdam : Gordon and Breach Science Publishers, 1998,
— id: 4393, year: 1998, vol: , page: 171, stat: Chapter,

Spontaneous mutagenesis in mammalian cells is caused mainly by oxidative events and can be blocked by antioxidants and metallothionein
Rossman TG; Goncharova EI
1998 Jun 18;402(1-2):103-110, Mutation research
Little is known about endogenous processes causing spontaneous mutagenesis in mammalian cells. To study this problem, a mathematical model and method developed previously in our laboratory was used to measure the spontaneous mutation rate in mammalian cells at the transgenic gpt locus in Chinese hamster G12 cells. We found that spontaneous mutagenesis increased when cells were cultured in low (<0.25%) serum. These cells also contained higher oxidant levels, measured by dichloroflourescein (DCF) fluorescence, suggesting that the elevated spontaneous mutagenesis resulted from endogenous oxidants which are normally quenched by serum antioxidants. This was found to be the case. Spontaneous mutagenesis was significantly reduced in serum-depleted as well as control cells when catalase (100 ng/ml) or the antioxidants ascorbate (50 microg/ml) or mannitol (100-500 microg/ml) were added to the medium. Overexpression of metallothionein in these cells also suppressed spontaneous mutagenesis and mutagenesis induced by oxygen radical-generating compounds. Cells expressing metallothionein antisense RNA become mutators. Taken together, these results suggest that the major cause of spontaneous mutagenesis in mammalian cells is endogenously-generated oxidative DNA damage which can be blocked by metallothionein or by dietary antioxidants carried by the blood supply.
— id: 7771, year: 1998, vol: 402, page: 103, stat: Journal Article,

Chinese hamster cells expressing antisense to metallothionein become spontaneous mutators
Rossman TG; Goncharova EI; Nadas A; Dolzhanskaya N
1997 Jan 3;373(1):75-85, Mutation research
The functions of metallothioneins (MTs) have been debated for at least a decade. Because it seems unlikely that they evolved only to protect cells against exogenous heavy metals, it has been suggested that MTs have roles in scavenging reactive intermediates, controlling zinc and copper homeostasis, and controlling transfer of zinc to transcription factors and other proteins. Previously, we demonstrated that Chinese hamster G12 cells which overexpress MT have greatly reduced spontaneous mutation rates, suggesting that MT evolved to prevent spontaneous mutagenesis induced by free nuclear zinc ions. We have now isolated G12 transfectants which express antisense RNA to MT. Immunofluorescent staining reveals MT protein in both the nucleus and the cytoplasm in parental cells. A clone expressing high levels of antisense RNA (AMT30) shows reduced basal and induced levels of MT protein. AMT30 cells are hypersensitive to cadmium, zinc, copper and mercury chlorides as well as to menadione. Glutathione levels in AMT30 and G12 cells do not differ. AMT30 cells are spontaneous mutators, showing a spontaneous mutation rate 5-10 times that of G12 cells or G12 cells transfected with vector alone. Only transfectants which show a high level of MT antisense expression (i.e., AMT30) had greatly elevated spontaneous mutation rates. These results support our hypothesis that a major role of MT is to act as an endogenous antimutagen probably via scavenging of reactive intermediates in the nucleus. AMT30 cells should be useful in delineating the sources of spontaneous mutagenesis
— id: 10364, year: 1997, vol: 373, page: 75, stat: Journal Article,

Human cells lack the inducible tolerance to arsenite seen in hamster cells
Rossman TG; Goncharova EI; Rajah T; Wang Z
1997 Jun;386(3):307-314, Mutation research
Chinese hamster V79 cells and their arsenite-resistant variants were found to have an arsenite- and antimonite-inducible tolerance mechanism which protects against the subsequent cytotoxic effects of arsenate, arsenate and antimonite. Inducible tolerance requires de novo mRNA and protein synthesis, and is independent of the heat shock response. In contrast, we report that the arsenite hypersensitive variant line As/S27D lacks the inducible tolerance response. Numerous attempts were made to detect an inducible tolerance response to arsenite in a variety of human cells. An assay based on Neutral red uptake was used in order to study inducible tolerance in cells with poor clonability. Neither normal diploid cells nor human tumor cells of different origins were found to elicit an inducible tolerance response to arsenite. This finding may help to explain why rodents do not develop tumors after exposure to arsenite, while humans do. In addition, all human cell lines tested were much more sensitive to arsenite compared to Chinese hamster cells. Human keratinocytes were especially sensitive. In general, human cells resemble arsenic hypersensitive Chinese hamster As/R27D cells, which have lost a protective mechanism found in wild-type Chinese hamster cells
— id: 7253, year: 1997, vol: 386, page: 307, stat: Journal Article,

Metallothionein blocks mutagenicity of anticancer drugs
Goncharova E; Perez R; Rossman TG
1996 ;4:303-305, Metal ions in biology & medicine = Les ions metalliques en biologie et en medicine
— id: 72781, year: 1996, vol: 4, page: 303, stat: Journal Article,

Serum deprivation, but not inhibition of growth per se, induces a hypermutable state in Chinese hamster G12 cells
Goncharova EI; Nadas A; Rossman TG
1996 Feb 15;56(4):752-756, Cancer research
Spontaneous mutagenesis is thought to play a crucial role in spontaneous carcinogenesis. We recently described a new mathematical model for estimation of the spontaneous mutation rate (mutation/gene/generations) based on the assumption that mutations are fixed in the S-phase of the cell cycle. With this definition, the spontaneous mutation rate should be independent of the growth rate. In the present study, we tested this hypothesis, using cell line G12, a transgenic Chinese hamster V79 derivative, which contains a single copy of the Escherichia coli gpt gene as a target for mutagenesis. The growth rate was modulated by varying the serum concentration or the seeding density, or by addition of suramin, transforming growth factor beta, or dichlorobenzimidazole riboside to the medium. Significant increases in the spontaneous mutation rate occurred when cell proliferation was blocked by serum deprivation. Density-dependent inhibition of growth and inhibition of growth by suramin, transforming growth factor beta, or dichlorobenzimidazole riboside did not result in significant increases in spontaneous mutation rates. The level of oxidants in cells cultivated in the presence of low concentrations of serum was higher compared to control cells, suggesting that the increases in the spontaneous mutation rates under low serum conditions may be partly a result of oxidative stress due to a lack of serum antioxidants. This was shown to be the case, because spontaneous mutation rates were significantly reduced in serum-depleted cells when antioxidants were added to the medium. We suggest that during carcinogenesis, when tumors are in a prevascularized state, the spontaneous mutation rate may be elevated, and this process may contribute to the genetic instability of the tumor cells
— id: 6912, year: 1996, vol: 56, page: 752, stat: Journal Article,

Maximum likelihood estimation of spontaneous mutation rates from large initial populations
Nadas A; Goncharova EI; Rossman TG
1996 Mar 26;351(1):9-17, Mutation research
When estimating a spontaneous mutation rate from either a single culture (C=1) or from the C parallel cultures (C>1) of a fluctuation experiment, the use of a large initial population size N0 to seed each culture will permit a gaussian approximation for the probability distribution of the number M of mutants at the time when the culture(s) has (have) grown to size N=N02g, i.e., experienced g doublings. Using this gaussian approximation we find that the maximum likelihood estimate mu of the expected number mu of mutants present in a culture in generation g is (exactly) (equation: see text) where r = 2g / g and M 2 is the average of the squares of the C mutant counts. The maximum likelihood estimate p of the unknown mutation rate p is p = 2 mu / gN assuming an 'ideal' experiment and that there were no mutants in the initial population. A well-behaved maximum likelihood estimate is known to be efficient in large samples and we illustrate by Monte Carlo simulation that indeed p is better (has smaller mean squared error) than our previous (Rossman et al., 1995) estimator (equation: see text) (M is the average mutant count) provided N0 is of the order 1/p or larger. This advantage exists even without a fluctuation experiment, i.e., for C = 1
— id: 7022, year: 1996, vol: 351, page: 9, stat: Journal Article,

Mutations and infinity: improved statistical methods for estimating spontaneous rates
Nadas A; Goncharova EI; Rossman TG
1996 ;28(2):90-99, Environmental & molecular mutagenesis
Certain mathematical artifacts which had been appended by others to Luria and Delbruck's [Genetics 28: 491-511, 1943] model of spontaneous mutagenesis in bacterial populations have added confusion to the modeling and measurement of spontaneous mutation rates. Additional confusion arises when models which had been tuned for experiments with bacterial cultures grown from a small inoculum are adapted for use with mammalian cell cultures grown from a large initial population. As one consequence, biologists still tend to grow the large number of parallel cultures required by the fluctuation test in order to avoid large errors due to the high variability in the number of mutants in a growing culture. By avoiding models with infinite mean values and certain mathematical approximations that lead to conceptual and practical difficulties, the large variance of the number of mutants can be avoided (and the precision of the estimated mutation rate controlled) through the use of sufficiently large initial cell populations. A direct consequence is that simpler experiments with fewer cultures may suffice. In this paper, after a discussion of the confusions, we extend our previous approach [Rossman et al.: Mutat Res 328:21-30, 1995] by giving improved formulas for the standard error of the estimated mutation rate. The improvement results from using a more inclusive model based on consideration of the variability due to both the biological phenomenon of the growing culture (growth and mutation) and the protocols used for selection (sampling and plating efficiency). Also included is the situation where the initial cell population is not assumed to be free of mutants but the initial mutant fraction is measured instead. These standard error formulas are useful in planning experiments that yield mutation rate estimates with planned precision and for comparing and testing hypotheses about mutation rates in two or more populations which are grown under different conditions
— id: 7084, year: 1996, vol: 28, page: 90, stat: Journal Article,

Metallothionein (MT) expression affects spontaneous and induced mutagenesis
Rossman TG; Goncharova EI; Dolzhanskaya N
1996 ;30(1):88-88, Fundamental & applied toxicology
Chinese hamster G12 cells (a V79 derivative with a single copy of E coli gpt as a mutagenic target gene) were transfected with a vector containing the mouse MT-1 gene under control of its own promoter and MT-1 overproducing cells were isolated. G12 cells were also transfected with a vector containing Chinese hamster MT-II antisense cDNA, and antisense-expressing cells were isolated. MT-1 transfectants had decreased spontaneous mutagenesis and the antisense transfectants had elevated spontaneous mutagenesis. Modulation of MT expression showed that spontaneous mutagenesis, but not gene amplification (PALA-resistance) is inversely related to MT expression. MT-1 transfectants showed decreased cytotoxicity and mutagenesis in response to cadmium, mAMSA and other topoisomerase inhibitors which produce free radicals, 5-azacytidine, and menadione, but not to small alkylating agents. MT can block spontaneous and TPA-induced oxidative stress. A significant increase in spontaneous mutagenesis occurs when G12 cells are grown in high Zn2+ up to 12 uM; higher concentrations (which induce MT) resulted in decreased mutagenesis compared with controls (approx 2 uM Zn2+). In contrast, the low spontaneous mutation rate of MT-1 transfectants was unaffected by Zn2+. Although it does not redox cycle, Zn2+ unopposed by MT increases oxidative stress in cells. We suggest that MT evolved to play a protective role against mutagenesis by free Zn2+
— id: 6029, year: 1996, vol: 30, page: 88, stat: Journal Article,

Efflux-mediated resistance to arsenicals in arsenic-resistant and -hypersensitive Chinese hamster cells
Wang Z; Dey S; Rosen BP; Rossman TG
1996 Mar;137(1):112-119, Toxicology & applied pharmacology
Several Chinese hamster V79 cell line variants resistant to arsenite and one arsenite-hypersensitive variant have been isolated. The basis for the variation in arsenite sensitivity was studied by transport experiments using radiolabeled arsenite. Two arsenite-resistant variants (As/R7 and As/R27) exhibited decreased accumulation of arsenite, and the hypersensitive variant (As/S5) exhibited increased arsenite accumulation compared with the parental line. Cells depleted of endogenous energy reserves were loaded with radiolabeled arsenite, and the rate of arsenic efflux was measured. Arsenite-resistant variants exhibited an increased rate of efflux, while the hypersensitive variant exhibited a decreased efflux rate. Efflux was decreased in cells incubated with the protonophore carbonyl cyanide m-chlorophenylhydrazine, demonstrating its energy dependence. Two inhibitors of glutathione S-transferase also decreased arsenite efflux, suggesting the involvement of an arsenite-glutathione complex. However, separation of the products of extrusion and the intracellular arsenic species by paper chromatography followed by autoradiography failed to show the appearance of an arsenite-glutathione complex in either case. Rather, all label in the product of the transport reaction appeared to be arsenite whether cells were loaded with arsenate or arsenite, indicating first that intracellular reduction of As(V) to As(III) had occurred and second that the arsenite was transported as an unconjugated species. All intracellular label was associated with high-molecular-weight material, possibly protein. Our results demonstrate the existence of an energy-dependent arsenical efflux pump in mammalian cells and show that arsenic is extruded as arsenite
— id: 6972, year: 1996, vol: 137, page: 112, stat: Journal Article,

The antimutagenic effects of metallothionein may involve free radical scavenging
Goncharova E; Rossman TG
Genetic response to metals New York : Dekker, 1995,
— id: 4394, year: 1995, vol: , page: 87, stat: Chapter,

Metallothionein protects against mutagenicity of agents producing reactive oxygen species
Goncharova EI; Rossman TG
1995 ;25 (Suppl. 25):20-20, Environmental & molecular mutagenesis
Metallothioneins (MTs) are low molecular weight metal-binding proteins. There is some evidence that one of their biological functions is to protect against oxidative stress by scavenging free radicals. The transgenic cell line G12 contains a single copy of the E coli gpt gene as a target for mutagenesis (Klein and Rossman, Env Mol Mut 16:1, 1990), and has a very low level of endogenous MT expression. A number of G12-derived MT-overproducing cell lines were obtained after transfection with the mouse MT-I gene. The cytotoxicity and mutagenicity of three topoisomerase II inhibitors (amsacrine, ellipticine, and doxorubicin), which are known to generate free radicals, were examined in G12 cells, and the MT-overproducing cell line MTI-2A. MTI-2A cells are more resistant to amsacrine and ellipticine compared with parental cells, whereas both cell lines have the same sensitivity to doxorubicin. Amsacrine, ellipticine, and doxorubicin, cause dose-dependent increases in 6TG resistant variants in G12 cells. However, the mutagenic effect of these agents is greatly diminished in MTI-2A cells. The mutagenic effect of amsacrine is inversely related to MT expression. The cytotoxicity of menadione (MD), a synthetic analog of vitamin K1, results from hydroxyl radicals. MTI-2A cells are more resistant to the cytotoxic and mutagenic action of MD than parental G12 cells. Phorbol ester (TPA) action as a tumor promoter is thought to be mediated via the formation of reactive oxygen species. Levels of intracellular oxidants in MTI-2A cells were lower compared to G12 cells after treatment with TPA. These data provide support for an important biological role of MTs as free radicals scavengers
— id: 6034, year: 1995, vol: 25 (Suppl. 25), page: 20, stat: Journal Article,

Metal mutagenesis
Rossman TG
Toxicology of metals : biochemical aspects New York : Springer Verlag, 1995,
— id: 4395, year: 1995, vol: , page: 374, stat: Chapter,

Modeling and measurement of the spontaneous mutation rate in mammalian cells
Rossman TG; Goncharova EI; Nadas A
1995 Apr;328(1):21-30, Mutation research
The study of spontaneous mutation rates in mammalian cells has been hampered by the lack of an alternative to the cumbersome Luria and Delbruck fluctuation test. A brief review of mathematical treatments of spontaneous mutagenesis, along with some of the limitations of the fluctuation test, is presented. A new experimental method and a simple mathematical model for deriving the spontaneous mutation rate are described. Data from the transgenic Chinese hamster G12 cell line growing at two different rates is analyzed according to this model. The results support the concept that, at least for growing cells, the spontaneous mutation rate is independent of the growth rate, and the mutant fraction increases in a linear fashion with the number of generations
— id: 6733, year: 1995, vol: 328, page: 21, stat: Journal Article,

MOLECULAR MECHANISMS OF ARSENITE RESISTANCE IN MAMMALIAN-CELLS
ROSSMAN, TG; WANG, ZL
1995 MAR 10 ;14(1-6):250-250, Journal of cellular biochemistry
— id: 86745, year: 1995, vol: 14, page: 250, stat: Journal Article,

A role for metallothionein and zinc in spontaneous mutagenesis
Goncharova EI; Rossman TG
1994 Oct 15;54(20):5318-5323, Cancer research
G12, a transgenic Chinese hamster V79 cell derivative which contains a single copy of the Escherichia coli gpt gene as a target for mutagenesis, has little constitutive metallothionein (MT) expression. It was transfected with a vector containing the mouse MT-I gene, and MT-I-overproducing lines were isolated. MT-I transfectants had lower spontaneous mutation frequencies compared with the G12 parental cell line. Mutagenesis by alkylating agents was unchanged. MT expression in G12 and MT transfectants could be modulated by exposure to Zn(II) or Cd(II). The spontaneous mutation frequencies in Zn(II)- and Cd(II)-treated cells was inversely related to MT expression. In G12 cells grown in concentrations of Zn(II) up to 12 microM, a significant dose-dependent increase in spontaneous mutagenesis was observed. At higher (but subtoxic) concentrations in which endogenous MT was induced, a dramatic decrease in spontaneous mutagenesis was observed. In contrast, MT-I transfectants exhibited much lower spontaneous mutagenesis after growth in all concentrations of Zn(II). These data demonstrate a possible role for MT in modulating spontaneous mutagenesis and point to a role for Zn(II) in contributing to spontaneous mutagenesis. Because there is variability in human MT expression, low MT expression might be a risk factor for cancer
— id: 6633, year: 1994, vol: 54, page: 5318, stat: Journal Article,

Transgenic gpt+ V79 cell lines differ in their mutagenic response to clastogens
Klein CB; Su L; Rossman TG; Snow ET
1994 Jan 16;304(2):217-228, Mutation research
Several gpt+ transgenic cell lines were derived from hprt V79 cells to study mutagenesis mechanisms in mammalian cells. The G12 cell line was previously shown to be hypermutable by X-rays and UV at the gpt locus compared to the endogenous hprt gene of the parental V79 cells (Klein and Rossman, 1990), and is now shown to be highly mutable by the clastogenic anti-tumor agent bleomycin sulfate. A second transgenic cell line G10, which has a different gpt insertion site, was studied in comparison with G12. Both G12 and G10 cell lines carry the stable gpt locus at a single integration site in the Chinese hamster genome, and neither spontaneously deletes the integrated gpt sequence at a high frequency. Although spontaneous mutation to 6-thioguanine resistance in G10 cells is 3-4 times higher than in G12 cells, the cell lines differ to a much greater extent when mutated by clastogens. In comparison to G12 cells, the gpt locus in G10 cells is up to 13 times more sensitive to bleomycin mutagenesis and 5 times more responsive to X-ray mutagenesis. In contrast, there is much less difference in UV-induced mutagenesis and no differences in mutagenesis induced by alkylating agents such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The dose-dependent decrease in survival of the transgenic cells is the same for all mutagens tested, and does not differ from that of V79 cells. Neither transgenic cell line is generally hypermutable, since mutagenesis at an endogenous gene, Na+K+/ATPase, is similar to that of the parental V79 cell line. Although both cell lines can be induced to delete the transgene following clastogen exposure, deletions are not the only recovered mutations, and the cell lines can also be used to study mutations within the PCR recoverable gpt gene. The utility of these transgenic cells to investigate genome position effects related to mammalian mutagenesis mechanisms is discussed
— id: 6423, year: 1994, vol: 304, page: 217, stat: Journal Article,

Induction of arsenite tolerance and thermotolerance by arsenite occur by different mechanisms
Wang Z; Hou G; Rossman TG
1994 Sep;102 Suppl 3:97-100, Environmental health perspectives
Both V79 and As/R28A cells (an arsenite-resistant Chinese hamster V79 cell variant) show increased resistance to toxic concentrations of arsenite after pretreatment with a nontoxic concentration. The induced tolerance can be completely inhibited by actinomycin D or cycloheximide. Pretreatment with a nontoxic heat shock (45 degrees C, 10 min) resulted in a clear increased thermotolerance in both cell lines but failed to induce arsenite tolerance in either cell line. Pretreatment with arsenite induced a thermotolerance in V79 cells but not in As/R28A cells. These results are consistent with a model whereby the signal for induction of arsenite tolerance involves binding of arsenite to a protein effector which is amplified in the As/R28A line, thereby preventing action of arsenite in the regulation of heat shock factor which induces the heat shock response
— id: 6769, year: 1994, vol: 102 Suppl 3, page: 97, stat: Journal Article,

Isolation of DNA fragments from agarose gel by centrifugation
Wang Z; Rossman TG
1994 Jul 25;22(14):2862-2863, Nucleic acids research
— id: 6550, year: 1994, vol: 22, page: 2862, stat: Journal Article,

Large-scale supercoiled plasmid preparation by acidic phenol extraction
Wang Z; Rossman TG
1994 Mar;16(3):460-463, Biotechniques
A novel method for large-scale plasmid preparation is described. Crude extracts are subjected to acidic phenol extraction to remove any contaminants present in the aqueous phase. The supercoiled plasmid DNA, which preferentially remains in the organic phase and inter-phase, is extracted back into the aqueous phase with 1.5 M TRIZMA base, from which it is precipitated. The resultant plasmid DNA is highly pure and satisfactory for any subsequent procedures. The method is extremely economical and takes only 3-4 h
— id: 6551, year: 1994, vol: 16, page: 460, stat: Journal Article,

Mutagenicity of soluble and insoluble nickel compounds at the gpt locus in G12 Chinese hamster cells
Lee YW; Pons C; Tummolo DM; Klein CB; Rossman TG; Christie NT
1993 ;21(4):365-371, Environmental & molecular mutagenesis
Nickel is an established human and animal carcinogen, but efforts to demonstrate its mutagenicity in a number of cell types have not been successful. In this report we describe the mutational response to nickel compounds in the G12 cell line, an hprt deficient V79 cell line containing a single copy of the E. coli gpt gene. This cell line has a low spontaneous background, making it suitable for assessment of mutagenic responses to environmental contaminants. When G12 cells were treated with insoluble particles of crystalline nickel sulfide < 5 microns in diameter, a strong, dose-dependent mutagenic response was observed up to 80 times the spontaneous background. Of 48 mutant gpt(-) clones isolated that were induced by insoluble nickel, all were capable of DNA amplification of the gpt sequences by polymerase chain reaction (PCR). The ability to produce full-length PCR products is an indication that large deletions of gene sequences have not occurred. When G12 cells were treated with soluble nickel sulfate, the mutational response was not significantly increased over the spontaneous background. This difference in mutagenic response reflects a large difference in the mutagenic potential of soluble and insoluble nickel compounds, which reflects the carcinogenic potential of these forms of nickel
— id: 13287, year: 1993, vol: 21, page: 365, stat: Journal Article,

Stable and inducible arsenite resistance in Chinese hamster cells
Wang Z; Rossman TG
1993 Jan;118(1):80-86, Toxicology & applied pharmacology
A number of Chinese hamster V79 cell sublines that are arsenite resistant or arsenite sensitive were isolated. After more than 6 months of growth in the absence of arsenite, these sublines still maintain their arsenite-resistant or -sensitive phenotypes. At least some arsenite-resistant cell lines are also cross-resistant to sodium arsenate and potassium antimonyl tartrate. Wild-type or arsenite-resistant sublines show a further increase in resistance to toxic concentrations of arsenite after pretreatment with a nontoxic concentration. Pretreatment of cells with a nontoxic dose of arsenite also increased their survival to toxic doses of antimonite. Likewise, pretreatment with antimonite increased survival to arsenite as well as to antimonite. The inducible arsenite resistance increases with pretreatment time, reaching a plateau after 8 hr of pretreatment. Fusion of arsenite-resistant cells with arsenite-sensitive cells demonstrated a clear dominance of arsenite resistance. These results suggest that mammalian cells contain an arsenite/antimonite pump whose activity may be modulated by prior exposure to arsenite or antimonite
— id: 10389, year: 1993, vol: 118, page: 80, stat: Journal Article,

The role of Ni(II) in mutation
Christie NT; Tummolo DM; Klein CB; Rossman TG
Nickel and human health : current perspectives New York : Wiley, 1992,
— id: 4396, year: 1992, vol: , page: 305, stat: Chapter,

Is cadmium genotoxic?
Rossman TG; Roy NK; Lin WC
1992 ;(118):367-375, IARC scientific publications (Lyon)
Previous evidence that cadmium(II) causes gene mutations in bacteria or mammalian cells was weak. However, alterations in protocol have recently led to better evidence for its mutagenicity, especially in bacteria. Mutagenicity results may be confounded by tolerance mechanisms. Exposure of DNA in vitro to Cd2+ or to Cd2+ hydrogen peroxide does not result in strand breaks or alkali-labile sites. The fact that bacterial and mammalian cells appear to sustain some type of repairable DNA damage after exposure to Cd2+ suggests that the damage must be caused in an indirect manner. Recently, the ability of cadmium-metallothionein complex to cause DNA strand breaks has been described. Cd2+ also induces a 'pro-oxidant state' by causing a depletion of cellular glutathione. This finding is consistent with the role of Cd2+ as a clastogen and may explain its weak mutagenicity at loci which cannot detect complex mutations. Cd2+ can also inhibit DNA repair, and can therefore act synergistically with certain mutagens and, presumably, carcinogens
— id: 13804, year: 1992, vol: , page: 367, stat: Journal Article,

Differential susceptibility to carcinogen-induced amplification of SV40 and dhfr sequences in SV40-transformed human keratinocytes
Rossman TG; Wolosin D
1992 ;6(3):203-213, Molecular carcinogenesis
Gene amplification contributes to carcinogenesis by enhancing proto-oncogene activity and causing chromosomal instability. The ease of detecting amplified tumor-virus sequences has encouraged use of this system as a surrogate for studying the molecular events involved in endogenous gene amplification. We report here a new system for studying carcinogen-induced amplification of both endogenous and viral sequences in the SV40-transformed human keratinocyte line AG06. Treatment with carcinogens induced a transient dose-dependent amplification of the integrated SV40 sequences. The amplified sequences appeared in the extrachromosomal fraction. Treatment of these cells with carcinogens prior to methotrexate (MTX) selection increased the frequency of MTX-resistant colonies, 67% of which exhibited dihydrofolate reductase (dhfr) amplification. The abilities of five carcinogens with different DNA-damaging activities (the DNA-damaging agents N-methyl-N-nitro-N-nitrosoguanidine, mitomycin C (MMC), ultraviolet light C, and X-rays and the non-DNA-damaging agent arsenite) to induce SV40 and dhfr amplification at concentrations that result in 50% clonal survival were compared. All four DNA-damaging carcinogens (as well as growth arrest) were able to elicit some SV40 amplification, but responses varied markedly, from 1.8-fold for X-rays to sevenfold to eightfold for MMC. There was no correlation between the ability to elicit the two amplification responses. Arsenite, which did not induce SV40 amplification, was the best inducer of MTX resistance. These results point to different controls involved in the induction of viral and dhfr amplification. The signal for amplification of viral genes may be triggered by DNA damage and growth arrest, whereas amplification of dhfr, and perhaps other endogenous sequences, seems to be triggered by other signals as well
— id: 10396, year: 1992, vol: 6, page: 203, stat: Journal Article,

Induced effects of genotoxic agents in eukaryotic cells
Rossman, Toby G
Washington, D.C. : Hemisphere Pub. Corp. ; Bristol PA : Taylor & Francis [distributor], c1992,
— id: 402, year: 1992, vol: , page: , stat: ,

Mutagenesis and comutagenesis by lead compounds
Roy NK; Rossman TG
1992 Dec;298(2):97-103, Mutation research
We have previously reported that lead(II) is weakly mutagenic to Chinese hamster V79 cells. A transgenic cell line G12 containing a single copy of the E. coli gpt gene was developed in this laboratory from Chinese hamster V79 cells. The gpt locus in the G12 cells is more mutable by radiation and oxidative agents compared with the endogenous hprt locus of wild-type V79 cells. We have investigated the mutagenicity of two lead compounds at the gpt locus in G12 cells. Only at a toxic dose is lead acetate significantly mutagenic to G12 cells. Lead nitrate is not significantly mutagenic at any dose. Although both compounds are water-soluble, lead acetate, but not lead nitrate, forms a fine white insoluble precipitate upon addition to growth medium. A nick translation assay on cells treated with lead compounds and then permeabilized indicated that lead nitrate and, to a greater extent, lead acetate causes the appearance of nicks in chromosomal DNA. Lead ions in the presence of hydrogen peroxide, but not alone, introduced nicks into supercoiled plasmid DNA in vitro, suggesting that lead ions can partake in a Fenton reaction and thereby damage DNA. At lower nonmutagenic concentrations, lead acetate enhances the mutagenicity of MNNG and ultraviolet light. DNA damage by ultraviolet light is not enhanced by lead ions in vitro. Our data support the concept that non-toxic concentrations of lead(II) can inhibit DNA repair. Thus, at biologically relevant doses, lead(II) could act as a comutagen and possibly a cocarcinogen, but is not likely to act as an initiating genotoxic carcinogen
— id: 13363, year: 1992, vol: 298, page: 97, stat: Journal Article,

DNA damage by mercury compounds : an overview
Costa M; Christie NT; Cantoni O; Zelikoff JT; Wang XW; Rossman TG
Advances in mercury toxicology New York : Plenum Press, 1991,
— id: 4397, year: 1991, vol: , page: ?, stat: Chapter,

Mutagenicity, carcinogenicity, teratogenicity
Gebhart E; Rossman TG
Metals and their compounds in the environment : occurence, analysis, and biological relevance New York : VCH, 1991,
— id: 4398, year: 1991, vol: , page: 617, stat: Chapter,

Comutagenesis of sodium arsenite with ultraviolet radiation in Chinese hamster V79 cells
Li JH; Rossman TG
1991 ;4(4):197-200, Biology of metals
Solar ultraviolet radiation has been associated with the induction of skin cancer. Recent studies have indicated that near-ultraviolet, especially UVB, is mutagenic. Exposure to trivalent inorganic arsenic compounds has also been associated with increased skin cancer prevalence. Trivalent arsenic compounds are not mutagenic per se, but are comutagenic with a number of cancer agents. Here, we test the hypothesis that arsenite enhances skin cancer via its comutagenic action with solar ultraviolet radiation. Irradiation of Chinese hamster V79 cells with UVA (360 nm), UVB (310 nm) and UVC (254 nm) caused a fluence-dependent increase in mutations at the hprt locus. On an energy basis, UVC was the most mutagenic and UVA the least. However, when expressed as a function of toxicity, UVB was more mutagenic than UVC. Nontoxic concentrations of arsenite increased the toxicity of UVA, UVB and UVC. Arsenite acted as a comutagen at the three wavelengths; however, higher concentrations of arsenite were required to produce a significant (P less than 0.05) comutagenic response with UVB. The increased mutagenicity of UVB and UVA by arsenite may play a role in arsenite-related skin cancers
— id: 14218, year: 1991, vol: 4, page: 197, stat: Journal Article,

Performance of 133 compounds in the lambda prophage induction endpoint of the Microscreen assay and a comparison with S. typhimurium mutagenicity and rodent carcinogenicity assays
Rossman TG; Molina M; Meyer L; Boone P; Klein CB; Wang Z; Li F; Lin WC; Kinney PL
1991 Aug;260(4):349-367, Mutation research
The Microscreen assay was developed as a means of testing very small samples, as in complex mixture fractionation. It is a multi-endpoint assay which utilizes E. coli WP2s(lambda). Exposure takes place to serial dilutions of the test compound in microtitre wells (250 microliters) followed by sampling from wells in which growth has occurred ('non-toxic wells'). Although a number of different endpoints can be measured, only the prophage induction endpoint (the first one developed) has been extensively tested. Results with 133 compounds are presented. These include 111 compounds which have been tested in the S. typhimurium assay and 66 compounds for which both rodent bioassay and S. typhimurium assay data exists. The concordance for the Microscreen assay and the S. typhimurium assay was 71%. For this group of compounds, the sensitivity of the Microscreen assay in detecting carcinogens was 76% compared with 58% for the S. typhimurium assay. However, the S. typhimurium assay was somewhat more specific (69%) compared with the Microscreen (56%). The overall association between carcinogenicity and Microscreen results was statistically significant (p = 0.029), whereas for the S. typhimurium assay the association with carcinogenicity was non-significant (p = 0.086). The Microscreen assay was able to detect halogenated compounds better than the S. typhimurium assay. The Microscreen assay should prove useful in complex mixture fractionation, or in other situations where sample size is limiting
— id: 13955, year: 1991, vol: 260, page: 349, stat: Journal Article,

Transgenic Chinese hamster V79 cell lines which exhibit variable levels of gpt mutagenesis
Klein, C B; Rossman, T G
1990 ;16(1):1-12, Environmental & molecular mutagenesis
The Escherichia coli gpt gene coding for xanthine-guanine phosphoribosyl transferase has been stably transfected into HPRT- Chinese hamster V79 cells. Several gpt- cell lines have been established, which retain the sequence(s) even after long-term culture without selection for gpt. Each cell line exhibits a characteristic spontaneous mutation frequency (10(-5) to 10(-2)) in 6-thioguanine (6TG) selection. While spontaneous mutagenesis to gpt- occurs rather frequently for most cell lines, it cannot be correlated with either the number of plasmid integration sites or deletion of the plasmid sequence(s). One transgenic cell line (g12), which continuously maintains a low spontaneous mutation frequency (approximately 3 x 10(-5)), was used in comparative mutagenesis studies with wild-type V79 cells (gpt vs. hprt). Alkylating agents such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and beta-propiolactone (BPL) are shown to be equally toxic and mutagenic in both g12 and V79 cells. UV and X-rays are also equally toxic to both cell lines. The gpt locus of the g12 transfectants, however, is two to three times more sensitive to UV and 2.5-4.5 times more sensitive to X-ray mutagenesis than the endogenous hprt of wild-type V79 cells. The data presented here suggests that g12 cells may be useful to study mammalian mutagenesis by agents which yield limited response at the hprt locus. Future studies with these transgenic cells and other transgenic lines are planned to compare the mutability and repair of the same gene (gpt) at different integration sites in mammalian cells
— id: 132703, year: 1990, vol: 16, page: 1, stat: Journal Article,

THE GENOTOXIC CONTRIBUTION OF WOOD SMOKE TO INDOOR RESPIRABLE SUSPENDED PARTICLES
BOONE, PM; ROSSMAN, TG; DAISEY, JM
1989 ;15(1-6):361-368, Environment international
— id: 104618, year: 1989, vol: 15, page: 361, stat: Journal Article,

Proceedings of the First International Meeting on Molecular Mechanisms of Metal Toxicity and Carcinogensis, hedl Sept 19-22, 1988 in Urbino, Italy
Costa, Max; Rossman, Toby
Clifton NJ : Humana Press, 1989,
— id: 1218, year: 1989, vol: , page: , stat: ,

Inhibition of DNA ligase activity by arsenite: a possible mechanism of its comutagenesis
Li JH; Rossman TG
1989 Winter;2(1):1-9, Molecular toxicology
We have previously shown that the inhibition of MNU-induced DNA repair by arsenite occurs after the incision step in Chinese hamster V79 cells. We now report that nuclear DNA ligase activity is inhibited after arsenite treatment and that the inhibited activity is mostly DNA ligase II. Both constitutive and MNU-inducible levels of DNA ligase II are inhibited. The addition of arsenite in vitro also indicates that DNA ligase II is more sensitive to arsenite inhibition than DNA ligase I. Since DNA ligase II is reported to be involved in the ligation step of excision repair, its inhibition by arsenite is a likely mechanism for the inhibition of DNA repair by arsenite and may account for the fact that arsenite acts as a comutagen with a number of different types of mutagens. The carcinogenicity of arsenite may also be a result of ligase inhibition
— id: 10812, year: 1989, vol: 2, page: 1, stat: Journal Article,

Mechanism of comutagenesis of sodium arsenite with n-methyl-n-nitrosourea
Li JH; Rossman TG
1989 Jul-Sep;21:373-381, Biological trace element research
Arsenic compounds are known carcinogens. Although many carcinogens are also mutagens, we have previously shown that sodium arsenite is not mutagenic at either the Na+/K+ ATPase or hprt locus in Chinese hamster V79 cells. It can, however, enhance UV-mutagenesis. We now confirm the nonmutagenicity of sodium arsenite in line G12, a pSV2gpt-transformed V79 (hprt-) cell line, which is able to detect multilocus deletions in addition to point mutations and small deletions. The lack of arsenic mutagenicity has led to studies emphasizing its comutagenicity. Sodium arsenite at relatively nontoxic concentrations (5 microM for 24 h or 10 microM for 3 h) is comutagenic with N-methyl-N-nitrosourea (MMU) at the hprt locus in V79 cells. Using a nick translation assay, which measures DNA strand breaks by incorporating radioactive deoxyribonucleoside monophosphate at their 3'OH ends in permeabilized cells, we found that much more incorporation was seen in cells treated with MNU (4 mM, 15 min) followed by 3-h incubation with 10 microM sodium arsenite compared with cells exposed to the same MNU treatment followed by 3-h incubation without sodium arsenite. This result shows that in the presence of arsenite, strand breaks resulting from MNU or its repair accumulate over a 3-h period. We suggest that the repair of MNU-induced DNA lesions may be inhibited by arsenite either by affecting the incorporation of dNMPs into the MNU-damaged DNA template or by interfering with the ligation step
— id: 10578, year: 1989, vol: 21, page: 373, stat: Journal Article,

On the mechanism of the comutagenic effect of Cu(II) with ultraviolet light
Rossman TG
1989 Jul-Sep;21:383-388, Biological trace element research
Although CuCl2 alone is not mutagenic in E. coli or in Chinese hamster cells, exposure of E. coli to CuCl2 during UV-irradiation causes enhancement of UV-mutagenesis. The mechanism for this comutagenic effect appears to be owing to increased DNA damage by the combined treatment of UV and Cu(II) compared with UV or Cu(II) alone. Using a sequencing gel approach, UV alone is found to cause a particular pattern of alkali-labile sites, whereas CuCl2 alone caused few such sites. The combined action of UV + CuCl2 greatly increased the amount of sites over that of UV alone, and caused a change in their pattern. In the presence of high NaCl concentrations, however, Cu(II) is able to induce DNA damage. This latter effect is most likely owing to the formation of hypochlorite ion. The hypothesis that the comutagenic effect of Cu(II) plus UV might be owing to hydroxyl radical formed via a Fenton reaction involving Cu(II) and UV-generated H2O2 was not supported, since no H2O2 is detectable in aqueous medium after UV irradiation, and catalase did not block the DNA damage. These results favor the hypothesis that UV-irradiation of Cu(II) causes a photoactivation, enabling it to generate free radicals, perhaps by reacting with dissolved oxygen
— id: 10577, year: 1989, vol: 21, page: 383, stat: Journal Article,

THE PROCEEDINGS OF THE 1ST INTERNATIONAL MEETING ON MOLECULAR MECHANISMS OF METAL TOXICITY AND CARCINOGENICITY, HELD SE
ROSSMAN, TG; COSTA, M
1989 ;21(1-4):R1-R2, Biological trace element research
— id: 104619, year: 1989, vol: 21, page: R1, stat: Journal Article,

EFFECTS OF CUCL2 ON UV-MUTAGENESIS AND ON DNA DAMAGE IN A RESTRICTION FRAGMENT OF ESCHERICHIA-COLI GPT
Rossman, TG; Rubin, LM; Kneip, TJ
1989 Jul-Sep;23(1-4):65-72, Toxicological & environmental chemistry
— id: 31616, year: 1989, vol: 23, page: 65, stat: Journal Article,

Specific high frequency rearrangements induced by MNNG in SV40-infected human keratinocytes
Steinberg, M L; Rossman, T G; Morris, A; Chen, G T
1989 Oct;10(10):1801-1807, Carcinogenesis
In order to study carcinogen-induced changes in integrated viral sequences clonal sublines of SV40-transformed human keratinocytes were exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at sublethal concentrations ranging up to 10 micrograms/ml for a period of 15 min and then examined by Southern blot hybridization using full-length SV40 DNA as a probe. Of the clonal sublines tested, one (AG34) was found to exhibit certain consistent, dose-dependent changes at 4 days post-treatment: (i) loss of at least two EcoRI fragments of approximately 4.4 and 3 kb, with the concomitant appearance of two bands migrating between 1.8 and 2.3 kb; and (ii) loss of a 1.5-kb fragment and the appearance of 2, 3.8 and 5 kb fragments in KpnI digests. Minor variable changes in restriction patterns were seen at 24 h post-treatment but consistent and pronounced effects were observed only at 4 days post-treatment. The altered restriction fragment patterns indicate that MNNG caused highly specific rearrangements in some subset of the DNA sequences associated with the integrated SV40 sequences in human epithelial cells. This differs from what has been found for SV40 sequences in other cell lines where amplification has been reported. These results suggest that (i) the site of SV40 integration may determine the response of integrated SV40 segments after carcinogen treatment, and (ii) carcinogen treatment can result in the induction of a common genetic event throughout the entire population of exposed cells. Genomic libraries created in a lambda phage vector have been used to isolate BamHI fragments containing SV40 sequences. Isolates have been found which exhibit EcoRI and KpnI restriction patterns consistent with the polymorphisms displayed in Southern blots
— id: 146016, year: 1989, vol: 10, page: 1801, stat: Journal Article,

From DNA damage to mutation in mammalian cells: a review
Rossman TG; Klein CB
1988 ;11(1):119-133, Environmental & molecular mutagenesis
— id: 11233, year: 1988, vol: 11, page: 119, stat: Journal Article,

Colony hybridization to identify mammalian cells containing amplified, transfected, or expressed sequences
Rossman TG; Rubin LM
1988 Jul;14(4):321-328, Somatic cell & molecular genetics
The identification of variant cell clones has played an important role in the elucidation of various biochemical pathways. Such clones are typically selected by altering the medium or the growth conditions to give a selective advantage to the desired variant. The availability of cloned DNA probes has made it possible to identify bacterial colonies or viral plaques containing desired sequences, even in the absence of selection. We describe here a new method for the identification and isolation of mammalian cells containing any sequence for which a probe exists. Mammalian cell clones are first replicated onto nylon cloth. The original clones and the replicas are grown for a few days to enlarge the clones. All the clones on the original dish are transferred in situ to a filter and processed for hybridization. By altering the processing, either DNA or RNA sequences in the clones can be identified. When a clone of interest is located by hybridization, the cells can be isolated from the nylon replicas. We expect this method to be of value in the isolation of clones containing amplified, transfected, or mutated genes, as well as those exhibiting altered gene expression
— id: 11054, year: 1988, vol: 14, page: 321, stat: Journal Article,

IDENTIFICATION OF A HIGHLY MUTAGENIC METABOLITE OF BENZENE
Rossman, TG; Klein, CB; Snyder, CA
1988 Mar;29(5):124-124, Proceedings (American Association for Cancer Research)
— id: 31481, year: 1988, vol: 29, page: 124, stat: Journal Article,

Genetic toxicology of lead compounds
Zelikoff JT; Li JH; Hartwig A; Wang XW; Costa M; Rossman TG
1988 Oct;9(10):1727-1732, Carcinogenesis
We have investigated the activity of insoluble and soluble lead compounds in inducing mutagenesis, cell transformation and sister chromatid exchange in mammalian cells. Insoluble lead sulfide, readily phagocytized, was more than four times as toxic to V79 cells on a microM basis, than two moderately soluble lead compounds although the exposure time for the soluble salts was five times longer. These findings demonstrate the importance of different cellular mechanism(s) of metal uptake and bioavailability. Both insoluble lead sulfide and more soluble lead nitrate were mutagenic at the HPRT locus in V79 cells. Although less mutagenic at the higher concentrations, lead nitrate at a concentration of 500 microM enhanced the mutation frequency greater than 6-fold above background following a 5-day exposure. Although the mechanism(s) by which lead induces mutations is unknown, failure of both compounds to induce SCE and DNA single-strand breaks, detectable by alkaline elution, suggests that lead-induced mutations may not be a result of direct damage to DNA but may occur via indirect mechanisms including disturbances in enzyme functions important in DNA synthesis and/or repair, or in DNA-helical structure. Lead acetate also transformed SHE cells in a dose-response fashion following a 48-h exposure. Our results indicate that lead compounds may be genotoxic by an indirect mechanism, and lend support to the view that lead is a carcinogen
— id: 10946, year: 1988, vol: 9, page: 1727, stat: Journal Article,

Heterogeneity in the response of inserted viral sequences to carcinogen treatment : a clonal approach
Rossman TG; Rubin LM; Gilmer T; Steinberg ML
1987 ;2(1):83-94, Accomplisments in oncology
— id: 72784, year: 1987, vol: 2, page: 83, stat: Journal Article,

Probing mammalian clones : a new method with application for mutagenesis research
Rossman TG; Rubin LM; Li JH
1987 ;28:301-304, Banbury report
— id: 72783, year: 1987, vol: 28, page: 301, stat: Journal Article,

CLONAL BLOTS - A NEW METHOD FOR ISOLATING MAMMALIAN-CELLS CONTAINING SEQUENCES OF INTEREST
Rossman, TG; Rubin, LM
1987 Mar;3(1):90-90, Cell biology & toxicology
— id: 31170, year: 1987, vol: 3, page: 90, stat: Journal Article,

IDENTIFICATION AND ISOLATION OF MAMMALIAN-CELL CLONES CONTAINING NON-SELECTABLE AMPLIFIED, TRANSFECTED OR EXPRESSED SEQUENCES
Rossman, TG; Rubin, LM
1987 Feb;9(2):91-92, Environmental mutagenesis
— id: 31272, year: 1987, vol: 9, page: 91, stat: Journal Article,

GENETIC TOXICOLOGY OF METAL-COMPOUNDS - AN EXAMINATION OF APPROPRIATE CELLULAR-MODELS
ROSSMAN, TG; ZELIKOFF, JT; AGARWAL, S; KNEIP, TJ
1987 MAY ;14(4):251-262, Toxicological & environmental chemistry
— id: 41713, year: 1987, vol: 14, page: 251, stat: Journal Article,

Genetic effects of 5-hydroxymethyl-2'-deoxyuridine, a product of ionizing radiation
Shirname-More L; Rossman TG; Troll W; Teebor GW; Frenkel K
1987 Jun;178(2):177-186, Mutation research
Ionizing radiation causes formation of heterogeneous types of damage to DNA. Among those, 5-hydroxymethyl-2'-deoxyuridine (HMdU) was identified as a major thymidine derivative in gamma-irradiated HeLa cells [G.W. Teebor, K. Frenkel and M.S. Goldstein (1984) Proc. Natl. Acad. Sci. (U.S.A.), 81, 318-321]. We report here that HMdU is a strong inducer of lambda prophage in Escherichia coli WP2s(lambda) and is highy mutagenic in Salmonella typhimurium. HMdU causes his+ revertants in strains TA100, which reverts predominantly by base-pair substitution at G-C sites, and TA97, which reverts mainly by frameshift mutation at G-C sites. It does not cause reversion in TA98, another frameshift-sensitive strain, nor in strains TA1535 and TA1537. Of those tested, only the last two strains do not contain pkM101, a plasmid which enhances mutagenic effects of ionizing radiation. HMdU also causes reversion in strains TA102 and TA104, which detect oxidative damage and can revert by base-pair substitution at A-T base pairs at the hisG428 site. We show that HMdU can be incorporated into DNA of TA100 and that, in addition to causing point mutations, it causes suppressor mutations as well. The ability of HMdU to induce lambda prophage and its strong mutagenicity in Salmonella typhimurium provide evidence that the presence of HMdU in DNA is biologically significant and may play a major role in the genetic consequences of ionizing radiation and other types of oxidative damage
— id: 34049, year: 1987, vol: 178, page: 177, stat: Journal Article,

MNNG-INDUCED REARRANGEMENTS OF VIRAL-ASSOCIATED DNA IN SV40- TRANSFORMED HUMAN KERATINOCYTES
Steinberg, ML; Rossman, T; Morris, A
1987 Mar;28(3):1-1, Proceedings (American Association for Cancer Research)
— id: 31380, year: 1987, vol: 28, page: 1, stat: Journal Article,

CYTOTOXICITY AND MUTAGENICITY OF INSOLUBLE METAL-SALTS IN V79 CELLS
Zelikoff, JT; Hartwig, A; Li, JH; Rossman, TG
1987 Mar;3(1):93-93, Cell biology & toxicology
— id: 31171, year: 1987, vol: 3, page: 93, stat: Journal Article,

Comutagens in E. coli and Chinese hampster cells with special attention to arsenite
Rossman TG; Molina M; Klein CB
Genetic toxicology of environmental chemicals. Pt. A New York : A.R. Liss, 1986,
— id: 4399, year: 1986, vol: , page: 403, stat: Chapter,

ASCORBATE ENHANCES UV-MUTAGENESIS IN ESCHERICHIA-COLI BUT INHIBITS IT IN CHINESE-HAMSTER CELLS
ROSSMAN, TG; KLEIN, CB; NASLUND, M
1986 MAY ;7(5):727-732, Carcinogenesis
— id: 41599, year: 1986, vol: 7, page: 727, stat: Journal Article,

INDUCTION OF LAMBDA-PROPHAGE AS A SCREEN FOR GENOTOXIC AGENTS
ROSSMAN, TG; MEYER, LW; MOLINA, M
1986 MAY 1 ;463(1):347-348, Annals of the New York Academy of Sciences
— id: 41586, year: 1986, vol: 463, page: 347, stat: Journal Article,

THE ADDITION OF A FORWARD MUTATION MARKER TO THE MICROSCREEN ASSAY
ROSSMAN, TG; MOLINA, M
1986 FEB ;8(2):70-70, Environmental mutagenesis
— id: 41509, year: 1986, vol: 8, page: 70, stat: Journal Article,

THE GENETIC TOXICOLOGY OF METAL-COMPOUNDS .2. ENHANCEMENT OF ULTRAVIOLET LIGHT-INDUCED MUTAGENESIS IN ESCHERICHIA-COLI WP2
ROSSMAN, TG; MOLINA, M
1986 MAY 1 ;8(2):263-271, Environmental mutagenesis
— id: 41604, year: 1986, vol: 8, page: 263, stat: Journal Article,

5-HYDROXYMETHYL-2'-DEOXYURIDINE, A PRODUCT OF IONIZING-RADIATION, IS GENOTOXIC IN BACTERIAL SYSTEMS
SHIRNAMEMORE, L; FRENKEL, K; TROLL, W; TEEBOR, GW; ROSSMAN, TG
1986 FEB ;8(2):78-78, Environmental mutagenesis
— id: 41511, year: 1986, vol: 8, page: 78, stat: Journal Article,

MUTAGENICITY OF SOLUBLE METAL-SALTS USING THE V79/HGPRT MUTATION ASSAY
ZELIKOFF, JT; ATKINS, N; ROSSMAN, TG
1986 FEB ;8(2):95-95, Environmental mutagenesis
— id: 41512, year: 1986, vol: 8, page: 95, stat: Journal Article,

COMPARISON OF THE CYTOTOXICITY OF SOLUBLE AND INSOLUBLE METAL-SALTS ON V79 CELLS
ZELIKOFF, JT; LI, JH; ROSSMAN, TG
1986 MAR ;22(3):A47-A47, In vitro
— id: 41348, year: 1986, vol: 22, page: A47, stat: Journal Article,

Use of the microscreen assay for airborne particulate organic matter
Rossman TG; Meyer LW; Butler JP; Daisey JM
Short-term bioassays in the analysis of complex environmental mixtures IV New York : Plenum Press, 1985,
— id: 4400, year: 1985, vol: , page: 9, stat: Chapter,

MAMMALIAN SOS SYSTEM - A CASE OF MISPLACED ANALOGIES
Rossman, TG; Klein, CB
1985 ;3(2):175-187, Cancer investigation
— id: 30739, year: 1985, vol: 3, page: 175, stat: Journal Article,

BASE PAIR SUBSTITUTION AND FRAMESHIFT REVERTIBLE V79 CELL-LINES
Rossman, TG; Klein, CB; Stonewolff, DS
1985 ;7(1):7-7, Environmental mutagenesis
— id: 30880, year: 1985, vol: 7, page: 7, stat: Journal Article,

HGPRT- MUTANTS OF V79 CELLS THAT REVERT SPECIFICALLY BY BASE PAIR SUBSTITUTION AND FRAMESHIFT MUTATIONS
STONEWOLFF, DS; KLEIN, CB; ROSSMAN, TG
1985 ;7(3):281-291, Environmental mutagenesis
— id: 41152, year: 1985, vol: 7, page: 281, stat: Journal Article,

A COMPARISON OF METAL TOXICITY IN A MICROTITRE ASSAY SYSTEM, USING ESCHERICHIA-COLI AND V79 CELLS
Zelikoff, JT; Agarwal, S; Rossman, TG
1985 ;7(1):7-8, Environmental mutagenesis
— id: 30881, year: 1985, vol: 7, page: 7, stat: Journal Article,

CYTO-TOXICITY OF FINE PARTICLES WITH AND WITHOUT ADSORBED POLYCYCLIC AROMATIC-HYDROCARBONS USING CHINESE-HAMSTER LUNG-CELLS (V79)
ZELIKOFF, JT; ATKINS, NM; ROSSMAN, TG; DAISEY, JM
1985 ;11(2-4):331-339, Environment international
— id: 41200, year: 1985, vol: 11, page: 331, stat: Journal Article,

MUTAGENIC SPECIFICITY OF BETA-PROPIOLACTONE IN BACTERIA AND CHINESE-HAMSTER V79-CELLS
KLEIN, CB; ROSSMAN, TG
1984 ;6(3):426-426, Environmental mutagenesis
— id: 40938, year: 1984, vol: 6, page: 426, stat: Journal Article,

MICROSCREEN - A RAPID SMALL-SCALE SYSTEM TO DETECT MULTIPLE GENETIC ENDPOINTS
MEYER, LW; MOLINA, M; ROSSMAN, TG
1984 ;6(3):413-413, Environmental mutagenesis
— id: 40937, year: 1984, vol: 6, page: 413, stat: Journal Article,

THE GENETIC TOXICOLOGY OF METAL-COMPOUNDS .1. INDUCTION OF LAMBDA-PROPHAGE IN ESCHERICHIA-COLI WP2S(LAMBDA)
ROSSMAN, TG; MOLINA, M; MEYER, LW
1984 ;6(1):59-69, Environmental mutagenesis
— id: 41106, year: 1984, vol: 6, page: 59, stat: Journal Article,

CELLULAR UPTAKE AND CYTO-TOXICITY OF FINE PARTICLES WITH ADSORBED BENZO(A)PYRENE USING CHINESEHAMSTER LUNG CELLS(V79)
ZELIKOFF, JT; ATKINS, N; ROSSMAN, T; DAISEY, JM
1984 ;6(3):435-435, Environmental mutagenesis
— id: 40939, year: 1984, vol: 6, page: 435, stat: Journal Article,

EFFECTS OF BISULFITE (SULFUR-DIOXIDE) ON DNA-SYNTHESIS AND FIDELITY BY DNA-POLYMERASE-I
Mallon, RG; Rossman, TG
1983 ;46(1):101-108, Chemico-biological interactions
— id: 30609, year: 1983, vol: 46, page: 101, stat: Journal Article,

The effects of bisulfite on growth and macromolecular synthesis in Escherichia coli
Robakis NK; Rossman TG; Shapiro R; Szer W
1983 Mar;43(3):289-298, Chemico-biological interactions
Bisulfite reversibly inhibits the growth of a variety of microorganisms and has been used as a preservative in foods and beverages for that reason. We have now measured macromolecule synthesis in Escherichia coli K12 after bisulfite treatment. RNA synthesis, the synthesis of total protein, and of an inducible enzyme, beta-galactosidase, stopped almost immediately upon addition of 2 mM (or higher concentrations) of bisulfite. These functions resumed after a lag whose duration depended on the concentration of bisulfite added. The synthesis of DNA was slowed upon bisulfite addition, but did not stop entirely. The inhibition of RNA synthesis by bisulfite took place in both stringent and relaxed strains of E. coli and was not relieved upon addition of chloramphenicol. Stringent control was therefore not involved in this effect. No effect on protein synthesis was observed in the cell-free system of E. coli (using poly(U) or MS2 RNA as messenger) at bisulfite concentrations up to 10 mM. Protein synthesis inhibition in vivo was apparently not due to a reaction of bisulfite with a component of this system. In additional experiments, RNA polymerase was not impaired by bisulfite, and the growth inhibition effect was shown to proceed in the presence of inhibitors of free radical chain reactions
— id: 17475, year: 1983, vol: 43, page: 289, stat: Journal Article,

Rat liver S9 preparations contain comutagenic activity
Rossman, T G; Molina, M
1983 Nov;122(2):103-109, Mutation research
Rat liver S9 preparations contain material which causes enhancement of UV mutagenesis in Escherichia coli WP2. This comutagenic activity is present in S9 preparations from both uninduced and Aroclor-induced rats. Strains of E. coli which are defective in the uvr-dependent excision repair pathway fail to show comutagenic action by S9. The comutagenic material is heat-labile and non-dialyzable, suggesting that it might be protein. This differs from the small amount of mutagenic material present in rat liver S9, as the latter is dialyzable and can be demonstrated in the repair-deficient strain E. coli WP2s (uvrA)
— id: 133280, year: 1983, vol: 122, page: 103, stat: Journal Article,

Muconaldehyde, a potential toxic intermediate of benzene metabolism
Goldstein BG; Witz G; Javid J; Amoruso MA; Rossman T; Wolder B
Biological reactive intermediates II : chemical mechanisms and biological effects New York : Plenum Press, 1982,
— id: 4401, year: 1982, vol: , page: 331, stat: Chapter,

MUCONALDEHYDE, A POTENTIAL TOXIC INTERMEDIATE OF BENZENE METABOLISM
GOLDSTEIN, BD; WITZ, G; JAVID, J; AMORUSO, MA; ROSSMAN, T; WOLDER, B
1982 ;136(3):331-339, Advances in experimental medicine & biology
— id: 40427, year: 1982, vol: 136, page: 331, stat: Journal Article,

COMUTAGENIC MATERIAL PRESENT IN RAT LIVER-S9
Rossman, TG
1982 ;4(3):415-415, Environmental mutagenesis
— id: 30399, year: 1982, vol: 4, page: 415, stat: Journal Article,

INHIBITION OF DNA-SYNTHESIS IS NOT SUFFICIENT TO CAUSE MUTAGENESIS IN CHINESE-HAMSTER CELLS
Rossman, TG; Stonewolff, DS
1982 ;64(8-9):809-813, Biochimie
— id: 30306, year: 1982, vol: 64, page: 809, stat: Journal Article,

DEMONSTRATION OF RECOVERY FROM THE POTENTIALLY MUTAGENIC EFFECTS OF ULTRAVIOLET-LIGHT BY REPLICATION-INHIBITED CHINESE- HAMSTER V79 CELLS
Stonewolff, DS; Rossman, TG
1982 ;95(2-3):493-503, Mutation research. DNA repair reports
— id: 30312, year: 1982, vol: 95, page: 493, stat: Journal Article,

Muconaldehyde, a potential toxic intermediate of benzene metabolism
Goldstein, B D; Witz, G; Javid, J; Amoruso, M A; Rossman, T; Wolder, B
1981 ;136 Pt A:331-339, Advances in experimental medicine & biology
— id: 145616, year: 1981, vol: 136 Pt A, page: 331, stat: Journal Article,

BISULFITE (SULFUR-DIOXIDE) IS A COMUTAGEN IN ESCHERICHIA-COLI AND IN CHINESE-HAMSTER CELLS
MALLON, RG; ROSSMAN, TG
1981 ;88(2):125-133, Mutation research. DNA repair reports
— id: 40354, year: 1981, vol: 88, page: 125, stat: Journal Article,

EFFECT OF METALS ON MUTAGENESIS AND DNA-REPAIR
Rossman, TG
1981 ;40(AUG):189-195, Environmental health perspectives
— id: 30196, year: 1981, vol: 40, page: 189, stat: Journal Article,

ENHANCEMENT OF UV-MUTAGENESIS BY LOW CONCENTRATIONS OF ARSENITE IN ESCHERICHIA-COLI
ROSSMAN, TG
1981 ;91(3):207-211, Mutation research. DNA repair reports
— id: 40336, year: 1981, vol: 91, page: 207, stat: Journal Article,

INHIBITION OF GROWTH AND MACROMOLECULAR-SYNTHESIS IN ESCHERICHIA-COLI
Shapiro, R; Robakis, NK; Rossman, T
1981 ;40(6):1621-1621, Federation Proceedings (Federation of American Societies for Experimental Biology)
— id: 30252, year: 1981, vol: 40, page: 1621, stat: Journal Article,

Effects of inhibitors of de novo protein synthesis on UV-mutagenesis in Chinese hamster cells. Evidence against mutagenesis via inducible, error-prone DNA repair
Stone-Wolff, D S; Rossman, T G
1981 Jun;82(1):147-157, Mutation research
Experiments were designed to test whether UV-mutagenesis in animal cells requires an inducible error-phone DNA-repair system similar to the 'SOS system' in E. coli. Chinese hamster (V79) cells were exposed to either 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB, a transcription inhibitor), cycloheximide, or puromycin for various times (3-6 h) following UV-irradiation (2-8 J/m2). Post-irradiation treatment with DRB resulted in a reproducible enhancement of UV-induced mutagenesis, whereas post-irradiation treatment with either cycloheximide or puromycin resulted in decreased UV-mutagenesis. Thus, the frequency of UV-mutagenesis does not appear to be dependent on an inducible error-prone DNA-repair pathway, since all 3 agents share the ability to inhibit de novo protein synthesis. In order to understand the effects of these inhibitors on mutation frequency, DNA synthesis in the presence of these agents was examined. DRB stimulated DNA synthesis in both irradiated and unirradiated cells. On the other hand, cycloheximide and puromycin caused an immediate inhibition of DNA synthesis in both irradiated and unirradiated cells. Therefore, it appears that UV-mutagenesis reflects changes in post-irradiation DNA synthesis rather than post-irradiation de novo protein synthesis
— id: 133295, year: 1981, vol: 82, page: 147, stat: Journal Article,

Protese inhibitors in carcinogenesis : possible sites of action
Rossman TG; Troll W
Modifiers of chemical carcinogenesis : an approach to the biochemical mechanism and cancer prevention New York : Raven Press, 1980,
— id: 4402, year: 1980, vol: , page: 127, stat: Chapter,

Absence of arsenite mutagenicity in E coli and Chinese hamster cells
Rossman, T G; Stone, D; Molina, M; Troll, W
1980 ;2(3):371-379, Environmental mutagenesis
Because exposure to compounds of arsenic has been implicated as a cause of cancer, an investigation of the mutagenicity of sodium aresenite in E coli and in Chinese hamster cells was performed. In the E coli system, Trp + revertants were not induced by arsenite in a variety of experimental protocols including spot tests, treat and plate protocols, and fluctuation tests. The mutator effect of a tif-1 strain was partially blocked by arsenite. Arsenite did not cause the induction of lambda prophage. In Chinese hamster cells, arsenite did not induce ouabain-resistant mutants or thioguanine-resistant mutants. We conclude that arsenite is not mutagenic to E coli or to Chinese hamster cells. When added to the plating medium, arsenite can act as an anti-mutagen by inhibition of induction of the error-prone SOS repair system in E coli
— id: 108467, year: 1980, vol: 2, page: 371, stat: Journal Article,

Protease inhibitors in carcinogenesis: possible sites of action
Rossman, T G; Troll, W
1980 ;5:127-143, Carcinogenesis: a comprehensive survey
— id: 108466, year: 1980, vol: 5, page: 127, stat: Journal Article,

COMUTAGENICITY OF BISULFITE
ROSSMAN, TG; MALLON, RG
1980 ;2(2):239-240, Environmental mutagenesis
— id: 104620, year: 1980, vol: 2, page: 239, stat: Journal Article,

ETHIONINE BLOCKS SOS FUNCTIONS IN THE TIF-1 MUTANT
WIESNER, R; EPSTEIN, E; ROSSMAN, T
1980 ;21(MAR):31-31, Proceedings (American Association for Cancer Research)
— id: 98660, year: 1980, vol: 21, page: 31, stat: Journal Article,

SUPPRESSION OF SOS FUNCTIONS IN ESCHERICHIA-COLI BY PROTEASE INHIBITOR ANTIPAIN
Meyn, MS; Rossman, T; Troll, W
1978 ;53(1):92-93, Mutation research. DNA repair reports
— id: 29861, year: 1978, vol: 53, page: 92, stat: Journal Article,

EFFECTS OF PROTEASE INHIBITORS ON SOME CONSEQUENCES OF DNA DAMAGE IN ESCHERICHIA-COLI
Rossman, TG; Meyn, MS; Gottlieb, P; Troll, W
1978 ;34(1):68-68, Journal of supramolecular structure
— id: 29854, year: 1978, vol: 34, page: 68, stat: Journal Article,

PROTEOLYTIC SPECIFICITY OF REC A GENE PRODUCT (PROTEIN-X)
ROSSMAN, TG; QUIGLEY, JP; SCHEINER, C; STONE, DS; ROBERTS, J; TROLL, W
1978 ;37(6):1435-1435, Federation Proceedings (Federation of American Societies for Experimental Biology)
— id: 104621, year: 1978, vol: 37, page: 1435, stat: Journal Article,

Mechanisms of protease action in carcinogenesis
Troll W; Meyn MS; Rossman TG
Mechanisms of tumor promotion and cocarcinogenesis New York : Raven Press, 1978,
— id: 4403, year: 1978, vol: , page: 301, stat: Chapter,

A protease inhibitor blocks SOS functions in Escherichia coli: antipain prevents lambda repressor inactivation, ultraviolet mutagenesis, and filamentous growth
Meyn, M S; Rossman, T; Troll, W
1977 Mar;74(3):1152-1156, Proceedings of the National Academy of Sciences of the United States of America
Inhibition of DNA synthesis in E. coli by treatment with carcinogenic and mutagenic agents results in the coordinate expression of a group of diverse functions (SOS functions) including lambda prophage induction, filamentous growth, and an error-prone DNA repair activity (SOS repair) believed to be responsible for ultraviolet mutagenesis. It has been proposed that this SOS induction proceeds via irreversible proteolytic inactivation of repressor(s) for SOS functions. To test this hypothesis, we investigated the effect of a protease inhibitor, antipain [(1-carboxy-2-phenylethyl)carbamoyl-L-arginyl-L-valylargininal], on SOS induction. We found that 0.5 mM antipain (which has no effect on cell growth, overall RNA and protein synthesis, or induction of beta-galactosidase) drastically decreases mutagenesis. Antipain also blocks expression of thermally induced mutator activity (another manifestation of SOS repair) and filamentous growth in a tif-1 mutant that expresses SOS functions at 42 degrees without inhibition of DNA synthesis or detectable DNA damage. Furthermore, antipain inhibits thermal induction of lambda prophage in the tif-1 mutant without affecting the kinetics of thermal induction of lambdacI857 prophage. This lambda mutant codes a temperature-sensitive repressor that is directly destroyed by heat and does not require the SOS induction pathway for inactivation at 42 degrees. From our results we conclude that antipain inhibits lambda prophage induction by blocking proteolytic inactivation of lambda repressor and that it inhibits the induction or expression of SOS repair and filamentous growth. Our results suggest a role for proteolytic cleavage in the regulation of SOS functions
— id: 108477, year: 1977, vol: 74, page: 1152, stat: Journal Article,

Ultrastructural changes and viral morphogenesis during the growth of the mouse preputial gland tumor ESR 586
Prutkin, L; Rossman, T G; Wheatley, V R
1977 Feb;37(2):551-556, Cancer research
A study was undertaken to observe morphological changes and viral morphogenesis during the growth of the mouse preputial gland tumor ESR 586. The acinar cells of the normal preputial gland have an extensive agranular endoplasmic reticulum and Golgi apparatus and large lipid droplets. No viral particles are present. During tumor growth, and numerous lipid droplets never attain the size of those found in the normal gland. There is a decrease in the Golgi apparatus and agranular endoplasmic reticulum and an increase in the rough endoplasmic reticulum which could reflect a change in composition of tumor secretory product from the normal gland. Indeed, there is a decrease in triglycerides as the tumor ages and an increase in the sterol esters and waxes. In addition, intracisternal A-particles are observed budding from thickened endoplasmic reticulum membranes. Thickening of these membranes occur early in A-particle formation. One side of the membrane is first thickened while the opposing membrane appears is first thickened while the opposing membrane appears morphologically unaffected. The thickening of the affected membrane is initially confined to the outer (cytoplasmic) face of the membrane. In the older tumor, both opposing membranes of the reticulum are thickened and can assume an elongated whorled pattern
— id: 124551, year: 1977, vol: 37, page: 551, stat: Journal Article,

ULTRASTRUCTURAL CHANGES AND VIRAL MORPHOGENESIS DURING GROWTH OF MOUSE PREPUTIAL GLAND TUMOR
Prutkin, L; Rossman, T; Wheatley, V
1977 ;187(4):687-688, Anatomical record
— id: 29610, year: 1977, vol: 187, page: 687, stat: Journal Article,

Effects of arsenite on DNA repair in Escherichia coli
Rossman, T G; Meyn, M S; Troll, W
1977 Aug;19:229-233, Environmental health perspectives
Since environmental exposure to arsenicals has been correlated with a high skin cancer risk among populations exposed to sunlight, it is possible that arsenicals might interfere with the repair of damage to DNA (mostly thymine dimers) resulting from the ultraviolet rays in sunlight. To test this hypothesis, strains of E. coli, differing from each other only in one or more repair functions, were exposed to UV light and then plated in the presence or absence of sodium arsenite. Survival after irradiation of wild type E. coli (WP(2)) was significantly decreased by 0.5mM arsenite. This effect was also seen in strains which are unable to carry out excision repair, suggesting that arsenite inhibits one or more steps in the post-replication repair pathways. This is confirmed by the finding that arsenite has no effect on the post-irradiation survival of a recA mutant, which does not carry out post-replication repair. Mutagenesis after ultraviolet irradiation depends on the rec(+) and lex(+) genes. Arsenite decreases mutagenesis in strains containing these genes. In order to determine its mechanism of action, dose-response relationships of arsenite on a number of cellular functions were carried out. The most sensitive cellular functions found were the induction of beta-galactosidase and the synthesis of RNA. Since error-prone repair in E. coli is an inducible process, the inhibition of mutagenesis after UV irradiation may be the result of inhibition of messenger RNA synthesis
— id: 108476, year: 1977, vol: 19, page: 229, stat: Journal Article,

Culture of cloned cells from the mouse preputial gland tumor ESR 586
Rossman, T G; Prutkin, L; Wheatley, V R
1977 Feb;37(2):557-560, Cancer research
Cells from the mouse preputial gland tumor ESR 586 have been cultured and cloned. Trypsin-ethylenediaminetetraacetate was used to obtain single cells. The cells are grown in a modified CMRL-1415 medium supplemented with 10% fetal calf serum. Clones tend to fall into two classes: Class 1, those that undergo morphological differentiation in liquid medium to form round bodies filled with lipid vaculoes; and Class 2, those that do not differentiate. Preliminary studies on the control of differentiation in Class 1 clones suggest that a minimum cell density is required before differentiation takes place. Analysis of the lipids from differentiating and nondifferentiating clones reveals the presence of sebaceous-type lipids in differentiating clones only. No requirement for testosterone was found for these cells
— id: 124552, year: 1977, vol: 37, page: 557, stat: Journal Article,

EVIDENCE FOR AN INDUCIBLE DNA-REPAIR SYSTEM IN ANIMAL-CELLS
ROSSMAN, T; LUSTIG, D; TROLL, W
1977 ;13(3):201-201, In vitro
— id: 39976, year: 1977, vol: 13, page: 201, stat: Journal Article,

CULTURE OF MOUSE PREPUTIAL SEBOCYTE TUMOR-CELLS
ROSSMAN, T; STONE, D; PRUTKIN, L; WHEATLEY, V; TROLL, W
1977 ;13(3):165-166, In vitro
— id: 39973, year: 1977, vol: 13, page: 165, stat: Journal Article,

CLONAL CULTURE OF A LINE OF MOUSE EPIDERMAL-CELLS
Rossman, TG; Stone, D; Troll, W
1976 ;12(4):295-295, In vitro
— id: 28769, year: 1976, vol: 12, page: 295, stat: Journal Article,

Effects of sodium arsenite on the survival of UV-irradiated Escherichia coli: inhibition of a recA-dependent function
Rossman, T; Meyn, M S; Troll, W
1975 Nov;30(2):157-162, Mutation research
Epidemiological studies and clinical observation suggesting potential hazards of arsenic compounds in increasing the incidence of cancer have been in complete contradiction with experimental findings in animals. Because of the predominance of skin cancers in the epidemiological reports, we decided to investigate the possibility that arsenic compounds might interfere with DNA repair. Using Escherichia coli as a test system, we show that this is indeed the case. Sodium arsenite, at concentrations of 0.1 mM and higher, decreases the survival of ultraviolet-irradiated E. coli WP2, a strain which possesses the full complement of repair genes. The effect of the arsenite increases with increasing ultraviolet dose. Similar results were obtained with the excision repair deficient strains WWP2 (uvrA) and WP6 (polA). Sodium arsenite had no effect on the survival of a recA mutant, WP10. Survival of ultraviolet-irradiated WP5 (exrA) was enhanced by sodium ardenite, the effect being greatest at low ultraviolet doses. It is postulated that arsenite inhibits a recA-dependent step in DNA repair. To account for the increased survival of the exrA mutant, we suggest that in the absence of the exr+ gene, the arsenite-sensitive recA-dependent function is deleterious. The ability of arsenite to inhibit DNA repair may account for the clinical and epidemiological reports linking arsenicals with an increased incidence of cancer
— id: 108483, year: 1975, vol: 30, page: 157, stat: Journal Article,

Proteinases in tumor promotion and hormone action
Troll W; Rossman T; Katz J; Levitz M; Sugimura T
Proteases and biological control [Cold Spring Harbor NY] : Cold Spring Harbor Laboratory, 1975,
— id: 4404, year: 1975, vol: , page: 977, stat: Chapter,

RAPID REACTION OF PROTEASE INHIBITOR TOSYLLYSINE CHLOROMETHYL KETONE WITH GLUTATHIONE
Kessner, A; Rossman, T; Troll, W
1974 ;33(5):1568-1568, Federation Proceedings (Federation of American Societies for Experimental Biology)
— id: 28366, year: 1974, vol: 33, page: 1568, stat: Journal Article,

Inhibition of macromolecular synthesis in Escherichia coli by protease inhibitors. Specific reversal by glutathione of the effects of chloromethyl ketones
Rossman, T; Norris, C; Troll, W
1974 Jun 10;249(11):3412-3417, Journal of biological chemistry
— id: 108488, year: 1974, vol: 249, page: 3412, stat: Journal Article,

The effect of levorphanol tartrate on ribonucleic acid synthesis in normal and regenerating rat liver
Becker FF; Rossman T; Reiss B; Simon EJ
1972 Jan;3(1):105-116, Research communications in chemical pathology & pharmacology
— id: 63710, year: 1972, vol: 3, page: 105, stat: Journal Article,

ROLE OF ESCHERICHIA-COLI PROTEASE IN BETA-GALACTOSIDASE INDUCTION
ROSSMAN, TG; TROLL, W
1972 ;31(2):A492-&, Federation Proceedings (Federation of American Societies for Experimental Biology)
— id: 104622, year: 1972, vol: 31, page: A492, stat: Journal Article,

An investigation into the mechanism of cytotoxicity of levorphanol
Rossman, T; Becker, F F; Vilcek, J
1971 Jul;7(4):480-483, Molecular pharmacology
— id: 15656, year: 1971, vol: 7, page: 480, stat: Journal Article,

Blocking of interferon action by a component of normal serum
Rossman TG; Vilcek J
1970 ;31(1):18-27, Archiv fur die gesamte virusforschung
— id: 15661, year: 1970, vol: 31, page: 18, stat: Journal Article,

Influence of the rate of cell growth and cell density on interferon action in chick embryo cells
Rossman TG; Vilcek J
1969 Jul;4(1):7-11, Journal of virology
— id: 15663, year: 1969, vol: 4, page: 7, stat: Journal Article,

Differential effects of actinomycin D and puromycin on the release of interferon induced by double stranded RNA
Vilcek J; Rossman TG; Varacalli F
1969 May 17;222(194):682-683, Nature
— id: 15664, year: 1969, vol: 222, page: 682, stat: Journal Article,

Studies on the action of interferon in cellular and cell-free systems
Vilcek J; Ng MH; Rossman TG
The interferons : an international symposium New York : Academic Press, 1968,
— id: 4405, year: 1968, vol: , page: 185, stat: Chapter,