Catherine G Klein, Ph.D.

Genes expressed in Atoh1 neuronal lineages arising from the r1/isthmus rhombic lip
Machold, R; Klein, C; Fishell, G
2011 Jun-Jul;11(5-6):349-359, Gene expression patterns
During embryogenesis, the rhombic lip of the fourth ventricle is the germinal origin of a diverse collection of neuronal populations that ultimately reside in the brainstem and cerebellum. Rhombic lip neurogenesis requires the bHLH transcription factor Atoh1 (Math1), and commences shortly after neural tube closure (E9.5). Within the rhombomere 1 - isthmus region, the rhombic lip first produces brainstem and deep cerebellar neurons (E9.5-E12), followed by granule cell precursors after E12. While Atoh1 function is essential for all of these populations to be specified, the downstream genetic programs that confer specific properties to early and late born Atoh1 lineages are not well characterized. We have performed a comparative microarray analysis of gene expression within early and later born cohorts of Atoh1 expressing neural precursors purified from E14.5 embryos using a transgenic labeling strategy. We identify novel transcription factors, cell surface molecules, and cell cycle regulators within each pool of Atoh1 lineages that likely contribute to their distinct developmental trajectories and cell fates. In particular, our analysis reveals new insights into the genetic programs that regulate the specification and proliferation of granule cell precursors, the putative cell of origin for the majority of medulloblastomas
— id: 132573, year: 2011, vol: 11, page: 349, stat: Journal Article,

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,

Caffeic acid phenethyl ester (CAPE), derived from a honeybee product propolis, exhibits a diversity of anti-tumor effects in pre-clinical models of human breast cancer
Wu, Jing; Omene, Coral; Karkoszka, Jerzy; Bosland, Maarten; Eckard, Jonathan; Klein, Catherine B; Frenkel, Krystyna
2011 Sep 1;308(1):43-53, Cancer letters
Breast cancer (BC) patients use alternative and natural remedies more than patients with other malignancies. Specifically, 63-83% use at least one type of alternative medicine and 25-63% use herbals and vitamins. Propolis is a naturopathic honeybee product, and CAPE (caffeic acid phenethyl ester), is a major medicinal component of propolis. CAPE, in a concentration dependent fashion, inhibits MCF-7 (hormone receptor positive, HR+) and MDA-231 (a model of triple negative BC (TNBC) tumor growth, both in vitro and in vivo without much effect on normal mammary cells and strongly influences gene and protein expression. It induces cell cycle arrest, apoptosis and reduces expression of growth and transcription factors, including NF-kappaB. Notably, CAPE down-regulates mdr-1 gene, considered responsible for the resistance of cancer cells to chemotherapeutic agents. Further, CAPE dose-dependently suppresses VEGF formation by MDA-231 cells and formation of capillary-like tubes by endothelial cells, implicating inhibitory effects on angiogenesis. In conclusion, our results strongly suggest that CAPE inhibits MDA-231 and MCF-7 human breast cancer growth via its apoptotic effects, and modulation of NF-kappaB, the cell cycle, and angiogenesis
— id: 134448, year: 2011, vol: 308, page: 43, stat: Journal Article,

DNA methylation in pre-diagnostic serum samples of breast cancer cases: Results of a nested case-control study
Brooks, Jennifer D; Cairns, Paul; Shore, Roy E; Klein, Catherine B; Wirgin, Isaac; Afanasyeva, Yelena; Zeleniuch-Jacquotte, Anne
2010 Dec;34(6):717-723, Cancer Epidemiology
Background: Promoter methylation of tumor suppressor genes is a frequent and early event in breast carcinogenesis. Paired tumor tissue and serum samples from women with breast cancer show that promoter methylation is detectable in both sample types, with good concordance. This suggests the potential for these serum markers to be used for breast cancer detection. Methods: The current study was a case-control study nested within the prospective New York University Women's Health Study cohort aimed to assess the ability of promoter methylation in serum to detect pre-clinical disease. Cases were women with blood samples collected within the 6 months preceding breast cancer diagnosis (n=50). Each case was matched to 2 healthy cancer-free controls and 1 cancer-free control with a history of benign breast disease (BBD). Results: Promoter methylation analysis of four cancer-related genes: -RASSF1A, GSTP1, APC and RARbeta2, - was conducted using quantitative methylation-specific PCR. Results showed that the frequency of methylation was lower than expected among cases and higher than expected among controls. Methylation was detected in the promoter region of: RASSF1A in 22.0%, 22.9% and 17.2% of cases, BBD controls and healthy controls respectively; GSTP1 in 4%, 10.4% and 7.1% respectively; APC in 2.0%, 4.4% and 4.2% respectively and RARbeta2 in 6.7%, 2.3% and 1.1% respectively. Conclusion: Methylation status of the four genes included in this study was unable to distinguish between cases and either control group. This study highlights some methodological issues to be addressed in planning prospective studies to evaluate methylation markers as diagnostic biomarkers
— id: 114817, year: 2010, vol: 34, page: 717, stat: Journal Article,

A genome-wide deletion mutant screen identifies pathways affected by nickel sulfate in Saccharomyces cerevisiae
Arita, Adriana; Zhou, Xue; Ellen, Thomas P; Liu, Xin; Bai, Jingxiang; Rooney, John P; Kurtz, Adrienne; Klein, Catherine B; Dai, Wei; Begley, Thomas J; Costa, Max
2009 ;10:524-524, BMC genomics
BACKGROUND: The understanding of the biological function, regulation, and cellular interactions of the yeast genome and proteome, along with the high conservation in gene function found between yeast genes and their human homologues, has allowed for Saccharomyces cerevisiae to be used as a model organism to deduce biological processes in human cells. Here, we have completed a systematic screen of the entire set of 4,733 haploid S. cerevisiae gene deletion strains (the entire set of nonessential genes for this organism) to identify gene products that modulate cellular toxicity to nickel sulfate (NiSO(4)). RESULTS: We have identified 149 genes whose gene deletion causes sensitivity to NiSO(4) and 119 genes whose gene deletion confers resistance. Pathways analysis with proteins whose absence renders cells sensitive and resistant to nickel identified a wide range of cellular processes engaged in the toxicity of S. cerevisiae to NiSO(4). Functional categories overrepresented with proteins whose absence renders cells sensitive to NiSO(4) include homeostasis of protons, cation transport, transport ATPases, endocytosis, siderophore-iron transport, homeostasis of metal ions, and the diphthamide biosynthesis pathway. Functional categories overrepresented with proteins whose absence renders cells resistant to nickel include functioning and transport of the vacuole and lysosome, protein targeting, sorting, and translocation, intra-Golgi transport, regulation of C-compound and carbohydrate metabolism, transcriptional repression, and chromosome segregation/division. Interactome analysis mapped seven nickel toxicity modulating and ten nickel-resistance networks. Additionally, we studied the degree of sensitivity or resistance of the 111 nickel-sensitive and 72 -resistant strains whose gene deletion product has a similar protein in human cells. CONCLUSION: We have undertaken a whole genome approach in order to further understand the mechanism(s) regulating the cell's toxicity to nickel compounds. We have used computational methods to integrate the data and generate global models of the yeast's cellular response to NiSO(4). The results of our study shed light on molecular pathways associated with the cellular response of eukaryotic cells to nickel compounds and provide potential implications for further understanding the toxic effects of nickel compounds to human cells
— id: 105506, year: 2009, vol: 10, page: 524, stat: Journal Article,

Persistence of Epigenetic Changes Induced by Chronic Submicromolar Arsenic
Klein, CB; Mauro, M
2009 AUG ;50(7):552-552, Environmental & molecular mutagenesis
— id: 101939, year: 2009, vol: 50, page: 552, stat: Journal Article,

A genome-wide screen in Saccharomyces cerevisiae reveals pathways affected by arsenic toxicity
Zhou, Xue; Arita, Adriana; Ellen, Thomas P; Liu, Xin; Bai, Jingxiang; Rooney, John P; Kurtz, Adrienne D; Klein, Catherine B; Dai, Wei; Begley, Thomas J; Costa, Max
2009 Nov;94(5):294-307, Genomics
We have used Saccharomyces cerevisiae to identify toxicologically important proteins and pathways involved in arsenic-induced toxicity and carcinogenicity in humans. We performed a systemic screen of the complete set of 4733 haploid S. cerevisiae single-gene-deletion mutants to identify those that have decreased or increased growth, relative to wild type, after exposure to sodium arsenite (NaAsO(2)). IC(50) values for all mutants were determined to further validate our results. Ultimately we identified 248 mutants sensitive to arsenite and 5 mutants resistant to arsenite exposure. We analyzed the proteins corresponding to arsenite-sensitive mutants and determined that they belonged to functional categories that include protein binding, phosphate metabolism, vacuolar/lysosomal transport, protein targeting, sorting, and translocation, cell growth/morphogenesis, cell polarity and filament formation. Furthermore, these data were mapped onto a protein interactome to identify arsenite-toxicity-modulating networks. These networks are associated with the cytoskeleton, ubiquitination, histone acetylation and the MAPK signaling pathway. Our studies have potential implications for understanding toxicity and carcinogenesis in arsenic-induced human conditions, such as cancer and aging
— id: 104719, year: 2009, vol: 94, page: 294, stat: Journal Article,

Modulation of gene methylation by genistein or lycopene in breast cancer cells
King-Batoon, Audrey; Leszczynska, Joanna M; Klein, Catherine B
2008 Jan;49(1):36-45, Environmental & molecular mutagenesis
Dietary agents with chemopreventive potential, including soy-derived genistein and tomato-derived lycopene, have been shown to alter gene expression in ways that can either promote or potentially inhibit the carcinogenic processes. To begin to explore the mechanisms by which these agents may be acting we have examined the DNA methylation modulating capacity of genistein or lycopene for several genes relevant to breast cancer in the breast cancer cell lines MCF-7 and MDA-MB-468, as well as in immortalized but noncancer fibrocystic MCF10A breast cells. We find using methylation specific PCR (MSP) that a low, nontoxic concentration of genistein (3.125 microM, resupplemented every 48 hr for 1 week) or a single dose of lycopene (2 microM) partially demethylates the promoter of the GSTP1 tumor suppressor gene in MDA-MB-468 cells. RT-PCR studies confirm a lack of GSTP1 expression in untreated MDA-MB-468, with restoration of GSTP1 expression after genistein or lycopene treatment. The RARbeta2 gene however, was not demethylated by genistein or lycopene in either of these breast cancer cell lines. But, lycopene (2 microM, once per week for 2 weeks) did induce demethylation of RARbeta2 and the HIN-1 genes in the noncancer MCF10A fibrocystic breast cells. These data show for the first time that the tomato carotenoid lycopene has direct DNA demethylating activity. In summary, both genistein and lycopene, at very low, dietarily relevant concentrations can potentially mitigate tumorigenic processes via promoter methylation modulation of gene expression
— id: 76766, year: 2008, vol: 49, page: 36, 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,

Mechanisms underlying prevention of genomic instability in breast tumor cells by Genistein and lycopene
Batoon, AK; Leszczynska, J; Klein, CB
2007 AUG ;48(7):618-618, Environmental & molecular mutagenesis
— id: 98041, year: 2007, vol: 48, page: 618, stat: Journal Article,

Nickel compounds
Cohen M; Klein C; Costa M
Environmental and occupational medicine Philadelphia : Wolters Kluwer/Lippincott Williams & Wilkins, 2007,
— id: 4440, year: 2007, vol: , page: ?, stat: Chapter,

Antimutagenicity of cinnamaldehyde and vanillin in human cells: Global gene expression and possible role of DNA damage and repair
King, Audrey A; Shaughnessy, Daniel T; Mure, Kanae; Leszczynska, Joanna; Ward, William O; Umbach, David M; Xu, Zongli; Ducharme, Danica; Taylor, Jack A; Demarini, David M; Klein, Catherine B
2007 Mar 1;616(1-2):60-69, Mutation research
Vanillin (VAN) and cinnamaldehyde (CIN) are dietary flavorings that exhibit antimutagenic activity against mutagen-induced and spontaneous mutations in bacteria. Although these compounds were antimutagenic against chromosomal mutations in mammalian cells, they have not been studied for antimutagenesis against spontaneous gene mutations in mammalian cells. Thus, we initiated studies with VAN and CIN in human mismatch repair-deficient (hMLH1(-)) HCT116 colon cancer cells, which exhibit high spontaneous mutation rates (mutations/cell/generation) at the HPRT locus, permitting analysis of antimutagenic effects of agents against spontaneous mutation. Long-term (1-3 weeks) treatment of HCT116 cells with VAN at minimally toxic concentrations (0.5-2.5mM) reduced the spontaneous HPRT mutant fraction (MF, mutants/10(6) survivors) in a concentration-related manner by 19-73%. A similar treatment with CIN at 2.5-7.5microM yielded a 13-56% reduction of the spontaneous MF. Short-term (4-h) treatments also reduced the spontaneous MF by 64% (VAN) and 31% (CIN). To investigate the mechanisms of antimutagenesis, we evaluated the ability of VAN and CIN to induce DNA damage (comet assay) and to alter global gene expression (Affymetrix GeneChip) after 4-h treatments. Both VAN and CIN induced DNA damage in both mismatch repair-proficient (HCT116+chr3) and deficient (HCT116) cells at concentrations that were antimutagenic in HCT116 cells. There were 64 genes whose expression was changed similarly by both VAN and CIN; these included genes related to DNA damage, stress responses, oxidative damage, apoptosis, and cell growth. RT-PCR results paralleled the Affymetrix results for four selected genes (HMOX1, DDIT4, GCLM, and CLK4). Our results show for the first time that VAN and CIN are antimutagenic against spontaneous mutations in mammalian (human) cells. These and other data lead us to propose that VAN and CIN may induce DNA damage that elicits recombinational DNA repair, which reduces spontaneous mutations
— id: 71922, year: 2007, vol: 616, page: 60, stat: Journal Article,

Nickel
Klein CB; Costa M
Handbook on the toxicology of metals Burlington MA : Academic Press, 2007,
— id: 4437, year: 2007, vol: , page: 743, stat: Chapter,

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,

Response to comments by post and stern on article "Toxicity and carcinogenicity of chromium compounds in humans"
Costa, M; Klein, C
2006 OCT ;36(9):779-779, Critical reviews in toxicology
— id: 68959, year: 2006, vol: 36, page: 779, stat: Journal Article,

Toxicity and carcinogenicity of chromium compounds in humans
Costa, Max; Klein, Catherine B
2006 Feb;36(2):155-163, Critical reviews in toxicology
Chromium is a human carcinogen primarily by inhalation exposure in occupational settings. Although lung cancer has been established as a consequence of hexavalent chromium exposure in smokers and nonsmokers, some cancers of other tissues of the gastrointestinal and central nervous systems have also been noted. Except for a few reports from China, little is known about the health risks of environmental exposures to chromium. Likewise, there has been a lack of epidemiological studies of human exposure to hexavalent Cr by drinking water or ingestion, and it has been suggested that humans can perhaps tolerate hexavalent Cr at higher levels than the current drinking water standard of 50 ppb. This review highlights the most recent data on the induction of skin tumors in mice by chronic drinking-water exposure to hexavalent chromium in combination with solar ultraviolet light. This experimental system represents an important new animal model for chromate-induced cancers by ingestion of drinking water, and it suggests by extrapolation that chromate can likely be considered a human carcinogen by ingestion as well. The potential use of this animal model for future risk assessment is discussed
— id: 64671, year: 2006, vol: 36, page: 155, stat: Journal Article,

Prevention of spontaneous and x-ray induced genomic instability in breast cancer cells by the dietary antimutagens genistein and lycopene
King, AA; Leszczynska, J; Hickey, CA; Klein, CB
2006 JUL ;47(6):425-425, Environmental & molecular mutagenesis
— id: 98062, year: 2006, vol: 47, page: 425, 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,

Modulation of gene methylation by genistein or lycopene in breast cells
Leszczynska, J; King, AA; Klein, CB
2006 JUL ;47(6):470-470, Environmental & molecular mutagenesis
— id: 69545, 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, mode of action at biologically plausible low doses: What are the implications for low dose cancer risk?
Snow, Elizabeth T; Sykora, Peter; Durham, Troy R; Klein, Catherine B
2005 Sep 1;207(2S):557-564, Toxicology & applied pharmacology
Arsenic is an established human carcinogen. However, there has been much controversy about the shape of the arsenic response curve, particularly at low doses. This controversy has been exacerbated by the fact that the mechanism(s) of arsenic carcinogenesis are still unclear and because there are few satisfactory animal models for arsenic-induced carcinogenesis. Recent epidemiological studies have shown that the relative risk for cancer among populations exposed to 10 muM), As induces down-regulation of DNA repair, oxidative DNA damage and apoptosis. This low dose adaptive (protective) response by a toxic agent is known as hormesis and is characteristic of many agents that induce oxidative stress. A mechanistic model for arsenic carcinogenesis based on these data would predict that the low dose risk for carcinogenesis should be sub-linear. The threshold dose where toxicity outweighs protection is hard to predict based on in vitro dose response data, but might be estimated if one could determine the form (metabolite) and concentration of arsenic responsible for changes in gene regulation in the target tissues.
— id: 72708, year: 2005, vol: 207, page: 557, stat: Journal Article,

Mechanisms of inhibition of X-ray-induced mutations in Chinese hamster G12 cells by antioxidants
Leszczynska, J; Lasano, S; Klein, CB
2004 NOV 15 ;44(3):212-212, Environmental & molecular mutagenesis
— id: 46884, year: 2004, vol: 44, page: 212, stat: Journal Article,

Effects of soybean processing by-product on spontaneous mutation in mismatch-repair deficient cells
Mure, K; Plewa, MJ; Takeshita, T; Rossman, TG; Klein, CB
2004 NOV 15 ;44(3):217-217, Environmental & molecular mutagenesis
— id: 46885, year: 2004, vol: 44, page: 217, stat: Journal Article,

Lycopene prevents spontaneous mutagenesis in mismatch repair deficient human cells by inhibiting insertions but leaving deletion mutations
Mure, K; Takeshita, T; Rossman, TG; Klein, CB
2004 NOV ;13(11):1875S-1875S, Cancer epidemiology biomarkers & prevention
— id: 50166, year: 2004, vol: 13, page: 1875S, stat: Journal Article,

Arsenic mode of action at biologically plausible low doses: What are the implications for low dose cancer risk?
Snow, ET; Sykora, P; Durham, TR; Klein, CB
2004 JUN 15 ;197(3):170-170, Toxicology & applied pharmacology
— id: 46526, year: 2004, vol: 197, page: 170, stat: Journal Article,

Can dietary antioxidants prevent deletion mutations?
Klein, CB; Mure, K; Leszczynska, J; Matz, J; King, A; Rossman, TG
2003 NOV ;12(11):1346S-1347S, Cancer epidemiology biomarkers & prevention
— id: 55378, year: 2003, vol: 12, page: 1346S, stat: Journal Article,

Lycopene prevents spontaneous mutagenesis in mismatch repair deficient human cells mainly by inhibiting point mutations
Mure, K; Takeshita, T; Rossman, TG; Klein, CB
2003 NOV ;12(11):1308S-1309S, Cancer epidemiology biomarkers & prevention
— id: 55374, year: 2003, vol: 12, page: 1308S, stat: Journal Article,

Chromate-induced epimutations in mammalian cells
Klein, Catherine B; Su, Lin; Bowser, Darlene; Leszczynska, Joanna
2002 Oct;110 Suppl 5(5):739-743, Environmental health perspectives
Epigenetic gene silencing by aberrant DNA methylation of gene promoter regions is a nonmutagenic but heritable epigenetic mechanism that may mistakenly cause the silencing of important cancer-related tumor suppressor genes. Using a transgenic, V79-derived, mammalian cell line (G12) that contains a bacterial gpt reporter gene in its DNA, we can study carcinogen-induced gene inactivation by mutagenic as well as epigenetic DNA methylation mechanisms. Whereas numerous carcinogens have previously been shown to be mutagenic in these cells, a few carcinogens, including nickel, diethylstilbestrol, and X-rays, are also capable of silencing the G12 cell gpt transgene by aberrant DNA methylation. Here we report for the first time that carcinogenic potassium chromate salts can also induce aberrant DNA methylation in this system. In contrast insoluble barium chromate produced significant level of mutations in these cells but did not cause DNA methylation changes associated with transgene expression
— id: 39564, year: 2002, vol: 110 Suppl 5, page: 739, stat: Journal Article,

Mutagenesis assays in Mammalian cells
Klein, C B; Broday, L; Costa, M
2001 May;Chapter 3:Unit3.3-Unit3.3, Current protocols in toxicology
Mutagenesis assays in mammalian cells are frequently used to complement bacterial mutagenesis assays. This unit describes a mutagenesis assay using either Chinese hamster V79 cells or V79-derivative gpt transgenic cell line to assess the effects of chemical agents on mammalian cells
— id: 113815, year: 2001, vol: Chapter 3, page: Unit3.3, stat: Journal Article,

Synergism in nitric oxide and hydrogen peroxide induced mutagenesis in G12 Chinese hamster cells
Abu-Shakra, A; Klein, CB
1999 DEC ;27(4):S71-S71, Free radical biology & medicine
— id: 53794, year: 1999, vol: 27, page: S71, stat: Journal Article,

Nickel carcinogenesis, mutation, epigenetics, or selection
Costa, M; Klein, CB
1999 SEP ;107(9):A438-A439, Environmental health perspectives
— id: 53956, year: 1999, vol: 107, page: A438, stat: Journal Article,

Mutagenesis assays in mammalian cells
Klein CB; Broday L; Costa M
1999 ;1:3.3.1-3.3.7, Current protocols in toxicology
— id: 72791, year: 1999, vol: 1, page: 3.3.1, stat: Journal Article,

DNA methylation and gene expression: introduction and overview
Klein CB; Costa M
1997 Apr;386(2):103-105, Mutation research
— id: 12337, year: 1997, vol: 386, page: 103, stat: Journal Article,

DNA methylation, heterochromatin and epigenetic carcinogens
Klein CB; Costa M
1997 Apr;386(2):163-180, Mutation research
This paper will explore emerging concepts related to alternative carcinogenic mechanisms of 'non-mutagenic,' and hence epigenetic, carcinogens that may heritably alter DNA methylation without changing the underlying DNA sequence. In this review, we will touch on the basic concepts of DNA methylation, and will elaborate in greater detail on related topics including chromatin condensation, and heterochromatin spreading that is well known to induce gene silencing by position effect variegation in Drosophila and other species. Data from our model transgenic G12 cell system will be presented to support our hypothesis that certain carcinogens, such as nickel, may be carcinogenic not primarily because of their overt mutability, but rather as the result of their ability to promote DNA hypermethylation of important cancer-related genes. We will conclude with a discussion of the broader relevance of our findings and its application to other so-called 'epigenetic' carcinogens
— id: 8210, year: 1997, vol: 386, page: 163, stat: Journal Article,

Characterization of gpt deletion mutations in transgenic Chinese hamster cell lines
Klein CB; Su L; Singh J; Snow ET
1997 ;30(4):418-428, Environmental & molecular mutagenesis
The transgenic cell lines G12 and G10, each with a bacterial gpt gene stably integrated at a single but different position in the Chinese hamster genome, were evaluated for deletion of the gpt transgene following exposures to several clastogens. More than 150 independently cloned G12 and G10 6-thioguanine-resistant mutants have been characterized by polymerase chain reaction (PCR) amplification and Southern blots in this study. Despite differences in the integration sites for the gpt gene in the G12 and G10 cells, PCR amplification of the gpt gene from both cell lines can be performed using the same single set of primers. By PCR deletion screening, about 20% of recovered spontaneous 6-thioguanine resistant (6TG) gpt G12 mutants had deleted the transgene, whereas the deletion mutant frequency was increased to about 50% of the X-ray- and bleomycin-induced G12 mutants. In contrast, both spontaneous and induced deletion frequencies are considerably higher for the G10 cell line. Among spontaneous G10 mutants, up to 50% have deleted the gpt transgene, whereas almost all of the X-ray- and bleomycin-induced G10 mutants have lost the integrated gene sequence. These results are discussed in the context of the transgene integration sites and the influences of the surrounding genome that may render certain genetic regions prone to deletion
— id: 57177, year: 1997, vol: 30, page: 418, stat: Journal Article,

Mutagenicity of cobalt and reactive oxygen producers
Kitahara J; Yamanaka K; Kato K; Lee YW; Klein CB; Costa M
1996 Oct 1;370(3-4):133-140, Mutation research
Oxidative stress has been implicated in carcinogenesis yet there are chemicals that produce oxidative stress that are not carcinogenic. Mutations are the inherited results of DNA damage and are critical events in carcinogenesis. The mutagenicity of oxidative stress induced by peroxide, paraquat and cobalt compounds was examined in transgenic gpt+ Chinese hamster cell lines (G12 and G10). These two cell lines are known to be more sensitive to mutagens such as X-rays and UV than their parental V-79 cells. In these studies, the mutagenic activity of cobalt chloride, a metal that induces oxidative stress but is not carcinogenic, was measured to be 7.7 times higher than the spontaneous mutant frequency in G12, but was only 1.5 to 2.5 times higher than spontaneous mutant frequency in G10 cells. The mutant frequency of cobalt sulfide was somewhat lower. Hydrogen peroxide was found to be only weakly mutagenic in G12 cells, and treatment of cells with a combination of hydrogen peroxide and cobalt did not alter the mutation frequency induced by cobalt sulfide alone. Paraquat did not elicit mutagenesis in either cell line. These results indicate that agents producing oxidative stress are not necessarily mutagenic and these results are discussed in the context of the oxidative stress produced by other carcinogens such as nickel compounds
— id: 10369, year: 1996, vol: 370, page: 133, stat: Journal Article,

Carcinogenic nickel silences gene expression by chromatin condensation and DNA methylation: a new model for epigenetic carcinogens
Lee YW; Klein CB; Kargacin B; Salnikow K; Kitahara J; Dowjat K; Zhitkovich A; Christie NT; Costa M
1995 May;15(5):2547-2557, Molecular & cellular biology
A transgenic gpt+ Chinese hamster cell line (G12) was found to be susceptible to carcinogenic nickel-induced inactivation of gpt expression without mutagenesis or deletion of the transgene. Many nickel-induced 6-thioguanine-resistant variants spontaneously reverted to actively express gpt, as indicated by both reversion assays and direct enzyme measurements. Since reversion was enhanced in many of the nickel-induced variant cell lines following 24-h treatment with the demethylating agent 5-azacytidine, the involvement of DNA methylation in silencing gpt expression was suspected. This was confirmed by demonstrations of increased DNA methylation, as well as by evidence indicating condensed chromatin and heterochromatinization of the gpt integration site in 6-thioguanine-resistant cells. Upon reversion to active gpt expression, DNA methylation and condensation are lost. We propose that DNA condensation and methylation result in heterochromatinization of the gpt sequence with subsequent inheritance of the now silenced gene. This mechanism is supported by direct evidence showing that acute nickel treatment of cultured cells, and of isolated nuclei in vitro, can indeed facilitate gpt sequence-specific chromatin condensation. Epigenetic mechanisms have been implicated in the actions of some nonmutagenic carcinogens, and DNA methylation changes are now known to be important in carcinogenesis. This paper further supports the emerging theory that nickel is a human carcinogen that can alter gene expression by enhanced DNA methylation and compaction, rather than by mutagenic mechanisms
— id: 6675, year: 1995, vol: 15, page: 2547, stat: Journal Article,

Molecular mechanisms of nickel carcinogenesis
Costa M; Salnikow K; Cosentino S; Klein CB; Huang X; Zhuang Z
1994 Sep;102 Suppl 3:127-130, Environmental health perspectives
Carcinogenic, water-insoluble Ni compounds are phagocytized by cells; and the particles undergo dissolution inside the cell, releasing Ni ions that interact with chromatin. Ni produces highly selective damage to heterochromatin. The longest contiguous region of heterochromatin in the Chinese hamster genome is found on the q arm of the X chromosome, and this region is selectively damaged by Ni. More than half of the male mice in which there were Ni-induced transformations of Chinese hamster cells exhibited complete deletion of the long arm of the X chromosome. The introduction of a normal X chromosome into these cells resulted in cellular senescence, suggesting that the Ni interacted with Chinese hamster genome to inactivate a senescence gene. Investigations were conducted into the mechanisms by which Ni produced damage to chromatin. Ni ions have a much higher affinity for proteins and amino acids than for DNA (by five to seven orders of magnitude). Therefore, Ni interacted with chromatin because of the protein present, not because of its reactivity for DNA. Studies have shown that Ni produced an increase in oxidative products in cells as indicated by oxidation of the fluorescent dye dichlorofluorescein; Ni has also been shown to produce oxidation of proteins in cells, as measured by carbonyl formation. Ni cross-linked certain amino acids and proteins to DNA. These covalent cross-links were not dissociated by EDTA and are inconsistent with direct Ni involvement, but they are consistent with Ni acting catalytically. Using subtractive hybridization, we have isolated a number of clones that are expressed in normal but not in Ni-transformed cells.(ABSTRACT TRUNCATED AT 250 WORDS)
— id: 8073, year: 1994, vol: 102 Suppl 3, page: 127, stat: Journal Article,

Molecular mechanisms of nickel carcinogenesis
Costa M; Zhuang Z; Huang X; Cosentino S; Klein CB; Salnikow K
1994 Jun 6;148(2-3):191-199, Science of the total environment
Nickel treatment of intact cultured cells oxidized dichlorofluorescin to a fluorescent product indicating that nickel elevated the level of oxidants in cells. Nickel also caused an increase in crosslinking of amino acids to DNA and these complexes did not appear to involve the direct participation of Ni2+. Histidine, cysteine and tyrosine were prominent among the amino acids crosslinked to DNA. Nickel selectively damaged heterochromatin and this resulted in deletions of heterochromatic regions during nickel carcinogenesis. Thrombospondin was one of the genes expressed in normal cells that was not expressed in nickel-transformed cells. Other aspects of the molecular mechanism of nickel carcinogenesis are discussed
— id: 10380, year: 1994, vol: 148, page: 191, stat: Journal Article,

2ND INTERNATIONAL MEETING ON MOLECULAR MECHANISMS OF METAL TOXICITY AND CARCINOGENICITY - JANUARY 10-17, 1993 MADONNA-DI-CAMPIGLIO, ITALY - PREFACE
COSTA, M; CANTONI, O; KLEIN, C; ROSSMAN, T; SNOW, E; SUK, W
1994 SEP ;102(1):2-2, Environmental health perspectives
— id: 52335, year: 1994, vol: 102, page: 2, stat: Journal Article,

Crystalline Ni3S2 specifically enhances the formation of oxidants in the nuclei of CHO cells as detected by dichlorofluorescein
Huang X; Klein CB; Costa M
1994 Mar;15(3):545-548, Carcinogenesis
Dichlorofluorescein (DCF) was used as a fluorescent probe to detect oxidants formed in cultured CHO cells during nickel treatment. Crystalline Ni3S2 specifically enhanced the formation of oxidants in the nuclei of these living cells, but Ni3S2 particles did not enhance DCF fluorescence as much when added in vitro to isolated nuclei. Our results add to the emerging concept that oxidants mediated by nickel compounds may play an important role in nickel-induced genotoxicity
— id: 6409, year: 1994, vol: 15, page: 545, stat: Journal Article,

The role of nickel and nickel-mediated reactive oxygen species in the mechanism of nickel carcinogenesis
Huang X; Zhuang Z; Frenkel K; Klein CB; Costa M
1994 Sep;102 Suppl 3:281-284, Environmental health perspectives
Increasing evidence demonstrates the reactive oxygen species (ROS) are implicated in metal carcinogenesis. Exposure of cultured Chinese hamster ovary (CHO) cells to several nickel compounds, i.e. NiS, Ni3S2, NiO (black and green), and NiCl2 has been shown to increase oxidation of 2',7-dichlorofluorescein to the fluorescent 2',7-dichlorofluorescein (DCF), suggesting that nickel compounds increased the concentration of oxidants in CHO cells. This fluorescence can be attenuated by addition of exogenous catalase to the extracellular media, indicating that H2O2 is one of the formed oxidants in this system. Fluorimetric measurements of chromogens following thiobarbituric acid reaction showed that nickel compounds also induce lipid peroxidation with a decreasing potency NiS, Ni3S2 > black NiO > green NiO > NiCl2. These results suggest that lipid hydroperoxides may also be produced through the action of nickel in intact cells. MgCl2, an antagonist of Ni-induced DNA strand breaks and cell transformation, has no effect on the formation of DCF fluorescence induced in CHO cells by nickel. The results suggest that nickel is an active inducer of ROS in intact mammalian cells and that the molecular mechanism of nickel carcinogenesis may involve multiple steps of nickel-mediated ROS
— id: 6647, year: 1994, vol: 102 Suppl 3, page: 281, stat: Journal Article,

Metal mutagenesis in transgenic Chinese hamster cell lines
Klein CB; Kargacin B; Su L; Cosentino S; Snow ET; Costa M
1994 Sep;102 Suppl 3:63-67, Environmental health perspectives
Metals are toxic agents for which genotoxic effects are often difficult to demonstrate. To study metal mutagenesis, we have used two stable hprt/gpt+ transgenic cell lines that were derived from Chinese hamster V79 cells. Both the G12 and G10 cell lines are known to be very sensitive to clastogens such as X-rays and bleomycin, with the mutagenic response of the integrated xanthine guanine phosphoribosyl transferase (gpt) gene in G10 usually exceeding that of the same gene in the transgenic G12 cells. In studies with carcinogenic insoluble nickel compounds, a high level of mutagenesis was found at the gpt locus of G12 cells but not at the endogenous hypoxanthine phosphoribosyl transferase (hprt) locus of V79 cells. We have since demonstrated the similar recovery of a high frequency of viable G12 mutants with other insoluble nickel salts including nickel oxides (black and green). The relative mutant yield for the insoluble nickel compounds (G12 > G10) is the opposite of that obtained with nonmetal clastogens (G10 > G12). In the G12 cells, nickel mutagenesis may be related to the integration of the gpt sequence into a heterochromatic region of the genome. For some of the insoluble nickel compounds, significant inhibition of both cytotoxicity and mutant yield resulted when the G12 cells were pretreated with vitamin E. In comparison with the nickel studies, the mutagenic responses to chromium compounds in these cell lines were not as dramatic. Mutagenesis of the gpt target could not be demonstrated with other metals such as mercury or vanadium
— id: 6661, year: 1994, vol: 102 Suppl 3, page: 63, 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,

Loss of thrombospondin transcriptional activity in nickel-transformed cells
Salnikow K; Cosentino S; Klein C; Costa M
1994 Jan;14(1):851-858, Molecular & cellular biology
mRNA from normal Chinese hamster embryo (CHE) cells was transcribed to cDNA and subtracted with an excess of mRNA from Chinese hamster embryo cells transformed by nickel compounds. Here we report the recovery of a sequence found to be highly homologous to the mouse thrombospondin 1 gene that was obtained by this subtraction procedure. Since thrombospondin is antiangiogenic, cancer cells expressing high levels of thrombospondin cannot grow in vivo because capillaries will not proliferate to cells secreting thrombospondin. To examine expression of thrombospondin, normal CHE cells were stained with monoclonal antibodies to human thrombospondin. The protein was present abundantly in the cytoplasm of normal cells but at greatly reduced levels in Ni-transformed cells. Analysis of mRNA by Northern (RNA) blot revealed transcripts in normal cells but little thrombospondin mRNA in Ni-transformed cells. Loss of thrombospondin mRNA expression was related to Ni treatment rather than transformation, since Ni-resistant cells also exhibited fewer thrombospondin transcripts than did wild-type cells. Digestion of genomic DNA with various combinations of restriction enzymes revealed thrombospondin gene patterns that were identical in both cell types, suggesting that there were no major deletions or rearrangements of the gene in the nickel-transformed cells. The inactivation of the thrombospondin gene was further investigated by analyzing the promoter activity of this gene linked to a chloramphenicol acetyltransferase (CAT) reporter plasmid that was transfected into normal and Ni-transformed cells.(ABSTRACT TRUNCATED AT 250 WORDS)
— id: 6507, year: 1994, vol: 14, page: 851, stat: Journal Article,

The loss of thrombospondin expression in Ni-resistant and Ni-transformed cells
Salnikow K; Wang S; Gao M; Klein C; Costa M
1994 ;35:A1122-A1122, Proceedings of the annual meeting of the American Association for Cancer Research
Using subtractive hybridization, we have cloned and identified several genes which were not expressed in Ni-transformed Chinese hamster cells. It appeared that one of these genes, thrombospondin-1, was also downregulated in Ni-resistant mouse cells suggesting that this gene can be specifically affected by Ni. Using different fragments of the thrombospondin promoter linked to the CAT reporter gene, we investigated mechanisms of decreased expression of this gene in Ni-resistant and Ni-transformed cells. Cotransfection of these reporter plasmids with an Rb expression vector significantly stimulated activity of the thrombospondin promoter, showing that the absence of some other transcription factor(s) that interacts with the Rb product resulted in the decrease of thrombospondin expression. Band-shift analysis confirmed that nuclear extracts of Ni-resistant cells less efficiently bind to an Sp-1 consensus sequence oligonucleotide. Identification of the transcriptional regulators involved in thrombospondin expression and its downregulation in Ni-resistant and Ni-transformed cells is ongoing
— id: 6019, year: 1994, vol: 35, page: A1122, stat: Journal Article,

Mechanisms of chromium carcinogenicity and toxicity
Cohen MD; Kargacin B; Klein CB; Costa M
1993 ;23(3):255-281, Critical reviews in toxicology
Chromium, like many transition metal elements, is essential to life at low concentrations yet toxic to many systems at higher concentrations. In addition to the overt symptoms of acute chromium toxicity, delayed manifestations of chromium exposure become apparent by subsequent increases in the incidence of various human cancers. Chromium is widely used in numerous industrial processes, and as a result is a contaminant of many environmental systems. Chromium, in its myriad chemical forms and oxidation states, has been well studied in terms of its general chemistry and its interactions with biological molecules. However, the precise mechanisms by which chromium is both an essential metal and a carcinogen are not yet fully clear. The following review does not seek to embellish upon the proposed mechanisms of the toxic and carcinogenic actions of chromium, but rather provides a comprehensive review of these theories. The chemical nature of chromium compounds and how these properties impact upon the interactions of chromium with cellular and genetic targets, including animal and human hosts, are discussed
— id: 6337, year: 1993, vol: 23, page: 255, stat: Journal Article,

Methods used for analyses of "environmentally" damaged nucleic acids
Frenkel K; Klein CB
1993 Aug 25;618(1-2):289-314, Journal of chromatography
In this review, we present various techniques, currently applied in many laboratories, which are useful in the detection of 'environmentally'-induced damage to DNA. These techniques include: (a) chromatographic methods, which allow determination of chemical changes within DNA, be they formation of adducts with or oxidation of bases in DNA; (b) electrophoretic methods, which facilitate finding the site(s) in DNA where that chemical modification occurred; and (c) immunological assays, which help to detect DNA damage using externally produced antibodies that recognize the specific chemical changes in DNA or its fragments, as well as by detection of autoantibodies that develop in response to environmental exposures of animals and humans
— id: 6373, year: 1993, vol: 618, page: 289, stat: Journal Article,

METHODS USED FOR ANALYSES OF ENVIRONMENTALLY DAMAGED NUCLEIC-ACIDS
FRENKEL, K; KLEIN, CB
1993 AUG 25 ;618(1-2):289-314, Journal of chromatography. Pt. B. Biomedical applications
In this review, we present various techniques, currently applied in many laboratories, which are useful in the detection of ''environmentally''-induced damage to DNA. These techniques include: (a) chromatographic methods, which allow determination of chemical changes within DNA, be they formation of adducts with or oxidation of bases in DNA; (b) electrophoretic methods, which facilitate finding the site(s) in DNA where that chemical modification occurred; and (c) immunological assays, which help to detect DNA damage using externally produced antibodies that recognize the specific chemical changes in DNA or its fragments, as well as by detection of autoantibodies that develop in response to environmental exposures of animals and humans
— id: 52242, year: 1993, vol: 618, page: 289, stat: Journal Article,

Nickel induces increased oxidants in intact cultured mammalian cells as detected by dichlorofluorescein fluorescence
Huang X; Frenkel K; Klein CB; Costa M
1993 May;120(1):29-36, Toxicology & applied pharmacology
Exposure of intact cultured Chinese hamster ovary (CHO) cells to water-soluble nickel (Ni) salts and to relatively water-insoluble crystalline nickel subsulfide (Ni3S2) resulted in an increased formation of the fluorescent oxidized compound, dichlorofluorescein (DCF) from the parent nonfluorescent compound, 2,7-dichlorofluorescin diacetate. This fluorescent product was also formed in vitro following oxidation with relatively strong oxidants such as hydrogen peroxide in the presence of peroxidase, suggesting that Ni increased the concentration of hydrogen peroxide in intact cells. However, formation of other strong oxidants such as hydroperoxides is possible since they have also been shown to cause the oxidation of the nonfluorescent dichlorofluorescin to the fluorescent product DCF in vitro. Localization of the oxidized fluorescent DCF in intact cells was also examined by fluorescence microscopy. Both Ni3S2 and NiCl2 appeared to increase the degree of fluorescence in intact CHO cells around the nuclear membranes. This increase in fluorescence was greater in the presence of relatively water-insoluble Ni3S2 than water-soluble NiCl2. These results add to the emerging concept that Ni-induced genotoxicity may be mediated by oxygen radical intermediates
— id: 10384, year: 1993, vol: 120, page: 29, stat: Journal Article,

Mutagenic responses of nickel oxides and nickel sulfides in Chinese hamster V79 cell lines at the xanthine-guanine phosphoribosyl transferase locus
Kargacin B; Klein CB; Costa M
1993 Jun;300(1):63-72, Mutation research
Mutagenesis of several insoluble nickel compounds--crystalline nickel sulfide NiS, nickel subsulfide Ni3S2, nickel oxides (black and green) and soluble NiCl2 was studied in three Chinese hamster cell lines--at the hprt gene of the well-defined V79 cell line, and at gpt in two transgenic derivative cell lines G12 and G10. The transgenic cell line G12 responded very strongly to the insoluble Ni compounds, such that the gpt mutagenesis was at least 20 times higher than the spontaneous mutagenesis and in some experiments was even higher. In contrast the response of the G10 cells was much lower--the mutant frequencies only increased 2-3 times over the controls. In V79 cells, NiS and NiO (black) did not induce a mutagenic response at hprt. Soluble NiCl2 also exhibited no mutagenic activity in V79 cells and induced considerably lower activity than the insoluble compounds in the transgenic G12 cells. Following vitamin E pretreatment of G12 cells for 24 h prior to nickel exposure, increased cell survival was observed for several insoluble Ni compounds whereas vitamin E had no effect on NiCl2 cytotoxicity. With vitamin E pretreatment, significantly lower mutagenic responses in G12 cells were also noted for some insoluble Ni compounds, while no such effect was observed for NiCl2
— id: 10383, year: 1993, vol: 300, page: 63, 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,

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,

Forward mutations and DNA-protein crosslinks induced by ammonium metavanadate in cultured mammalian cells
Cohen MD; Klein CB; Costa M
1992 Sep;269(1):141-148, Mutation research
Ammonium metavanadate yielded a dose-dependent increase in mutation frequency at the V79 hprt locus following a 24-h exposure period in serum-free F12 medium. Vanadate also increased the mutation frequency of V79 cells by exposure of cells in salts-glucose medium, but these effects were not as striking, or as dose-dependent as they were in serum-free F12 medium. Ammonium metavanadate enhanced the mutation frequency in a V79 variant containing a transfected bacterial gpt gene. These cells are known to be more responsive to oxidative type mutations, and to mutations involving deletions. Although the absolute level of mutations was greater in these cells with ammonium metavanadate, so was the background, and these cells did not exhibit an enhanced mutagenic response to vanadate when compared to the wild-type V79 cells. The vanadate results were compared to a positive control potassium chromate, which exhibited a dose-dependent increase in mutation frequency. Ammonium metavanadate induced DNA-protein crosslinks formation in both Chinese hamster ovary and human MOLT4 cells, and the role of these relatively unrepaired genetic lesions in the mutations produced by vanadate and chromate are discussed
— id: 13468, year: 1992, vol: 269, page: 141, stat: Journal Article,

A conserved region in human and Chinese hamster X chromosomes can induce cellular senescence of nickel-transformed Chinese hamster cell lines
Wang XW; Lin X; Klein CB; Bhamra RK; Lee YW; Costa M
1992 Apr;13(4):555-561, Carcinogenesis
Cellular senescence is the genetically programmed cessation of cellular proliferation. We have recently mapped a putative senescence gene(s) on the X chromosome of Chinese hamster embryo (CHE) cells. In the present study, we have utilized microcell-mediated chromosome transfer (microcell fusion) to test whether: (i) the human X chromosome exhibits similar genetic potential to induce senescence and (ii) the deletion or inactivation of the X-linked senescence gene(s) in CHE cells is associated with nickel-induced immortalization. A normal CHE or human X chromosome was first introduced into mouse-cell hybrids, then transferred by microcell fusion into a nickel-transformed, immortal male CHE cell line (Ni-2/TGR) with an X deletion (Xq1). Microcell fusion of the normal CHE X chromosome into tumorigenic Ni-2/TGR cells yielded senescence of all X recipient clones. The normal human X chromosome induced dominant senescence of tumorigenic Ni-2/TGR cells in only 17% of the resulting microcell hybrids (14/81). Karyotypic analyses of 13 non-senescing human X chromosome-derived microcell hybrid clones revealed that none of these clones retained the complete X. A normal CHE X chromosome induced senescence of 75% of hybrids obtained with another immortal and tumorigenic nickel-transformed male CHE cell line (Ni-6/TGR), which exhibited no visible deletion of the X chromosome, while the normal human X chromosome, only induced senescence in 19% of these hybrids. Transfer of the normal CHE or human X chromosome into spontaneously transformed and tumorigenic cell lines, CHO/TGR or V79/TGR, had little or no effect on their growth. These data suggest that both human and CHE cells possess similar X-linked genetic activities that regulate the process of cellular senescence, and that in Chinese hamster cells nickel-induced immortalization but not that of CHO or V79 cells is associated with inactivation of an X-linked senescence gene
— id: 13643, year: 1992, vol: 13, page: 555, stat: Journal Article,

Senescence of nickel-transformed cells by an X chromosome: possible epigenetic control
Klein CB; Conway K; Wang XW; Bhamra RK; Lin XH; Cohen MD; Annab L; Barrett JC; Costa M
1991 Feb 15;251(4995):796-799, Science
Transfer of a normal Chinese hamster X chromosome (carried in a mouse A9 donor cell line) to a nickel-transformed Chinese hamster cell line with an Xq chromosome deletion resulted in senescense of these previously immortal cells. At early passages of the A9/CX donor cells, the hamster X chromosome was highly active, inducing senescence in 100% of the colonies obtained after its transfer into the nickel-transformed cells. However, senescence was reduced to 50% when Chinese hamster X chromosomes were transferred from later passage A9 cells. Full senescing activity of the intact hamster X chromosome was restored by treatment of the donor mouse cells with 5-azacytidine, which induced demethylation of DNA. These results suggest that a senescence gene or genes, which may be located on the Chinese hamster X chromosome, can be regulated by DNA methylation, and that escape from senescence and possibly loss of tumor suppressor gene activity can occur by epigenetic mechanisms
— id: 8211, year: 1991, vol: 251, page: 796, stat: Journal Article,

The role of oxidative processes in metal carcinogenesis
Klein CB; Frenkel K; Costa M
1991 Nov-Dec;4(6):592-604, Chemical research in toxicology
— id: 13852, year: 1991, vol: 4, page: 592, 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,

Antigenic phenotypes of cultured malignant astrocytomas: identification of lineage-consistent, lineage-independent and putative tumor-restricted antigenic expression
Jennings, M T; Jennings, V D; Asadourian, L L; Ebrahim, S A; Klein, C E; Old, L J
1989 Jan;89(1):79-92, Journal of the neurological sciences
The treatment of CNS neoplasms with monoclonal antibody-mediated immunotherapy optimally requires the identification of tumor restricted cell surface antigens. However, little is known regarding the antigenic phenotype(s) of malignant astrocytomas. The interrelated expression of four neuroectodermal tumor antigens, CNT/11, AJ8, A010 and CNT/2, has been studied in cultured malignant gliomas and correlated with anchorage independent growth, morphology, glial fibrillary acidic protein, and the surface expression of other antigens. Many of these latter antigens have been reported to be expressed by specific fetal and differentiated adult cell lineages or tissues, as well as certain classes of malignant tumors. The tumor-associated expression of these antigens may be broadly classified as lineage-consistent, lineage-independent or putatively tumor-restricted. Malignant glioma tumor antigenic heterogeneity represents the expression of neuroectodermal and non-neuroectodermal cell surface markers. The importance of this observation is 2-fold. Lineage-independent antigen expression may be an indication of altered genome regulatory processes within tumor cells, and thus reflect the degree of anaplasia. The identification of lineage-consistent and lineage-independent tumor associated antigens may contribute to the selection of 'target' antigens and the prediction of toxicity for monoclonal antibody mediated immunotherapy
— id: 145175, year: 1989, vol: 89, page: 79, stat: Journal Article,

Mutagenic metabolites of benzene detected in the Microscreen assay
Rossman RG; Klein CB; Snyder CA
1989 May;81:77-79, Environmental health perspectives
The reactive metobolite responsible for benzene hematotoxicity and carcinogenicity is unknown. It can be hypothesized that the ultimate carcinogen derived from benzene metabolism might also act as a mutagen. This laboratory has recently developed a new assay that can detect mutagens of all types, using a single strain of bacteria, E. coli WP2s (lambda), as a target. Different genetic end points can be monitored in the same exposed population of bacteria. When a number of known metabolites of benzene were assayed, only trans,trans-muconic acid gave a strong positive response. Mutations were induced at two genetic loci (Trp+ revertants and T5 resistance). The mutagenic activity was greatly increased when a rat liver metabolizing system was added. We speculate that trans,trans-muconic acid is metabolized to a diepoxide, which may be the ultimate mutagen and possibly the ultimate carcinogen
— id: 10646, year: 1989, vol: 81, page: 77, stat: Journal Article,

A transformation-associated 130-kD cell surface glycoprotein is growth controlled in normal human cells
Klein, C E; Ozer, H L; Traganos, F; Atzpodien, J; Oettgen, H F; Old, L J
1988 May 1;167(5):1684-1696, Journal of experimental medicine
Two characteristics of cell surface molecules involved in the regulation of cell proliferation are altered expression in relation to growth phase in normal cells and overexpression in transformed cells. Here, we describe a similar pattern of expression for a 130-kD cell surface glycoprotein (gp 130) in human cells. Synthesis and cell surface expression of gp130 were greatly increased in both virally and chemically transformed fibroblasts, fibrosarcomas, a squamous cell carcinoma of the skin, and T cell leukemia lines. Furthermore, gp130 expression was induced in serum-starved fetal fibroblasts by serum stimulation, and in fresh T cells by various activating agents. Expression in response to serum stimulation was associated primarily with the transition from a quiescent state (G0) into the cell cycle (G1)
— id: 145186, year: 1988, vol: 167, page: 1684, 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,

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,

Changes in cell surface glycoprotein expression during differentiation of human keratinocytes
Klein, C E; Cordon-Cardo, C; Soehnchen, R; Cote, R J; Oettgen, H F; Eisinger, M; Old, L J
1987 Nov;89(5):500-506, Journal of investigative dermatology
Six cell surface glycoproteins defined by monoclonal antibodies were selected for study on human epidermal cells. In tests on tissue sections, three of the glycoproteins [J143 (gp140/30); T43 (gp85/36); H99 (gp38)] were expressed in the basal cell layer of the epidermis, whereas the other three glycoproteins [T179 (gp140/95); T16 (gp40/50); BT15 (gp80)] were preferentially expressed in maturing keratinocytes above the basal layer. We compared synthesis of these glycoproteins in fresh epidermis and in primary epidermal short term cultures using [35S]methionine for metabolic labeling. Synthesis of J143 was 8- to 20-fold higher and synthesis of T43 was 4- to 10-fold lower in cultured cells compared with fresh epidermis. BT15, an antigen strongly expressed on terminally differentiating keratinocytes, was synthesized at 5- to 15-fold higher levels in fresh epidermis than in cultured cells. Biosynthesis levels of H99, T179, and T16 did not change in cultured epidermal cells. Based on our findings, we propose a model of surface antigenic changes that occur during keratinocyte differentiation in vivo
— id: 145203, year: 1987, vol: 89, page: 500, 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,

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,

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,