Lawrence B. Gardner, M.D.

The sarcoplasmic reticulum luminal thiol oxidase ERO1 regulates cardiomyocyte excitation-coupled calcium release and response to hemodynamic load
Chin, King-Tung; Kang, Guoxin; Qu, Jiaxiang; Gardner, Lawrence B; Coetzee, William A; Zito, Ester; Fishman, Glenn I; Ron, David
2011 Aug;25(8):2583-2591, FASEB journal
Two related ER oxidation 1 (ERO1) proteins, ERO1alpha and ERO1beta, dynamically regulate the redox environment in the mammalian endoplasmic reticulum (ER). Redox changes in cysteine residues on intralumenal loops of calcium release and reuptake channels have been implicated in altered calcium release and reuptake. These findings led us to hypothesize that altered ERO1 activity may affect cardiac functions that are dependent on intracellular calcium flux. We established mouse lines with loss of function insertion mutations in Ero1l and Ero1lb encoding ERO1alpha and ERO1beta. The peak amplitude of calcium transients in homozygous Ero1alpha mutant adult cardiomyocytes was reduced to 42.0 +/- 2.2% (n=10, P</=0.01) of values recorded in wild-type cardiomyocytes. Decreased ERO1 activity blunted cardiomyocyte inotropic response to adrenergic stimulation and sensitized mice to adrenergic blockade. Whereas all 12 wild-type mice survived challenge with 4 mg/kg esmolol, 6 of 8 compound Ero1l and Ero1lb mutant mice succumbed to this level of beta adrenergic blockade (P</=0.01). In addition, mice lacking ERO1alpha were partially protected against progressive heart failure in a transaortic constriction model [at 10 wk postprocedure, fractional shortening was 0.31+/-0.02 in the mutant (n=20) vs. 0.23+/-0.03 in the wild type (n=18); P</=0.01]. These findings establish a role for ERO1 in calcium homeostasis and suggest that modifying the lumenal redox environment may affect the progression of heart failure.-Chin, K. T., Kang, G., Qu, J., Gardner, L. B., Coetzee, W. A., Zito, E., Fishman, G. I., Ron, R. The sarcoplasmic reticulum luminal thiol oxidase ERO1 regulates cardiomyocyte excitation-coupled calcium release and response to hemodynamic load
— id: 135555, year: 2011, vol: 25, page: 2583, stat: Journal Article,

Hypoxia is present in murine atherosclerotic plaques and has multiple adverse effects on macrophage lipid metabolism
Parathath, Sajesh; Mick, Stephanie L; Feig, Jonathan E; Joaquin, Victor; Grauer, Lisa; Habiel, David M; Gassmann, Max; Gardner, Lawrence B; Fisher, Edward A
2011 Oct 28;109(10):1141-1152, Circulation research
Rationale: Human atherosclerotic plaques contain large numbers of cells deprived of O(2). In murine atherosclerosis, because the plaques are small, it is controversial whether hypoxia can occur. Objective: To examine if murine plaques contain hypoxic cells, and whether hypoxia regulates changes in cellular lipid metabolism and gene expression in macrophages. Methods and Results: Aortic plaques from apolipoprotein-E-deficient mice were immunopositive for hypoxia-inducible transcription factor (HIF-1alpha) and some of its downstream targets. Murine J774 macrophages rendered hypoxic demonstrated significant increases in cellular sterol and triglycerides. The increase in sterol content in hypoxic macrophages correlated with elevated 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase activity and mRNA levels. In addition, when macrophages were incubated with cholesterol complexes, hypoxic cells accumulated 120% more cholesterol, predominately in the free form. Cholesterol-efflux assays showed that hypoxia significantly decreased efflux mediated by ATP-binding cassette subfamily A member 1 (ABCA1), whose sub cellular localization was altered in both J774 and primary macrophages. Furthermore, in vivo expression patterns of selected genes from cells in hypoxic regions of murine plaques were similar to those from J774 and primary macrophages incubated in hypoxia. The hypoxia-induced accumulation of sterol and decreased cholesterol efflux was substantially reversed in vitro by reducing the expression of the hypoxia-inducible transcription factor, HIF-1alpha. Conclusion: Hypoxic regions are present in murine plaques. Hypoxic macrophages have increased sterol content due to the induction of sterol synthesis and the suppression of cholesterol efflux, effects that are in part mediated by HIF-1alpha
— id: 140525, year: 2011, vol: 109, page: 1141, stat: Journal Article,

Overexpression of the c-myc Oncogene Inhibits Nonsense-mediated RNA Decay in B Lymphocytes
Wang, Ding; Wengrod, Jordan; Gardner, Lawrence B
2011 Nov 18;286(46):40038-40043, Journal of biological chemistry
The Myc transcription factor plays a vital role in both normal cellular physiology and in many human cancers. We have recently demonstrated that nonsense-mediated RNA decay (NMD), a mechanism that rapidly degrades select mRNAs, is inhibited by the stress-induced phosphorylation of translation initiation factor eIF2alpha, and this inhibition stabilizes many transcripts necessary for tumorigenesis. Here, we demonstrate that NMD is inhibited by high Myc expression. We show that the phosphorylation of eIF2alpha, likely due to the ability of Myc to generate reactive oxygen species and augment endoplasmic reticulum stress, is necessary for the inhibition of NMD by Myc. The inhibition of NMD both stabilizes and up-regulates multiple Myc targets, suggesting that the inhibition of NMD may play an important role in the dynamic regulation of genes by Myc
— id: 145775, year: 2011, vol: 286, page: 40038, stat: Journal Article,

Inhibition of nonsense-mediated RNA decay by the tumor microenvironment promotes tumorigenesis
Wang, Ding; Zavadil, Jiri; Martin, Leenus; Parisi, Fabio; Friedman, Eugene; Levy, David; Harding, Heather; Ron, David; Gardner, Lawrence B
2011 Sep;31(17):3670-3680, Molecular & cellular biology
While nonsense-mediated RNA decay (NMD) is an established mechanism to rapidly degrade select transcripts, the physiological regulation and biological significance of NMD are not well characterized. We previously demonstrated that NMD is inhibited in hypoxic cells. Here we show that the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha) translation initiation factor by a variety of cellular stresses leads to the inhibition of NMD and that eIF2alpha phosphorylation and NMD inhibition occur in tumors. To explore the significance of this NMD regulation, we used an unbiased approach to identify approximately 750 NMD-targeted mRNAs and found that these mRNAs are overrepresented in stress response and tumor-promoting pathways. Consistent with these findings, the inhibition of NMD promotes cellular resistance to endoplasmic reticulum stress and encourages tumor formation. The transcriptional and translational regulations of gene expression by the microenvironment are established mechanisms by which tumor cells adapt to stress. These data indicate that NMD inhibition by the tumor microenvironment is also an important mechanism to dynamically regulate genes critical for the response to cellular stress and tumorigenesis
— id: 136513, year: 2011, vol: 31, page: 3670, stat: Journal Article,

Nonsense-mediated RNA decay regulation by cellular stress: implications for tumorigenesis
Gardner, Lawrence B
2010 Mar;8(3):295-308, Molecular cancer research
Nonsense-mediated RNA decay (NMD) has long been viewed as an important constitutive mechanism to rapidly eliminate mutated mRNAs. More recently, it has been appreciated that NMD also degrades multiple nonmutated transcripts and that NMD can be regulated by wide variety of cellular stresses. Many of the stresses that inhibit NMD, including cellular hypoxia and amino acid deprivation, are experienced in cells exposed to hostile microenvironments, and several NMD-targeted transcripts promote cellular adaptation in response to these environmental stresses. Because adaptation to the microenvironment is crucial in tumorigenesis, and because NMD targets many mutated tumor suppressor gene transcripts, the regulation of NMD may have particularly important implications in cancer. This review briefly outlines the mechanisms by which transcripts are identified and targeted by NMD and reviews the evidence showing that NMD is a regulated process that can dynamically alter gene expression. Although much of the focus in NMD research has been in identifying the proteins that play a role in NMD and identifying NMD-targeted transcripts, recent data about the potential functional significance of NMD regulation, including the stabilization of alternatively spliced mRNA isoforms, the validation of mRNAs as bona fide NMD targets, and the role of NMD in tumorigenesis, are explored. Mol Cancer Res; 8(3); 295-308
— id: 108429, year: 2010, vol: 8, page: 295, stat: Journal Article,

Regulation of the unfolded protein response by eif2bdelta isoforms
Martin, Leenus; Kimball, Scot R; Gardner, Lawrence B
2010 Oct 15;285(42):31944-31953, Journal of biological chemistry
Cells respond to a variety of stresses, including unfolded proteins in the endoplasmic reticulum (ER), by phosphorylating a subunit of translation initiation factor eIF2, eIF2alpha. eIF2alpha phosphorylation inactivates the eIF2B complex. The inactivation of eIF2B not only suppresses the initiation of protein translation but paradoxically up-regulates the translation and expression of transcription factor ATF-4. Both of these processes are important for the cellular response to ER stress, also termed the unfolded protein response. Here we demonstrate that cellular response resulting from eIF2alpha phosphorylation is attenuated in several cancer cell lines. The deficiency of the unfolded protein response in these cells correlates with the expression of a specific isoform of a regulatory eIF2B subunit, eIF2Bdelta variant 1 (V1). Replacement of total eIF2Bdelta with V1 renders cells insensitive to eIF2alpha phosphorylation; specifically, they neither up-regulate ATF-4 and ATF-4 targets nor suppress protein translation. Expression of variant 2 eIF2Bdelta in ER stress response-deficient cells restores the stress response. Our data suggest that V1 does not interact with the eIF2 complex, a requisite for eIF2B inhibition by eIF2alpha phosphorylation. Together, these data delineate a novel physiological mechanism to regulate the ER stress response with a large potential impact on a variety of diseases that result in ER stress
— id: 113943, year: 2010, vol: 285, page: 31944, stat: Journal Article,

The Presence of Hypoxia in Murine Atherosclerotic Plaques and Its Adverse Effects on Macrophage Lipid Metabolism
Parathath, Saj; Mick, Stephanie L.; Feig, Jonathan E.; Lisa, Grauer; Joaquin, Victor; Gassmann, Max; Gardner, Lawrence B.; Fisher, Edward A.
2010 NOV ;30(11):E253-E253, Arteriosclerosis, thrombosis, & vascular biology
— id: 117307, year: 2010, vol: 30, page: E253, stat: Journal Article,

Perifosine in combination with bortezomib and dexamethasone extends progression-free survival and overall survival in relapsed/refractory multiple myeloma patients previously treated with bortezombib: Updated phase I/II trial results
Richardson P.; Lee Wolf J.; Jakubowiak A.; Zonder J.A.; Lonial S.; Irwin D.H.; Krishnan A.; Densmore J.; Raje N.; Bar M.H.; Schlossman R.L.; Ghobrial I.; Munshi N.C.; Martin T.; Laubach J.; Allerton J.P.; Hideshima T.; Gardner L.; Sportelli P.; Anderson K.C.
2009 ;114(22):?-? #1868, Blood
— id: 112213, year: 2009, vol: 114, page: ?, stat: Journal Article,

Regression of HIV-related diffuse large B-cell lymphoma in response to antiviral therapy alone
Amengual, Jennifer E; Zhang, Xinmin; Ibrahim, Sherif; Gardner, Lawrence B
2008 Nov 15;112(10):4359-4360, Blood
— id: 95588, year: 2008, vol: 112, page: 4359, stat: Journal Article,

Heparin-induced antibodies and cardiovascular risk in patients on dialysis
Asmis, Lars M; Segal, Jodi B; Plantinga, Laura C; Fink, Nancy E; Kerman, Jonathan S; Kickler, Thomas S; Coresh, Josef; Gardner, Lawrence B
2008 Sep;100(3):498-504, Thrombosis & haemostasis
The clinical relevance of heparin-induced antibodies (HIA) in the absence of thrombocytopenia remains to be defined. The aims of this study were (i) to determine the prevalence of HIA in patients treated by dialysis, (ii) to determine the prevalence of thrombocytopenia and heparin-induced thrombocytopenia (HIT), and (iii) to test whether HIA are associated with adverse outcomes. Sera from 740 patients treated by hemodialysis (HD, n=596) and peritoneal dialysis (PD, n=144) were tested for HIA (IgG, IgA or IgM) by masked investigators at approximately six months after enrolment in the Choices for Healthy Outcomes in Caring for End-Stage Renal Disease (CHOICE) study. We assessed, with time-to-event Cox proportional hazards models, whether the presence of HIA predicted any of four clinical outcomes: arterial cardiovascular events, venous thromboembolism, vascular access occlusion and mortality. HIA prevalence was 10.3% overall. HIA positivity did not predict development of thrombocytopenia or any of the four clinical outcomes over a mean follow-up of 3.6 years, with hazard ratios for arterial cardiovascular events of 0.98 (95% confidence interval 0.70-1.37), venous thromboembolism 1.39 (0.17-11.5), vascular access occlusion 0.82 (0.40-1.71), and mortality 1.18 (0.85-1.64). Chronic intermittent heparin exposure was associated with a high seroprevalence of HIA. In dialysis patients these antibodies were not an independent risk factor for cardiovascular events and mortality. Our data do not suggest that dialysis patients should be monitored for HIA antibodies in the absence of thrombocytopenia
— id: 115357, year: 2008, vol: 100, page: 498, stat: Journal Article,

Hypoxic inhibition of nonsense-mediated RNA decay regulates gene expression and the integrated stress response
Gardner, Lawrence B
2008 Jun;28(11):3729-3741, Molecular & cellular biology
Nonsense-mediated RNA decay (NMD) rapidly degrades both mutated mRNAs and nonmutated cellular mRNAs in what is thought to be a constitutive fashion. Here we demonstrate that NMD is inhibited in hypoxic cells and that this inhibition is dependent on phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha). eIF2alpha phosphorylation is known to promote translational and transcriptional up-regulation of genes important for the cellular response to stress. We show that the mRNAs of several of these stress-induced genes are NMD targets and that the repression of NMD stabilizes these mRNAs, thus demonstrating that the inhibition of NMD augments the cellular stress response. Furthermore, hypoxia-induced formation of cytoplasmic stress granules is also dependent on eIF2alpha phosphorylation, and components of the NMD pathway are relocalized to these granules in hypoxic cells, providing a potential mechanism for the hypoxic inhibition of NMD. Our demonstration that NMD is inhibited in hypoxic cells reveals that the regulation of NMD can dynamically alter gene expression and also establishes a novel mechanism for hypoxic gene regulation
— id: 79298, year: 2008, vol: 28, page: 3729, stat: Journal Article,

Hypoxic regulation of mRNA expression
Gardner, Lawrence B; Corn, Paul G
2008 Jul 1;7(13):1916-1924, Cell cycle
Many tumors are hypoxic, and cells that are experimentally rendered hypoxic display a variety of phenotypes which allow them to adapt to the micro-environment. These phenotypes include a shift from aerobic to anaerobic metabolism, a diminution of reactive oxygen species, an arrest of proliferation, apoptosis, and a secretion of pro-angiogenic growth factors. Some of these hypoxic phenotypes are re-capitulated in normoxic tumor cells (e.g., an increase in anaerobic metabolism), and some tumors have undergone mutations that allow them to bypass the cell cycle arrest and apoptosis typically seen in hypoxic cells. Hypoxic regulation of gene expression is responsible for many hypoxia-induced phenotypes, and here we review a variety of mechanisms by which gene expression is altered in hypoxic cells. These include transcription by HIF-1, the hypoxia inducible transcription factor, and other hypoxia-inducible transcription factors, including ones generated by hypoxic activation of the integrated stress response. Recent data from our laboratory demonstrate that nonsense mediated RNA decay is also regulated in hypoxic cells and thus may play an important role in hypoxic gene regulation and hypoxic phenotypes
— id: 86650, year: 2008, vol: 7, page: 1916, stat: Journal Article,

Role of hypoxia and cAMP in the transdifferentiation of human fetal cardiac fibroblasts: implications for progression to scarring in autoimmune-associated congenital heart block
Clancy, Robert M; Zheng, Ping; O'Mahony, Marguerita; Izmirly, Peter; Zavadil, Jiri; Gardner, Lawrence; Buyon, Jill P
2007 Dec;56(12):4120-4131, Arthritis & rheumatism
OBJECTIVE: Identification of isolated congenital heart block (CHB) predicts, with near certainty, the presence of maternal anti-SSA/Ro antibodies; however, the 2% incidence of CHB in first offspring of anti-SSA/Ro+ mothers, 20% recurrence in subsequent pregnancies, and discordance in identical twins suggest that an environmental factor amplifies the effect of the antibody. Accordingly, this study was carried out to explore the hypothesis that hypoxia potentiates a profibrosing phenotype of the fetal cardiac fibroblast. METHODS: Evidence of an effect of hypoxia was sought by immunohistologic evaluation of CHB-affected fetal heart tissue and by determination of erythropoietin levels in cord blood. The in vitro effect of hypoxia on gene expression and phenotype in fibroblasts derived from fetal hearts and lungs was investigated by Affymetrix arrays, quantitative polymerase chain reaction (PCR), immunofluorescence, and immunoblotting. RESULTS: In vivo hypoxic exposure was supported by the prominent intracellular fibroblast expression of hypoxia-inducible factor 1alpha in conduction tissue from 2 fetuses in whom CHB led to death. The possibility that hypoxia was sustained was suggested by significantly elevated erythropoietin levels in cord blood from CHB-affected, as compared with unaffected, anti-SSA/Ro-exposed neonates. In vitro exposure of cardiac fibroblasts to hypoxia resulted in transdifferentiation to myofibroblasts (a scarring phenotype), as demonstrated on immunoblots and immunofluorescence by increased expression of smooth muscle actin (SMA), an effect not seen in lung fibroblasts. Hypoxia-exposed cardiac fibroblasts expressed adrenomedullin at 4-fold increased levels, as determined by Affymetrix array, quantitative PCR, and immunofluorescence, thus focusing attention on cAMP as a modulator of fibrosis. MDL12,330A, an adenylate cyclase inhibitor that lowers the levels of cAMP, increased expression of fibrosis-related proteins (mammalian target of rapamycin, SMA, plasminogen activator inhibitor type 1, and type I collagen), while the cAMP activator forskolin attenuated transforming growth factor beta-elicited fibrosing end points in the cardiac fibroblasts. CONCLUSION: These findings provide evidence that hypoxia may amplify the injurious effects of anti-SSA/Ro antibodies. Modulation of cAMP may be a key component in the scarring phenotype. Further assessment of the susceptibility of cardiac fibroblasts to cAMP modulation offers a new research direction in CHB
— id: 75771, year: 2007, vol: 56, page: 4120, stat: Journal Article,

Inhibition of nonsense mediated RNA decay in hypoxic cells; Implications for thalassemia
Gardner, LB
2007 NOV 16 ;110(11):528A-528A, Blood
— id: 76179, year: 2007, vol: 110, page: 528A, stat: Journal Article,

Hypoxic regulation of Id-1 and activation of the unfolded protein response are aberrant in neuroblastoma
Nemetski, S Maureen; Gardner, Lawrence B
2007 Jan 5;282(1):240-248, Journal of biological chemistry
The Id proteins play an important role in proliferation, differentiation and tumorigenesis. Many tumors are hypoxic, but it is unknown if expression of Id proteins is regulated in hypoxic cells. Here we show that Id-1 is down-regulated in multiple primary, immortalized, and neoplastic hypoxic cell lines, and the transcriptional repressor ATF-3 is both necessary and sufficient for this hypoxia-induced repression of Id-1. Hypoxic up-regulation of ATF-3 is due in part to activation of the unfolded protein response, a cellular stress response. Remarkably, we observe that the unfolded protein response is de-regulated in all neuroblastoma cell lines tested. Indeed, in the absence of ATF-3 the hypoxia-induced transcription factor HIF-1 up-regulates Id-1 in hypoxic neuroblastoma cells. Hypoxic neuroblastoma cells diminish expression of some neuronal differentiation markers, and forced expression of ATF-3 in hypoxic neuroblastoma cells represses Id-1 and prevents the loss of these markers. The divergent regulation of Id proteins in distinct hypoxic cells may explain some of the varied effects hypoxia has on cellular differentiation and proliferation
— id: 70311, year: 2007, vol: 282, page: 240, stat: Journal Article,

Hypoxia-inducible factor-1alpha promotes nonhypoxia-mediated proliferation in colon cancer cells and xenografts
Dang, Duyen T; Chen, Fang; Gardner, Lawrence B; Cummins, Jordan M; Rago, Carlo; Bunz, Fred; Kantsevoy, Sergey V; Dang, Long H
2006 Feb 1;66(3):1684-1936, Cancer research
Hypoxia-inducible factor-1alpha (HIF-1alpha) is a transcription factor that directly transactivates genes important for the growth and metabolism of solid tumors. HIF-1alpha is overexpressed in cancer, and its level of expression is correlated with patient mortality. Increased synthesis or stability of HIF-1alpha can be induced by hypoxia-dependent or hypoxia-independent factors. Thus, HIF-1alpha is expressed in both nonhypoxic and hypoxic cancer cells. The role of HIF-1alpha in nonhypoxia-mediated cancer cell proliferation remains speculative. We have disrupted HIF-1alpha by targeted homologous recombination in HCT116 and RKO human colon cancer cells. Loss of HIF-1alpha significantly reduced nonhypoxia-mediated cell proliferation in vitro and in vivo. Paradoxically, loss of HIF-1alpha expression did not grossly affect the hypoxic compartments within tumor xenografts in vivo, although HIF-1alpha promoted cell proliferation and survival under hypoxia in vitro. To further test the role of HIF-1alpha within tumor compartments, we generated cells with combined disruptions of both HIF-1alpha and vascular endothelial growth factor (VEGF). In all xenografts, disruption of VEGF led to marked expansion of the hypoxic compartments and growth delay. Nonetheless, the presence or absence of HIF-1alpha did not grossly affect these expanded hypoxic compartments. These data provide compelling evidence that, in a subset of colon cancers, (a) HIF-1alpha is a positive factor for nonhypoxia-mediated cell proliferation in vitro and in vivo and (b) HIF-1alpha is a positive factor for cell proliferation and survival under hypoxic conditions in vitro, but does not grossly contribute to the tumor hypoxic compartments in vivo
— id: 115358, year: 2006, vol: 66, page: 1684, stat: Journal Article,

Severe macrophage hypoxia alters expression of genes of cholesterol metabolism and transport and converts them to a foam-cell like phenotype
Mick, SL; Feig, JE; Habiel, DM; Gardner, LB; Fisher, EA
2006 MAY ;26(5):E79-E79, Arteriosclerosis, thrombosis, & vascular biology
— id: 63869, year: 2006, vol: 26, page: E79, stat: Journal Article,

Hypoxia, an environmental stress, in initiation and progression of the pathologic cascade to congenital heart block
Clancy, R; Zheng, P; Gardner, L; Buyon, JP
2005 SEP ;52(9):S303-S303, Arthritis & rheumatism
— id: 59276, year: 2005, vol: 52, page: S303, stat: Journal Article,

The novel cyclophilin binding compound, sanglifehrin A, disassociates G1 cell cycle arrest from tolerance induction
Allen, Amy; Zheng, Yan; Gardner, Lawrence; Safford, Meredith; Horton, Maureen R; Powell, Jonathan D
2004 Apr 15;172(8):4797-4803, Journal of immunology
T cell anergy has been demonstrated to play a role in maintaining peripheral tolerance to self Ags as well as a means by which tumors can evade immune destruction. Although the precise pathways involved in anergy induction have yet to be elucidated, it has been linked to TCR engagement in the setting of cell cycle arrest. Indeed, rapamycin, which inhibits T cell proliferation in G(1), has the ability to promote tolerance even in the presence of costimulation. To better define the role of the cell cycle in regulating anergy induction, we used the novel cyclophilin-binding ligand, sanglifehrin A (SFA). We demonstrate that SFA can inhibit TCR-induced cytokine and chemokine production without preventing TCR-induced anergy. Our data also indicate that despite its ability to induce G(1) arrest, SFA does not induce anergy in the presence of costimulation. Furthermore, although SFA blocks proliferation to exogenous IL-2, it does not prevent IL-2-induced reversal of anergy. When we examined the phosphorylation of 4EBP-1, a downstream substrate of the mammalian target of rapamycin, we found that rapamycin, but not SFA, inhibited the mammalian target of rapamycin activity. Based on these data, we propose that the decision as to whether TCR engagement will lead to productive activation or tolerance is dictated by a rapamycin -inhibitable pathway, independent of the G(1)-->S phase cell cycle progression
— id: 115359, year: 2004, vol: 172, page: 4797, stat: Journal Article,

Erythropoietin-deficient anemia associated with autoimmune polyglandular syndrome type I
Toonkel, Rebecca; Levine, Michael; Gardner, Lawrence
2004 Feb;75(2):84-88, American journal of hematology
Autoimmune polyglandular syndrome type I (APS1), a relatively common disorder in some populations, is frequently associated with adrenal insufficiency, hypoparathyroidism, and other endocrine and skin abnormalities. We describe an 18-year-old male with APS1, as documented by genotyping, who presented with hypoparathyroidism and a normocytic, hypoproliferative, isolated anemia. An extensive hematological work-up revealed a low serum erythropoietin, without any other hematological abnormalities. His renal function was normal, and he did not have many of the laboratory or clinical findings associated with an anemia of chronic disease. His anemia was responsive to superphysiologic doses of erythropoietin. We thus suggest that erythropoietin deficiency may be one of the endocrine abnormalities associated with APS1, and clinicians should be cognizant of the association of treatable anemia in patients with APS1
— id: 115360, year: 2004, vol: 75, page: 84, stat: Journal Article,

Hypoxia inhibits G1/S transition through regulation of p27 expression
Gardner LB; Li Q; Park MS; Flanagan WM; Semenza GL; Dang CV
2001 Mar 16;276(11):7919-7926, Journal of biological chemistry
Mammalian cellular responses to hypoxia include adaptive metabolic changes and a G1 cell cycle arrest. Although transcriptional regulation of metabolic genes by the hypoxia-induced transcription factor (HIF-1) has been established, the mechanism for the hypoxia-induced G1 arrest is not known. By using genetically defined primary wild-type murine embryo fibroblasts and those nullizygous for regulators of the G1/S checkpoint, we observed that the retinoblastoma protein is essential for the G1/S hypoxia-induced checkpoint, whereas p53 and p21 are not required. In addition, we found that the cyclin-dependent kinase inhibitor p27 is induced by hypoxia, thereby inhibiting CDK2 activity and forestalling S phase entry through retinoblastoma protein hypophosphorylation. Reduction or absence of p27 abrogated the hypoxia-induced G1 checkpoint, suggesting that it is a key regulator of G1/S transition in hypoxic cells. Intriguingly, hypoxic induction of p27 appears to be transcriptional and through an HIF-1-independent region of its proximal promoter. This demonstration of the molecular mechanism of hypoxia-induced G1/S regulation provides insight into a fundamental response of mammalian cells to low oxygen tension
— id: 38007, year: 2001, vol: 276, page: 7919, stat: Journal Article,