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Han D, Chen S, Han W, Gao S, Owiredu JN, Li M, Balk SP, He HH, Cai C. ZBTB7A Mediates the Transcriptional Repression Activity of the Androgen Receptor in Prostate Cancer. Cancer Res 2019; 79:5260-5271. [PMID: 31444154 DOI: 10.1158/0008-5472.can-19-0815] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Revised: 07/09/2019] [Accepted: 08/20/2019] [Indexed: 01/15/2023]
Abstract
Loss of expression of context-specific tumor suppressors is a critical event that facilitates the development of prostate cancer. Zinc finger and BTB domain containing transcriptional repressors, such as ZBTB7A and ZBTB16, have been recently identified as tumor suppressors that play important roles in preventing prostate cancer progression. In this study, we used combined ChIP-seq and RNA-seq analyses of prostate cancer cells to identify direct ZBTB7A-repressed genes, which are enriched for transcriptional targets of E2F, and identified that the androgen receptor (AR) played a critical role in the transcriptional suppression of these E2F targets. AR recruitment of the retinoblastoma protein (Rb) was required to strengthen the E2F-Rb transcriptional repression complex. In addition, ZBTB7A was rapidly recruited to the E2F-Rb binding sites by AR and negatively regulated the transcriptional activity of E2F1 on DNA replication genes. Finally, ZBTB7A suppressed the growth of castration-resistant prostate cancer (CRPC) in vitro and in vivo, and overexpression of ZBTB7A acted in synergy with high-dose testosterone treatment to effectively prevent the recurrence of CRPC. Overall, this study provides novel molecular insights of the role of ZBTB7A in CRPC cells and demonstrates globally its critical role in mediating the transcriptional repression activity of AR. SIGNIFICANCE: ZBTB7A is recruited to the E2F-Rb binding sites by AR and negatively regulates the transcriptional activity of E2F1 on DNA replication genes.
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Affiliation(s)
- Dong Han
- Center for Personalized Cancer Therapy, University of Massachusetts Boston, Boston, Massachusetts
| | - Sujun Chen
- Princess Margaret Cancer Center/University Health Network, Toronto, Ontario, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Wanting Han
- Center for Personalized Cancer Therapy, University of Massachusetts Boston, Boston, Massachusetts
| | - Shuai Gao
- Center for Personalized Cancer Therapy, University of Massachusetts Boston, Boston, Massachusetts
| | - Jude N Owiredu
- Center for Personalized Cancer Therapy, University of Massachusetts Boston, Boston, Massachusetts
| | - Muqing Li
- Center for Personalized Cancer Therapy, University of Massachusetts Boston, Boston, Massachusetts
| | - Steven P Balk
- Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - Housheng Hansen He
- Princess Margaret Cancer Center/University Health Network, Toronto, Ontario, Canada.
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Changmeng Cai
- Center for Personalized Cancer Therapy, University of Massachusetts Boston, Boston, Massachusetts.
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2
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Araki T, Liu NA, Tone Y, Cuevas-Ramos D, Heltsley R, Tone M, Melmed S. E2F1-mediated human POMC expression in ectopic Cushing's syndrome. Endocr Relat Cancer 2016; 23:857-870. [PMID: 27935805 PMCID: PMC5152695 DOI: 10.1530/erc-16-0206] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 09/05/2016] [Indexed: 12/26/2022]
Abstract
Cushing's syndrome is caused by excessive adrenocorticotropic hormone (ACTH) secretion derived from pituitary corticotroph tumors (Cushing disease) or from non-pituitary tumors (ectopic Cushing's syndrome). Hypercortisolemic features of ectopic Cushing's syndrome are severe, and no definitive treatment for paraneoplastic ACTH excess is available. We aimed to identify subcellular therapeutic targets by elucidating transcriptional regulation of the human ACTH precursor POMC (proopiomelanocortin) and ACTH production in non-pituitary tumor cells and in cell lines derived from patients with ectopic Cushing's syndrome. We show that ectopic hPOMC transcription proceeds independently of pituitary-specific Tpit/Pitx1 and demonstrate a novel E2F1-mediated transcriptional mechanism regulating hPOMC We identify an E2F1 cluster binding to the proximal hPOMC promoter region (-42 to +68), with DNA-binding activity determined by the phosphorylation at Ser-337. hPOMC mRNA expression in cancer cells was upregulated (up to 40-fold) by the co-expression of E2F1 and its heterodimer partner DP1. Direct and indirect inhibitors of E2F1 activity suppressed hPOMC gene expression and ACTH by modifying E2F1 DNA-binding activity in ectopic Cushing's cell lines and primary tumor cells, and also suppressed paraneoplastic ACTH and cortisol levels in xenografted mice. E2F1-mediated hPOMC transcription is a potential target for suppressing ACTH production in ectopic Cushing's syndrome.
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Affiliation(s)
| | | | - Yukiko Tone
- Pituitary CenterCedars-Sinai Medical Center, Los Angeles, California, USA
| | | | - Roy Heltsley
- Pituitary CenterCedars-Sinai Medical Center, Los Angeles, California, USA
| | - Masahide Tone
- Pituitary CenterCedars-Sinai Medical Center, Los Angeles, California, USA
| | - Shlomo Melmed
- Pituitary CenterCedars-Sinai Medical Center, Los Angeles, California, USA
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3
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Lagarrigue S, Lopez-Mejia IC, Denechaud PD, Escoté X, Castillo-Armengol J, Jimenez V, Chavey C, Giralt A, Lai Q, Zhang L, Martinez-Carreres L, Delacuisine B, Annicotte JS, Blanchet E, Huré S, Abella A, Tinahones FJ, Vendrell J, Dubus P, Bosch F, Kahn CR, Fajas L. CDK4 is an essential insulin effector in adipocytes. J Clin Invest 2015; 126:335-48. [PMID: 26657864 DOI: 10.1172/jci81480] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 11/06/2015] [Indexed: 12/11/2022] Open
Abstract
Insulin resistance is a fundamental pathogenic factor that characterizes various metabolic disorders, including obesity and type 2 diabetes. Adipose tissue contributes to the development of obesity-related insulin resistance through increased release of fatty acids, altered adipokine secretion, and/or macrophage infiltration and cytokine release. Here, we aimed to analyze the participation of the cyclin-dependent kinase 4 (CDK4) in adipose tissue biology. We determined that white adipose tissue (WAT) from CDK4-deficient mice exhibits impaired lipogenesis and increased lipolysis. Conversely, lipolysis was decreased and lipogenesis was increased in mice expressing a mutant hyperactive form of CDK4 (CDK4(R24C)). A global kinome analysis of CDK4-deficient mice following insulin stimulation revealed that insulin signaling is impaired in these animals. We determined that insulin activates the CCND3-CDK4 complex, which in turn phosphorylates insulin receptor substrate 2 (IRS2) at serine 388, thereby creating a positive feedback loop that maintains adipocyte insulin signaling. Furthermore, we found that CCND3 expression and IRS2 serine 388 phosphorylation are increased in human obese subjects. Together, our results demonstrate that CDK4 is a major regulator of insulin signaling in WAT.
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Denechaud PD, Lopez-Mejia IC, Giralt A, Lai Q, Blanchet E, Delacuisine B, Nicolay BN, Dyson NJ, Bonner C, Pattou F, Annicotte JS, Fajas L. E2F1 mediates sustained lipogenesis and contributes to hepatic steatosis. J Clin Invest 2015; 126:137-50. [PMID: 26619117 DOI: 10.1172/jci81542] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 10/22/2015] [Indexed: 12/16/2022] Open
Abstract
E2F transcription factors are known regulators of the cell cycle, proliferation, apoptosis, and differentiation. Here, we reveal that E2F1 plays an essential role in liver physiopathology through the regulation of glycolysis and lipogenesis. We demonstrate that E2F1 deficiency leads to a decrease in glycolysis and de novo synthesis of fatty acids in hepatocytes. We further demonstrate that E2F1 directly binds to the promoters of key lipogenic genes, including Fasn, but does not bind directly to genes encoding glycolysis pathway components, suggesting an indirect effect. In murine models, E2F1 expression and activity increased in response to feeding and upon insulin stimulation through canonical activation of the CDK4/pRB pathway. Moreover, E2F1 expression was increased in liver biopsies from obese, glucose-intolerant humans compared with biopsies from lean subjects. Finally, E2f1 deletion completely abrogated hepatic steatosis in different murine models of nonalcoholic fatty liver disease (NAFLD). In conclusion, our data demonstrate that E2F1 regulates lipid synthesis and glycolysis and thus contributes to the development of liver pathology.
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Yin YW, Jin HJ, Zhao W, Gao B, Fang J, Wei J, Zhang DD, Zhang J, Fang D. The Histone Acetyltransferase GCN5 Expression Is Elevated and Regulated by c-Myc and E2F1 Transcription Factors in Human Colon Cancer. Gene Expr 2015; 16:187-96. [PMID: 26637399 PMCID: PMC5584536 DOI: 10.3727/105221615x14399878166230] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The histone acetyltransferase GCN5 has been suggested to be involved in promoting cancer cell growth. But its role in human colon cancer development remains unknown. Herein we discovered that GCN5 expression is significantly upregulated in human colon adenocarcinoma tissues. We further demonstrate that GCN5 is upregulated in human colon cancer at the mRNA level. Surprisingly, two transcription factors, the oncogenic c-Myc and the proapoptotic E2F1, are responsible for GCN5 mRNA transcription. Knockdown of c-Myc inhibited colon cancer cell proliferation largely through downregulating GCN5 transcription, which can be fully rescued by the ectopic GCN5 expression. In contrast, E2F1 expression induced human colon cancer cell death, and suppression of GCN5 expression in cells with E2F1 overexpression further facilitated cell apoptosis, suggesting that GCN5 expression is induced by E2F1 as a possible negative feedback in suppressing E2F1-mediated cell apoptosis. In addition, suppression of GCN5 with its specific inhibitor CPTH2 inhibited human colon cancer cell growth. Our studies reveal that GCN5 plays a positive role in human colon cancer development, and its suppression holds a great therapeutic potential in antitumor therapy.
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Affiliation(s)
- Yan-Wei Yin
- *Department of Oncology, Linyi People’s Hospital, and Linyi Tumor Hospital, Linyi, P.R. China
| | - Hong-Jian Jin
- †Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Wenjing Zhao
- *Department of Oncology, Linyi People’s Hospital, and Linyi Tumor Hospital, Linyi, P.R. China
| | - Beixue Gao
- ‡Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Jiangao Fang
- ‡Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Junmin Wei
- §Department of Chemotherapy, Cancer Center, Qilu Hospital, Shandong University, Jinan, P.R. China
| | - Donna D. Zhang
- ¶Department of Pharmacology and Toxicology, University of Arizona, Tucson, AZ, USA
| | - Jianing Zhang
- #School of Life Science and Medicine, Dalian University of Technology, Panjin, P.R. China
| | - Deyu Fang
- ‡Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- #School of Life Science and Medicine, Dalian University of Technology, Panjin, P.R. China
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6
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Rosenfeldt MT, Bell LA, Long JS, O'Prey J, Nixon C, Roberts F, Dufès C, Ryan KM. E2F1 drives chemotherapeutic drug resistance via ABCG2. Oncogene 2014; 33:4164-72. [PMID: 24276245 DOI: 10.1038/onc.2013.470] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 09/12/2013] [Accepted: 10/06/2013] [Indexed: 12/18/2022]
Abstract
Multidrug resistance is a major barrier against successful chemotherapy, and this has been shown in vitro to be often caused by ATP-binding cassette (ABC) transporters. These transporters are frequently overexpressed in human cancers and confer an adverse prognosis in many common malignancies. The genetic factors, however, that initiate their expression in cancer are largely unknown. Here we report that the major multidrug transporter ABCG2 (BCRP/MXR) is directly and specifically activated by the transcription factor E2F1--a factor perturbed in the majority of human cancers. E2F1 regulates ABCG2 expression in multiple cell systems, and, importantly, we have identified a significant correlation between elevated E2F1 and ABCG2 expression in human lung cancers. We show that E2F1 causes chemotherapeutic drug efflux both in vitro and in vivo via ABCG2. Furthermore, the E2F1-ABCG2 axis suppresses chemotherapy-induced cell death that can be restored by the inhibition of ABCG2. These findings therefore identify a new axis in multidrug resistance and highlight a radical new function of E2F1 that is relevant to tumor therapy.
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Affiliation(s)
- M T Rosenfeldt
- Tumour Cell Death Laboratory, Cancer Research UK Beatson Institute, Glasgow, UK
| | - L A Bell
- Tumour Cell Death Laboratory, Cancer Research UK Beatson Institute, Glasgow, UK
| | - J S Long
- Tumour Cell Death Laboratory, Cancer Research UK Beatson Institute, Glasgow, UK
| | - J O'Prey
- Tumour Cell Death Laboratory, Cancer Research UK Beatson Institute, Glasgow, UK
| | - C Nixon
- Tumour Cell Death Laboratory, Cancer Research UK Beatson Institute, Glasgow, UK
| | - F Roberts
- Department of Pathology, Western Infirmary, Glasgow, UK
| | - C Dufès
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - K M Ryan
- Tumour Cell Death Laboratory, Cancer Research UK Beatson Institute, Glasgow, UK
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7
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Valdez CD, Kunju L, Daignault S, Wojno KJ, Day ML. The E2F1/DNMT1 axis is associated with the development of AR negative castration resistant prostate cancer. Prostate 2013; 73:1776-85. [PMID: 24038143 DOI: 10.1002/pros.22715] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 07/06/2013] [Indexed: 11/09/2022]
Abstract
BACKGROUND Research on castration resistant prostate cancer (CRPC) has focused primarily on functional alterations of the androgen receptor (AR). However, little is known about the loss of AR gene expression itself and the possible contribution of AR negative cells to CRPC. METHODS Human and murine prostate cancer tissue microarrays (TMAs) were evaluated with antibodies specific for E2F1, DNA methyltransferase 1 or AR. The human prostate cancer TMA consisted of clinical samples ranging from normal tissue to samples of metastatic disease. The murine TMA was comprised of benign, localized or metastatic prostate cancer acquired from TRAMP mice treated with castration and/or 5'-Aza-2'-deoxycytidine (5Aza). RESULTS Immunohistochemical analysis revealed increased nuclear DNMT1 staining in localized PCa (P < 0.0001) and metastatic PCa (P < 0.0001) compared to normal tissue. Examination of specific diagnoses revealed that Gleason seven tumors exhibited greater nuclear DNMT1 staining than Gleason six tumors (P < 0.05) and that metastatic tissue exhibited greater levels of nuclear DNMT1 than Gleason seven tumors (P < 0.01). Evaluation of the murine tissue cores revealed that 8.2% and 8.1% of benign tissue cores stained positive for E2F1 and DNMT1 respectively, while 97.0% were AR positive. Conversely, 81% and 100% of tumors were positive for E2F1 and DNMT1 respectively. This was in stark contrast to only 18% of tumors positive for AR. Treatment of mice with 5Aza reduced DNMT1 staining by 30%, while AR increased by 27%. CONCLUSIONS These findings demonstrate that the E2F1/DNMT1 inhibitory axis of AR transcription is activated during the emergence of CRPC.
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Affiliation(s)
- Conrad David Valdez
- Department of Urology, University of Michigan, Ann Arbor, Michigan; Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan
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8
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Garcia-Jove Navarro M, Basset C, Arcondéguy T, Touriol C, Perez G, Prats H, Lacazette E. Api5 contributes to E2F1 control of the G1/S cell cycle phase transition. PLoS One 2013; 8:e71443. [PMID: 23940755 PMCID: PMC3737092 DOI: 10.1371/journal.pone.0071443] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Accepted: 07/05/2013] [Indexed: 02/02/2023] Open
Abstract
Background The E2f transcription factor family has a pivotal role in controlling the cell fate in general, and in particular cancer development, by regulating the expression of several genes required for S phase entry and progression through the cell cycle. It has become clear that the transcriptional activation of at least one member of the family, E2F1, can also induce apoptosis. An appropriate balance of positive and negative regulators appears to be necessary to modulate E2F1 transcriptional activity, and thus cell fate. Methodology/Principal Findings In this report, we show that Api5, already known as a regulator of E2F1 induced-apoptosis, is required for the E2F1 transcriptional activation of G1/S transition genes, and consequently, for cell cycle progression and cell proliferation. Api5 appears to be a cell cycle regulated protein. Removal of Api5 reduces cyclin E, cyclin A, cyclin D1 and Cdk2 levels, causing G1 cell cycle arrest and cell cycle delay. Luciferase assays established that Api5 directly regulates the expression of several G1/S genes under E2F1 control. Using protein/protein and protein/DNA immunoprecipitation studies, we demonstrate that Api5, even if not physically interacting with E2F1, contributes positively to E2F1 transcriptional activity by increasing E2F1 binding to its target promoters, through an indirect mechanism. Conclusion/Significance The results described here support the pivotal role of cell cycle related proteins, that like E2F1, may act as tumor suppressors or as proto-oncogenes during cancer development, depending on the behavior of their positive and negative regulators. According to our findings, Api5 contributes to E2F1 transcriptional activation of cell cycle-associated genes by facilitating E2F1 recruitment onto its target promoters and thus E2F1 target gene transcription.
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Affiliation(s)
| | - Céline Basset
- INSERM UMR 1037, Cancer Research Center of Toulouse (CRCT), Cancer Department, Toulouse, France
| | - Tania Arcondéguy
- INSERM UMR 1037, Cancer Research Center of Toulouse (CRCT), Cancer Department, Toulouse, France
| | - Christian Touriol
- INSERM UMR 1037, Cancer Research Center of Toulouse (CRCT), Cancer Department, Toulouse, France
| | - Guillaume Perez
- INSERM UMR 1037, Cancer Research Center of Toulouse (CRCT), Cancer Department, Toulouse, France
| | - Hervé Prats
- INSERM UMR 1037, Cancer Research Center of Toulouse (CRCT), Cancer Department, Toulouse, France
| | - Eric Lacazette
- INSERM UMR 1037, Cancer Research Center of Toulouse (CRCT), Cancer Department, Toulouse, France
- * E-mail:
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Sáez-Ayala M, Montenegro MF, Sánchez-Del-Campo L, Fernández-Pérez MP, Chazarra S, Freter R, Middleton M, Piñero-Madrona A, Cabezas-Herrera J, Goding CR, Rodríguez-López JN. Directed phenotype switching as an effective antimelanoma strategy. Cancer Cell 2013; 24:105-19. [PMID: 23792190 DOI: 10.1016/j.ccr.2013.05.009] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 02/27/2013] [Accepted: 05/09/2013] [Indexed: 01/06/2023]
Abstract
Therapeutic resistance in melanoma and other cancers arises via irreversible genetic, and dynamic phenotypic, heterogeneity. Here, we use directed phenotype switching in melanoma to sensitize melanoma cells to lineage-specific therapy. We show that methotrexate (MTX) induces microphthalmia-associated transcription factor (MITF) expression to inhibit invasiveness and promote differentiation-associated expression of the melanocyte-specific Tyrosinase gene. Consequently, MTX sensitizes melanomas to a tyrosinase-processed antifolate prodrug 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin (TMECG), that inhibits the essential enzyme DHFR with high affinity. The combination of MTX and TMECG leads to depletion of thymidine pools, double-strand DNA breaks, and highly efficient E2F1-mediated apoptosis in culture and in vivo. Importantly, this drug combination delivers an effective and tissue-restricted antimelanoma therapy in vitro and in vivo irrespective of BRAF, MEK, or p53 status.
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Affiliation(s)
- Magalí Sáez-Ayala
- Department of Biochemistry and Molecular Biology A, School of Biology, Regional Campus of International Excellence Campus Mare Nostrum, University of Murcia, 30100 Murcia, Spain
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10
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Merrick BA, Phadke DP, Auerbach SS, Mav D, Stiegelmeyer SM, Shah RR, Tice RR. RNA-Seq profiling reveals novel hepatic gene expression pattern in aflatoxin B1 treated rats. PLoS One 2013; 8:e61768. [PMID: 23630614 PMCID: PMC3632591 DOI: 10.1371/journal.pone.0061768] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 03/13/2013] [Indexed: 01/16/2023] Open
Abstract
Deep sequencing was used to investigate the subchronic effects of 1 ppm aflatoxin B1 (AFB1), a potent hepatocarcinogen, on the male rat liver transcriptome prior to onset of histopathological lesions or tumors. We hypothesized RNA-Seq would reveal more differentially expressed genes (DEG) than microarray analysis, including low copy and novel transcripts related to AFB1’s carcinogenic activity compared to feed controls (CTRL). Paired-end reads were mapped to the rat genome (Rn4) with TopHat and further analyzed by DESeq and Cufflinks-Cuffdiff pipelines to identify differentially expressed transcripts, new exons and unannotated transcripts. PCA and cluster analysis of DEGs showed clear separation between AFB1 and CTRL treatments and concordance among group replicates. qPCR of eight high and medium DEGs and three low DEGs showed good comparability among RNA-Seq and microarray transcripts. DESeq analysis identified 1,026 differentially expressed transcripts at greater than two-fold change (p<0.005) compared to 626 transcripts by microarray due to base pair resolution of transcripts by RNA-Seq, probe placement within transcripts or an absence of probes to detect novel transcripts, splice variants and exons. Pathway analysis among DEGs revealed signaling of Ahr, Nrf2, GSH, xenobiotic, cell cycle, extracellular matrix, and cell differentiation networks consistent with pathways leading to AFB1 carcinogenesis, including almost 200 upregulated transcripts controlled by E2f1-related pathways related to kinetochore structure, mitotic spindle assembly and tissue remodeling. We report 49 novel, differentially-expressed transcripts including confirmation by PCR-cloning of two unique, unannotated, hepatic AFB1-responsive transcripts (HAfT’s) on chromosomes 1.q55 and 15.q11, overexpressed by 10 to 25-fold. Several potentially novel exons were found and exon refinements were made including AFB1 exon-specific induction of homologous family members, Ugt1a6 and Ugt1a7c. We find the rat transcriptome contains many previously unidentified, AFB1-responsive exons and transcripts supporting RNA-Seq’s capabilities to provide new insights into AFB1-mediated gene expression leading to hepatocellular carcinoma.
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MESH Headings
- Aflatoxin B1/toxicity
- Animals
- Carcinogens/toxicity
- Carcinoma, Hepatocellular/chemically induced
- Carcinoma, Hepatocellular/genetics
- Carcinoma, Hepatocellular/metabolism
- Cell Transformation, Neoplastic/chemically induced
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- E2F1 Transcription Factor/physiology
- Exons
- Gene Expression Regulation, Neoplastic/drug effects
- Gene Regulatory Networks
- Glucuronosyltransferase/genetics
- Glucuronosyltransferase/metabolism
- High-Throughput Nucleotide Sequencing
- Liver/drug effects
- Liver/metabolism
- Liver Neoplasms, Experimental/chemically induced
- Liver Neoplasms, Experimental/genetics
- Liver Neoplasms, Experimental/metabolism
- Male
- Oligonucleotide Array Sequence Analysis
- Precancerous Conditions/chemically induced
- Precancerous Conditions/metabolism
- Principal Component Analysis
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Sequence Analysis, RNA
- Transcriptome
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Affiliation(s)
- B Alex Merrick
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America.
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11
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Hochane M, Raison D, Coquard C, Imhoff O, Massfelder T, Moulin B, Helwig JJ, Barthelmebs M. Parathyroid hormone-related protein is a mitogenic and a survival factor of mesangial cells from male mice: role of intracrine and paracrine pathways. Endocrinology 2013; 154:853-64. [PMID: 23284101 DOI: 10.1210/en.2012-1802] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Glomerulonephritis is characterized by the proliferation and apoptosis of mesangial cells (MC). The parathyroid-hormone related protein (PTHrP) is a locally active cytokine that affects these phenomena in many cell types, through either paracrine or intracrine pathways. The aim of this study was to evaluate the effect of both PTHrP pathways on MC proliferation and apoptosis. In vitro studies were based on MC from male transgenic mice allowing PTHrP-gene excision by a CreLoxP system. MC were also transfected with different PTHrP constructs: wild type PTHrP, PTHrP devoid of its signal peptide, or of its nuclear localization sequence. The results showed that PTHrP deletion in MC reduced their proliferation even in the presence of serum and increased their apoptosis when serum-deprived. PTH1R activation by PTHrP(1-36) or PTH(1-34) had no effect on proliferation but improved MC survival. Transfection of MC with PTHrP devoid of its signal peptide significantly increased their proliferation and minimally reduced their apoptosis. Overexpression of PTHrP devoid of its nuclear localization sequence protected cells from apoptosis without changing their proliferation. Wild type PTHrP transfection conferred both mitogenic and survival effects, which seem independent of midregion and C-terminal PTHrP fragments. PTHrP-induced MC proliferation was associated with p27(Kip1) down-regulation and c-Myc/E2F1 up-regulation. PTHrP increased MC survival through the activation of cAMP/protein kinase A and PI3-K/Akt pathways. These results reveal that PTHrP is a cytokine of multiple roles in MC, acting as a mitogenic factor only through an intracrine pathway, and reducing apoptosis mainly through the paracrine pathway. Thus, PTHrP appears as a probable actor in MC injuries.
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Affiliation(s)
- Mazène Hochane
- Institut National de la Santé et de la Recherche Médicale U682, Equipe Cancer du Rein et Physiopathologie Rénale, Faculté de Médecine, 11 rue Humann, F-67085 Strasbourg, France.
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12
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Abstract
Cell growth is a prerequisite for cell proliferation, and ribosome biogenesis is a limiting factor for cell growth. In mammalian cells, the tumor suppressor p53 has been shown to induce cell-cycle arrest in response to impaired ribosome biogenesis. Recently, p53-independent mechanisms of cell-cycle arrest in response to alterations of ribosome biogenesis have been described. These findings provide a rational basis for the use of drugs that specifically impact ribosome biogenesis for the treatment of cancers lacking active p53 and extend the scenario of mechanisms involved in the relationship between cell growth and cell proliferation.
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Affiliation(s)
- Giulio Donati
- Department of Experimental Pathology, Alma Mater Studiorum, Università di Bologna, Bologna, Italy
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13
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Abstract
E2F is a family of transcription factors that regulate the expression of genes involved in a wide range of cellular processes, including cell-cycle progression, DNA replication, DNA repair, differentiation, and apoptosis. E2F1, the founding member of the family, undergoes posttranslational modifications in response to DNA damage, resulting in E2F1 stabilization. In some cases, E2F1 is important for DNA damage-induced apoptosis through the transcriptional activation of p73 and perhaps other proapoptotic target genes. However, in other contexts, E2F1 can stimulate DNA repair and promote survival in response to DNA damage. The E2F1 protein accumulates at sites of both DNA double-strand breaks and UV radiation-induced damage, indicating that E2F1 has a nontranscriptional function at sites of damage. This review summarizes recent progress made in understanding the role of E2F1 in the DNA damage response, including transcription-independent activities that facilitate DNA repair in the context of chromatin.
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Affiliation(s)
- Anup K Biswas
- Department of Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, Texas 78957, USA
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14
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Bénard J, Massard C. [RB, guardian of prostatic tumor progression]. Bull Cancer 2011; 98:91-92. [PMID: 21591299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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15
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Abstract
During cell proliferation, growth must occur to maintain homeostatic cell size. Here we show that E2F1 is capable of inducing growth by regulating mTORC1 activity. The activation of cell growth and mTORC1 by E2F1 is dependent on both E2F1's ability to bind DNA and to regulate gene transcription, demonstrating that a gene induction expression program is required in this process. Unlike E2F1, E2F3 is unable to activate mTORC1, suggesting that growth activity could be restricted to individual E2F members. The effect of E2F1 on the activation of mTORC1 does not depend on Akt. Furthermore, over-expression of TSC2 does not interfere with the effect of E2F1, indicating that the E2F1-induced signal pathway can compensate for the inhibitory effect of TSC2 on Rheb. Immunolocalization studies demonstrate that E2F1 induces the translocation of mTORC1 to the late endosome vesicles, in a mechanism dependent of leucine. E2F1 and leucine, or insulin, together affect the activation of S6K stronger than alone suggesting that they are complementary in activating the signal pathway. From these studies, E2F1 emerges as a key protein that integrates cell division and growth, both of which are essential for cell proliferation.
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Affiliation(s)
- Sebastian Real
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Spain
| | - Nathalie Meo-Evoli
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Spain
| | - Lilia Espada
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Spain
| | - Albert Tauler
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Spain
- * E-mail:
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16
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Abstract
The retinoblastoma tumor suppressor gene (RB1; encoding RB) is often cited as a gatekeeper, whose inactivation - direct or indirect - is a rate-limiting step for tumor initiation. However, in this issue of the JCI, Sharma et al. show that RB1 loss is a late event in human prostate cancer that is coincident with the emergence of castrate-resistant metastatic disease. This role for RB1 was linked to both E2F transcription factor 1-driven upregulation of the androgen receptor (AR) and increased recruitment of the AR to target gene promoters. This unexpected function for RB1 in late-stage cancer calls upon us to reassess the significance of RB1 inactivation in other cancers in terms of its timing, function in disease etiology, and relevance for cancer therapy.
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Affiliation(s)
- Kay F Macleod
- Ben May Department for Cancer Research, Gordon Center for Integrative Sciences, University of Chicago, Chicago, Illinois, USA.
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17
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Abstract
Thrombospondin 1 (TSP1) has been shown to play a critical role in inhibiting angiogenesis, resulting in inhibition of tumor growth and metastases. To figure out TSP1's regulators will lead to reveal its biological function mechanistically. In this study, we show that E2F-1 could activate the transcription of TSP1 by both promoter assays and Northern blot. Analysis of various TSP1 promoter mutant constructs showed that a sequence located −144/−137 up-stream of the transcriptional initiation site, related to the consensus E2F-responsive sequence, is necessary for the activation. In consistence with up-regulation of TSP-1 activity by over-expression of E2F-1, the knockdown of endogenous E2F-1 inhibited TSP-1 promoter activity significantly, implying that E2F-1 mediated regulation of TSP-1 is relevant in vivo. In addition, E2F-1 could also directly bind to the TSP1 promoter region covering −144/−137 region as revealed by ChIP assays. Furthermore, the E2F-1-induced activation of TSP1 gene transcription is suppressed by pRB1 in a dose-dependent manner. Taken together, the results demonstrate that TSP1 is a novel target for E2F1, which might imply that E2F-1 can affect angiogenesis by modulating TSP1 expression.
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Affiliation(s)
- Wei Ji
- Key Laboratory of Biodiversity and Conservation of Aquatic Organisms, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Wei Zhang
- Key Laboratory of Biodiversity and Conservation of Aquatic Organisms, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Wuhan Xiao
- Key Laboratory of Biodiversity and Conservation of Aquatic Organisms, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, People's Republic of China
- * E-mail:
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18
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Wichmann A, Uyetake L, Su TT. E2F1 and E2F2 have opposite effects on radiation-induced p53-independent apoptosis in Drosophila. Dev Biol 2010; 346:80-9. [PMID: 20659447 DOI: 10.1016/j.ydbio.2010.07.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 07/15/2010] [Accepted: 07/17/2010] [Indexed: 12/15/2022]
Abstract
The ability of ionizing radiation (IR) to induce apoptosis independent of p53 is crucial for successful therapy of cancers bearing p53 mutations. p53-independent apoptosis, however, remains poorly understood relative to p53-dependent apoptosis. IR induces both p53-dependent and p53-independent apoptoses in Drosophila melanogaster, making studies of both modes of cell death possible in a genetically tractable model. Previous studies have found that Drosophila E2F proteins are generally pro-death or neutral with regard to p53-dependent apoptosis. We report here that dE2F1 promotes IR-induced p53-independent apoptosis in larval imaginal discs. Using transcriptional reporters, we provide evidence that, when p53 is mutated, dE2F1 becomes necessary for the transcriptional induction of the pro-apoptotic gene hid after irradiation. In contrast, the second E2F homolog, dE2F2, as well as the net E2F activity, which can be depleted by mutating the common cofactor, dDp, is inhibitory for p53-independent apoptosis. We conclude that p53-dependent and p53-independent apoptoses show differential reliance on E2F activity in Drosophila.
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Affiliation(s)
- Anita Wichmann
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80209-0347, USA
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19
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Abstract
Pancreatic β-cells are sensors of circulating glucose levels that control insulin secretion through a finely-tuned process. Under hyperglycemic conditions, glucose enters the cell, generates ATP, leading to a subsequent closure of voltage-dependent ATP channels, membrane depolarization, Ca²(+) entry and exocytosis of insulin vesicles. In pathological conditions, such as during type 2 diabetes (T2D), chronic hyperglycemia will ultimately result in decreased capability of β-cells to secrete sufficient amount of insulin to regulate glycemia. Therefore, understanding of the mechanisms of modulation of insulin secretion could be of interest for the treatment of diabetes. We have demonstrated that a particular cell cycle regulator, E2F1, is involved in pancreatic post-natal growth through its functions in the control of β-cell proliferation. Based on the observation that cell cycle regulators were highly expressed in non-proliferating β-cell, we hypothesized that these proteins could also have a direct role in pancreatic β-cell function. Altogether our data unravel a new function for these factors in the control of insulin secretion and open up new avenues for the treatment of diabetes.
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Affiliation(s)
- Lluis Fajas
- Institut de Recherche en Cancérologie de Montpellier, France.
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20
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Konstantakou EG, Voutsinas GE, Karkoulis PK, Aravantinos G, Margaritis LH, Stravopodis DJ. Human bladder cancer cells undergo cisplatin-induced apoptosis that is associated with p53-dependent and p53-independent responses. Int J Oncol 2009; 35:401-416. [PMID: 19578756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023] Open
Abstract
Cisplatin is a first-line chemotherapeutic agent and a powerful component of standard treatment regimens for several human malignancies including bladder cancer. DNA-Pt adducts produced by cisplatin are mainly responsible for cellular toxicity and induction of apoptosis. Identification of the mechanisms that control sensitivity to cisplatin is central to improving its therapeutic index and to successfully encountering the acquired resistance frequently emerging during therapy. In the present study, using MTT-based assays, Western blotting and semi-quantitative RT-PCR, we examined the apoptosis-related cellular responses to cisplatin exposure in two human urinary bladder cancer cell lines characterized by different malignancy grade and p53 genetic status. Both RT4 (grade I; wild-type p53) and T24 (grade III; mutant p53) cell types proved to be vulnerable to cisplatin apoptotic activity, albeit in a grade-dependent and drug dose-specific manner, as demonstrated by the proteolytic processing profiles of Caspase-8, Caspase-9, Caspase-3, and the Caspase repertoire characteristic substrates PARP and Lamin A/C, as well. The differential resistance of RT4 and T24 cells to cisplatin-induced apoptosis was associated with an RT4-specific phosphorylation (Ser15; Ser392) pattern of p53, together with structural amputations of the Akt and XIAP anti-apoptotic regulators. Furthermore, cisplatin administration resulted in a Granzyme B-mediated proteolytic cleavage of Hsp90 molecular chaperone, exclusively occurring in RT4 cells. To generate functional networks, expression analysis of a number of genes, including Bik, Bim, Bcl-2, FAP-1, Fas, FasL, TRAIL, Puma, Caspase-10, ATP7A, ATP7B and MRP1, was performed, strongly supporting the role of p53-dependent and p53-independent transcriptional responses in cisplatin-induced apoptosis of bladder cancer cells.
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Affiliation(s)
- Eumorphia G Konstantakou
- Department of Cell Biology, Faculty of Biology, University of Athens, Panepistimiopolis, Zografou 157 84, Greece
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21
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Peirce SK, Findley HW. The MDM2 antagonist nutlin-3 sensitizes p53-null neuroblastoma cells to doxorubicin via E2F1 and TAp73. Int J Oncol 2009; 34:1395-1402. [PMID: 19360352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
Abstract
Neuroblastoma (NB) is a primitive neuroectodermal tumor and the second most common solid tumor in children. NB exhibits heterogeneous behavior and spontaneous regression can occur in patients under 12 months of age. Response to treatment is both age- and stage-specific; however, patients over 1 year of age are generally considered high risk. NB tumors from these patients are often characterized by alterations in p53 expression and murine double minute (MDM2) activity with concomitant resistance to chemotherapy. We evaluated the ability of nutlin-3 to sensitize a p53-null and doxorubicin-resistant NB cell line, LA155N, to doxorubicin. Nutlin-3 treatment upregulated TAp73 and E2F1 protein levels. It potentiated the ability of doxorubicin to block cell proliferation and activate apoptosis and TAp73 knockdown resulted in a reduction of this sensitization. Additionally, PUMA expression was induced by the combination treatment, but reduced by knockdown of either TAp73 or E2F1. We conclude that, following nutlin-3 treatment, TAp73 and E2F1 are released from MDM2 and activated by doxorubicin to induce PUMA and apoptosis. This study addresses p53-independent mechanisms of nutlin-3 action in chemoresistant NB, especially in combination with chemotherapeutics. We believe that this model has strong clinical relevance for chemoresistant and p53 dysfunctional NB.
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Affiliation(s)
- Susan K Peirce
- Department of Pediatrics, Division of Hematology and Oncology, Aflac Cancer Center and Blood Disorders Service, Emory University School of Medicine, Atlanta, GA 30322, USA.
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22
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Affiliation(s)
- Jennifer L Hall
- Lillehei Heart Institute, University of Minnesota, Minneapolis, MN 55455, USA.
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23
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Crawford EL, Blomquist T, Mullins DN, Yoon Y, Hernandez DR, Al-Bagdhadi M, Ruiz J, Hammersley J, Willey JC. CEBPG regulates ERCC5/XPG expression in human bronchial epithelial cells and this regulation is modified by E2F1/YY1 interactions. Carcinogenesis 2007; 28:2552-9. [PMID: 17893230 DOI: 10.1093/carcin/bgm214] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Marked inter-individual variation in lung cancer risk cannot be accounted for solely by cigarette smoke and other environmental exposures. Evidence suggests that variation in bronchial epithelial cell expression of key DNA repair genes plays a role. Variation in these genes correlates with variation in expression of CEBPG and E2F1 transcription factors. Here, we investigated the mechanistic basis for correlation of the DNA repair gene ERCC5 (previously known as XPG) with CEBPG and E2F1. CEBPG expression vector transfected into H23 or H460 cell lines up-regulated endogenous ERCC5 and also luciferase from a reporter construct containing 589 bp of ERCC5 5' regulatory region. A recognition site for CEBPG and a region containing sites for YY1 on the sense strand and E2F1 on the anti-sense strand participated in CEBPG up-regulation of ERCC5. CEBPG, E2F1 and YY1 binding to their respective sites were confirmed by electrophoretic mobility shift assay. Thus, we conclude that CEBPG regulates ERCC5 expression and this regulation is modified by E2F1/YY1 interactions. Several polymorphisms have been identified in these regions and, based on the data presented here, it is reasonable to hypothesize that they may contribute to risk for bronchogenic carcinoma.
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Affiliation(s)
- E L Crawford
- Department of Medicine, The University of Toledo, Toledo, OH 43614, USA
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24
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Li Q, Dashwood WM, Zhong X, Nakagama H, Dashwood RH. Bcl-2 overexpression in PhIP-induced colon tumors: cloning of the rat Bcl-2 promoter and characterization of a pathway involving beta-catenin, c-Myc and E2F1. Oncogene 2007; 26:6194-202. [PMID: 17404573 PMCID: PMC2267879 DOI: 10.1038/sj.onc.1210438] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 01/25/2007] [Accepted: 02/19/2007] [Indexed: 11/09/2022]
Abstract
Beta-catenin/T-cell factor (Tcf) signaling is constitutively active in the majority of human colorectal cancers, and there are accompanying changes in Bcl-2 expression. Similarly, 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP)-induced colon tumors in the rat have increased beta-catenin and elevated Bcl-2. To examine the possible direct transcriptional regulation of rat Bcl-2 by beta-catenin/Tcf, we cloned and characterized the corresponding promoter region and found 70.1% similarity with its human counterpart, BCL2. Bcl-2 promoter activity was increased in response to LiCl and exogenous beta-catenin, including oncogenic mutants of beta-catenin found in PhIP-induced colon tumors. Protein/DNA arrays identified E2F1, but not beta-catenin/Tcf, as interacting most strongly with the rat Bcl-2 promoter. Exogenous E2F1 increased the promoter activity of rat Bcl-2, except in mutants lacking the E2F1 sites. As expected, beta-catenin induced its downstream target c-Myc, as well as E2F1 and Bcl-2, and this was blocked by siRNA to c-Myc or E2F1. These findings suggest an indirect pathway for Bcl-2 over-expression in PhIP-induced colon tumors involving beta-catenin, c-Myc and E2F1.
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Affiliation(s)
- Q Li
- Linus Pauling Institute, Oregon State University, Corvallis, OR, USA
| | - WM Dashwood
- Linus Pauling Institute, Oregon State University, Corvallis, OR, USA
| | - X Zhong
- Linus Pauling Institute, Oregon State University, Corvallis, OR, USA
| | - H Nakagama
- National Cancer Center Research Institute, Tokyo, Japan
| | - RH Dashwood
- Linus Pauling Institute, Oregon State University, Corvallis, OR, USA
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25
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Tenbaum SP, Papaioannou M, Reeb CA, Goeman F, Escher N, Kob R, von Eggeling F, Melle C, Baniahmad A. Alien inhibits E2F1 gene expression and cell proliferation. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2007; 1773:1447-54. [PMID: 17570542 DOI: 10.1016/j.bbamcr.2007.04.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 04/25/2007] [Accepted: 04/28/2007] [Indexed: 12/24/2022]
Abstract
Recently, using a proteomic approach we have identified the corepressor Alien as a novel interacting factor of the cell cycle regulator E2F1. Unclear was whether this interaction influences cell proliferation and endogenous E2F1 target gene expression. Here, we show by chromatin immunoprecipitation (ChIP) that Alien is recruited in vivo to the E2F binding sites present in the E2F1 gene promoter, inhibits the transactivation of E2F1 and represses endogenous E2F1 gene expression. Interestingly, using synchronized cells to assess the expression of Alien profile during cell cycle the levels of endogenous Alien are increased during G1, G1/S and G2 phase. Furthermore, stable transfection of Alien leads to reduction of cell proliferation. Thus, the data suggest that Alien acts as a corepressor for E2F1 and is involved in cell cycle regulation.
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Affiliation(s)
- Stephan P Tenbaum
- Molecular Genetics, Institute of Human Genetics and Anthropology, Friedrich-Schiller-University, 07740 Jena, Germany
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26
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Yuan Z, Mei Y, Zhou J, Tan M, Song B, Ma C, Ying C, Li D, Ching YP, Li M. E2F1 is not essential for apoptosis induced by potassium deprivation in cerebellar granule neurons. Neurosci Lett 2007; 424:155-9. [PMID: 17728064 DOI: 10.1016/j.neulet.2007.07.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Revised: 06/29/2007] [Accepted: 07/01/2007] [Indexed: 01/27/2023]
Abstract
Cerebellar granule neurons (CGNs) undergo apoptosis when deprived of depolarizing concentration of potassium. A key regulator of cell cycle, E2F1, was believed to play a role in CGN apoptosis induced by potassium deprivation. However, here we demonstrated that although E2F1 was upregulated in wild type CGNs following potassium deprivation, CGNs that derived from E2F1 knockout mice underwent apoptosis at a similar rate as the wild type. Analysis of the apoptotic neurons revealed no difference in the activation of caspase-3 in E2F1 null and wild type CGNs. Furthermore, knockdown of E2F1 expression by RNA interference failed to attenuate the apoptosis of CGNs induced by potassium deprivation. Taken together, our results suggested that E2F1 is not essential for apoptosis induced by potassium deprivation in CGNs.
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Affiliation(s)
- Zhongmin Yuan
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan Road II, Guangzhou 510080, China
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27
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Lacerte A, Korah J, Roy M, Yang XJ, Lemay S, Lebrun JJ. Transforming growth factor-beta inhibits telomerase through SMAD3 and E2F transcription factors. Cell Signal 2007; 20:50-9. [PMID: 17881189 DOI: 10.1016/j.cellsig.2007.08.012] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Accepted: 08/14/2007] [Indexed: 11/30/2022]
Abstract
Cancer arises from multiple genetic changes within the cell, among which constitutive telomerase activity and attainment of immortality are central. Expression of hTERT, the protein component of telomerase, is increased in most cancer cells. Transforming growth factor-beta (TGFbeta), a potent tumor suppressor, has been reported to regulate hTERT expression. We found that TGFbeta represses hTERT expression in normal and cancer cells and that this effect is mediated through Smad3 but also requires Erk1/2, p38 kinase and histone deacetylase activity. Furthermore, we identified four critical E2F transcription factor binding sites within the hTERT gene promoter that confer the TGFbeta response. Finally, using the E2F-1 knockout model, we showed that loss of E2F-1 abolishes TGFbeta inhibition of telomerase expression. These findings highlight the prominent role of TGFbeta in regulating telomerase expression and identify Smad3 and E2F-1 as critical mediators of TGFbeta effects in both normal and cancer cells.
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Affiliation(s)
- Annie Lacerte
- Hormones and Cancer Research Unit, Department of Medicine, Royal Victoria Hospital, McGill University, 687 Pine Avenue West, H3A 1A1, Montreal, Quebec, Canada
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28
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Wang J, Yin DP, Liu YX, Baer R, Yin Y. Dual specificity phosphatase 1/CL100 is a direct transcriptional target of E2F-1 in the apoptotic response to oxidative stress. Cancer Res 2007; 67:6737-44. [PMID: 17638884 DOI: 10.1158/0008-5472.can-06-4402] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
E2F-1 mediates apoptosis through transcriptional regulation of its targets. We report here that E2F-1 acts as a direct transcriptional regulator of dual specificity phosphatase 1 (DUSP1; CL100), a threonine and tyrosine phosphatase that inhibits mitogen-activated protein (MAP) kinases. We found that DUSP1 is transcriptionally induced by ectopic E2F-1 expression and that extracellular signal-regulated kinase 1/2 are dephosphorylated in the presence of E2F-1 and DUSP1. E2F-1 mediates apoptosis in the cellular response to oxidative stress. DUSP1 levels are significantly increased in an E2F-1-dependent manner following oxidative stress but not other stresses examined. DUSP1 mediates the cellular response to oxidative stress. We found that E2F-1 binds to chromatin encompassing the DUSP1 promoter and greatly stimulates the promoter activity of the DUSP1 gene. In particular, E2F-1 physically binds to an E2F-1 consensus sequence and a palindromic motif in the DUSP1 promoter. Interestingly, E2F-1 is acetylated following oxidative stress. Our findings show that E2F-1 is a transcriptional activator of DUSP1 and that DUSP1 is a link between E2F-1 and MAP kinases.
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Affiliation(s)
- Jianli Wang
- Department of Radiation Oncology, Center for Radiological Research, College of Physicians and Surgeons, Columbia University Medical Center, 630 West 168th Street, New York, NY 10032, USA
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29
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Abstract
KAP1 is a nuclear corepressor with conserved domains for RING finger, B boxes, leucine zipper alpha helical coiled-coil region, plant homeo domain finger, and bromo domain. The plant homeo domain finger and bromo domain of KAP1 cooperatively function as a transcription repression domain by recruiting the histone deacetylase complex NuRD and histone H3 lysine 9-specific methyltransferase SETDB1. Here we report that KAP1 binds the E2F1 transcription factor in a retinoblastoma protein (pRb)-independent fashion and inhibits E2F1 activity. KAP1 stimulates formation of E2F1-HDAC1 complex and inhibits E2F1 acetylation. Ectopic expression of KAP1 represses E2F1 transcription and apoptosis functions independent of pRb. Depletion of endogenous KAP1 in pRb-deficient Saos2 cells by RNA interference increases E2F1 acetylation level, stimulates E2F1 transcriptional activity, and sensitizes apoptosis response to DNA damage. Therefore, KAP1 contributes to the negative regulation of E2F1 and may serve as a partial backup to prevent E2F1-mediated apoptosis in the absence of pRb.
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Affiliation(s)
- Chuangui Wang
- Molecular Oncology Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA
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30
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Abstract
Deregulated growth and blocks in differentiation collaborate in the multistage process of leukemogenesis. Previously, we have shown that ectopic expression of the zinc finger transcription factor Egr-1 in M1 myeloblastic leukemia cells promotes terminal differentiation with interleukin-6 (IL-6). In addition, we have shown that deregulated expression of the oncogene E2F-1 blocks the myeloid terminal differentiation program, resulting in proliferation of immature cells in the presence of IL-6. Here it is shown that the positive regulator of differentiation Egr-1 abrogates the E2F-1-driven block in myeloid terminal differentiation. The M1E2F-1/Egr-1 cells underwent G(0)/G(1) arrest and functional macrophage maturation following treatment with IL-6. Furthermore, Egr-1 diminished the aggressiveness of M1E2F-1 leukemias and abrogated the leukemic potential of IL-6-treated M1E2F-1 cells. Previously, we reported that Egr-1 abrogated the block in terminal myeloid differentiation imparted by deregulated c-myc, which blocks differentiation at a later stage than E2F-1, resulting in cells that have the characteristics of functionally mature macrophages that did not undergo G(0)/G(1) arrest. Taken together, this work extends and highlights the tumor suppressor role of Egr-1, with Egr-1 behaving as a tumor suppressor against two oncogenes, each blocking myeloid differentiation by a different mechanism. These findings suggest that Egr-1 and/or Egr-1 target genes may be useful tools to treat or suppress oncogene-driven hematological malignancies.
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Affiliation(s)
- J D Gibbs
- Fels Institute for Cancer Research and Molecular Biology, Temple University, Philadelphia, PA, USA
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31
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Abstract
Sunlight's UVB radiation triggers cell signaling at multiple sites to induce apoptosis. The integration of these signal entry sites is not understood. Here we show that P53 and E2f1 constitute a UV-inducible apoptosis switch. At low-UV doses, wild-type cells resemble the OFF state of an siP53-treated cell, whereas at high-UV doses, the apoptosis frequency transitions to the fully ON behavior of an siE2f1-treated cell. The switch's target is Bcl-2: Rapid Bcl-2 down-regulation in response to UVB-induced DNA photoproducts is lost in P53-deficient cells, but, as for apoptosis, is restored when both P53 and its inhibited target E2f1 are absent. P53's down-regulation of Bcl-2 is mediated entirely through E2f1. Bcl-2 is also down-regulated by a separate pathway triggered by DNA photoproducts in the absence of P53 and E2f1. Four UV pathways terminating on Bcl-2 contribute to apoptosis after UVB irradiation. The apoptosis lost in p53(-/-) is completely restored by siBcl-2, implying that Bcl-2 is a rate-limiting member of this network. These results identify Bcl-2 as an integrator of several UV-induced proapoptotic signals and show that it, in turn, suppresses a direct UV-apoptosis pathway. UV-induced apoptosis requires both UV activation of the direct pathway and a separate UV disinhibition of this pathway through P53-E2f1-Bcl-2.
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Affiliation(s)
- Dejan Knezevic
- Departments of *Therapeutic Radiology
- Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06525
| | | | | | - Douglas E. Brash
- Departments of *Therapeutic Radiology
- Genetics
- Dermatology, and
- To whom correspondence should be addressed. E-mail:
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32
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Stender JD, Frasor J, Komm B, Chang KCN, Kraus WL, Katzenellenbogen BS. Estrogen-regulated gene networks in human breast cancer cells: involvement of E2F1 in the regulation of cell proliferation. Mol Endocrinol 2007; 21:2112-23. [PMID: 17550982 DOI: 10.1210/me.2006-0474] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Estrogens generally stimulate the proliferation of estrogen receptor (ER)-containing breast cancer cells, but they also suppress proliferation of some ER-positive breast tumors. Using a genome-wide analysis of gene expression in two ER-positive human breast cancer cell lines that differ in their proliferative response to estrogen, we sought to identify genes involved in estrogen-regulated cell proliferation. To this end, we compared the transcriptional profiles of MCF-7 and MDA-MB-231ER+ cells, which have directionally opposite 17beta-estradiol (E2)-dependent proliferation patterns, MCF-7 cells being stimulated and 231ER+ cells suppressed by E2. We identified a set of approximately 70 genes regulated by E2 in both cells, with most being regulated by hormone in an opposite fashion. Using a variety of bioinformatics approaches, we found the E2F binding site to be overrepresented in the potential regulatory regions of many cell cycle-related genes stimulated by estrogen in MCF-7 but inhibited by estrogen in 231ER+ cells. Biochemical analyses confirmed that E2F1 and E2F downstream target genes were increased in MCF-7 and decreased in 231ER+ cells upon estrogen treatment. Furthermore, RNA interference-mediated knockdown of E2F1 blocked estrogen regulation of E2F1 target genes and resulted in loss of estrogen regulation of proliferation. These results demonstrate that regulation by estrogen of E2F1, and subsequently its downstream target genes, is critical for hormone regulation of the proliferative program of these breast cancer cells, and that gene expression profiling combined with bioinformatic analyses of transcription factor binding site enrichment in regulated genes can identify key components associated with nuclear receptor hormonal regulation of important cellular functions.
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Affiliation(s)
- Joshua D Stender
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3704, USA
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33
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Abstract
Transcription factor E2F-1 mediates apoptosis and suppresses tumorigenesis. The mechanisms by which E2F-1 functions in these processes are largely unclear. We report here that E2F-1 acts as a transcriptional regulator of MKP-2 (MAPK phosphatase-2), a dual specificity protein phosphatase (DUSP4) with stringent substrate specificity for MAPKs. We show that E2F-1 is required for the cellular apoptotic response to oxidative damage. MKP-2 is greatly increased following oxidative stress, and E2F-1 is necessary for that induction. We found that E2F-1 is physically associated with the MKP-2 promoter and can transactivate the promoter of the MKP-2 gene. Specifically, E2F-1 binds to a perfect palindromic motif in the MKP-2 promoter. Finally, we show that this E2F-1/MKP-2 pathway mediates apoptosis under oxidative stress and that MKP-2 suppresses tumor formation in nude mice. Our findings demonstrate that E2F-1 is a transcriptional activator of MKP-2 and that MKP-2 is an essential cell death mediator in the E2F-1 pathway. Characterization of MKP-2 as a cell death mediator may lead to the development of new strategies for cancer treatment.
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Affiliation(s)
- Jianli Wang
- Department of Radiation Oncology, College of Physicians and Surgeons, Columbia University, New York, New York 10032
| | - Wen Hong Shen
- Department of Radiation Oncology, College of Physicians and Surgeons, Columbia University, New York, New York 10032
| | - Yan J Jin
- Department of Radiation Oncology, College of Physicians and Surgeons, Columbia University, New York, New York 10032
| | - Paul W Brandt-Rauf
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032
| | - Yuxin Yin
- Department of Radiation Oncology, College of Physicians and Surgeons, Columbia University, New York, New York 10032; Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032.
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Espada L, Udapudi B, Podlesniy P, Fabregat I, Espinet C, Tauler A. Apoptotic action of E2F1 requires glycogen synthase kinase 3-β activity in PC12 cells. J Neurochem 2007; 102:2020-2028. [PMID: 17555552 DOI: 10.1111/j.1471-4159.2007.04686.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Both E2F1 and GSK3beta have been described as essential targets in neuronal apoptosis. Previous studies have demonstrated that GSK3beta binds to E2F1 in vivo. We wanted to investigate whether these proteins could share a common apoptotic signal pathway in neuronal cells. With this intention, we developed a PC12 ER-E2F1 stable cell line in which E2F1 activity was dependent on the presence of 4-hydroxitamoxifen. E2F1 activation produced apoptosis in naive and post-mitotic cells; serum and nerve growth factor respectively protected them from E2F1 apoptotic stimuli. The presence of specific GSK3beta inhibitors SB216763 and LiCl completely protected cells from apoptosis induced by E2F1 activation. In addition, knocked down GSK3beta experiments by small interference RNAs have demonstrated that a reduction of GSK3beta protein levels can lower the apoptotic effect of E2F1. Finally, we demonstrated that the apoptotic effect of E2F1 is not due to the regulation of GSK3beta activity, and that the inhibitory effect of GSK3beta inhibitor SB216763 on E2F1 induced apoptosis could be due to an alteration in the E2F1-regulated transcription gene pattern. In summary, we have demonstrated that the apoptotic action of E2F1 requires GSK3beta activity.
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Affiliation(s)
- Lilia Espada
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalunya, SpainLaboratori de Neuropatologia Molecular, Departament de Ciències Mèdiques Básiques, Universitat de Lleida, Lleida, Catalunya, SpainCentre d'Oncologia Molecular, Institut de Recerca Oncologica-Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet, Barcelona, Catalunya, Spain
| | - Basavaraj Udapudi
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalunya, SpainLaboratori de Neuropatologia Molecular, Departament de Ciències Mèdiques Básiques, Universitat de Lleida, Lleida, Catalunya, SpainCentre d'Oncologia Molecular, Institut de Recerca Oncologica-Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet, Barcelona, Catalunya, Spain
| | - Petar Podlesniy
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalunya, SpainLaboratori de Neuropatologia Molecular, Departament de Ciències Mèdiques Básiques, Universitat de Lleida, Lleida, Catalunya, SpainCentre d'Oncologia Molecular, Institut de Recerca Oncologica-Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet, Barcelona, Catalunya, Spain
| | - Isabel Fabregat
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalunya, SpainLaboratori de Neuropatologia Molecular, Departament de Ciències Mèdiques Básiques, Universitat de Lleida, Lleida, Catalunya, SpainCentre d'Oncologia Molecular, Institut de Recerca Oncologica-Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet, Barcelona, Catalunya, Spain
| | - Carme Espinet
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalunya, SpainLaboratori de Neuropatologia Molecular, Departament de Ciències Mèdiques Básiques, Universitat de Lleida, Lleida, Catalunya, SpainCentre d'Oncologia Molecular, Institut de Recerca Oncologica-Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet, Barcelona, Catalunya, Spain
| | - Albert Tauler
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Catalunya, SpainLaboratori de Neuropatologia Molecular, Departament de Ciències Mèdiques Básiques, Universitat de Lleida, Lleida, Catalunya, SpainCentre d'Oncologia Molecular, Institut de Recerca Oncologica-Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet, Barcelona, Catalunya, Spain
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Abstract
E2F-1 controls multiple cellular activities through transcriptional regulation of its target genes. As a mediator of cell death, E2F-1 can eliminate latent neoplastic cells through apoptosis. However, the mechanism by which E2F-1 mediates cancer cell killing is largely unknown. In this paper, we report that phosphatase of activated cells 1 (PAC1) phosphatase is a direct transcription target of E2F-1 in signaling apoptosis. We show that ectopic E2F-1 increases expression of PAC1 at both transcriptional and translational levels in breast cancer cells. E2F-1 physically interacts with the promoter of PAC1, binds to its consensus sequence in the promoter and transactivates the PAC1 promoter. E2F-1 suppresses extracellular signal-regulated kinase (ERK) phosphorylation through PAC1 and causes cancer cell death by apoptosis following treatment with a chemotherapeutic agent N-4-hydroxyphenylretinamide (4-HPR). Furthermore, ectopic PAC1 inhibits ERK phosphorylation and mediates cell killing. Moreover, endogenous E2F-1 upregulates PAC1 and suppresses ERK activity, leading to cell death in response to 4-HPR. These results reveal a crucial role of PAC1 in E2F-1-directed apoptosis. Our study demonstrates that E2F-1 mediates apoptosis through transcriptional regulation of PAC1 and subsequent suppression of the ERK signaling. Our findings establish a functional link between E2F-1 and mitogen-activated protein kinases. The E2F-1-PAC1 cascade in cancer cell killing may provide a molecular basis for cancer therapeutic intervention.
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Affiliation(s)
- J Wu
- Department of Radiation Oncology, Center for Radiological Research, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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36
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Abstract
E2F1 is a key regulator that links cell cycle progression and cell death. E2F1 activity is controlled by Cdk2-cyclin complexes via several mechanisms, such as phosphorylation of retinoblastoma protein (pRb) to release E2F1, direct phosphorylation, and stable physical interaction. We have demonstrated that cisplatin cytotoxicity depends on Cdk2 activity, and Cdk2 inhibition protects kidney cells from cisplatin-induced cell death in vitro and in vivo. Now we show that E2F1 is an important downstream effector of Cdk2 that accumulates in mouse kidneys and in cultured mouse proximal tubular cells (TKPTS) after cisplatin exposure by a Cdk2-dependent mechanism. Direct inhibition of E2F1 by transduction with adenoviruses expressing an E2F1-binding protein (TopBP1) protected TKPTS cells from cisplatin-induced apoptosis, whereas overexpression of E2F1 caused cell death. Moreover, E2F1 knockout mice were markedly protected against cisplatin nephrotoxicity by both functional and histological criteria. Collectively, cisplatin-induced cell death is dependent on Cdk2 activity, which is at least partly through the Cdk2-E2F1 pathway both in vitro and in vivo.
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Affiliation(s)
- Fang Yu
- Dept. of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, USA
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37
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Bozzetti C, Nizzoli R, Musolino A, Martella EM, Crafa P, Lagrasta CA, Camisa R, Bonati A, Lunghi P, Ardizzoni A. p73 and p53 Pathway in Human Breast Cancers. J Clin Oncol 2007; 25:1451-3; author reply 1453-4. [PMID: 17416871 DOI: 10.1200/jco.2006.09.2023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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Nowak K, Killmer K, Gessner C, Lutz W. E2F-1 regulates expression of FOXO1 and FOXO3a. ACTA ACUST UNITED AC 2007; 1769:244-52. [PMID: 17482685 DOI: 10.1016/j.bbaexp.2007.04.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Revised: 03/28/2007] [Accepted: 04/02/2007] [Indexed: 12/13/2022]
Abstract
E2F and FOXO transcription factors both play a role in neuronal apoptosis. In addition, both E2F-induced apoptosis and FOXO function are inhibited by the kinase Akt. We therefore tested whether FOXO is downstream of E2F-1 during neuronal apoptosis. We found that expression of endogenous FOXO1 and FOXO3a is induced by E2F-1. The presence of putative E2F binding sites in the promoters of both genes suggested that FOXO genes are direct targets of E2F-1. Indeed, a 4-hydroxytamoxifen activated E2F-1-ER fusion protein induced FOXO expression in the presence of cycloheximide. Moreover, E2F-1 activated the FOXO1 promoter in transient reporter assays, and E2F-1-ER as well as endogenous E2F bound to the FOXO1 promoter in vivo. Yet, E2F-1-mediated apoptosis of differentiated PC12 cells after withdrawal of NGF was not accompanied by changes in FOXO expression, indicating that no transcriptional induction of FOXO occurs during E2F-1-dependent neuronal apoptosis. In summary, our data identify E2F-1 as a first transcription factor regulating FOXO expression, providing a link between E2F and FOXO proteins in the control of cell fate.
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Affiliation(s)
- Katrin Nowak
- Institute of Molecular Biology and Tumor Research (IMT), Emil-Mannkopff-Strasse 2, 35033 Marburg, Germany
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39
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Abstract
Antisilencing function 1 (ASF1) is a conserved histone chaperone implicated in nucleosome assembly, transcriptional silencing, and the cellular response to DNA damage. Here, we report the identification of human ASF1B, but not ASF1A, as a direct transcriptional target of transcription factor E2F1. We demonstrated that overexpression of E2F1 by adenoviral-mediated gene transfer upregulated ASF1B mRNA expression in HeLa cells. Analysis of human ASF1B promoter constructs showed that an E2F-responsive sequence was necessary for E2F1-induced activation of the ASF1B gene transcription. Oligonucleotides including an E2F consensus sequence were specifically bound by E2F1 protein in vitro. Chromatin immunoprecipitation analysis demonstrated that E2F1 bound to an E2F-responsive sequence of the human ASF1B gene. Among the members of the E2F family, E2F1 to E2F5, but not E2F6, activated the ASF1B reporter construct. Sp1 and NFYA failed to induce the activity of the ASF1A and ASF1B promoter. ASF1A and ASF1B mRNA were upregulated by serum stimulation. Taken together, our results suggest that the expression of human ASF1A and ASF1B are upregulated followed by cell proliferation signal, but that of ASF1B is uniquely regulated by transcription factors E2F during cell cycle progression.
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Affiliation(s)
- Reiko Hayashi
- Department of Life Sciences, School of Agriculture, Meiji University, Kanagawa, Japan
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40
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Reimer D, Sadr S, Wiedemair A, Goebel G, Concin N, Hofstetter G, Marth C, Zeimet AG. Expression of the E2F family of transcription factors and its clinical relevance in ovarian cancer. Ann N Y Acad Sci 2007; 1091:270-81. [PMID: 17341621 DOI: 10.1196/annals.1378.073] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The E2F family of transcription factors plays a pivotal role in the regulation of cellular proliferation. On the basis of sequence homology and function, eight distinct members of E2F transcription factors (E2F-1 to E2F-8) have been distinguished to date. The regulation of E2F transcription factors is closely associated with the function of the retinoblastoma family of tumor suppressors (RB pathway). In the last decade various alterations of distinct components of the RB-E2F pathway were found to be associated with tumor progression. However, no data on the role of E2F family members are available in tumor biology of ovarian cancer. Here we describe an expression study of E2F transcription factors in various human ovarian cancer cell lines; its clinical relevance was examined in a training set of 77 ovarian cancer patients. Expression levels of E2F-1, E2F-2, and E2F-8 were elevated in all the ovarian cancer cell lines studied when compared with human peritoneal mesothelial cells (HPMCs). Interestingly, EGF treatment showed a time-dependent upregulation of the activating transcription factor E2F-3 and a simultaneous increase of DP-1, the heterodimeric partner of E2F-3. High expression of E2F-1, E2F-2, and E2F-8 was found to be associated with histopathologic grade 3 tumors and residual tumor over 2 cm in diameter after primary debulking surgery in ovarian cancer patients. Taken together, these data suggest that the proliferation-promoting E2F transcription factors E2F-1 and especially E2F-2 play a pivotal role in tumor biology of ovarian cancer and may be candidates for specific therapeutic targets.
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Affiliation(s)
- Daniel Reimer
- Department of Obstetrics and Gynecology, Medical University Innsbruck, Anichstrasse 35, A-6020 Innsbruck.
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41
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Abstract
The retinoblastoma tumor suppressor (RB) restricts cell proliferation by regulating members of the E2F family of transcription factors. In human tumors RB is often inactivated, resulting in aberrant E2F-dependent transcription and uncontrolled proliferation. One of the E2F proteins, E2F1, can also induce apoptosis. The extent of E2F1-induced apoptosis is known to be tissue- and cell-specific, but until now, it has been unclear what variables determine cellular sensitivity to E2F1-induced apoptosis in vivo. A recent study reveals epidermal growth factor receptor (EGFR) signaling to be one such variable, as EGFR signaling cooperates with RB in inhibiting E2F1-induced apoptosis. This finding raises the possibility that therapeutic manipulation of EGFR signaling may specifically trigger the death of cancer cells with inactive RB, thereby enabling "targeted" cancer treatments.
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Affiliation(s)
- Doron Ginsberg
- Mina and Everard Goodman Faculty of Life Science, Bar Ilan University, Ramat Gan 52900, Israel.
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42
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Abstract
Dmp1 (cyclin D binding myb-like protein 1; also called Dmtf1) is a transcription factor that was isolated in a yeast two-hybrid screen through its binding property to cyclin D2. Although it was initially predicted to be involved in the cyclin D-Rb pathway, overexpression of Dmp1 in primary cells induces cell cycle arrest in an Arf, p53-dependent fashion. Dmp1 is a unique Arf regulator, the promoter of which is activated by oncogenic Ras-Raf signaling. Dmp1 expression is repressed by physiological mitogenic stimuli as well as by overexpressed E2F proteins; thus, it is a novel marker of cells that have exited from the cell cycle. Spontaneous and oncogene-induced tumor formation is accelerated in both Dmp1(+/-) and Dmp1(-/-) mice; the Dmp1(+/-) tumors often retain and express the wild-type allele; thus, Dmp1 is haplo-insufficient for tumor suppression. Tumors from Dmp1(+/-) and Dmp1(-/-) mice often retain wild-type Arf and p53, suggesting that Dmp1 is a physiological regulator of the Arf-p53 pathway. The human DMP1 (hDMP1) gene is located on chromosome 7q21, the locus of which is often deleted in myeloid leukemia and also in some types of solid tumors. Post-translational modification of Dmp1 and its role in human malignancy remain to be investigated.
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Affiliation(s)
- K Inoue
- Department of Pathology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157-0001, USA.
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43
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Timmers C, Sharma N, Opavsky R, Maiti B, Wu L, Wu J, Orringer D, Trikha P, Saavedra HI, Leone G. E2f1, E2f2, and E2f3 control E2F target expression and cellular proliferation via a p53-dependent negative feedback loop. Mol Cell Biol 2007; 27:65-78. [PMID: 17167174 PMCID: PMC1800646 DOI: 10.1128/mcb.02147-05] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
E2F-mediated control of gene expression is believed to have an essential role in the control of cellular proliferation. Using a conditional gene-targeting approach, we show that the targeted disruption of the entire E2F activator subclass composed of E2f1, E2f2, and E2f3 in mouse embryonic fibroblasts leads to the activation of p53 and the induction of p53 target genes, including p21(CIP1). Consequently, cyclin-dependent kinase activity and retinoblastoma (Rb) phosphorylation are dramatically inhibited, leading to Rb/E2F-mediated repression of E2F target gene expression and a severe block in cellular proliferation. Inactivation of p53 in E2f1-, E2f2-, and E2f3-deficient cells, either by spontaneous mutation or by conditional gene ablation, prevented the induction of p21(CIP1) and many other p53 target genes. As a result, cyclin-dependent kinase activity, Rb phosphorylation, and E2F target gene expression were restored to nearly normal levels, rendering cells responsive to normal growth signals. These findings suggest that a critical function of the E2F1, E2F2, and E2F3 activators is in the control of a p53-dependent axis that indirectly regulates E2F-mediated transcriptional repression and cellular proliferation.
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Affiliation(s)
- Cynthia Timmers
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Nidhi Sharma
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Rene Opavsky
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Baidehi Maiti
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Lizhao Wu
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Juan Wu
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Daniel Orringer
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Prashant Trikha
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Harold I. Saavedra
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
| | - Gustavo Leone
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Department of Molecular Genetics, Comprehensive
Cancer Center, The Ohio State University, Columbus, Ohio
43210
- Correspondingauthor. Mailing address: 410 W. 12th Avenue, Rm. 455B, Columbus, OH
43210. Phone: (614) 688-4567. Fax: (614) 292-3312. E-mail:
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Cucina A, Biava PM, D'Anselmi F, Coluccia P, Conti F, di Clemente R, Miccheli A, Frati L, Gulino A, Bizzarri M. Zebrafish embryo proteins induce apoptosis in human colon cancer cells (Caco2). Apoptosis 2006; 11:1617-28. [PMID: 16820966 DOI: 10.1007/s10495-006-8895-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Previous studies have shown that proteins extracted from Zebrafish embryo share some cytostatic characteristics in cancer cells. Our study was conducted to ascertain the biological properties of this protein network. Cancer cell growth and apoptosis were studied in Caco2 cells treated with embryonic extracts. Cell proliferation was significantly inhibited in a dose-dependent manner. Cell-cycle analysis in treated cells revealed a marked accumulation in the G(2)/M phase preceding induction of apoptosis. Embryo proteins induced a significant reduction in FLIP levels, and increased caspase-3 and caspase-8 activity as well as the apoptotic rate. Increased phosphorylated pRb values were obtained in treated Caco2 cells: the modified balance in pRb phosphorylation was associated with an increase in E2F1 values and c-Myc over-expression. Our data support previous reports of an apoptotic enhancing effect displayed by embryo extracts, mainly through the pRb/E2F1 apoptotic pathway, which thus suggests that Zebrafish embryo proteins have complex anti-cancer properties.
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Affiliation(s)
- Alessandra Cucina
- Department of Surgery, Pietro Valdoni, Università La Sapienza, Roma, Rome
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45
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Tort F, Bartkova J, Sehested M, Orntoft T, Lukas J, Bartek J. Retinoblastoma pathway defects show differential ability to activate the constitutive DNA damage response in human tumorigenesis. Cancer Res 2006; 66:10258-63. [PMID: 17079443 DOI: 10.1158/0008-5472.can-06-2178] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Loss of G(1)-S control and aberrations of the p16(Ink4a)-cyclin D1/cyclin-dependent kinase (CDK) 4(6)-pRb-E2F-cyclin E/CDK2 pathway are common in human cancer. Previous studies showed that oncogene-induced aberrant proliferation, such as on cyclin E overexpression, causes DNA damage and checkpoint activation. Here, we show that, in a series of human colorectal adenomas, those with deregulation of cyclin D1 and/or p16(Ink4a) showed little evidence of constitutive DNA damage response (DDR), contrary to cyclin E-overexpressing higher-grade cases. These observations were consistent with diverse cell culture models with differential defects of retinoblastoma pathway components, as overexpression of cyclin D1 or lack of p16(Ink4a), either alone or combined, did not elicit detectable DDR. In contrast, inactivation of pRb, the key component of the pathway, activated the DDR in cultured human or mouse cells, analogous to elevated cyclin E. These results highlight differential effect of diverse oncogenic events on driving the 'cancer cell cycles' and their ability to deregulate the replication-driving CDK2 kinase and to alarm the DDR as a potential anticancer barrier in accordance with their hierarchical positions along the retinoblastoma pathway. Our data provide new insights into oncogene-evoked DDR in human tumorigenesis, with potential implications for individualized management of tumors with elevated cyclin D1 versus cyclin E, due to their distinct clinical variables and biological behavior.
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Affiliation(s)
- Frederic Tort
- Institute of Cancer Biology and Centre for Genotoxic Stress Research, Danish Cancer Society, Copenhagen, Denmark
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46
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Lee JJ, Kim S, Yeom YI, Heo DS. Enhanced specificity of the p53 family proteins-based adenoviral gene therapy in uterine cervical cancer cells with E2F1-responsive promoters. Cancer Biol Ther 2006; 5:1502-10. [PMID: 17012841 DOI: 10.4161/cbt.5.11.3300] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
p63 and p73, the p53 family proteins, are similar to p53 in many aspects: structural homology, transactivation of p53-downstream genes, and induction of apoptosis. Interestingly, they also differ from p53; in particular, they are not inhibited by viral oncoproteins such as HPV E6. This feature would be an advantage over p53 in HPV-associated cancers and therefore, we evaluated the therapeutic potentials of various p53 family proteins (p73alpha, p73beta, p63alpha and p63gamma) against HPV-infected cervical cancers. In clonogenic assay, exogenous expression of p73alpha, p73beta and p63gamma inhibited the colony formation of HPV-positive cervical cancer cells under G418- selection while p53 could not. Recombinant adenoviruses Ad/CMVp73alpha, Ad/CMVp73beta and Ad/CMVp63gamma induced potent apoptosis in all infected cervical cancers (CasKi, SiHa, HeLa, C33A, SNU682, SNU17, SNU1005, SNU703), irrespective of their HPV-infection status. Unfortunately however, Ad/CMVp73alpha, Ad/CMVp73beta, and Ad/CMVp63gamma inhibited also normal cells such as endothelial cells, fibroblasts, and keratinocytes thus, tumorspecific promoter was indispensable to the p53 family proteins-based therapy. Here we report a stringent tumor killing by p73beta in combination with ESM6, a synthetic promoter targeting the DNA tumor virusassociated cancers. Recombinant adenoviruses encoding p73beta by ESM6 (Ad/ESM6p73beta and Ad/ESM6p73bENH) expressed p73beta and induced apoptosis only in the cancer cells but not in normal cells. Collectively, we suggest that the p53 family proteins are potent therapeutic agents for HPV-associated uterine cervical cancers and ESM6 mediated expression of the p53 family proteins would be a safe and strong tumor targeting strategy.
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Affiliation(s)
- Jae-Jung Lee
- Cancer Research Institute, Seoul National University Hospital, Seoul, Korea
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Shimizu S, Khan MZ, Hippensteel RL, Parkar A, Raghupathi R, Meucci O. Role of the transcription factor E2F1 in CXCR4-mediated neurotoxicity and HIV neuropathology. Neurobiol Dis 2006; 25:17-26. [PMID: 17011204 PMCID: PMC1762194 DOI: 10.1016/j.nbd.2006.08.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 08/08/2006] [Accepted: 08/15/2006] [Indexed: 11/28/2022] Open
Abstract
This study sought to determine the role of the transcription factor E2F1 in CXCR4-mediated neurotoxicity and HIV neuropathology. We studied the effect of the HIV envelope protein gp120 on the expression of E2F1-dependent apoptotic proteins in human and rodent neurons and examined the expression pattern of E2F1 in the brain of HIV-infected individuals. Our findings suggest that in cultured neurons gp120 increased E2F1 levels in the nucleus, stimulated its transcriptional activity and enhanced the expression of the E2F1 target proteins Cdc2 and Puma. Studies with neuronal cultures from E2F1 deficient mice demonstrated that the transcription factor is required for gp120-induced neurotoxicity and up-regulation of Cdc2 and Puma. Levels of E2F1 protein were greater in the nucleus of neurons in brains of HIV-infected patients exhibiting dementia when compared to HIV-negative subjects or HIV-positive neurologically normal patients. Overall, these studies indicate that E2F1 is primarily involved in CXCR4-mediated neurotoxicity and HIV neuropathogenesis.
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Affiliation(s)
| | | | | | | | - Ramesh Raghupathi
- Neurobiology and Anatomy, Drexel University, College of
Medicine, 245 North 15 Street, NCB 8804, Philadelphia, PA 19102,
USA
| | - Olimpia Meucci
- Departments of Pharmacology and Physiology and
- Correspondence to: Olimpia Meucci, M.D., Ph.D.,
Department of Pharmacology and Physiology, Drexel University College of
Medicine, 245 North 15 Street, Philadelphia, PA 19102, Phone: (215)
762-2597, Fax: (215) 762-2299,
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Sharma N, Timmers C, Trikha P, Saavedra HI, Obery A, Leone G. Control of the p53-p21CIP1 Axis by E2f1, E2f2, and E2f3 is essential for G1/S progression and cellular transformation. J Biol Chem 2006; 281:36124-31. [PMID: 17008321 DOI: 10.1074/jbc.m604152200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The E2F family of transcription factors is believed to have an essential role in the control of cellular proliferation by regulating the transcription of genes involved in cell cycle progression. Previous work has demonstrated that the targeted inactivation of E2f1, E2f2, and E2f3 results in elevated p21(CIP1) protein levels, loss of E2F target gene expression, and cell cycle arrest at G1/S and G2/M, suggesting a strict requirement for these E2Fs in the control of normal cellular proliferation. We now demonstrate that E2f1, E2f2, and E2f3 are also required for oncogene-mediated transformation of mouse embryonic fibroblasts. Analysis of synchronized populations of mouse embryonic fibroblasts revealed that the inactivation of p21(CIP1) restores the ability of E2f1-3-deficient cells to enter and transit through G1/S (but not G2/M). In contrast, loss of p53 restored the ability of these cells to progress through both G1/S and mitosis, leading to their continued proliferation. The inactivation of p53 (but not p21(CIP1)) rendered E2f1-3-deficient cells sensitive to transformation and tumorigenesis. These results suggest that the negative regulation of the p53-p21(CIP1) axis by the E2F1-3 factors is critical for cell cycle progression and cellular transformation.
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Affiliation(s)
- Nidhi Sharma
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology, and Medical Genetics, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA
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Chong ZZ, Li F, Maiese K. Attempted cell cycle induction in post-mitotic neurons occurs in early and late apoptotic programs through Rb, E2F1, and caspase 3. Curr Neurovasc Res 2006; 3:25-39. [PMID: 16472123 PMCID: PMC1986668 DOI: 10.2174/156720206775541741] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Either the absence or dysfunction of a number of critical pathways, such as those that involve the nuclear retinoblastoma protein (Rb) and the transcription factor E2F1, may account for the aberrant induction of the cell cycle in post-mitotic neurons that can be responsible for oxidative stress-induced apoptotic cellular destruction. Yet, it is unclear whether early programs of apoptotic injury that involve membrane phosphatidylserine (PS) exposure and calreticulin expression as well as later phases of apoptotic injury with nuclear DNA injury require the critical modulation of Rb and E2F1. We demonstrate that both the post-translational of phosphorylation of Rb to prevent E2F1 transcription as well as the protein integrity of Rb are closely aligned with the modulation of cell cycle induction in post mitotic neurons during oxidative stress. More importantly, we illustrate that both the initial onset of apoptosis with either membrane PS exposure or calreticulin analysis as well as the more terminal phases of apoptosis that involve nuclear DNA degradation proceed concurrently in the same neuronal cells with cell cycle induction. Progression of attempted cell cycle induction is closely associated with the phosphorylation of Rb, its inability to bind to E2F1, and the degradation of the Rb protein. Inhibition of Rb phosphorylation using cyclin dependent kinase inhibitors maintains the integrity of the E2F1/Rb complex and is neuroprotective during free radical exposure. Furthermore, maintenance of the integrity of the Rb protein is specifically dependent upon caspase 3-like activity, since caspase 3 can cleave Rb during free radical activity and this degradation of Rb can be blocked during the inhibition of caspase 3 activity. Our studies not only highlight the critical role of attempted cell cycle induction during oxidative stress-induced neuronal apoptotic injury, but also bring to light the significant impact of the Rb and E2F1 pathways upon early apoptotic programs that can directly influence both intrinsic cell survival as well as extrinsic inflammatory cell activation.
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Affiliation(s)
- Zhao Zhong Chong
- Division of Cellular and Molecular Cerebral Ischemia, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Faqi Li
- Division of Cellular and Molecular Cerebral Ischemia, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Kenneth Maiese
- Division of Cellular and Molecular Cerebral Ischemia, Wayne State University School of Medicine, Detroit, Michigan 48201
- Departments of Neurology and Anatomy & Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan 48201
- Center for Molecular and Cellular Toxicology, Wayne State University School of Medicine, Detroit, Michigan 48201
- *Address corresponding to this author at the Department of Neurology, 8C-1 UHC, Wayne State University School of Medicine, 4201 St. Antoine, Detroit, MI 48201, USA; Tel: 313-966-0833; Fax: 313-966-0486; E-mail: ,
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Ebelt H, Liu Z, Müller-Werdan U, Werdan K, Braun T. Making omelets without breaking eggs: E2F-mediated induction of cardiomyoycte cell proliferation without stimulation of apoptosis. Cell Cycle 2006; 5:2436-9. [PMID: 17102628 DOI: 10.4161/cc.5.21.3402] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The fundamental role of E2F transcription factors in the regulation of proliferation is well established. According to a widely accepted model, E2F1, E2F2, and E2F3 are classified as "activating" E2Fs since they induce proliferation of quiescent cells whereas E2F4 and E2F5 do not have the power to incite cell cycle progression but are related to differentiation processes and were therefore considered to be "repressive". In addition, it has been postulated that "activating" E2Fs induce apoptosis in a wide variety of cell types depending on their expression level. However, we demonstrated recently that this 'threshold model' does not hold true for cardiomyocytes. In a series of experiments in which we overexpressed individual E2Fs we found that directed expression of E2F2, unlike E2F1, E2F3 and E2F5, did not induce apoptosis but even suppressed expression of several pro-apoptotic genes in primary cardiomyocytes. Furthermore, we established that not only E2F1, E2F2, and E2F3 but also E2F4 was able to induce S-phase entry of primary cardiomyocytes. Our results suggest that it is possible to utilize the proliferation-inducing properties of the E2Fs in cardiomyocytes without activation of potentially harmful pro-apoptotic traits. This finding might open a new access to stimulate regeneration in postmitotic tissues such as the heart.
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Affiliation(s)
- Henning Ebelt
- Department of Medicine III, Martin-Luther-University, Halle, Germany
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