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Parisi T, Balsamo M, Gertler F, Lees JA. The Rb tumor suppressor regulates epithelial cell migration and polarity. Mol Carcinog 2018; 57:1640-1650. [PMID: 30084175 DOI: 10.1002/mc.22886] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 07/30/2018] [Indexed: 12/18/2022]
Abstract
Altered cell polarity and migration are hallmarks of cancer and metastases. Here we show that inactivation of the retinoblastoma gene (Rb) tumor suppressor causes defects in tissue closure that reflect the inability of Rb null epithelial cells to efficiently migrate and polarize. These defects occur independently of pRB's anti-proliferative role and instead correlate with upregulation of RhoA signaling and mislocalization of apical-basal polarity proteins. Notably, concomitant inactivation of tp53 specifically overrides the motility defect, and not the aberrant polarity, thereby uncovering previously unappreciated mechanisms by which Rb and tp53 mutations cooperate to promote cancer development and metastases.
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Affiliation(s)
- Tiziana Parisi
- The David H. Koch Institute for Integrative Cancer Research, Cambridge, Massachusetts
| | - Michele Balsamo
- The David H. Koch Institute for Integrative Cancer Research, Cambridge, Massachusetts
| | - Frank Gertler
- The David H. Koch Institute for Integrative Cancer Research, Cambridge, Massachusetts.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Jacqueline A Lees
- The David H. Koch Institute for Integrative Cancer Research, Cambridge, Massachusetts.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
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2
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Long noncoding RNA GAS5 promotes bladder cancer cells apoptosis through inhibiting EZH2 transcription. Cell Death Dis 2018; 9:238. [PMID: 29445179 PMCID: PMC5833416 DOI: 10.1038/s41419-018-0264-z] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 12/16/2017] [Accepted: 12/22/2017] [Indexed: 12/24/2022]
Abstract
Aberrant expression of long noncoding RNA GAS5 in bladder cancer (BC) cells was identified in recent studies. However, the regulatory functions and underlying molecular mechanisms of GAS5 in BC development remain unclear. Here, we confirmed that there was a negative correlation between GAS5 level and bladder tumor clinical stage. Functionally, overexpression of GAS5 reduced cell viability and induced cell apoptosis in T24 and EJ bladder cancer cells. Mechanistically, GAS5 effectively repressed EZH2 transcription by directly interacting with E2F4 and recruiting E2F4 to EZH2 promoter. We previously reported that miR-101 induced the apoptosis of BC cells by inhibiting the expression of EZH2. Interestingly, the present study showed that downregulation of EZH2 by GAS5 resulted in overexpression of miR-101 in T24 and EJ cells. Furthermore, the level of GAS5 was increased under the treatment of Gambogic acid (GA), a promising natural anti-cancer compound, whereas knockdown of GAS5 suppressed the inhibitory effect of GA on cell viability and abolished GA-induced apoptosis in T24 and EJ cells. Taken together, our findings demonstrated a tumor-suppressor role of GAS5 by inhibiting EZH2 on transcriptional level, and additionally provided a novel therapeutic strategy for treating human bladder cancer.
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Inactivation of the retinoblastoma gene yields a mouse model of malignant colorectal cancer. Oncogene 2015; 34:5890-9. [PMID: 25745996 PMCID: PMC4668801 DOI: 10.1038/onc.2015.30] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 11/22/2014] [Accepted: 11/25/2014] [Indexed: 02/07/2023]
Abstract
The retinoblastoma gene (Rb) is mutated at significant frequency in various human epithelial tumors, including colorectal cancer, and is strongly associated with metastatic disease. However, sole inactivation of Rb in the mouse has so far failed to yield epithelial cancers. Here, we specifically inactivate Rb and/or p53 in the urogenital epithelium and the intestine. We find that loss of both tumor suppressors is unable to yield tumors in the transitional epithelium lining the bladder, kidneys and ureters. Instead, these mice develop highly metastatic tumors of neuroendocrine, not epithelial, origin within the urogenital tract to give prostate cancer in the males and vaginal tumors in the females. Additionally, we discovered that the sole inactivation of Rb in the intestine was sufficient to induce formation of metastatic colorectal adenocarcinomas. These tumors closely mirror the human disease in regard to age of onset, histological appearance, invasiveness and metastatic potential. Like most human colorectal carcinomas, our murine Rb-deficient tumors demonstrate genomic instability and they show activation of β-catenin. Deregulation of the Wnt/β-catenin pathway is specific to the intestinal tumors, as genomic instability but not activation of β-catenin was observed in the neuroendocrine tumors. To date, attempts to generate genetically engineered mouse models of colorectal cancer tumors have yielded mostly cancer of the small intestine, which rarely occurs in humans. Our system provides the opportunity to accurately model and study colorectal cancer in the mouse via a single gene mutation.
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Costa C, Paramio JM, Santos M. Skin Tumors Rb(eing) Uncovered. Front Oncol 2013; 3:307. [PMID: 24381932 PMCID: PMC3865458 DOI: 10.3389/fonc.2013.00307] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 12/04/2013] [Indexed: 11/23/2022] Open
Abstract
The Rb1 gene was the first bona fide tumor suppressor identified and cloned more than 25 years ago. Since then, a plethora of studies have revealed the functions of pRb and the existence of a sophisticated and strictly regulated pathway that modulates such functional roles. An emerging paradox affecting Rb1 in cancer connects the relatively low number of mutations affecting Rb1 gene in specific human tumors, compared with the widely functional inactivation of pRb in most, if not in all, human cancers. The existence of a retinoblastoma family of proteins pRb, p107, and p130 and their potential unique and overlapping functions as master regulators of cell cycle progression and transcriptional modulation by similar processes, may provide potential clues to explain such conundrum. Here, we will review the development of different genetically engineered mouse models, in particular those affecting stratified epithelia, and how they have offered new avenues to understand the roles of the Rb family members and their targets in the context of tumor development and progression.
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Affiliation(s)
- Clotilde Costa
- Molecular Oncology Unit, Department of Basic Research, Centro de Investigaciones Energéticas Medioambientales y Teconológicas (ed70A) , Madrid , Spain
| | - Jesús M Paramio
- Molecular Oncology Unit, Department of Basic Research, Centro de Investigaciones Energéticas Medioambientales y Teconológicas (ed70A) , Madrid , Spain
| | - Mirentxu Santos
- Molecular Oncology Unit, Department of Basic Research, Centro de Investigaciones Energéticas Medioambientales y Teconológicas (ed70A) , Madrid , Spain
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Di Fiore R, D'Anneo A, Tesoriere G, Vento R. RB1 in cancer: different mechanisms of RB1 inactivation and alterations of pRb pathway in tumorigenesis. J Cell Physiol 2013; 228:1676-87. [PMID: 23359405 DOI: 10.1002/jcp.24329] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 01/15/2013] [Indexed: 12/14/2022]
Abstract
Loss of RB1 gene is considered either a causal or an accelerating event in retinoblastoma. A variety of mechanisms inactivates RB1 gene, including intragenic mutations, loss of expression by methylation and chromosomal deletions, with effects which are species-and cell type-specific. RB1 deletion can even lead to aneuploidy thus greatly increasing cancer risk. The RB1gene is part of a larger gene family that includes RBL1 and RBL2, each of the three encoding structurally related proteins indicated as pRb, p107, and p130, respectively. The great interest in these genes and proteins springs from their ability to slow down neoplastic growth. pRb can associate with various proteins by which it can regulate a great number of cellular activities. In particular, its association with the E2F transcription factor family allows the control of the main pRb functions, while the loss of these interactions greatly enhances cancer development. As RB1 gene, also pRb can be functionally inactivated through disparate mechanisms which are often tissue specific and dependent on the scenario of the involved tumor suppressors and oncogenes. The critical role of the context is complicated by the different functions played by the RB proteins and the E2F family members. In this review, we want to emphasize the importance of the mechanisms of RB1/pRb inactivation in inducing cancer cell development. The review is divided in three chapters describing in succession the mechanisms of RB1 inactivation in cancer cells, the alterations of pRb pathway in tumorigenesis and the RB protein and E2F family in cancer.
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Affiliation(s)
- Riccardo Di Fiore
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Polyclinic, University of Palermo, Palermo, Italy
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Tong Y, Zheng Y, Zhou J, Oyesiku NM, Koeffler HP, Melmed S. Genomic characterization of human and rat prolactinomas. Endocrinology 2012; 153:3679-91. [PMID: 22635680 PMCID: PMC3404356 DOI: 10.1210/en.2012-1056] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Although prolactinomas can be effectively treated with dopamine agonists, about 20% of patients develop dopamine resistance or tumor recurrence after surgery, indicating a need for better understanding of underlying disease mechanisms. Although estrogen-induced rat prolactinomas have been widely used to investigate the development of this tumor, the extent that the model recapitulates features of human prolactinomas is unclear. To prioritize candidate genes and gene sets regulating human and rat prolactinomas, microarray results derived from human prolactinomas and pituitaries of estrogen-treated ACI rats were integrated and analyzed. A total of 4545 differentially expressed pituitary genes were identified in estrogen-treated ACI rats [false discovery rate (FDR) < 0.01]. By comparing pituitary microarray results derived from estrogen-treated Brown Norway rats (a strain not sensitive to estrogen), 4073 genes were shown specific to estrogen-treated ACI rats. Human prolactinomas exhibited 1177 differentially expressed genes (FDR < 0.05). Combining microarray data derived from human prolactinoma and pituitaries of estrogen-treated ACI rat, 145 concordantly expressed genes, including E2F1, Myc, Igf1, and CEBPD, were identified. Gene set enrichment analysis revealed that 278 curated pathways and 59 gene sets of transcription factors were enriched (FDR < 25%) in estrogen-treated ACI rats, suggesting a critical role for Myc, E2F1, CEBPD, and Sp1 in this rat prolactinoma. Similarly increased Myc, E2F1, and Sp1 expression was validated using real-time PCR and Western blot in estrogen-treated Fischer rat pituitary glands. In summary, characterization of individual genes and gene sets in human and in estrogen-induced rat prolactinomas validates the model and provides insights into genomic changes associated with this commonly encountered pituitary tumor.
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Affiliation(s)
- Yunguang Tong
- Department of Medicine, Cedars-Sinai Medical Center, Academic Affairs, Room 2015, 8700 Beverly Boulevard, Los Angeles, California 90048, USA
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Jiang Y, Yim SH, Xu HD, Jung SH, Yang SY, Hu HJ, Jung CK, Chung YJ. A potential oncogenic role of the commonly observed E2F5 overexpression in hepatocellular carcinoma. World J Gastroenterol 2011; 17:470-7. [PMID: 21274376 PMCID: PMC3027013 DOI: 10.3748/wjg.v17.i4.470] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 11/25/2010] [Accepted: 12/02/2010] [Indexed: 02/06/2023] Open
Abstract
AIM: To explore the expression pattern of E2F5 in primary hepatocellular carcinomas (HCCs) and elucidate the roles of E2F5 in hepatocarcinogenesis.
METHODS: E2F5 expression was analyzed in 120 primary HCCs and 29 normal liver tissues by immunohistochemistry analysis. E2F5-small interfering RNA was transfected into HepG2, an E2F5-overexpressed HCC cell line. After E2F5 knockdown, cell growth capacity and migrating potential were examined.
RESULTS: E2F5 was significantly overexpressed in primary HCCs compared with normal liver tissues (P = 0.008). The E2F5-silenced cells showed significantly reduced proliferation (P = 0.004). On the colony formation and soft agar assays, the number of colonies was significantly reduced in E2F5-silenced cells (P = 0.004 and P = 0.009, respectively). E2F5 knockdown resulted in the accumulation of G0/G1 phase cells and a reduction of S phase cells. The number of migrating/invading cells was also reduced after E2F5 knockdown (P = 0.021).
CONCLUSION: To our knowledge, this is the first evidence that E2F5 is commonly overexpressed in primary HCC and that E2F5 knockdown significantly repressed the growth of HCC cells.
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Ríos Y, Melmed S, Lin S, Liu NA. Zebrafish usp39 mutation leads to rb1 mRNA splicing defect and pituitary lineage expansion. PLoS Genet 2011; 7:e1001271. [PMID: 21249182 PMCID: PMC3020934 DOI: 10.1371/journal.pgen.1001271] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Accepted: 12/08/2010] [Indexed: 11/30/2022] Open
Abstract
Loss of retinoblastoma (Rb) tumor suppressor function is associated with human malignancies. Molecular and genetic mechanisms responsible for tumorigenic Rb downregulation are not fully defined. Through a forward genetic screen and positional cloning, we identified and characterized a zebrafish ubiquitin specific peptidase 39 (usp39) mutation, the yeast and human homolog of which encodes a component of RNA splicing machinery. Zebrafish usp39 mutants exhibit microcephaly and adenohypophyseal cell lineage expansion without apparent changes in major hypothalamic hormonal and regulatory signals. Gene expression profiling of usp39 mutants revealed decreased rb1 and increased e2f4, rbl2 (p130), and cdkn1a (p21) expression. Rb1 mRNA overexpression, or antisense morpholino knockdown of e2f4, partially reversed embryonic pituitary expansion in usp39 mutants. Analysis of pre-mRNA splicing status of critical cell cycle regulators showed misspliced Rb1 pre-mRNA resulting in a premature stop codon. These studies unravel a novel mechanism for rb1 regulation by a neuronal mRNA splicing factor, usp39. Zebrafish usp39 regulates embryonic pituitary homeostasis by targeting rb1 and e2f4 expression, respectively, contributing to increased adenohypophyseal sensitivity to these altered cell cycle regulators. These results provide a mechanism for dysregulated rb1 and e2f4 pathways that may result in pituitary tumorigenesis. Previous studies have shown that Rb+/− mice develop pituitary adenomas; however, RB1 mutations have not been found in human pituitary tumors. In the present study, we uncovered a novel genetic pathway that may lead to Rb downregulation through RNA splicing mediated by usp39, a gene involved in assembly of the spliceosome. Our forward genetic study in zebrafish suggests that loss of usp39 results in aberrant rb1 mRNA splicing, which likely causes elevated expression of its target e2f4, a key regulator known to have oncogenic activity when overexpressed. We established that e2f4 upregulation is a main factor responsible for the adenohypophyseal cell lineage hyperplasia observed in the zebrafish usp39 mutant. It should be of interest to investigate if mutations or downregulation of USP39 would contribute to pituitary tumorigenesis in humans.
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Affiliation(s)
- Yesenia Ríos
- Department of Molecular, Cell, and Developmental Biology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Shlomo Melmed
- Department of Medicine, Cedars-Sinai Medical Center, University of California Los Angeles, Los Angeles, California, United States of America
| | - Shuo Lin
- Department of Molecular, Cell, and Developmental Biology, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail: (SL); (NAL)
| | - Ning-Ai Liu
- Department of Medicine, Cedars-Sinai Medical Center, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail: (SL); (NAL)
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Brown KC, Witte TR, Hardman WE, Luo H, Chen YC, Carpenter AB, Lau JK, Dasgupta P. Capsaicin displays anti-proliferative activity against human small cell lung cancer in cell culture and nude mice models via the E2F pathway. PLoS One 2010; 5:e10243. [PMID: 20421925 PMCID: PMC2857654 DOI: 10.1371/journal.pone.0010243] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Accepted: 03/24/2010] [Indexed: 11/18/2022] Open
Abstract
Background Small cell lung cancer (SCLC) is characterized by rapid progression and low survival rates. Therefore, novel therapeutic agents are urgently needed for this disease. Capsaicin, the active ingredient of chilli peppers, displays anti-proliferative activity in prostate and epidermoid cancer in vitro. However, the anti-proliferative activity of capsaicin has not been studied in human SCLCs. The present manuscript fills this void of knowledge and explores the anti-proliferative effect of capsaicin in SCLC in vitro and in vivo. Methodology/Principal Findings BrdU assays and PCNA ELISAs showed that capsaicin displays robust anti-proliferative activity in four human SCLC cell lines. Furthermore, capsaicin potently suppressed the growth of H69 human SCLC tumors in vivo as ascertained by CAM assays and nude mice models. The second part of our study attempted to provide insight into molecular mechanisms underlying the anti-proliferative activity of capsaicin. We found that the anti-proliferative activity of capsaicin is correlated with a decrease in the expression of E2F-responsive proliferative genes like cyclin E, thymidylate synthase, cdc25A and cdc6, both at mRNA and protein levels. The transcription factor E2F4 mediated the anti-proliferative activity of capsaicin. Ablation of E2F4 levels by siRNA methodology suppressed capsaicin-induced G1 arrest. ChIP assays demonstrated that capsaicin caused the recruitment of E2F4 and p130 on E2F-responsive proliferative promoters, thereby inhibiting cell proliferation. Conclusions/Significance Our findings suggest that the anti-proliferative effects of capsaicin could be useful in the therapy of human SCLCs.
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Affiliation(s)
- Kathleen C. Brown
- Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, United States of America
| | - Ted R. Witte
- Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, United States of America
| | - W. Elaine Hardman
- Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, United States of America
| | - Haitao Luo
- Department of Biology, Alderson-Broaddus College, Phillipi, West Virginia, United States of America
| | - Yi C. Chen
- Department of Biology, Alderson-Broaddus College, Phillipi, West Virginia, United States of America
| | - A. Betts Carpenter
- Department of Anatomy and Pathology, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, United States of America
| | - Jamie K. Lau
- Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, United States of America
| | - Piyali Dasgupta
- Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, United States of America
- * E-mail:
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Schaffer BE, Park KS, Yiu G, Conklin JF, Lin C, Burkhart DL, Karnezis AN, Sweet-Cordero EA, Sage J. Loss of p130 accelerates tumor development in a mouse model for human small-cell lung carcinoma. Cancer Res 2010; 70:3877-83. [PMID: 20406986 DOI: 10.1158/0008-5472.can-09-4228] [Citation(s) in RCA: 175] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Small-cell lung carcinoma (SCLC) is a neuroendocrine subtype of lung cancer. Although SCLC patients often initially respond to therapy, tumors nearly always recur, resulting in a 5-year survival rate of less than 10%. A mouse model has been developed based on the fact that the RB and p53 tumor suppressor genes are mutated in more than 90% of human SCLCs. Emerging evidence in patients and mouse models suggests that p130, a gene related to RB, may act as a tumor suppressor in SCLC cells. To test this idea, we used conditional mutant mice to delete p130 in combination with Rb and p53 in adult lung epithelial cells. We found that loss of p130 resulted in increased proliferation and significant acceleration of SCLC development in this triple-knockout mouse model. The histopathologic features of the triple-mutant mouse tumors closely resembled that of human SCLC. Genome-wide expression profiling experiments further showed that Rb/p53/p130-mutant mouse tumors were similar to human SCLC. These findings indicate that p130 plays a key tumor suppressor role in SCLC. Rb/p53/p130-mutant mice provide a novel preclinical mouse model to identify novel therapeutic targets against SCLC.
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Affiliation(s)
- Bethany E Schaffer
- Department of Pediatrics, Stanford Medical School, Stanford, California 94305-5149, USA
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Zhang J, Lee EY, Liu Y, Berman SD, Lodish HF, Lees JA. pRB and E2F4 play distinct cell-intrinsic roles in fetal erythropoiesis. Cell Cycle 2010; 9:371-6. [PMID: 20023434 DOI: 10.4161/cc.9.2.10467] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The retinoblastoma tumor suppressor protein pRB functions, at least in part, by directly binding to and modulating the activity of the E2F transcription factors. Previous studies have shown that both E2F4 and pRB play important roles in fetal erythropoiesis. Given that these two proteins interact directly we investigated the overlap of E2F4 and pRB function in this process by analyzing E2f4(-/-), conditional Rb knockout (Rb(1lox/1lox)), and compound E2f4(-/-);Rb(1lox/1lox) embryos. At E15.5 E2f4(-/-) and Rb(1lox/1lox) fetal erythroid cells display distinct abnormalities in their differentiation profiles. When cultured in vitro, both E2f4(-/-) and Rb(1lox/1lox) erythroid cells show defects in cell cycle progression. Surprisingly, analysis of cell cycle profiling suggests that E2F4 and pRB control cell cycle exit through different mechanisms. Moreover, only pRB, but not E2F4, promotes cell survival in erythroid cells. We observed an additive rather than a synergistic impact upon the erythroid defects in the compound E2f4(-/-);Rb(1lox/1lox) embryos. We further found that fetal liver macrophage development is largely normal regardless of genotype. Taken together, our results show that E2F4 and pRB play independent cell-intrinsic roles in fetal erythropoiesis.
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Affiliation(s)
- Jing Zhang
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA, USA
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van Amerongen MJ, Diehl F, Novoyatleva T, Patra C, Engel FB. E2F4 is required for cardiomyocyte proliferation. Cardiovasc Res 2009; 86:92-102. [DOI: 10.1093/cvr/cvp383] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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Abstract
Mutations of the retinoblastoma tumour suppressor gene (RB1) or components regulating the RB pathway have been identified in almost every human malignancy. The E2F transcription factors function in cell cycle control and are intimately regulated by RB. Studies of model organisms have revealed conserved functions for E2Fs during development, suggesting that the cancer-related proliferative roles of E2F family members represent a recent evolutionary adaptation. However, given that some human tumours have concurrent RB1 inactivation and E2F amplification and overexpression, we propose that there are alternative tumour-promoting activities for the E2F family, which are independent of cell cycle regulation.
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Affiliation(s)
- Hui-Zi Chen
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics and Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA
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Lee EY, Yuan TL, Danielian PS, West JC, Lees JA. E2F4 cooperates with pRB in the development of extra-embryonic tissues. Dev Biol 2009; 332:104-15. [PMID: 19433082 DOI: 10.1016/j.ydbio.2009.05.541] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 04/09/2009] [Accepted: 05/04/2009] [Indexed: 12/20/2022]
Abstract
The retinoblastoma gene, RB-1, was the first identified tumor suppressor. Rb(-/-) mice die in mid-gestation with defects in proliferation, differentiation and apoptosis. The activating E2F transcription factors, E2F1-3, contribute to these embryonic defects, indicating that they are key downstream targets of the retinoblastoma protein, pRB. E2F4 is the major pRB-associated E2F in vivo, yet its role in Rb(-/-) embryos is unknown. Here we establish that E2f4 deficiency reduced the lifespan of Rb(-/-) embryos by exacerbating the Rb mutant placental defect. We further show that this reflects the accumulation of trophectoderm-like cells in both Rb and Rb;E2f4 mutant placentas. Thus, Rb and E2f4 play cooperative roles in placental development. We used a conditional mouse model to allow Rb(-/-);E2f4(-/-) embryos to develop in the presence of Rb wild-type placentas. Under these conditions, Rb(-/-);E2f4(-/-) mutants survived to birth. These Rb(-/-);E2f4(-/-) embryos exhibited all of the defects characteristic of the Rb and E2f4 single mutants and had no novel defects. Taken together, our data show that pRB and E2F4 cooperate in placental development, but play largely non-overlapping roles in the development of many embryonic tissues.
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Affiliation(s)
- Eunice Y Lee
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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