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Jiang YN, Gao Y, Lai X, Li X, Liu G, Ding M, Wang Z, Guo Z, Qin Y, Li X, Sun L, Wang ZQ, Zhou ZW. Microcephaly Gene Mcph1 Deficiency Induces p19ARF-Dependent Cell Cycle Arrest and Senescence. Int J Mol Sci 2024; 25:4597. [PMID: 38731817 PMCID: PMC11083351 DOI: 10.3390/ijms25094597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 03/11/2024] [Revised: 04/10/2024] [Accepted: 04/15/2024] [Indexed: 05/13/2024] Open
Abstract
MCPH1 has been identified as the causal gene for primary microcephaly type 1, a neurodevelopmental disorder characterized by reduced brain size and delayed growth. As a multifunction protein, MCPH1 has been reported to repress the expression of TERT and interact with transcriptional regulator E2F1. However, it remains unclear whether MCPH1 regulates brain development through its transcriptional regulation function. This study showed that the knockout of Mcph1 in mice leads to delayed growth as early as the embryo stage E11.5. Transcriptome analysis (RNA-seq) revealed that the deletion of Mcph1 resulted in changes in the expression levels of a limited number of genes. Although the expression of some of E2F1 targets, such as Satb2 and Cdkn1c, was affected, the differentially expressed genes (DEGs) were not significantly enriched as E2F1 target genes. Further investigations showed that primary and immortalized Mcph1 knockout mouse embryonic fibroblasts (MEFs) exhibited cell cycle arrest and cellular senescence phenotype. Interestingly, the upregulation of p19ARF was detected in Mcph1 knockout MEFs, and silencing p19Arf restored the cell cycle and growth arrest to wild-type levels. Our findings suggested it is unlikely that MCPH1 regulates neurodevelopment through E2F1-mediated transcriptional regulation, and p19ARF-dependent cell cycle arrest and cellular senescence may contribute to the developmental abnormalities observed in primary microcephaly.
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Affiliation(s)
- Yi-Nan Jiang
- Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.-N.J.); (X.L.)
| | - Yizhen Gao
- Shenzhen Key Laboratory of Pathogenic Microbes and Biosafety, School of Public Health (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.G.); (L.S.)
| | - Xianxin Lai
- Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.-N.J.); (X.L.)
| | - Xinjie Li
- Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.-N.J.); (X.L.)
| | - Gen Liu
- Shenzhen Key Laboratory of Pathogenic Microbes and Biosafety, School of Public Health (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.G.); (L.S.)
| | - Mingmei Ding
- Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.-N.J.); (X.L.)
| | - Zhiyi Wang
- Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.-N.J.); (X.L.)
| | - Zixiang Guo
- Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.-N.J.); (X.L.)
| | - Yinying Qin
- Shenzhen Key Laboratory of Pathogenic Microbes and Biosafety, School of Public Health (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.G.); (L.S.)
| | - Xin Li
- Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.-N.J.); (X.L.)
| | - Litao Sun
- Shenzhen Key Laboratory of Pathogenic Microbes and Biosafety, School of Public Health (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.G.); (L.S.)
| | - Zhao-Qi Wang
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China;
| | - Zhong-Wei Zhou
- Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen 518107, China; (Y.-N.J.); (X.L.)
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Boşoteanu LA, Gheorghe E, Aşchie M, Cozaru GC, Deacu M, Orășanu CI, Boşoteanu M. Immunophenotypic p14 and p16 correlations with CDKN2A mutations in primary multiple and familial melanoma: An observational study. Medicine (Baltimore) 2023; 102:e36756. [PMID: 38134090 PMCID: PMC10735120 DOI: 10.1097/md.0000000000036756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 12/01/2023] [Indexed: 12/24/2023] Open
Abstract
Melanoma represents an aggressive malignant tumor, encapsulating frequent loss of differentiation markers, with familial melanoma constituting a relatively commonly encountered entity, in direct relationship with cyclin-dependent kinase inhibitor 2A (CDKN2A). The present study aims to identify the association between the immunohistochemical p14-p16 profile, the molecular CDKN2A findings and clinically diagnosed familial or multiple primary melanomas (MPM). We conducted a 5-year retrospective cross-sectional study, on patients diagnosed with familial or MPM. P14 and p16 immunohistochemical staining has been applied on the selected surgical specimens simultaneously with the performance of fluorescence in situ hybridization (FISH) CDKN2A testing. 13 out of the 23 included cases displayed p14 and/or p16 immunohistochemical absence and the main positive relationships were encountered between CDKN2A homozygous deletion and p14 ± p16 negative immunoreactions. Cases with exclusive p16 absent reaction (n = 7) were more frequently associated with the presence of distant metastases (85.71%), while samples with exclusive p14 immunohistochemical loss exhibited more favorable histopathological prognostic markers. The average percentage of p16-stained nuclei in the superficial dermis and the deep dermis were equal (29.54% for each), therefore infirming its potential predictive and/or prognostic utility. The present study is the first of its type to approach the clinical, evolutionary and immunophenotypic correlations between p14-p16 immunohistochemical testing, CDKN2A molecular biology pattern, familial melanoma and spontaneous MPM in a cohort of Romanian patients. This analysis highlighted the value of singular p16 immunohistochemical absence as a predictor for aggressive biological behavior and unfavorable prognosis in familial melanoma and/or MPM, in comparison with the exclusive loss of p14, indifferent to the histopathological subtype. The present study emphasizes the utility of immunohistochemistry as a less expensive method of complementing the current testing arsenal and could represent the starting point for the elaboration of tailored diagnostic and therapeutic algorithms, based on the discovered p14-p16-CDKN2A significant correlation.
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Affiliation(s)
- Luana-Andreea Boşoteanu
- Department of Dermatovenerology, “Elias” Emergency University Hospital, Bucharest, Romania
- Institute of Doctoral Studies, Doctoral School of Medicine, “Ovidius” University of Constanţa, Constanţa, Romania
| | - Emma Gheorghe
- Department of Dermatology, “Sf. Apostol Andrei” Emergency County Hospital, Constanţa, Romania
- Department of Histology, Faculty of Medicine, “Ovidius” University of Constanţa, Constanţa, Romania
| | - Mariana Aşchie
- Clinical Service of Pathology, “Sf. Apostol Andrei” Emergency County Hospital, Constanţa, Romania
- Department of Pathology, Faculty of Medicine, “Ovidius” University of Constanţa, Constanţa, Romania
- Department VIII – Medical Sciences, Academy of Romanian Scientists, Bucharest, Romania
| | - Georgeta Camelia Cozaru
- Clinical Service of Pathology, “Sf. Apostol Andrei” Emergency County Hospital, Constanţa, Romania
- Center for Research and Development of the Morphological and Genetic Studies of Malignant Pathology (CEDMOG), Constanța, Romania
| | - Mariana Deacu
- Clinical Service of Pathology, “Sf. Apostol Andrei” Emergency County Hospital, Constanţa, Romania
- Department of Pathology, Faculty of Medicine, “Ovidius” University of Constanţa, Constanţa, Romania
| | - Cristian Ionuț Orășanu
- Clinical Service of Pathology, “Sf. Apostol Andrei” Emergency County Hospital, Constanţa, Romania
- Center for Research and Development of the Morphological and Genetic Studies of Malignant Pathology (CEDMOG), Constanța, Romania
| | - Mădălina Boşoteanu
- Clinical Service of Pathology, “Sf. Apostol Andrei” Emergency County Hospital, Constanţa, Romania
- Department of Pathology, Faculty of Medicine, “Ovidius” University of Constanţa, Constanţa, Romania
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Li Q, Huang C, Liu L, Hu R, Qu J. Effect of Surface Coating of Gold Nanoparticles on Cytotoxicity and Cell Cycle Progression. Nanomaterials (Basel) 2018; 8:E1063. [PMID: 30562921 DOI: 10.3390/nano8121063] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 12/12/2018] [Accepted: 12/12/2018] [Indexed: 12/13/2022]
Abstract
Gold nanoparticles (GNPs) are usually wrapped with biocompatible polymers in biomedical field, however, the effect of biocompatible polymers of gold nanoparticles on cellular responses are still not fully understood. In this study, GNPs with/without polymer wrapping were used as model probes for the investigation of cytotoxicity and cell cycle progression. Our results show that the bovine serum albumin (BSA) coated GNPs (BSA-GNPs) had been transported into lysosomes after endocytosis. The lysosomal accumulation had then led to increased binding between kinesin 5 and microtubules, enhanced microtubule stabilization, and eventually induced G2/M arrest through the regulation of cadherin 1. In contrast, the bare GNPs experienced lysosomal escape, resulting in microtubule damage and G0/G1 arrest through the regulation of proliferating cell nuclear antigen. Overall, our findings showed that both naked and BSA wrapped gold nanoparticles had cytotoxicity, however, they affected cell proliferation via different pathways. This will greatly help us to regulate cell responses for different biomedical applications.
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Abstract
Oxidative DNA damage constitutes a major threat to genetic integrity, and has thus been implicated in the pathogenesis of a wide variety of diseases, including cancer and neurodegeneration. 7,8-dihydro-8oxo-deoxyGuanine (8-oxo-G) is one of the best characterised oxidative DNA lesions, and it can give rise to point mutations due to its miscoding potential that instructs most DNA polymerases (Pols) to preferentially insert Adenine (A) opposite 8-oxo-G instead of the correct Cytosine (C). If uncorrected, A:8-oxo-G mispairs can give rise to C:G→A:T transversion mutations. Cells have evolved a variety of pathways to mitigate the mutational potential of 8-oxo-G that include i) mechanisms to avoid incorporation of oxidized nucleotides into DNA through nucleotide pool sanitisation enzymes (by MTH1, MTH2, MTH3 and NUDT5), ii) base excision repair (BER) of 8-oxo-G in DNA (involving MUTYH, OGG1, Pol λ, and other components of the BER machinery), and iii) faithful bypass of 8-oxo-G lesions during replication (using a switch between replicative Pols and Pol λ). In the following, the fate of 8-oxo-G in mammalian cells is reviewed in detail. The differential origins of 8-oxo-G in DNA and its consequences for genetic stability will be covered. This will be followed by a thorough discussion of the different mechanisms in place to cope with 8-oxo-G with an emphasis on Pol λ-mediated correct bypass of 8-oxo-G during MUTYH-initiated BER as well as replication across 8-oxo-G. Furthermore, the multitude of mechanisms in place to regulate key proteins involved in 8-oxo-G repair will be reviewed. Novel functions of 8-oxo-G as an epigenetic-like regulator and insights into the repair of 8-oxo-G within the cellular context will be touched upon. Finally, a discussion will outline the relevance of 8-oxo-G and the proteins involved in dealing with 8-oxo-G to human diseases with a special emphasis on cancer.
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Affiliation(s)
- Enni Markkanen
- Institute of Veterinary Pharmacology and Toxicology, Vetsuisse Faculty, University of Zürich, Winterthurerstr. 260, 8057 Zürich, Switzerland.
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Subash-Babu P, Alshammari GM, Ignacimuthu S, Alshatwi AA. Epoxy clerodane diterpene inhibits MCF-7 human breast cancer cell growth by regulating the expression of the functional apoptotic genes Cdkn2A, Rb1, mdm2 and p53. Biomed Pharmacother 2017; 87:388-396. [DOI: 10.1016/j.biopha.2016.12.091] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 12/15/2016] [Accepted: 12/22/2016] [Indexed: 02/07/2023] Open
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Al-Saran N, Subash-Babu P, Al-Nouri DM, Alfawaz HA, Alshatwi AA. Zinc enhances CDKN2A , pRb1 expression and regulates functional apoptosis via upregulation of p53 and p21 expression in human breast cancer MCF-7 cell. Environ Toxicol Pharmacol 2016; 47:19-27. [PMID: 27567443 DOI: 10.1016/j.etap.2016.08.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 07/12/2016] [Accepted: 08/01/2016] [Indexed: 06/06/2023]
Abstract
Zinc (Zn) is an essential trace elements, its deficiency is associated with increased incidence of human breast cancer. We aimed to study the effect of Zn on human breast cancer MCF-7 cells cultured in Zn depleted and Zn adequate medium. We found increased cancer cell growth in zinc depleted condition, further Zn supplementation inhibits the viability of breast cancer MCF-7 cell cultured in Zn deficient condition and the IC25, IC50 value for Zn is 6.2μM, 15μM, respectively after 48h. Zn markedly induced apoptosis through the characteristic apoptotic morphological changes and DNA fragmentation after 48h. In addition, Zn deficient cells significantly triggered intracellular ROS level and develop oxidative stress induced DNA damage; it was confirmed by elevated expression of CYP1A, GPX, GSK3β and TNF-α gene. Zinc depleted MCF-7 cells expressed significantly (p≤0.001) decreased levels of CDKN2A, pRb1, p53 and increased the level of mdm2 expression. Zn supplementation (IC50=15μM), increased significantly CDKN2A, pRB1 & p53 and markedly reduced mdm2 expression; also protein expression levels of CDKN2A and pRb1 was significantly increased. In addition, intrinsic apoptotic pathway related genes such as Bax, caspase-3, 8, 9 & p21 expression was enhanced and finally induced cell apoptosis. In conclusion, physiological level of zinc is important to prevent DNA damage and MCF-7 cell proliferation via regulation of tumor suppressor gene.
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Affiliation(s)
- Nada Al-Saran
- Cancer Molecular Biology Research Lab, Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia
| | - Pandurangan Subash-Babu
- Cancer Molecular Biology Research Lab, Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia.
| | - Doha M Al-Nouri
- Cancer Molecular Biology Research Lab, Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia
| | - Hanan A Alfawaz
- Cancer Molecular Biology Research Lab, Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia
| | - Ali A Alshatwi
- Cancer Molecular Biology Research Lab, Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia.
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Bieging-Rolett KT, Johnson TM, Brady CA, Beaudry VG, Pathak N, Han S, Attardi LD. p19(Arf) is required for the cellular response to chronic DNA damage. Oncogene 2016; 35:4414-21. [PMID: 26725325 DOI: 10.1038/onc.2015.490] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 11/03/2015] [Accepted: 11/09/2015] [Indexed: 01/13/2023]
Abstract
The p53 tumor suppressor is a stress sensor, driving cell-cycle arrest or apoptosis in response to DNA damage or oncogenic signals. p53 activation by oncogenic signals relies on the p19Arf tumor suppressor, while p53 activation downstream of acute DNA damage is reported to be p19Arf-independent. Accordingly, p19Arf-deficient mouse embryo fibroblasts (MEFs) arrest in response to acute DNA damage. However, p19Arf is required for replicative senescence, a condition associated with an activated DNA damage response, as p19Arf−/− MEFs do not senesce after serial passage. A possible explanation for these seemingly disparate roles for p19Arf is that acute and chronic DNA damage responses are mechanistically distinct. Replicative senescence may result from chronic, low-dose DNA damage responses in which p19Arf has a specific role. We therefore examined the role of p19Arf in cellular responses to chronic, low-dose DNA damaging agent treatment by maintaining MEFs in low oxygen and administering 0.5 Gy γ-irradiation daily or 150μM hydroxyurea, a replication stress-inducer. In contrast to their response to acute DNA damage, p19Arf−/− MEFs exposed to chronic DNA damage do not senesce, revealing a selective role for p19Arf in senescence upon low-level, chronic DNA damage. We show further that p53 pathway activation in p19Arf−/− MEFs exposed to chronic DNA damage is attenuated relative to wild-type MEFs, suggesting a role for p19Arf in fine-tuning p53 activity. However, combined Nutlin3a and chronic DNA damaging agent treatment is insufficient to promote senescence in p19Arf−/− MEFs, suggesting that the role of p19Arf in the chronic DNA damage response may be partially p53-independent. These data suggest the importance of p19Arf for the cellular response to the low-level DNA damage incurred in culture or upon oncogene expression, providing new insight into how p19Arf serves as a tumor suppressor. Moreover, our study helps reconcile reports suggesting crucial roles for both p19Arf and DNA damage signaling pathways in tumor suppression.
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Abstract
The transcription factor Miz1 negatively regulates TNF-induced JNK activation and cell death by suppressing TRAF2 K63-polyubiquitination; upon TNF stimulation, the suppression is relieved by Mule/ARF-BP1-mediated Miz1 ubiquitination and subsequent degradation. It is not known how Mule is activated by TNF. Here we report that TNF activates Mule by inducing the dissociation of Mule from its inhibitor ARF. ARF binds to and thereby inhibits the E3 ligase activity of Mule in the steady state. TNF induces tyrosine phosphorylation of Mule, which subsequently dissociates from ARF and becomes activated. Inhibition of Mule phosphorylation by silencing of the Spleen Tyrosine Kinase (Syk) prevents its dissociation from ARF, thereby inhibiting Mule E3 ligase activity and TNF-induced JNK activation and cell death. Our data provides a missing link in TNF signaling pathway that leads to JNK activation and cell death.
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Ho CC, Huang AC, Yu CS, Lien JC, Wu SH, Huang YP, Huang HY, Kuo JH, Liao WY, Yang JS, Chen PY, Chung JG. Ellagic acid induces apoptosis in TSGH8301 human bladder cancer cells through the endoplasmic reticulum stress- and mitochondria-dependent signaling pathways. Environ Toxicol 2014; 29:1262-1274. [PMID: 23554011 DOI: 10.1002/tox.21857] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 01/30/2013] [Accepted: 02/02/2013] [Indexed: 06/02/2023]
Abstract
To investigate the effects of ellagic acid on the growth inhibition of TSGH8301 human bladder cancer cells in vitro, cells were incubated with various doses of ellagic acid for different time periods. The phase-contrast microscope was used for examining and photographing the morphological changes in TSGH8301 cells. Flow cytometric assay was used to measure the percentage of viable cells, cell cycle distribution, apoptotic cells, ROS, mitochondrial membrane potential (ΔΨm), Ca(2+) , caspase-9 and -3 activities in TSGH8301 cells after exposure to ellagic acid. Western blotting was used to examine the changes of cell cycle and apoptosis associated proteins levels. Results indicated that ellagic acid induced morphological changes, decreased the percentage of viable cells through the induction of G0/G1 phase arrest and apoptosis, and also showed that ellagic acid promoted ROS and Ca(2+) productions and decreased the level of ΔΨm and promoted activities of caspase-9 and -3. The induction of apoptosis also confirmed by annexin V staining, comet assay, DAPI staining and DNA gel electrophoresis showed that ellagic acid induced apoptosis and DNA damage in TSGH8301 cells. Western blotting assay showed that ellagic acid promoted p21, p53 and decreased CDC2 and WEE1 for leading to G0/G1 phase arrest and promoting BAD expression, AIF and Endo G, cytochrome c, caspase-9 and -3 for leading to apoptosis in TSGH8301 cells. On the basis of these observations, we suggest that ellagic acid induced cytotoxic effects for causing a decrease in the percentage of viable cells via G0/G1 phase arrest and induction of apoptosis in TSGH8301 cells.
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Affiliation(s)
- Chin-Chih Ho
- Department of Biological Science and Technology, China Medical University, Taichung 404, Taiwan
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Levav-Cohen Y, Goldberg Z, Tan KH, Alsheich-Bartok O, Zuckerman V, Haupt S, Haupt Y. The p53-Mdm2 loop: a critical juncture of stress response. Subcell Biochem 2014; 85:161-86. [PMID: 25201194 DOI: 10.1007/978-94-017-9211-0_9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The presence of a functional p53 protein is a key factor for the proper suppression of cancer development. A loss of p53 activity, by mutations or inhibition, is often associated with human malignancies. The p53 protein integrates various stress signals into a growth restrictive cellular response. In this way, p53 eliminates cells with a potential to become cancerous. Being a powerful decision maker, it is imperative that p53 will be activated properly, efficiently and temporarily in response to stress. Equally important is that p53 activation will be extinguished upon recovery from stress, and that improper activation of p53 will be avoided. Failure to achieve these aims is likely to have catastrophic consequences for the organism. The machinery that governs this tight regulation is largely based on the major inhibitor of p53, Mdm2, which both blocks p53 activities and promotes its destabilization. The interplay between p53 and Mdm2 involves a complex network of positive and negative feedback loops. Relief from Mdm2 suppression is required for p53 to be stabilized and activated in response to stress. Protection from Mdm2 entails a concerted action of modifying enzymes and partner proteins. The association of p53 with the PML-nuclear bodies may provide an infrastructure in which this complex regulatory network can be orchestrated. In this chapter we use examples to illustrate the regulatory machinery that drives this network.
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Affiliation(s)
- Yaara Levav-Cohen
- Lautenberg Center, IMRIC, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
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Abstract
Cellular senescence limits proliferation of potentially detrimental cells, preventing tumorigenesis and restricting tissue damage. However, the function of senescence in nonpathological conditions is unknown. Here, Krizhanovsky and colleagues discover a new pathway to activate senescence cell fusion. The authors find that fusion-induced senescence occurs during embryonic development in the placenta. A counterpart of this process is also observed after infection by the measles virus. The results suggest that fusion-induced senescence is essential during development, and reuse of this program later in life protects agains viral infections. Cellular senescence limits proliferation of potentially detrimental cells, preventing tumorigenesis and restricting tissue damage. However, the function of senescence in nonpathological conditions is unknown. We found that the human placental syncytiotrophoblast exhibited the phenotype and expressed molecular markers of cellular senescence. During embryonic development, ERVWE1-mediated cell fusion results in formation of the syncytiotrophoblast, which serves as the maternal/fetal interface at the placenta. Expression of ERVWE1 caused cell fusion in normal and cancer cells, leading to formation of hyperploid syncytia exhibiting features of cellular senescence. Infection by the measles virus, which leads to cell fusion, also induced cellular senescence in normal and cancer cells. The fused cells activated the main molecular pathways of senescence, the p53- and p16–pRb-dependent pathways; the senescence-associated secretory phenotype; and immune surveillance-related proteins. Thus, fusion-induced senescence might be needed for proper syncytiotrophoblast function during embryonic development, and reuse of this senescence program later in life protects against pathological expression of endogenous fusogens and fusogenic viral infections.
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Affiliation(s)
- Anna Chuprin
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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Velimezi G, Liontos M, Vougas K, Roumeliotis T, Bartkova J, Sideridou M, Dereli-oz A, Kocylowski M, Pateras IS, Evangelou K, Kotsinas A, Orsolic I, Bursac S, Cokaric-brdovcak M, Zoumpourlis V, Kletsas D, Papafotiou G, Klinakis A, Volarevic S, Gu W, Bartek J, Halazonetis TD, Gorgoulis VG. Functional interplay between the DNA-damage-response kinase ATM and ARF tumour suppressor protein in human cancer. Nat Cell Biol 2013; 15:967-77. [DOI: 10.1038/ncb2795] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 05/24/2013] [Indexed: 12/25/2022]
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Chen D, Kon N, Zhong J, Zhang P, Yu L, Gu W. Differential effects on ARF stability by normal versus oncogenic levels of c-Myc expression. Mol Cell 2013; 51:46-56. [PMID: 23747016 DOI: 10.1016/j.molcel.2013.05.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 01/18/2013] [Accepted: 05/02/2013] [Indexed: 12/20/2022]
Abstract
ARF suppresses aberrant cell growth upon c-Myc overexpression by activating p53 responses. Nevertheless, the precise mechanism by which ARF specifically restrains the oncogenic potential of c-Myc without affecting its normal physiological function is not well understood. Here, we show that low levels of c-Myc expression stimulate cell proliferation, whereas high levels inhibit by activating the ARF/p53 response. Although the mRNA levels of ARF are induced in both scenarios, the accumulation of ARF protein occurs only when ULF-mediated degradation of ARF is inhibited by c-Myc overexpression. Moreover, the levels of ARF are reduced through ULF-mediated ubiquitination upon DNA damage. Blocking ARF degradation by c-Myc overexpression dramatically stimulates the apoptotic responses. Our study reveals that ARF stability control is crucial for differentiating normal (low) versus oncogenic (high) levels of c-Myc expression and suggests that differential effects on ULF- mediated ARF ubiquitination by c-Myc levels act as a barrier in oncogene-induced stress responses.
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Affiliation(s)
- Delin Chen
- Institute for Cancer Genetics and Department of Pathology and Cell Biology, Herbert Irving Comprehensive Cancer Center, College of Physicians & Surgeons, Columbia University, 1130 St. Nicholas Avenue, New York, NY 10032, USA
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Monasor A, Murga M, Lopez-Contreras AJ, Navas C, Gomez G, Pisano DG, Fernandez-Capetillo O. INK4a/ARF limits the expansion of cells suffering from replication stress. Cell Cycle 2013; 12:1948-54. [PMID: 23676215 DOI: 10.4161/cc.25017] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Replication stress (RS) is a source of DNA damage that has been linked to cancer and aging, which is suppressed by the ATR kinase. In mice, reduced ATR levels in a model of the ATR-Seckel syndrome lead to RS and accelerated aging. Similarly, ATR-Seckel embryonic fibroblasts (MEF) accumulate RS and undergo cellular senescence. We previously showed that senescence of ATR-Seckel MEF cannot be rescued by p53-deletion. Here, we show that the genetic ablation of the INK4a/Arf locus fully rescues senescence on ATR mutant MEF, but also that induced by other conditions that generate RS such as low doses of hydroxyurea or ATR inhibitors. In addition, we show that a persistent exposure to RS leads to increased levels of INK4a/Arf products, revealing that INK4a/ARF behaves as a bona fide RS checkpoint. Our data reveal an unknown role for INK4a/ARF in limiting the expansion of cells suffering from persistent replication stress, linking this well-known tumor suppressor to the maintenance of genomic integrity.
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Affiliation(s)
- Angela Monasor
- Genomic Instability Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
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15
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Abstract
Base excision repair (BER) is a frontline repair system that is responsible for maintaining genome integrity and thus preventing premature aging, cancer and many other human diseases by repairing thousands of DNA lesions and strand breaks continuously caused by endogenous and exogenous mutagens. This fundamental and essential function of BER not only necessitates tight control of the continuous availability of basic components for fast and accurate repair, but also requires temporal and spatial coordination of BER and cell cycle progression to prevent replication of damaged DNA. The major goal of this review is to critically examine controversial and newly emerging questions about mammalian BER pathways, mechanisms regulating BER capacity, BER responses to DNA damage and their links to checkpoint control of DNA replication.
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Affiliation(s)
- Grigory L Dianov
- Department of Oncology, Gray Institute for Radiation Oncology and Biology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK.
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16
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Carlos AR, Escandell JM, Kotsantis P, Suwaki N, Bouwman P, Badie S, Folio C, Benitez J, Gomez-Lopez G, Pisano DG, Jonkers J, Tarsounas M. ARF triggers senescence in Brca2-deficient cells by altering the spectrum of p53 transcriptional targets. Nat Commun 2013; 4:2697. [PMID: 24162189 DOI: 10.1038/ncomms3697] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [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: 08/27/2013] [Accepted: 10/02/2013] [Indexed: 01/12/2023] Open
Abstract
ARF is a tumour suppressor activated by oncogenic stress, which stabilizes p53. Although p53 is a key component of the response to DNA damage, a similar function for ARF has not been ascribed. Here we show that primary mouse and human cells lacking the tumour suppressor BRCA2 accumulate DNA damage, which triggers checkpoint signalling and ARF activation. Furthermore, senescence induced by Brca2 deletion in primary mouse and human cells is reversed by the loss of ARF, a phenotype recapitulated in cells lacking RAD51. Surprisingly, ARF is not necessary for p53 accumulation per se but for altering the spectrum of genes activated by this transcription factor. Specifically, ARF enables p53 transcription of Dusp4 and Dusp7, which encode a pair of phosphatases known to inactivate the MAP kinases ERK1/2. Our results ascribe a previously unanticipated function to the ARF tumour suppressor in genome integrity, controlled by replicative stress and ATM/ATR-dependent checkpoint responses.
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Affiliation(s)
- Ana Rita Carlos
- 1] Telomere and Genome Stability Group, The CR-UK/MRC Gray Institute for Radiation Oncology and Biology, Old Campus Road, Oxford OX3 7DQ, UK [2] [3]
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17
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Li Z, Hou J, Sun L, Wen T, Wang L, Zhao X, Xie Q, Zhang SQ. NMI mediates transcription-independent ARF regulation in response to cellular stresses. Mol Biol Cell 2012; 23:4635-46. [PMID: 23034180 PMCID: PMC3510024 DOI: 10.1091/mbc.e12-04-0304] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
ETOC: NMI is a novel ARF-interacting protein identified in a yeast two-hybrid screen. NMI inhibits ULF-induced ubiquitin degradation of ARF protein. It mediates transcription-independent ARF regulation and is required for the stabilization and up-regulation of ARF in response to cellular stresses. The ARF tumor suppressor is a product of the INK4a/ARF locus, which is frequently mutated in human cancer. The expression of ARF is up-regulated in response to certain types of DNA damage, oncogene activation, and interferon stimuli. Through interaction with the p53 negative regulator MDM2, ARF controls a well-described p53/MDM2-dependent checkpoint. However, the mechanism of ARF induction is poorly understood. Using a yeast two-hybrid screen, we identify a novel ARF-interacting protein, N-Myc and STATs interactor (NMI). Previously, NMI was known to be a c-Myc–interacting protein. Here we demonstrate that through competitive binding to the ARF ubiquitin E3 ligase (ubiquitin ligase for ARF [ULF]), NMI protects ARF from ULF-mediated ubiquitin degradation. In response to cellular stresses, NMI is induced, and a fraction of NMI is translocated to the nucleus to stabilize ARF. Thus our work reveals a novel NMI-mediated, transcription-independent ARF induction pathway in response to cellular stresses.
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Affiliation(s)
- Zengpeng Li
- State Key Laboratory of Cellular Stress Biology and School of Life Sciences, Xiamen University, Xiamen, Fujian 361005, China
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18
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19
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Hines J, Ju R, Dutschman GE, Cheng YC, Crews CM. Reversal of TNP-470-induced endothelial cell growth arrest by guanine and guanine nucleosides. J Pharmacol Exp Ther 2010; 334:729-38. [PMID: 20571059 DOI: 10.1124/jpet.110.169110] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The mechanism of action of TNP-470 [O-(chloroacetyl-carbamoyl) fumagillol], which potently and selectively inhibits the proliferation of endothelial cells, is incompletely understood. Previous studies have established its binding protein and the most distal effector of its growth arrest activity as methionine aminopeptidase 2 (MetAP-2) and p21(WAF1/CIP1), respectively. However, the mechanistic steps between these two effectors have not been identified. We have found that addition of exogenous guanine and guanine-containing nucleosides to culture medium will completely reverse the cytostatic effect of TNP-470 on both cultured bovine aortic and mouse pulmonary endothelial cells. Western blotting showed that supplementation with exogenous guanosine reverses the induction of p21(WAF1/CIP1) by TNP-470. This "rescue" by guanine/guanosine was abolished when the guanine salvage pathway of nucleotide biosynthesis was inhibited with Immucillin H, suggesting that TNP-470 might reduce de novo guanine synthesis in endothelial cells. However, an analysis of inosine 5'-monophosphate dehydrogenase, the rate-limiting enzyme in de novo guanine synthesis and target of the antiangiogenic drug mycophenolic acid, showed no TNP-470-induced changes. Curiously, quantitation of cellular nucleotides confirmed that GTP levels were not reduced after TNP-470 treatment. Addition of guanosine at the start of G(1) phase causes a doubling in GTP levels that persists to the G(1)/S phase transition, where commitment to TNP-470 growth arrest occurs. Thus, guanine rescue involves an augmentation of cellular GTP beyond physiological levels rather than a restoration of a drug-induced GTP deficit. Determining the mechanism whereby this causes restoration of endothelial cell proliferation is an ongoing investigation.
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Affiliation(s)
- John Hines
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
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20
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Abstract
Loss of p53 function occurs during the development of most, if not all, tumour types. This paves the way for genomic instability, tumour-associated changes in metabolism, insensitivity to apoptotic signals, invasiveness and motility. However, the nature of the causal link between early tumorigenic events and the induction of the p53-mediated checkpoints that constitute a barrier to tumour progression remains uncertain. This Review considers the role of the DNA damage response, which is activated during the early stages of tumour development, in mobilizing the tumour suppression function of p53. The relationship between these events and oncogene-induced p53 activation through the ARF pathway is also discussed.
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Affiliation(s)
- David W Meek
- Biomedical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
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21
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Prindull G. Final checkup of neoplastic DNA replication: Evidence for failure in decision-making at the mitotic cell cycle checkpoint G1/S. Exp Hematol 2008; 36:1403-16. [DOI: 10.1016/j.exphem.2008.07.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Revised: 07/29/2008] [Accepted: 07/29/2008] [Indexed: 11/24/2022]
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22
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Saiko P, Szakmary A, Jaeger W, Szekeres T. Resveratrol and its analogs: defense against cancer, coronary disease and neurodegenerative maladies or just a fad? Mutat Res 2007; 658:68-94. [PMID: 17890139 DOI: 10.1016/j.mrrev.2007.08.004] [Citation(s) in RCA: 319] [Impact Index Per Article: 18.8] [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: 07/14/2006] [Revised: 08/09/2007] [Accepted: 08/13/2007] [Indexed: 01/30/2023]
Abstract
Resveratrol (3,5,4'-trihydroxy-trans-stilbene; RV), a dietary constituent found in grapes and wine, exerts a wide variety of pharmacological activities. Because the grape skins are not fermented in the production process of white wines, only red wines contain considerable amounts of this compound. RV is metabolized into sulfated and glucuronidated forms within approximately 15min of entering the bloodstream, and moderate consumption of red wine results in serum levels of RV that barely reach the micromolar concentrations. In contrast, its metabolites, which may be the active principle, circulate in serum for up to 9h. RV has been identified as an effective candidate for cancer chemoprevention due its ability to block each step in the carcinogenesis process by inhibiting several molecular targets such as kinases, cyclooxygenases, ribonucleotide reductase, and DNA polymerases. In addition, RV protects the cardiovascular system by a large number of mechanisms, including defense against ischemic-reperfusion injury, promotion of vasorelaxation, protection and maintenance of intact endothelium, anti-atherosclerotic properties, inhibition of low-density lipoprotein oxidation, and suppression of platelet aggregation, thereby strongly supporting its role in the prevention of coronary disease. Promising data within the use of RV have also been obtained regarding progressive neurodegenerative maladies such as Alzheimer's, Huntington's, and Parkinson's diseases. Because neurotoxicity is often related to mitochondrial dysfunction and may be ameliorated through the inclusion of metabolic modifiers and/or antioxidants, RV may provide an alternative (and early) intervention approach that could prevent further damage. RV induces a multitude of effects that depend on the cell type (e.g., NF-kappaB modulation in cancer cells vs. neural cells), cellular condition (normal, stressed, or malignant), and concentration (proliferative vs. growth arrest), and it can have opposing activities. RV affects whole pathways and sets of intracellular events rather than a single enzyme and, therefore, may be an effective therapy to restore homoestasis. Nonetheless, the question of whether RV or its metabolites can accumulate to bioactive levels in target organs remains to be addressed.
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Affiliation(s)
- Philipp Saiko
- Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, General Hospital of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
| | - Akos Szakmary
- Department of Medicine I, Division of Cancer Research, Medical University of Vienna, Borschkegasse 8a, A-1090 Vienna, Austria
| | - Walter Jaeger
- Department of Clinical Pharmacy and Diagnostics, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Thomas Szekeres
- Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, General Hospital of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria
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23
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Khoo CM, Carrasco DR, Bosenberg MW, Paik JH, DePinho RA. Ink4a/Arf tumor suppressor does not modulate the degenerative conditions or tumor spectrum of the telomerase-deficient mouse. Proc Natl Acad Sci U S A 2007; 104:3931-6. [PMID: 17360455 PMCID: PMC1820686 DOI: 10.1073/pnas.0700093104] [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] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The Rb/p16(Ink4a) and p53/p19Arf tumor suppressor pathways have been linked to diverse cancer-relevant processes, including those governing the cellular responses to telomere dysfunction. In this study, we sought to provide direct genetic evidence of a role for the Ink4a/Arf tumor suppressor gene, encoding both p16(Ink4a) and p19(Arf), in modulating the cellular and tissue phenotypes associated with telomere dysfunction by using the mTerc Ink4a/Arf mouse model. In contrast to the rescue associated with p53 deficiency, Ink4a/Arf deficiency did not attenuate the degenerative phenotypes elicited by telomere dysfunction in the late-generation mTerc-/- mice. Furthermore, in contrast to accelerated cancer onset and increased epithelial cancers of late-generation mTerc-/- p53 mutant mice, late-generation mTerc-/- Ink4a/Arf mutant mice experienced a delayed tumor onset and maintained the lymphoma and sarcoma spectrum. Consistent with the negligible role of Ink4a/Arf in the telomere checkpoint response in vivo, late-generation mTerc-/- Ink4a/Arf-/- tissues show activated p53, and derivative tumor cell lines sustain frequent loss of p53 function, whereas all early generation mTerc Ink4a/Arf-/- tumor cell lines remain intact for p53. In addition, the late-generation mTerc-/- Ink4a/Arf-/- tumors showed activation of the alternative lengthening of telomere mechanism, underscoring the need for adaptation to the presence of telomere dysfunction in the absence of p16(Ink4a) and p19(Arf). These observations highlight the importance of genetic context in dictating whether telomere dysfunction promotes or suppresses age-related degenerative conditions as well as the rate of initiation and type of spontaneous cancers.
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Affiliation(s)
- Christine M. Khoo
- *Department of Medical Oncology and
- Departments of Medicine and Genetics, Harvard Medical School, Boston, MA 02115; and
| | - Daniel R. Carrasco
- *Department of Medical Oncology and
- Department of Pathology, Brigham and Women's Hospital, and
- Departments of Medicine and Genetics, Harvard Medical School, Boston, MA 02115; and
| | | | - Ji-Hye Paik
- *Department of Medical Oncology and
- Departments of Medicine and Genetics, Harvard Medical School, Boston, MA 02115; and
| | - Ronald A. DePinho
- *Department of Medical Oncology and
- Center for Applied Cancer Science, Belfer Foundation Institute for Innovative Cancer Science, Dana–Farber Cancer Institute
- Departments of Medicine and Genetics, Harvard Medical School, Boston, MA 02115; and
- To whom correspondence should be addressed at:
Harvard Medical School, Dana–Farber Cancer Institute, Mayer Building, Room 413, 44 Binney Street, Boston, MA 02115. E-mail:
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24
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Martins CP, Brown-Swigart L, Evan GI. Modeling the therapeutic efficacy of p53 restoration in tumors. Cell 2006; 127:1323-34. [PMID: 17182091 DOI: 10.1016/j.cell.2006.12.007] [Citation(s) in RCA: 460] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 11/09/2006] [Accepted: 12/08/2006] [Indexed: 10/23/2022]
Abstract
Although restoration of p53 function is an attractive tumor-specific therapeutic strategy, it remains unclear whether p53 loss is required only for transition through early bottlenecks in tumorigenesis or also for maintenance of established tumors. To explore the efficacy of p53 reinstatement as a tumor therapy, we used a reversibly switchable p53 knockin (KI) mouse model that permits modulation of p53 status from wild-type to knockout, at will. Using the well-characterized Emu-myc lymphoma model, we show that p53 is spontaneously activated when restored in established Emu-myc lymphomas in vivo, triggering rapid apoptosis and conferring a significant increase in survival. Nonetheless, reimposition of p53 function potently selects for emergence of p53-resistant tumors through inactivation of p19(ARF) or p53. Our study provides important insights into the nature and timing of p53-activating signals in established tumors and how resistance to p53 evolves, which will aid in the optimization of p53-based tumor therapies.
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Affiliation(s)
- Carla P Martins
- Cancer Research Institute and Department of Cellular and Molecular Pharmacology, Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA
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25
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Tompkins VS, Hagen J, Frazier AA, Lushnikova T, Fitzgerald MP, di Tommaso A, Ladeveze V, Domann FE, Eischen CM, Quelle DE. A novel nuclear interactor of ARF and MDM2 (NIAM) that maintains chromosomal stability. J Biol Chem 2006; 282:1322-33. [PMID: 17110379 DOI: 10.1074/jbc.m609612200] [Citation(s) in RCA: 32] [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] [Indexed: 01/10/2023] Open
Abstract
The ARF tumor suppressor signals through p53 and other poorly defined anti-proliferative pathways to block carcinogenesis. In a search for new regulators of ARF signaling, we discovered a novel nuclear protein that we named NIAM (nuclear interactor of ARF and MDM2) for its ability to bind both ARF and the p53 antagonist MDM2. NIAM protein is normally expressed at low to undetectable levels in cells because of, at least in part, MDM2-mediated ubiquitination and proteasomal degradation. When reintroduced into cells, NIAM activated p53, caused a G1 phase cell cycle arrest, and collaborated with ARF in an additive fashion to suppress proliferation. Notably, NIAM retains growth inhibitory activity in cells lacking ARF and/or p53, and knockdown experiments revealed that it is not essential for ARF-mediated growth inhibition. Thus, NIAM and ARF act in separate anti-proliferative pathways that intersect mechanistically and suppress growth more effectively when jointly activated. Intriguingly, silencing of NIAM accelerated chromosomal instability, and microarray analyses showed reduced NIAM mRNA expression in numerous primary human tumors. This study identifies a novel protein with tumor suppressor-like behaviors and functional links to ARF-MDM2-p53 signaling.
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Affiliation(s)
- Van S Tompkins
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, 52242-1109, USA, and the Laboratoire de Genetique Cellulaire et Moleculaire, UPRES EA2622, Centre Hospitalier Universitaire de Poitiers, France
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26
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Gizatullin F, Yao Y, Kung V, Harding MW, Loda M, Shapiro GI. The Aurora kinase inhibitor VX-680 induces endoreduplication and apoptosis preferentially in cells with compromised p53-dependent postmitotic checkpoint function. Cancer Res 2006; 66:7668-77. [PMID: 16885368 DOI: 10.1158/0008-5472.can-05-3353] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [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: 01/11/2023]
Abstract
VX-680 is a potent inhibitor of Aurora kinases that induces the accumulation of cells with > or =4N DNA content, followed by cell death. Here, we define the role of p53 and p21(Waf1/Cip1) in cell cycle perturbations following exposure to VX-680. Endoreduplication and apoptosis in response to VX-680 are limited in A549 and MCF-7 cells expressing wild-type p53, and markedly enhanced in cells lacking p53, including those engineered to express the HPV16-E6 oncoprotein or short interfering RNA pools targeting p53. In contrast, endoreduplication and apoptosis occur in the p53 wild-type cell lines, RKO and U2OS. The difference in response to VX-680 among these cell lines correlates with the timing of induction of p21(Waf1/Cip1) and its ability to inhibit cyclin E-cdk2 activity. In A549 cells, VX-680 induces the expression of p53 and p21(Waf1/Cip1) within 24 hours, with consequent inhibition of cyclin E-cdk2, and reduction of retinoblastoma protein phosphorylation, limiting endoreduplication. In RKO and U2OS cells, the induction of p21(Waf1/Cip1) is delayed and associated with higher residual cyclin E-cdk2 kinase activity and retinoblastoma protein phosphorylation, followed by progressive endoreduplication and apoptosis. Abrogation of p21(Waf1/Cip1) expression by short interfering RNA targeting in A549 cells results in a substantial increase in the degree of endoreduplication, whereas inducible expression of p21(Waf1/Cip1) in p53-negative NCI-H1299 cells inhibits VX-680-induced endoreduplication and cell death. These data suggest that the integrity of the p53-p21(Waf1/Cip1)-dependent postmitotic checkpoint governs the response to Aurora kinase inhibition. Although cells with intact checkpoint function arrest with 4N DNA content, those with compromised checkpoint function are more likely to undergo endoreduplication followed by eventual apoptosis.
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Affiliation(s)
- Farid Gizatullin
- Department of Medical Oncology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA
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27
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Abstract
Mammalian cells that sustain oncogenic insults can invoke defensive programmes that either halt their division or trigger their apoptosis, but these countermeasures must be finely tuned to discriminate between physiological and potentially harmful growth-promoting states. By functioning specifically to oppose abnormally prolonged and sustained proliferative signals produced by activated oncogenes, the ARF tumour suppressor antagonizes functions of MDM2 to induce protective responses that depend on the p53 transcription factor and its many target genes. However, ARF has been reported to physically associate with proteins other than MDM2 and to have p53-independent activities, most of which remain controversial and poorly understood.
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Affiliation(s)
- Charles J Sherr
- Howard Hughes Medical Institute, St. Jude Children's Research Hospital, 332 North Lauderdale, Memphis, Tennessee 38105, USA.
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28
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Hopkins-Donaldson S, Belyanskaya LL, Simões-Wüst AP, Sigrist B, Kurtz S, Zangemeister-Wittke U, Stahel R. p53-induced apoptosis occurs in the absence of p14(ARF) in malignant pleural mesothelioma. Neoplasia 2006; 8:551-9. [PMID: 16867217 PMCID: PMC1601933 DOI: 10.1593/neo.06148] [Citation(s) in RCA: 37] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Malignant pleural mesotheliomas (MPMs) are usually wild type for the p53 gene but contain homozygous deletions in the INK4A locus that encodes p14(ARF), an inhibitor of p53-MDM2 interaction. Previous findings suggest that lack of p14(ARF) expression and the presence of SV40 large T antigen (L-Tag) result in p53 inactivation in MPM. We did not detect SV40 L-Tag mRNA in either MPM cell lines or primary cultures, and treatment of p14(ARF)-deficient cells with cisplatin (CDDP) increased both total and phosphorylated p53 and enhanced p53 DNA-binding activity. On incubation with CDDP, levels of positively regulated p53 transcriptional targets p21(WAF), PIG3, MDM2, Bax, and PUMA increased in p14(ARF)-deficient cells, whereas negatively regulated survivin decreased. Significantly, p53-induced apoptosis was activated by CDDP in p14(ARF)-deficient cells, and treatment with p53-specific siRNA rendered them more CDDP-resistant. p53 was also activated by: 1) inhibition of MDM2 (using nutlin-3); 2) transient overexpression of p14(ARF); and 3) targeting of survivin using antisense oligonucleotides. However, it is noteworthy that only survivin downregulation sensitized cells to CDDP-induced apoptosis. These results suggest that p53 is functional in the absence of p14(ARF) in MPM and that targeting of the downstream apoptosis inhibitor survivin can sensitize to CDDP-induced apoptosis.
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Affiliation(s)
- Sally Hopkins-Donaldson
- Laboratory for Molecular Oncology, University Hospital Zurich, Haeldeliweg 4, CH-8044 Zurich, Switzerland.
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29
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Abstract
The p53/p14ARF/mdm2 stress response pathway plays a central role in mediating cellular responses to oncogene activation, genome instability, and therapy-induced DNA damage. Abrogation of the pathway occurs in most if not all cancers, and may be essential for tumor development. The high frequency with which the pathway is disabled in cancer and the fact that the pathway appears to be incompatible with tumor cell growth, has made it an important point of focus in cancer research and therapeutics development. Recently, Nucleophosmin (NPM, B23, NO38 and numatrin), a multifunctional nucleolar protein, has emerged as a p14ARF binding protein and regulator of p53. While complex formation between ARF and NPM retains ARF in the nucleolus and prevents ARF from activating p53, DNA damaging treatments promote a transient subnuclear redistribution of ARF to the nucleoplasm, where it interacts with mdm2 and promotes p53 activation. The results add support to a recently proposed model in which the nucleolus serves as a p53-uspstream sensor of stress, and where ARF links nucleolar stress signals to nucleoplasmic effectors of the stress response. A better understanding of ARF's nucleolar interactions could further elucidate the regulation of the p53 pathway and suggest new therapeutic approaches to restore p53 function.
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Affiliation(s)
- Ruth A Gjerset
- Sidney Kimmel Cancer Center, 10835 Road to the Cure (previously Altman Row), San Diego, CA 92121, USA.
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30
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Quignon F, Rozier L, Lachages AM, Bieth A, Simili M, Debatisse M. Sustained mitotic block elicits DNA breaks: one-step alteration of ploidy and chromosome integrity in mammalian cells. Oncogene 2006; 26:165-72. [PMID: 16832348 DOI: 10.1038/sj.onc.1209787] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Following prolonged mitotic spindle disruption by microtubule poisons, mammalian cells delay their entry into anaphase, then progressively slip out of mitosis and become tetraploid. Normal cells then stop cycling before S-phase onset, but the mechanisms underlying this arrest are still unclear. Here we show that a double block prevents endo-reduplication. First, cells that exit mitosis without a functional microtubule network are driven toward G0. Reconstitution of the network unmasks a second block that relies on DNA double-strand breaks occurring early in the G1 phase that follows the mitotic block. We propose that a stress signal elicited upon mitotic impairment triggers breakage, which couples the leaky spindle checkpoint to the stringent DNA damage response. Consistent with this finding, cells defective for the damage response continue cycling and acquire, within a single cell cycle, both chromosome rearrangements and abnormal chromosome numbers that remarkably mimic the complex genetic hallmark of tumorigenesis.
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Affiliation(s)
- F Quignon
- Institut Curie, Université Pierre et Marie Curie-Paris 6, CNRS UMR 7147, 26 Rue d'Ulm, 75248, Paris Cédex 05, France
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31
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Eymin B, Claverie P, Salon C, Leduc C, Col E, Brambilla E, Khochbin S, Gazzeri S. p14ARF activates a Tip60-dependent and p53-independent ATM/ATR/CHK pathway in response to genotoxic stress. Mol Cell Biol 2006; 26:4339-50. [PMID: 16705183 PMCID: PMC1489086 DOI: 10.1128/mcb.02240-05] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [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: 01/25/2023] Open
Abstract
p14ARF is a tumor suppressor that controls a well-described p53/Mdm2-dependent checkpoint in response to oncogenic signals. Here, new insights into the tumor-suppressive function of p14ARF are provided. We previously showed that p14ARF can induce a p53-independent G2 cell cycle arrest. In this study, we demonstrate that the activation of ATM/ATR/CHK signaling pathways contributes to this G2 checkpoint and highlight the interrelated roles of p14ARF and the Tip60 protein in the initiation of this DNA damage-signaling cascade. We show that Tip60 is a new direct p14ARF binding partner and that its expression is upregulated and required for ATM/CHK2 activation in response to p14ARF. Strikingly, both p14ARF and Tip60 products accumulate following a cell treatment with alkylating agents and are absolutely required for ATM/CHK2 activation in this setting. Moreover, and consistent with p14ARF being a determinant of CHK2 phosphorylation in lung carcinogenesis, a strong correlation between p14ARF and phospho-CHK2 (Thr68) protein expression is observed in human lung tumors (P < 0.00006). Overall, these data point to a novel regulatory pathway that mediates the p53-independent negative-cell-growth control of p14ARF. Inactivation of this pathway is likely to contribute to lung carcinogenesis.
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Affiliation(s)
- Béatrice Eymin
- Groupe de Recherche sur le Cancer du Poumon, INSERM U578, Institut Albert Bonniot, 38706 La Tronche Cedex, France
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Abstract
The E2F1 transcription factor, which is deregulated in most human cancers by mutations in the p16-cyclin D-Rb pathway, has both oncogenic and tumor-suppressive properties. This is dramatically illustrated by the phenotype of an E2F1 transgenic mouse model that spontaneously develops tumors in the skin and other epithelial tissues but is resistant to papilloma formation when subjected to a two-stage carcinogenesis protocol. Here, this E2F1 transgenic model was used to further explore the tumor-suppressive property of E2F1. Transgenic expression of E2F1 was found to inhibit ras-driven skin carcinogenesis at the promotion stage independent of the type of promoting agent used. E2F1 transgenic epidermis displayed increased expression of p19(ARF), p53, and p21(Cip1). Inactivation of either p53 or Arf in E2F1 transgenic mice restored sensitivity to two-stage skin carcinogenesis. While Arf inactivation impaired tumor suppression and p21 induction by E2F1, it did not reduce the level of apoptosis observed in E2F1 transgenic mice. Based on these findings, we propose that E2F1 suppresses ras-driven skin carcinogenesis through a nonapoptotic mechanism involving ARF and p53.
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Affiliation(s)
- J L Russell
- Department of Carcinogenesis, The University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, TX 78957, USA
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Wang J, He X, Luo Y, Yarbrough W. A novel ARF-binding protein (LZAP) alters ARF regulation of HDM2. Biochem J 2006; 393:489-501. [PMID: 16173922 PMCID: PMC1360699 DOI: 10.1042/bj20050960] [Citation(s) in RCA: 43] [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] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Revised: 08/31/2005] [Accepted: 09/21/2005] [Indexed: 12/13/2022]
Abstract
The tumour suppressor ARF (alternative reading frame) is encoded by the INK4a (inhibitor of cyclin-dependent kinase 4)/ARF locus, which is frequently altered in human tumours. ARF binds MDM2 (murine double minute 2) and releases p53 from inhibition by MDM2, resulting in stabilization, accumulation and activation of p53. Recently, ARF has been found to associate with other proteins, but, to date, little is known about ARF-associated proteins that are implicated in post-translational regulation of ARF activity. Using a yeast two-hybrid screen, we have identified a novel protein, LZAP (LXXLL/leucine-zipper-containing ARF-binding protein), that interacts with endogenous ARF in mammalian cells. In the present study, we show that LZAP reversed the ability of ARF to inhibit HDM2's ubiquitin ligase activity towards p53, but simultaneously co-operated with ARF, maintaining p53 stability and increasing p53 transcriptional activity. Expression of LZAP, in addition to ARF, increased the percentage of cells in the G1 phase of the cell cycle. Expression of LZAP also caused activation of p53 and a p53-dependent G1 cell-cycle arrest in the absence of ARF. Taken together, our data suggest that LZAP can regulate ARF biochemical and biological activity. Additionally, LZAP has p53-dependent cell-cycle effects that are independent of ARF.
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Key Words
- alternative reading frame protein (arf)
- c53
- lxxll/leucine-zipper-containing arf-binding protein (lzap)
- murine double minute 2 (mdm2)
- p53
- ubiquitination
- arf, alternative reading frame
- cdk, cyclin-dependent kinase
- dapi, 4,6-diamidino-2-phenylindole
- gapdh, glyceraldehyde-3-phosphate dehydrogenase
- gfp, green fluorescent protein
- ha, haemagglutinin
- hrp, horseradish peroxidase
- ink4a, inhibitor of cdk4
- iptg, isopropyl β-d-thiogalactoside
- klh, keyhole-limpet haemocyanin
- lzap, lxxll/leucine-zipper-containing arf-binding protein
- mdm2, murine double minute 2
- hdm2, human homologue of mdm2
- mef, mouse embryonic fibroblast
- prb, retinoblastoma protein
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Affiliation(s)
- Jialiang Wang
- *Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, U.S.A
- †Departments of Otolaryngology and Cancer Biology, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, TN 37232, U.S.A
| | - Xiaping He
- ‡Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, U.S.A
| | - Ying Luo
- §Shanghai Genomics, Inc., 647 Song Tao Road, Building 1, Shanghai, 201203, China
| | - Wendell G. Yarbrough
- †Departments of Otolaryngology and Cancer Biology, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, TN 37232, U.S.A
- ∥Barry Baker Laboratory for Head and Neck Oncology, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, TN 37232, U.S.A
- ¶Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, TN 37232, U.S.A
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Lee C, Smith BA, Bandyopadhyay K, Gjerset RA. DNA damage disrupts the p14ARF-B23(nucleophosmin) interaction and triggers a transient subnuclear redistribution of p14ARF. Cancer Res 2005; 65:9834-42. [PMID: 16267006 DOI: 10.1158/0008-5472.can-05-1759] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [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
The p14 alternate reading frame (ARF) tumor suppressor plays a central role in cancer by binding to mdm2 (Hdm2 in humans) and enhancing p53-mediated apoptosis following DNA damage and oncogene activation. It is unclear, however, how ARF initiates its involvement in the p53/mdm2 pathway, as p53 and mdm2 are located in the nucleoplasm, whereas ARF is largely nucleolar in tumor cells. We have used immunofluorescence and coimmunoprecipitation to examine how the subnuclear distribution and protein-protein interactions of ARF change immediately after DNA damage and over the time course of the DNA damage response in human tumor cells. We find that DNA damage disrupts the interaction of ARF with the nucleolar protein B23(nucleophosmin) and promotes a transient p53-independent translocation of ARF to the nucleoplasm, resulting in a masking of the ARF NH2 terminus that correlates with the appearance of ARF-Hdm2 complexes. The translocation also results in an unmasking of the ARF COOH terminus, suggesting that redistribution disrupts a nucleolar interaction of ARF involving this region. By 24 hours after irradiation, DNA repair has ceased and the pretreatment immunofluorescence patterns and complexes of ARF have been restored. Although the redistribution of ARF is independent of p53 and likely to be regulated by interactions other than Hdm2, ARF does not promote UV sensitization unless p53 is expressed. The results implicate the nucleolus and nucleolar interactions of the ARF, including potentially novel interactions involving its COOH terminus as sites for early DNA damage and stress-mediated cellular events.
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Affiliation(s)
- Casey Lee
- Department of Cancer Cell Biology, Sidney Kimmel Cancer Center, San Diego, California 92121, USA
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Abstract
Ionizing radiation leads to rapid stabilization and activation of the p53 tumor suppressor. Previous reports demonstrate that murine p19ARF cooperates with p53 in the cellular response to gamma irradiation. Here, we show that endogenous ARF sequentially interacts with p53 and MDM2 following irradiation of primary human and mouse embryonic fibroblasts. Shortly after irradiation, p14ARF binds p53 independently of MDM2. As nuclear pools of p53 decline, endogenous p14ARF co-immunoprecipitates with MDM2 and is localized within the nucleolus. Interestingly, p14ARF nucleolar localization during this response is abrogated in cells lacking functional p53. Taken together, our data suggest that human and murine ARF contribute to the mammalian DNA damage response.
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Affiliation(s)
- Shireen Khan
- Department of Discovery Research, DNAX Research Incorporated, Palo Alto, CA 94304, USA
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36
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Abstract
The p53 tumour suppressor protein is a highly potent transcription factor which, under normal circumstances, is maintained at low levels through the action of MDM2, an E3 ubiquitin ligase which directs p53 ubiquitylation and degradation. Expression of the mdm2 gene is stimulated by p53 and this reciprocal relationship forms the basis of a negative feedback loop. Both genotoxic and non-genotoxic stresses that induce p53 focus principally on interruption of the p53-MDM2 loop with the consequence that p53 becomes stabilised, leading to changes in the expression of p53-responsive genes. The biological outcome of inducing this pathway can be either growth arrest or apoptosis: factors affecting the functioning of the loop, the biochemical activity of p53 itself and the cellular environment govern the choice between these outcomes in a cell type- and stress-specific manner.
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Affiliation(s)
- David W Meek
- Biomedical Research Centre, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.
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Abstract
Mutations that drive uncontrolled cell-cycle progression are requisite events in tumorigenesis. But evolution has installed in the proliferative programmes of mammalian cells a variety of innate tumour-suppressive mechanisms that trigger apoptosis or senescence, should proliferation become aberrant. These contingent processes rely on a series of sensors and transducers that act in a coordinated network to target the machinery responsible for apoptosis and cell-cycle arrest at different points. Although oncogenic mutations that disable such networks can have profound and varied effects on tumour evolution, they may leave intact latent tumour-suppressive potential that can be harnessed therapeutically.
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Affiliation(s)
- Scott W Lowe
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA.
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Vestey SB, Sen C, Calder CJ, Perks CM, Pignatelli M, Winters ZE. p14ARF expression in invasive breast cancers and ductal carcinoma in situ--relationships to p53 and Hdm2. Breast Cancer Res 2004; 6:R571-85. [PMID: 15318938 PMCID: PMC549173 DOI: 10.1186/bcr912] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [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: 01/12/2004] [Revised: 05/06/2004] [Accepted: 06/17/2004] [Indexed: 12/24/2022] Open
Abstract
Introduction p14ARF stabilises nuclear p53, with a variable expression of p14ARF mRNA in breast cancers. In vitro, nuclear p14ARF binds Hdm2 to block Hdm2-dependent nucleocytoplasmic shuttling of p53, which is required before cytoplasmic degradation of p53. p14ARF is negatively regulated by p53 and through p53-independent pathways. No studies have yet examined levels of p14ARF protein expression in breast cancer and their relationship to Hdm2/p53 immunoreactivity or subcellular localisation. Previously, immunohistochemical expression of cytoplasmic p14ARF, p53 and Hdm2 has been described. HER-2 (c-erbB2/neu) predicts prognosis and interacts with the p14ARF/Hdm2 pathway to inactivate p14ARF and to influence Hdm2 activity and localisation. This study examined p14ARF and p53/Hdm2 expression and subcellular localisation by using immunohistochemistry in a series of invasive ductal breast cancers (IDCs) with concomitant ductal carcinoma in situ (DCIS), to evaluate whether findings in vitro were related to clinicopathological parameters such as HER-2 and their effect on patient outcome. Methods The 4C6 anti-p14ARF monoclonal antibody and Dako Envision Plus system were used to evaluate p14ARF expression in 103 patients; p53/Hdm2 staining was performed. Results p14ARF was evaluable in 96 patients, with nuclear p14ARF expression (modified Quick-score ≥ 3) in 79% (n = 76) of IDCs and in associated DCIS in 74 patients. Cytoplasmic p14ARF was detectable in 23 breast cancers. Nuclear and cytoplasmic p14ARF showed no correlation with p53 subcellular immunoreactivity. Increasing levels of cytoplasmic p14ARF were associated with nuclear and cytoplasmic Hdm2 expression (P < 0.001). Subcellular ARF expression was not associated with clinicopathological parameters, and although not an independent prognosticator, these preliminary findings suggest that cytoplasmic p14ARF might be associated with a better overall survival (P = 0.09; log rank). The association between HER-2 positivity and nuclear p14ARF (P = 0.038), as well as nuclear Hdm2 (P = 0.019), reflects the in vitro findings of HER-2 interaction with the ARF/Hdm2 pathway. Cytoplasmic p53 and Hdm2 expression might have biological implications, through an association of cytoplasmic p53 with increased tumour proliferation (P = 0.005), and an improved overall survival (P = 0.002, log rank) in cytoplasmic Hdm2-expressing tumours, that independently predict favourable overall survival (P = 0.02) and disease-free survival (P = 0.03). Conclusions Nuclear p14ARF expression is similar in IDCs and DCIS and is associated with Hdm2 immunoreactivity. Nuclear p14ARF and Hdm2 might be regulated by HER-2. Clearly, our findings in vivo suggest a complexity of p14ARF/Hdm2 and p53 pathways in which consideration of cytoplasmic p14ARF and Hdm2 might have tumorigenic implications.
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MESH Headings
- Adult
- Aged
- Aged, 80 and over
- Breast Neoplasms/metabolism
- Breast Neoplasms/mortality
- Breast Neoplasms/pathology
- Carcinoma, Ductal, Breast/metabolism
- Carcinoma, Ductal, Breast/mortality
- Carcinoma, Ductal, Breast/pathology
- Carcinoma, Intraductal, Noninfiltrating/metabolism
- Carcinoma, Intraductal, Noninfiltrating/mortality
- Carcinoma, Intraductal, Noninfiltrating/pathology
- Humans
- Immunohistochemistry
- Middle Aged
- Nuclear Proteins/metabolism
- Prognosis
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins c-mdm2
- Receptor, ErbB-2/metabolism
- Survival Analysis
- Tumor Suppressor Protein p14ARF/metabolism
- Tumor Suppressor Protein p53/metabolism
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Affiliation(s)
- SB Vestey
- University of Bristol Division of Surgery, Bristol Royal Infirmary, Bristol, UK
| | - C Sen
- Department of Histopathology, United Bristol Healthcare NHS Trust, Bristol Royal Infirmary, Bristol, UK
| | - CJ Calder
- Department of Histopathology, United Bristol Healthcare NHS Trust, Bristol Royal Infirmary, Bristol, UK
| | - CM Perks
- University of Bristol Division of Surgery, Bristol Royal Infirmary, Bristol, UK
| | - M Pignatelli
- Department of Histopathology, United Bristol Healthcare NHS Trust, Bristol Royal Infirmary, Bristol, UK
| | - ZE Winters
- University of Bristol Division of Surgery, Bristol Royal Infirmary, Bristol, UK
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40
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Abstract
P14/p19ARF (ARF) plays a major role in the activation of p53 by oncogenic signals. The biochemical basis of this has not been fully elucidated. We report here that forced expression of p14ARF enhances phosphorylation of p53 serine 15 (p53S15) in NIH3T3, IMR90 and MCF7 cells. Ectopic expression of the oncogenes c-myc, E2F1 and E1A, all of which activate p53 at least partially via ARF, lead to p53S15 phosphorylation in IMR90 cells. In addition, ectopic expression of p53 also results in p53S15 phosphorylation, suggesting that this is a common event in the ARF-p53 tumor suppression system. Furthermore, p53-, p14ARF-, c-myc- and E2F1-, but not E1A-, induced p53S15 phosphorylation was substantially reduced in AT fibroblasts (GM05823). Downregulation of ATM in MCF7 cells using RNA interference (RNAi) technology significantly attenuated p14ARF- and p53-induced phosphorylation of p53S15. Ectopically expressed ARF in NIH3T3 cells induced ATM nuclear foci and activated ATM kinase. Functionally, ectopic expression of p14ARF and c-myc inhibited the proliferation of IMR90 but not ATM null GM05823 cells, and p14ARF-induced inhibition of MCF7 cell proliferation was significantly attenuated by downregulation of ATM by RNAi. Taken together, these data show a functional role for ATM in ARF-mediated tumor suppression.
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Affiliation(s)
- Yanxia Li
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, ON, Canada
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41
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Abstract
Inactivation of the ARF-p53 tumor suppressor pathway leads to immortalization of murine fibroblasts. The role of this pathway in immortalization of human epithelial cells is not clear. We analyzed the functionality of the p14(ARF)-p53 pathway in human mammary epithelial cells (MEC) immortalized by human papillomavirus 16 (HPV16) E6, the p53 degradation-defective E6 mutant Y54D, or hTERT. E6-MEC or E6Y54D-MEC maintains high-level expression of p14(ARF). Late-passage hTERT-immortalized MEC express p53 but down-regulate p14(ARF). Enforced expression of p14(ARF) induces p53-dependent senescence in hTERT-MEC, while both E6-MEC and E6Y54D-MEC are resistant. We show that E6Y54D inhibits p14(ARF)-induced activation of p53 without inactivation of the p53-dependent DNA damage response. Hence, p53 degradation and inhibition of p14(ARF) signaling to p53 are independent functions of HPV16 E6. Our observations imply that long-term proliferation of MEC requires inactivation of the p14(ARF)-p53 pathway.
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Affiliation(s)
- Vladimir A Shamanin
- Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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42
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Rodríguez IP. The ARF protein in tumor suppression: lessons from mouse models and human tumors. Clin Transl Oncol 2004; 6:73-80. [DOI: 10.1007/bf02710031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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43
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Abstract
Tumor suppressor proteins must be exquisitely regulated since they can induce cell death while preventing cancer. For example, the p19(ARF) tumor suppressor (p14(ARF) in humans) appears to stimulate the apoptotic function of the p53 tumor suppressor to prevent lymphomagenesis and carcinogenesis induced by oncogene overexpression. Here we present a genetic approach to defining the role of p19(ARF) in regulating the apoptotic function of p53 in highly proliferating, homeostatic tissues. In contrast to our expectation, p19(ARF) did not activate the apoptotic function of p53 in lymphocytes or epithelial cells. These results demonstrate that the mechanisms that control p53 function during homeostasis differ from those that are critical for tumor suppression. Moreover, the Mdm2/p53/p19(ARF) pathway appears to exist only under very restricted conditions.
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Affiliation(s)
- Kathleen A O'Leary
- Department of Oncology, University of Wisconsin, Madison, Wisconsin 53706, USA
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44
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Affiliation(s)
- Jenny O'Nions
- Faculty of Medicine, Department of Virology and Ludwig Institute for Cancer Research, Imperial College London, Norfolk Place, London W2 1PG, UK
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45
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Abstract
p53 is believed to sense cellular ribonucleotide depletion in the absence of DNA strand breaks and to respond by imposition of a p21-dependent G1 cell cycle arrest. We now report that the p53-dependent G1 checkpoint is blocked in human carcinoma cell lines after inhibition of de novo purine synthesis by folate analogs inhibitory to glycinamide ribonucleotide formyltransferase (GART). p53 accumulated in HCT116, MCF7, or A549 carcinoma cells upon GART inhibition, but, surprisingly, transcription of several p53 targets, including p21cip1/waf1, was impaired. The mechanism of this defect was examined. The p53 accumulating in these cells was nuclear but was not phosphorylated at serines 6, 15, and 20, nor was it acetylated at lysines 373 or 382. The DDATHF-stabilized p53 bound to the p21 promoter in vitro and in vivo but did not activate histone acetylation over the p53 binding sites in the p21 promoter that is an integral part of the transcriptional response mediated by the DNA damage pathway. We concluded that the robust initial response of the p53 pathway to GART inhibitors is not transcriptionally propagated to target genes due to a defect in p53 post-translational modifications and a failure to open chromatin structure despite promoter binding of this unmodified p53.
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Affiliation(s)
- Julie L Bronder
- Department of Pharmacology and Toxicology and The Massey Cancer Center, Medical College of Virginia Campus of Virginia Commonwealth University, Richmond, Virginia 23298, USA
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46
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Abstract
The HDM2 protein plays an important role in regulating the stability and function of the p53 tumor suppressor protein. In this report, we show that the ribosomal protein L11 can interact with HDM2 and inhibit HDM2 function, thus leading to the stabilization and activation of p53. The inhibition of HDM2 activity by L11 shows some similarity to the previously described activity of ARF, and expression of either ARF or L11 can induce a p53 response. Enhancement of the interaction between endogenous L11 and HDM2 following treatment of cells with low levels of actinomycin-D suggests that the HDM2/L11 interaction represents a novel pathway for p53 stabilization in response to perturbations in ribosome biogenesis.
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Affiliation(s)
- Marion A E Lohrum
- Regulation of Cell Growth Laboratory, NCI-FRCDC, Frederick, MD 21702, USA
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47
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Abstract
Checkpoints suppress improper cell cycle progression to ensure that cells maintain the integrity of their genome. During mitosis, a metaphase checkpoint requires the integration of all chromosomes into a metaphase array in the mitotic spindle prior to mitotic exit. Still, mitotic errors occur in mammalian cells with a relatively high frequency. Metaphase represents the last point of control in mitosis. Once the cell commits to anaphase there are no checkpoints to sense segregation defects. In this context, we will explore our recent finding that non-transformed mammalian cells have a checkpoint that acts subsequent to mitotic errors to block the proliferation of cells that have entered G1 with tetraploid status. This arrest is dependent upon both p53 and pRb, and may represent an important function of both p53 and pRb as tumor suppressors. Further, we discuss the possibility that this mechanism may similarly impose G1 arrest in cells that become aneuploid through errors in mitosis.
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Affiliation(s)
- Robert L Margolis
- Institut de Biologie Structurale J-P Ebel (CEA-CNRS), 38027 Grenoble cedex 1, France.
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48
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Rizos H, Diefenbach E, Badhwar P, Woodruff S, Becker TM, Rooney RJ, Kefford RF. Association of p14ARF with the p120E4F transcriptional repressor enhances cell cycle inhibition. J Biol Chem 2003; 278:4981-9. [PMID: 12446718 DOI: 10.1074/jbc.m210978200] [Citation(s) in RCA: 38] [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: 01/07/2023] Open
Abstract
The p14(ARF) tumor suppressor is a key regulator of cellular proliferation and is frequently inactivated in human cancer. This tumor suppressor functions in the p53 and pRb cell cycle regulatory pathways and can effectively activate both pathways to induce growth arrest or cell death. We now report that p14(ARF) forms a complex with the E1A-regulated transcriptional repressor, p120(E4F). p120(E4F) contacts p14(ARF) and p53 to form a ternary complex in vivo and enhances p14(ARF)-induced G(2) cell cycle arrest in a p53-dependent manner. We suggest that the interaction of p14(ARF) and p120(E4F) forms an important link between the p14(ARF) and p53 tumor suppressor proteins, both of which exhibit enhanced cell cycle inhibitory activity in the presence of this transcriptional repressor.
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Affiliation(s)
- Helen Rizos
- Westmead Institute for Cancer Research, University of Sydney, Westmead Hospital, Westmead, New South Wales 2145, Australia.
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49
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Kannan K, Sharpless NE, Xu J, O'Hagan RC, Bosenberg M, Chin L. Components of the Rb pathway are critical targets of UV mutagenesis in a murine melanoma model. Proc Natl Acad Sci U S A 2003; 100:1221-5. [PMID: 12538879 PMCID: PMC298754 DOI: 10.1073/pnas.0336397100] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2002] [Indexed: 01/17/2023] Open
Abstract
Epidemiological studies support a link between melanoma risk and UV exposure early in life, yet the molecular targets of UV's mutagenic actions are not known. By using well characterized murine models of melanoma, we provide genetic and molecular evidence that identifies components of the Rb pathway as the principal targets of UV mutagenesis in murine melanoma development. In a melanoma model driven by H-RAS activation and loss of p19(ARF) function, UV exposure resulted in a marked acceleration in melanoma genesis, with nearly half of these tumors harboring amplification of cyclin-dependent kinase (cdk) 6, whereas none of the melanomas arising in the absence of UV treatment possessed cdk6 amplification. Moreover, UV-induced melanomas showed a strict reciprocal relationship between cdk6 amplification and p16(INK4a) loss, which is consistent with the actions of UV along the Rb pathway. Most significantly, UV exposure had no impact on the kinetics of melanoma driven by H-RAS activation and p16(INK4a) deficiency. Together, these molecular and genetic data identify components of the Rb pathway as critical biological targets of UV-induced mutagenesis in the development of murine melanoma in vivo.
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Affiliation(s)
- Karuppiah Kannan
- Department of Medical Oncology, Dana-Farber Cancer Institute, Brigham and Women's Hospital, Boston, MA 02115, USA
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50
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Tsai KY, MacPherson D, Rubinson DA, Nikitin AY, Bronson R, Mercer KL, Crowley D, Jacks T. ARF mutation accelerates pituitary tumor development in Rb+/- mice. Proc Natl Acad Sci U S A 2002; 99:16865-70. [PMID: 12486224 PMCID: PMC139235 DOI: 10.1073/pnas.262499599] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [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: 11/18/2022] Open
Abstract
Mice heterozygous for the retinoblastoma (Rb) tumor suppressor gene develop pituitary and thyroid tumors with high penetrance. We demonstrate here that loss of the ARF tumor suppressor strongly accelerates intermediate lobe pituitary tumorigenesis in Rb heterozygous mice. These effects in the pituitary are greater than those conferred by p53 loss in that Rb+-;ARF-- mice display significantly more early atypical lesions than Rb+-; p53-- mice. Also, Rb+-;ARF-- compound mutants do not develop many of the novel tumors or precancerous lesions seen in Rb+-;p53-- compound mutants. Although complete loss of ARF expression is not obligatory for pituitary tumorigenesis in Rb+- mice, alterations of the ARF locus are observed in tumors from Rb+-;ARF+- mice, consistent with a selective advantage of ARF inactivation in this context. We conclude that inactivation of ARF acts more broadly than that of p53 in connecting abrogation of the Rb pathway to tumorigenesis.
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Affiliation(s)
- Kenneth Y Tsai
- Department of Biology and Center for Cancer Research, and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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