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Daks A, Fedorova O, Parfenyev S, Nevzorov I, Shuvalov O, Barlev NA. The Role of E3 Ligase Pirh2 in Disease. Cells 2022; 11:1515. [PMID: 35563824 PMCID: PMC9101203 DOI: 10.3390/cells11091515] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 02/04/2023] Open
Abstract
The p53-dependent ubiquitin ligase Pirh2 regulates a number of proteins involved in different cancer-associated processes. Targeting the p53 family proteins, Chk2, p27Kip1, Twist1 and others, Pirh2 participates in such cellular processes as proliferation, cell cycle regulation, apoptosis and cellular migration. Thus, it is not surprising that Pirh2 takes part in the initiation and progression of different diseases and pathologies including but not limited to cancer. In this review, we aimed to summarize the available data on Pirh2 regulation, its protein targets and its role in various diseases and pathological processes, thus making the Pirh2 protein a promising therapeutic target.
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Affiliation(s)
- Alexandra Daks
- Institute of Cytology RAS, 194064 St. Petersburg, Russia; (O.F.); (S.P.); (I.N.); (O.S.)
| | | | | | | | | | - Nickolai A. Barlev
- Institute of Cytology RAS, 194064 St. Petersburg, Russia; (O.F.); (S.P.); (I.N.); (O.S.)
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2
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Wang Q, Chen Q, Sui J, Tu Y, Guo X, Li F. Celecoxib prevents tumor necrosis factor-α (TNF-α)-induced cellular senescence in human chondrocytes. Bioengineered 2021; 12:12812-12820. [PMID: 34895043 PMCID: PMC8809908 DOI: 10.1080/21655979.2021.2003661] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Osteoarthritis (OA) is a cartilage degenerative disease commonly observed in the elderly population and significantly impacts the normal life of OA patients. It has been reported that the development of pathological cell senescence in chondrocytes is involved in the pathogenesis of OA. Celecoxib is a common non-steroidal anti-inflammatory drug, and it has been recently reported to exert therapeutic effects on OA. However, its underlying mechanism is still unclear. The present study intends to explore its mechanism and provide fundamental evidence for the application of Celecoxib in the treatment of clinical OA. Tumor necrosis factor-α (TNF-α) was utilized to establish an in vitro model of chondrocytes senescence. The elevated reactive oxygen species (ROS) generation, increased cell cycle arrest in G0/G1 phase, reduced telomerase activity, and upregulated senescence-associatedβ-galactosidase (SA-β-Gal) staining were all observed in TNF-α-treated chondrocytes, which were then dramatically reversed by 10 and 20 μM Celecoxib. In addition, the upregulated DNA damage biomarkers, p-ATM, and p-CHK2, observed in TNF-α-treated chondrocytes were significantly downregulated by 10 and 20 μM Celecoxib. Lastly, the expression level of p21 and p53 was greatly elevated in chondrocytes by stimulation with TNF-α which was then pronouncedly repressed by treatment with Celecoxib. Taken together, our data reveal that Celecoxib ameliorated TNF-α-induced cellular senescence in human chondrocytes.
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Affiliation(s)
- Qunli Wang
- Department of Orthopaedic Center, Affiliated Haikou Hospital of Xiangya Medical College, Central South University, Haikou, Hainan, China
| | - Qi Chen
- Department of Orthopedics, The 928th Hospital of the Joint Logistic Support Force of the People's Liberation Army, Haikou, Hainan, China
| | - Jie Sui
- Department of Orthopedics, The 904th Hospital of the Joint Logistic Support Force of the People's Liberation Army, Changzhou, Jiangsu, China
| | - Yuanyuan Tu
- Department of Orthopaedic Center, Affiliated Haikou Hospital of Xiangya Medical College, Central South University, Haikou, Hainan, China
| | - Xiang Guo
- Department of Orthopaedic Center, Affiliated Haikou Hospital of Xiangya Medical College, Central South University, Haikou, Hainan, China
| | - Feng Li
- Department of Orthopedics, The 928th Hospital of the Joint Logistic Support Force of the People's Liberation Army, Haikou, Hainan, China
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3
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Eischen CM, Lozano G. The Mdm network and its regulation of p53 activities: a rheostat of cancer risk. Hum Mutat 2014; 35:728-37. [PMID: 24488925 DOI: 10.1002/humu.22524] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 01/31/2014] [Indexed: 11/07/2022]
Abstract
The potent transcriptional activity of p53 (Trp53, TP53) must be kept in check for normal cell growth and survival. Tumors, which drastically deviate from these parameters, have evolved multiple mechanisms to inactivate TP53, the most prevalent of which is the emergence of TP53 missense mutations, some of which have gain-of-function activities. Another important mechanism by which tumors bypass TP53 functions is via increased levels of two TP53 inhibitors, MDM2, and MDM4. Studies in humans and in mice reveal the complexity of TP53 regulation and the exquisite sensitivity of this pathway to small changes in regulation. Here, we summarize the factors that impinge on TP53 activity and thus cell death/arrest or tumor development.
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Affiliation(s)
- Christine M Eischen
- Vanderbilt University Medical Center, Department of Pathology, Microbiology and Immunology, Nashville, Tennessee
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4
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Eischen CM, Boyd K. Decreased Mdm2 expression inhibits tumor development and extends survival independent of Arf and dependent on p53. PLoS One 2012; 7:e46148. [PMID: 23029416 PMCID: PMC3461014 DOI: 10.1371/journal.pone.0046148] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 08/27/2012] [Indexed: 11/22/2022] Open
Abstract
Inactivation of the Arf-Mdm2-p53 tumor suppressor pathway is a necessary event for tumorigenesis. Arf controls Mdm2, which in turn regulates p53, but Arf and Mdm2 also have p53-independent functions that affect tumor development. Moreover, inhibition of oncogene-induced tumorigenesis relies on Arf and p53, but the requirements of Arf and p53 in tumor development initiated in the absence of overt oncogene overexpression and the role of Mdm2 in this process remain unclear. In a series of genetic experiments in mice with defined deficiencies in Arf, Mdm2 and/or p53, we show Mdm2 haploinsufficiency significantly delayed tumorigenesis in mice deficient in Arf and p53. Mdm2 heterozygosity significantly inhibited tumor development in the absence of Arf, and in contrast to Myc oncogene-driven cancer, this delay in tumorigenesis could not be rescued with the presence of one allele of Arf. Notably, Mdm2 haploinsufficieny blocked the accelerated tumor development in Arf deficient mice caused by p53 heterozygosity. However, tumorigenesis was not inhibited in Mdm2 heterozygous mice lacking both alleles of p53 regardless of Arf status. Surprisingly, loss of Arf accelerated tumor development in p53-null mice. Tumor spectrum was largely dictated by Arf and p53 status with Mdm2 haploinsufficiency only modestly altering the tumor type in some of the genotypes and not the number of primary tumors that arose. Therefore, the significant effects of Mdm2 haploinsufficiency on tumor latency were independent of Arf and required at least one allele of p53, and an Mdm2 deficiency had minor effects on the types of tumors that developed. These data also demonstrate that decreased levels of Mdm2 are protective in the presence of multiple genetic events in Arf and p53 genes that normally accelerate tumorigenesis.
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Affiliation(s)
- Christine M Eischen
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
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5
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Leventaki V, Rodic V, Tripp SR, Bayerl MG, Perkins SL, Barnette P, Schiffman JD, Miles RR. TP53 pathway analysis in paediatric Burkitt lymphoma reveals increased MDM4 expression as the only TP53 pathway abnormality detected in a subset of cases. Br J Haematol 2012; 158:763-71. [PMID: 22845047 DOI: 10.1111/j.1365-2141.2012.09243.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 06/15/2012] [Indexed: 12/21/2022]
Abstract
The TP53 (p53) pathway can be inhibited by TP53 mutation or deletion or by MDM2 overexpression. Both occur in Burkitt lymphoma (BL), but many cases lack either abnormality. Expression patterns of the TP53 inhibitor MDM4 have not been reported in BL, and increased MDM4 could deregulate the TP53 pathway in cases without TP53 or MDM2 abnormalities. We investigated TP53 pathway disruption in paediatric BL patient samples (n = 30) by studying MDM4, MDM2, and CDKN1A (p21) protein and mRNA expression; TP53 mutations; TP53 protein expression; and gene copy number abnormalities. MDM4 protein was expressed in 30/30 tumours, and MDM2 protein was weakly expressed in 7/30 (23%). All cases were negative for CDKN1A protein, and CDKN1A mRNA levels were decreased. TP53 mutations were detected in 5/28 (18%) cases and confirmed by sequencing. TP53 protein was expressed in 15/30 (50%) cases, including 7/8 with TP53 genetic alterations. MDM2 protein and mRNA expression levels did not correlate with lack of TP53 genetic changes or TP53 protein expression; however, there was an inverse relationship between detectable TP53 protein expression and MDM4 copy number gains and mRNA expression. The TP53 pathway is deregulated in paediatric BL cases, and increased MDM4 expression may be the primary mechanism in some cases.
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Affiliation(s)
- Vasiliki Leventaki
- Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, UT 84112-0565, USA
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6
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Abbas HA, Maccio DR, Coskun S, Jackson JG, Hazen AL, Sills TM, You MJ, Hirschi KK, Lozano G. Mdm2 is required for survival of hematopoietic stem cells/progenitors via dampening of ROS-induced p53 activity. Cell Stem Cell 2011; 7:606-17. [PMID: 21040902 DOI: 10.1016/j.stem.2010.09.013] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 05/20/2010] [Accepted: 08/25/2010] [Indexed: 01/13/2023]
Abstract
Mdm2 is an E3 ubiquitin ligase that targets p53 for degradation. p53(515C) (encoding p53R172P) is a hypomorphic allele of p53 that rescues the embryonic lethality of Mdm2(-/-) mice. Mdm2(-/-) p53(515C/515C) mice, however, die by postnatal day 13 resulting from hematopoietic failure. Hematopoietic stem cells and progenitors of Mdm2(-/-) p53(515C/515C) mice were normal in fetal livers but were depleted in postnatal bone marrows. After birth, these mice had elevated reactive oxygen species (ROS) thus activating p53R172P. In the absence of Mdm2, stable p53R172P induced ROS and cell cycle arrest, senescence, and cell death in the hematopoietic compartment. This phenotype was partially rescued with antioxidant treatment and upon culturing of hematopoietic cells in methycellulose at 3% oxygen. p16 was also stabilized because of ROS, and its loss increased cell cycling and partially rescued hematopoiesis and survival. Thus, Mdm2 is required to control ROS-induced p53 levels for sustainable hematopoiesis.
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Affiliation(s)
- Hussein A Abbas
- Program in Genes and Development of The Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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7
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Wang Z, Yang B, Dong L, Peng B, He X, Liu W. A novel oncoprotein Pirh2: rising from the shadow of MDM2. Cancer Sci 2011; 102:909-17. [PMID: 21284766 DOI: 10.1111/j.1349-7006.2011.01899.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Pirh2 (p53-induced RING-H2) is an E3 ubiquitin ligase that can target p53 for degradation and thereby repress a diverse group of biological activities regulated by p53. Notably, Pirh2, rather than MDM2, is the primary degrader of active p53 under conditions of DNA damage. Moreover, Pirh2 is highly expressed in multiple cancer cell lines regardless of p53 status. Recent research has shown that Pirh2 is involved in many signalling pathways related to the genesis and evolution of cancer. This review aims to summarize a comprehensive picture of the role of Pirh2 in cellular processes and its significance to tumorigenesis. Furthermore, this review focuses on its potential role as a cancer therapeutic target.
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Affiliation(s)
- Zhihao Wang
- School of Medicine, Wuhan University, Wuhan, China
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8
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Small-molecule inhibitors of MDM2 as new anticancer therapeutics. Semin Cancer Biol 2009; 20:10-8. [PMID: 19897042 DOI: 10.1016/j.semcancer.2009.10.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Accepted: 10/29/2009] [Indexed: 11/23/2022]
Abstract
It has long been known that traditional anticancer radio- and chemotherapies in part work through direct or indirect activation of the p53 tumour suppressor pathway. However, many of these strategies are nonselective and genotoxic. The emerging understanding of the pathways that regulate p53 has led to the notion that it should be possible to activate the p53 pathway in ways that are inherently nongenotoxic. Important targets for pharmacological interference in this respect are MDM2 and MDMX, key negative regulators of p53. Genetic and pharmacologic studies suggest that blocking the physical interaction of these proteins with p53, or inhibiting the catalytic role of MDM2 in tagging p53 for proteasomal degradation, both of which lead to an increase in the transcriptional activity of p53, may indeed be an efficient and safe way to eradicate tumour cells that retain wild-type p53. Here we review the rationale for such strategies, as well as the current state in the discovery and development of drugs that reactivate p53 by inhibiting its inhibitors MDM2 and MDMX. The first compounds that have been shown in model systems to be able selectively to kill cancer cells in this way are now entering clinical trials and the promise of MDM2 inhibitors as a new therapeutic anticancer modality should therefore become clear in the not-too-distant future.
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9
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The intestinal epithelium compensates for p53-mediated cell death and guarantees organismal survival. Cell Death Differ 2008; 15:1772-81. [PMID: 18636077 DOI: 10.1038/cdd.2008.109] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mdm2 is the major inhibitor of the p53 tumor suppressor. Loss of Mdm2 in mice or in specific tissues of the mouse always yields p53-dependent lethal phenotypes. However, the role of Mdm2 in tissues with high turnover capacity is unknown. We have engineered mice lacking Mdm2 in the intestinal epithelium using the Cre/LoxP system. Loss of Mdm2 (Mdm2(intDelta)) results in viable animals, but neonates display multiple intestinal abnormalities such as hyperplasia, enterocyte vacuolization, and inflammation. These defects correlate with a drastic increase in p53-dependent apoptosis in highly proliferative and differentiated cells. Unexpectedly, the observed phenotypes disappear with age. The tissue selects against Mdm2-null cells and increases its proliferative capacity. Additionally, the intestinal stem and progenitor cell populations are enriched leading to an increase in crypt fission events. Enhanced proliferation is achieved by activation of the canonical Wnt and EGFR-mediated Ras/MAPK pathways. While Mdm2 is a critical inhibitor of p53 in the intestinal epithelium, the tissue employs a series of processes that compensate for cell death.
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10
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Fischer PM. Peptide, Peptidomimetic, and Small-molecule Antagonists of the p53-HDM2 Protein-Protein Interaction. Int J Pept Res Ther 2006; 12:3-19. [PMID: 19617922 PMCID: PMC2710987 DOI: 10.1007/s10989-006-9016-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2005] [Indexed: 12/19/2022]
Abstract
Modulation of intracellular protein-protein interactions has been - and remains - a challenging goal for the discovery and development of small-molecule therapeutic agents. Progress in the pharmacological targeting and understanding at the molecular level of one such interaction that is relevant to cancer drug research, viz. that between the tumour suppressor protein p53 and its negative regulator HDM2, is reviewed here. The first X-ray crystal structure of a complex between a small peptide from the trans-activation domain of p53 and the N-terminal domain of HDM2 was reported almost 10 years ago. The nature of this interaction, which involves just three residue side chains in the p53 peptide ligand and a compact hydrophobic binding pocket in the HDM2 receptor, together with the attractive concept of reactivating the anti-proliferative functions of p53 in tumour cells, has spurned a great deal of effort aimed at finding drug-like antagonists of this interaction. A variety of approaches, including both structure-guided peptidomimetic and de novo design, as well as high through-put screening campaigns, have provided a wealth of leads that might be turned into actual drugs. There is still some way to go as far as optimisation and preclinical development of such leads is concerned, but it is clear already now that antagonists of the p53-HDM2 protein-protein interaction have a good chance of ultimately being successful in providing a new anti-cancer therapy modality, both in monotherapy and to potentiate the effectiveness of existing chemotherapies.
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Affiliation(s)
- Peter M. Fischer
- Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, NG7 2RD Nottingham, UK
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11
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Wang P, Greiner TC, Lushnikova T, Eischen CM. Decreased Mdm2 expression inhibits tumor development induced by loss of ARF. Oncogene 2006; 25:3708-18. [PMID: 16491126 DOI: 10.1038/sj.onc.1209411] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The tumor suppressor p14/p19(ARF) regulates Mdm2, which is known for controlling the p53 tumor suppressor. Here we report that loss of one allele of Mdm2 in cells that lack ARF resulted in a decreased rate of proliferation, fewer chromosomal aberrations, and suppression of Ras-induced transformation. Moreover, a haploinsufficiency of Mdm2 inhibited spontaneous tumor development in ARF-null mice. Remarkably, Mdm2(+/-)ARF(-/-) mice survived an average of 6 months longer than Mdm2(+/+)ARF(-/-) mice. The spectrum of tumors that arose in Mdm2(+/-)ARF(-/-) mice did not significantly differ from those that developed in mice lacking only ARF. However, the extended tumor latency allowed for the emergence of multiple primary tumors in a third of the Mdm2(+/-)ARF(-/-) mice, as compared to the single tumor type that arose in ARF-null only mice. Therefore, a decrease in Mdm2 levels restored regulation of critical cellular processes that are altered during transformation and that occur in the absence of ARF. Our findings also indicate that Mdm2 can function independently from ARF and imply that targeting Mdm2 in tumors that lack ARF expression should be an effective therapeutic approach.
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Affiliation(s)
- P Wang
- Eppley Institute for Research in Cancer, University of Nebraska Medical Center, Omaha, 68198, USA
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12
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Komori H, Enomoto M, Nakamura M, Iwanaga R, Ohtani K. Distinct E2F-mediated transcriptional program regulates p14ARF gene expression. EMBO J 2005; 24:3724-36. [PMID: 16211008 PMCID: PMC1276720 DOI: 10.1038/sj.emboj.7600836] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Accepted: 09/14/2005] [Indexed: 12/19/2022] Open
Abstract
The tumor suppressor p14(ARF) gene is induced by ectopically expressed E2F, a positive regulator of the cell cycle. The gene is expressed at low levels in normally growing cells in contrast to high levels in varieties of tumors. How p14(ARF) gene is regulated by E2F in normally growing cells and tumor cells remains obscure. Here we show that regulation of p14(ARF) gene by E2F is distinct from that of classical E2F targets. It is directly mediated by E2F through a novel E2F-responsive element that varies from the typical E2F site. The element responds to E2F activity resulting from ectopic E2F1 expression, inactivation of pRb by adenovirus E1a or shRNA, but not to phosphorylation of pRb by serum stimulation or ectopic cyclin D1/cyclin-dependent kinase-4 expression in normal human fibroblasts. The element has activity in various tumor cells with defective pRb, but not in normally growing cells. These results indicate that the distinct regulation constitutes the basis of p14(ARF) function as a tumor suppressor, discriminating abnormal growth signals caused by defects in pRb function from normal growth signals.
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Affiliation(s)
- Hideyuki Komori
- Human Gene Sciences Center, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan
| | - Mitsuru Enomoto
- Human Gene Sciences Center, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan
| | - Masataka Nakamura
- Human Gene Sciences Center, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan
| | - Ritsuko Iwanaga
- Human Gene Sciences Center, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan
| | - Kiyoshi Ohtani
- Human Gene Sciences Center, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan
- Human Gene Sciences Center, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan. Tel.: +81 3 5803 4547; Fax: +81 3 5803 0234; E-mail:
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13
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Alt JR, Bouska A, Fernandez MR, Cerny RL, Xiao H, Eischen CM. Mdm2 binds to Nbs1 at sites of DNA damage and regulates double strand break repair. J Biol Chem 2005; 280:18771-81. [PMID: 15734743 DOI: 10.1074/jbc.m413387200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Mdm2 directly regulates the p53 tumor suppressor. However, Mdm2 also has p53-independent activities, and the pathways that mediate these functions are unresolved. Here we report the identification of a specific association of Mdm2 with Mre11, Nbs1, and Rad50, a DNA double strand break repair complex. Mdm2 bound to the Mre11-Nbs1-Rad50 complex in primary cells and in cells containing inactivated p53 or p14/p19ARF, a regulator of Mdm2. Further analysis revealed that Mdm2 directly bound to Nbs1 but not to Mre11 or Rad50. Amino acids 198-314 of Mdm2 were required for Mdm2/Nbs1 association, and neither the N terminus forkhead-associated and breast cancer C-terminal domains nor the C terminus Mre11 binding domain of Nbs1 mediated the interaction of Nbs1 with Mdm2. Mdm2 co-localized with Nbs1 to sites of DNA damage following gamma-irradiation. Notably, Mdm2 overexpression inhibited DNA double strand break repair, and this was independent of p53 and ARF, the alternative reading frame of the Ink4alocus. The delay in DNA repair imposed by Mdm2 required the Nbs1 binding domain of Mdm2, but the ubiquitin ligase domain in Mdm2 was dispensable. Therefore, Nbs1 is a novel p53-independent Mdm2 binding protein and links Mdm2 to the Mre11-Nbs1-Rad50-regulated DNA repair response.
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Affiliation(s)
- Jodi R Alt
- Eppley Institute for Research in Cancer and Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha 68198, USA
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14
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Korgaonkar C, Hagen J, Tompkins V, Frazier AA, Allamargot C, Quelle FW, Quelle DE. Nucleophosmin (B23) targets ARF to nucleoli and inhibits its function. Mol Cell Biol 2005; 25:1258-71. [PMID: 15684379 PMCID: PMC548001 DOI: 10.1128/mcb.25.4.1258-1271.2005] [Citation(s) in RCA: 218] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Revised: 07/06/2004] [Accepted: 11/15/2004] [Indexed: 02/03/2023] Open
Abstract
The ARF tumor suppressor is a nucleolar protein that activates p53-dependent checkpoints by binding Mdm2, a p53 antagonist. Despite persuasive evidence that ARF can bind and inactivate Mdm2 in the nucleoplasm, the prevailing view is that ARF exerts its growth-inhibitory activities from within the nucleolus. We suggest ARF primarily functions outside the nucleolus and provide evidence that it is sequestered and held inactive in that compartment by a nucleolar phosphoprotein, nucleophosmin (NPM). Most cellular ARF is bound to NPM regardless of whether cells are proliferating or growth arrested, indicating that ARF-NPM association does not correlate with growth suppression. Notably, ARF binds NPM through the same domains that mediate nucleolar localization and Mdm2 binding, suggesting that NPM could control ARF localization and compete with Mdm2 for ARF association. Indeed, NPM knockdown markedly enhanced ARF-Mdm2 association and diminished ARF nucleolar localization. Those events correlated with greater ARF-mediated growth suppression and p53 activation. Conversely, NPM overexpression antagonized ARF function while increasing its nucleolar localization. These data suggest that NPM inhibits ARF's p53-dependent activity by targeting it to nucleoli and impairing ARF-Mdm2 association.
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15
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Zhang Z, Li M, Rayburn ER, Hill DL, Zhang R, Wang H. Oncogenes as Novel Targets for Cancer Therapy (Part IV). ACTA ACUST UNITED AC 2005; 5:397-407. [PMID: 16336004 DOI: 10.2165/00129785-200505060-00006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This is the final part of a four-part serial review on oncogenes and their potential use as targets for cancer therapy. Previous sections discussed various categories of oncogenes (growth factors, tyrosine kinases, intermediate signaling molecules, and transcription factors) and the advances made in various strategies being used to alter their actions. This part describes four oncogenes, MDM2, BCL2, XIAP, and Survivin, that are involved in regulation of the cell cycle and apoptosis.
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Affiliation(s)
- Zhuo Zhang
- Division of Clinical Pharmacology, Department of Pharmacology and Toxicology, University of Alabama, Birmingham, Alabama 35294-0019, USA
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16
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Chen D, Padiernos E, Ding F, Lossos IS, Lopez CD. Apoptosis-stimulating protein of p53-2 (ASPP2/53BP2L) is an E2F target gene. Cell Death Differ 2004; 12:358-68. [PMID: 15592436 DOI: 10.1038/sj.cdd.4401536] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The p53 pathway is a central apoptotic regulator. Deregulation of the Rb/E2F pathway occurs in a majority of tumors, resulting in both unrestrained proliferation and enhanced apoptosis sensitivity via p53-dependent and independent mechanisms. However, the mechanisms coupling the p53 and Rb/E2F pathways remain incompletely understood. We report that ASPP2/53BP2L, a p53/p73-binding protein that promotes p53/p73-dependent apoptosis, is an E2F target gene. The ASPP2/53BP2L promoter was identified and ectopic expression of transcription-competent E2F-1 (E2F-2 and E2F-3) stimulated an ASPP2/53BP2L promoter-luciferase reporter. Mutational analysis of the ASPP2/53BP2L promoter identified E2F-binding sites that cooperate for E2F-1 induction and basal repression of ASPP2/53BP2L. Moreover, endogenous ASPP2/53BP2L levels increased after E2F-1 expression, and E2F-1 bound the endogenous ASPP2/53BP2L promoter after chromatin immunoprecipitation. Typical for an E2F target, ASPP2/53BP2L expression was maximal in early S-phase. Thus, ASPP2/53BP2L is downstream of E2F, suggesting that it functions as a common link between the p53/p73 and Rb/E2F apoptotic pathways.
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Affiliation(s)
- D Chen
- Department of Medicine, Division of Hematology and Medical Oncology, L586B, Oregon Health & Science University, Portland, OR 97239, USA
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Abstract
The tumour suppressor p53 is a transcription factor with powerful antitumour activity that is controlled by its negative regulator MDM2 (mouse double minute 2, also termed HDM2 in humans) through a feedback mechanism. MDM2, which is overproduced in many tumours, binds p53 and inhibits its function by modulating its transcriptional activity and stability. Activation of p53 in tumour cells by inhibiting its physical interaction with MDM2 has been in the focus of cancer drug discovery. However, development of nonpeptidic MDM2 antagonists turned out to be challenging. Recently, the first potent and selective small-molecule antagonists of MDM2, the Nutlins, have been identified. Studies with Nutlins provided in vitro and in vivo proof-of-principle for targeting p53–MDM2 interaction for cancer therapy.
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Affiliation(s)
- C Klein
- Pharma Research, Roche Diagnostics GmbH, Penzberg D-82372, Germany
| | - L T Vassilev
- Discovery Oncology, Hoffmann-La Roche Inc., Nutley, NJ 07110, USA
- Discovery Oncology, Hoffmann-La Roche Inc., Nutley, NJ 07110, USA. E-mail:
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18
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Abstract
Interest in the tumour suppressor p53 has generated much information regarding the complexity of its function and regulation in carcinogenesis. However, gaps still exist in our knowledge regarding the role of p53 post-translational modifications in carcinogenesis and cancer prevention. A thorough understanding of p53 will be extremely useful in the development of new strategies for treating and preventing cancer, including restoration of p53 function and selective killing of tumours with mutant TP53.
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Affiliation(s)
- Ann M Bode
- The Hormel Institute, University of Minnesota, 801 16th Avenue NE, Austin, Minnesota 55912, USA
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19
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Eischen CM, Alt JR, Wang P. Loss of one allele of ARF rescues Mdm2 haploinsufficiency effects on apoptosis and lymphoma development. Oncogene 2004; 23:8931-40. [PMID: 15467748 DOI: 10.1038/sj.onc.1208052] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The tumor suppressor p19ARF inhibits Mdm2, which restricts the activity of p53. Complicated feedback and control mechanisms regulate ARF, Mdm2, and p53 interactions. Here we report that ARF haploinsufficiency completely rescued the p53-dependent effects of Mdm2 haploinsufficiency on B-cell development, survival, and transformation. In contrast to Mdm2+/- B cells, Mdm2+/- B cells deficient in ARF were similar to wild-type B cells in their rates of growth and apoptosis and activation of p53. Consequently, the profoundly reduced numbers of B cells in Mdm2+/-Emu-myc transgenic mice were restored to normal levels in ARF+/-Mdm2+/-Emu-myc transgenics. Additionally, ARF+/-Mdm2+/-Emu-myc transgenics developed lymphomas at rates analogous to those observed for wild-type Emu-myc transgenics, demonstrating that loss of one allele of ARF rescued the protracted lymphoma latency in Mdm2+/-Emu-myc transgenics. Importantly, in ARF+/-Mdm2+/-Emu-myc transgenic lymphomas, p53 was inactivated at the frequency observed in lymphomas of wild-type Emu-myc transgenics. Collectively, these results support a model whereby the stoichiometry of Mdm2 and ARF controls apoptosis and tumor development, which should have significant implications in the treatment of malignancies that have inactivated ARF.
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Affiliation(s)
- Christine M Eischen
- Eppley Institute for Research in Cancer, University of Nebraska Medical Center, Omaha, NE 68198, USA.
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Woods YL, Xirodimas DP, Prescott AR, Sparks A, Lane DP, Saville MK. p14 Arf promotes small ubiquitin-like modifier conjugation of Werners helicase. J Biol Chem 2004; 279:50157-66. [PMID: 15355988 DOI: 10.1074/jbc.m405414200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Here we demonstrate a novel p53-independent interaction between the nucleolar tumor suppressors, p14 Arf and Werners helicase (WRN). Binding of p14 Arf to WRN is multivalent and resembles the binding of p14 Arf to Mdm2. Residues 2-14 and 82-101 of p14 Arf and residues in the central region and C terminus of WRN have particular importance for binding. p14 Arf promotes small ubiquitin-like modifier (SUMO) modification of WRN in a synergistic manner with the SUMO-conjugating enzyme, UBCH9. p14 Arf causes redistribution of WRN within the nucleus, and this effect is reversed by expression of a SUMO-specific protease, thus implicating the SUMO conjugation pathway in WRN re-localization. We establish that the ability to promote SUMO conjugation is a general property of the p14 Arf tumor suppressor.
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Affiliation(s)
- Yvonne L Woods
- CR-UK Cell Transformation Research Group, Department of Surgery and Molecular Oncology, Ninewells Hospital and Medical School, Ninewells Avenue, Dundee DD1 9SY, UK.
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21
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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] [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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22
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Lane DP, Fischer PM. Magnifying endoscopic observation of the gastric mucosa, particularly in patients with atrophic gastritis. Endoscopy 1978; 427:789-90. [PMID: 14985740 DOI: 10.1038/427789a] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.
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