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Zhao L, Hsiao T, Stonesifer C, Daniels J, Garcia-Saleem TJ, Choi J, Geskin L, Rook AH, Wood GS. The Robust Tumoricidal Effects of Combined BET/HDAC Inhibition in Cutaneous T-Cell Lymphoma Can Be Reproduced by ΔNp73 Depletion. J Invest Dermatol 2022; 142:3253-3261.e4. [PMID: 35787399 PMCID: PMC9691518 DOI: 10.1016/j.jid.2022.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 05/11/2022] [Accepted: 06/07/2022] [Indexed: 01/05/2023]
Abstract
Combined BET inhibitor/histone deacetylase inhibitor treatment induces marked apoptosis of cutaneous T-cell lymphoma (CTCL) with minimal normal T-cell toxicity. At 96 hours when apoptosis was extensive, a majority of CTCL lines showed ≥2-fold suppression of T-cell survival factors (e.g., AKT1, BCL2 antiapoptotic factors, BIRC5, CD40, CD70, GADD45A, PRKCA, TNFRSF1B, ΔNp73) and ≥2-fold upregulation of proapoptotic factors and tumor suppressors (e.g., ATM, BAK, BIM, multiple caspases, FHIT, HIC1, MGMT, NOD1) (P < 0.05). The largest alterations were in TP73 isoform expression, resulting in increased TAp73/ΔNp73 ratios in CTCL lines and leukemic Sézary cells. Targeted ΔNp73 inhibition by small interfering RNA knockdown resulted in robust CTCL apoptosis comparable with that induced by BET inhibitor/histone deacetylase inhibitor with minimal normal T-cell toxicity. Chromatin immunoprecipitation analysis showed that BET inhibitor/histone deacetylase inhibitor treatment reduced RNA polymerase II binding to ΔNp73, MYC, and AKT1 while increasing its binding to TAp73. CTCL skin lesions expressed both TAp73 and ΔNp73 isoforms in situ. In aggregate, these findings implicate TAp73/ΔNp73 balance as a major factor governing CTCL survival, show that the expression of p73 isoforms can be altered by molecular biological and pharmaceutical means, show that p73 isoforms are expressed across the entire CTCL clinical spectrum, and identify the p73 pathway as a potential target for therapeutics.
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Affiliation(s)
- Lei Zhao
- Department of Dermatology, The School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Tony Hsiao
- Department of Dermatology, The School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Connor Stonesifer
- Department of Dermatology, Columbia University, New York, New York, USA
| | - Jay Daniels
- Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, Ilinois, USA
| | | | - Jaehyuk Choi
- Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, Ilinois, USA
| | - Larisa Geskin
- Department of Dermatology, Columbia University, New York, New York, USA
| | - Alain H Rook
- Department of Dermatology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Gary S Wood
- Department of Dermatology, The School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA.
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2
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Iscan E, Ekin U, Yildiz G, Oz O, Keles U, Suner A, Cakan-Akdogan G, Ozhan G, Nekulova M, Vojtesek B, Uzuner H, Karakülah G, Alotaibi H, Ozturk M. TAp73β Can Promote Hepatocellular Carcinoma Dedifferentiation. Cancers (Basel) 2021; 13:cancers13040783. [PMID: 33668566 PMCID: PMC7918882 DOI: 10.3390/cancers13040783] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 01/14/2021] [Accepted: 01/18/2021] [Indexed: 12/26/2022] Open
Abstract
Simple Summary Hepatocellular carcinoma (HCC) is a highly complex and heterogeneous type of cancer. Hepatocyte dedifferentiation is one of the important steps in the development of HCC. However, its molecular mechanisms are not well known. In this study, we report that transcriptionally active TAp73 isoforms are overexpressed in HCC. We also show that TAp73β suppresses the expression of the hepatocyte markers including CYP3A4, AFP, ALB, HNF4α, while increasing the expression of several cholangiocyte markers in HCC cell lines. In conclusion, this report reveals a pro-oncogenic role for TAp73β in liver cancer. Abstract Hepatocyte dedifferentiation is a major source of hepatocellular carcinoma (HCC), but its mechanisms are unknown. We explored the p73 expression in HCC tumors and studied the effects of transcriptionally active p73β (TAp73β) in HCC cells. Expression profiles of p73 and patient clinical data were collected from the Genomic Data Commons (GDC) data portal and the TSVdb database, respectively. Global gene expression profiles were determined by pan-genomic 54K microarrays. The Gene Set Enrichment Analysis method was used to identify TAp73β-regulated gene sets. The effects of TAp73 isoforms were analyzed in monolayer cell culture, 3D-cell culture and xenograft models in zebrafish using western blot, flow cytometry, fluorescence imaging, real-time polymerase chain reaction (RT-PCR), immunohistochemistry and morphological examination. TAp73 isoforms were significantly upregulated in HCC, and high p73 expression correlated with poor patient survival. The induced expression of TAp73β caused landscape expression changes in genes involved in growth signaling, cell cycle, stress response, immunity, metabolism and development. Hep3B cells overexpressing TAp73β had lost hepatocyte lineage biomarkers including ALB, CYP3A4, AFP, HNF4α. In contrast, TAp73β upregulated genes promoting cholangiocyte lineage such as YAP, JAG1 and ZO-1, accompanied with an increase in metastatic ability. Our findings suggest that TAp73β may promote malignant dedifferentiation of HCC cells.
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Affiliation(s)
- Evin Iscan
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Izmir 35000, Turkey
| | - Umut Ekin
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Izmir 35000, Turkey
| | - Gokhan Yildiz
- Department of Medical Biology, Faculty of Medicine, Karadeniz Technical University, Trabzon 61000, Turkey;
| | - Ozden Oz
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Izmir 35000, Turkey
- Izmir Bozyaka Education and Research Hospital, University of Health Sciences, Izmir 35000, Turkey
| | - Umur Keles
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Izmir 35000, Turkey
| | - Aslı Suner
- Department of Biostatistics and Medical Informatics, Faculty of Medicine, Ege University, Izmir 35000, Turkey;
| | - Gulcin Cakan-Akdogan
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Department of Medical Biology, Faculty of Medicine, Dokuz Eylul University, Izmir 35000, Turkey
| | - Gunes Ozhan
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Izmir 35000, Turkey
| | - Marta Nekulova
- RECAMO, Masaryk Memorial Cancer Institute, 60200 Brno, Czech Republic; (M.N.); (B.V.)
| | - Borivoj Vojtesek
- RECAMO, Masaryk Memorial Cancer Institute, 60200 Brno, Czech Republic; (M.N.); (B.V.)
| | - Hamdiye Uzuner
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Izmir 35000, Turkey
| | - Gökhan Karakülah
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Izmir 35000, Turkey
| | - Hani Alotaibi
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Izmir 35000, Turkey
| | - Mehmet Ozturk
- Izmir Biomedicine and Genome Center, Izmir 35000, Turkey; (E.I.); (U.E.); (O.O.); (U.K.); (G.C.-A.); (G.O.); (H.U.); (G.K.); (H.A.)
- Correspondence:
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3
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Cetin M, Odabas G, Douglas LR, Duriez PJ, Balcik-Ercin P, Yalim-Camci I, Sayan AE, Yagci T. ROR1 Expression and Its Functional Significance in Hepatocellular Carcinoma Cells. Cells 2019; 8:cells8030210. [PMID: 30832318 PMCID: PMC6468649 DOI: 10.3390/cells8030210] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 02/26/2019] [Indexed: 02/07/2023] Open
Abstract
Background: Hepatocellular carcinoma (HCC) is a common and deadly cancer; however, very little improvement has been made towards its diagnosis and prognosis. The expression and functional contribution of the receptor tyrosine kinase ROR1 have not been investigated in HCC before. Hence, we investigated the expression of ROR1 in HCC cells and assessed its involvement in hepatocarcinogenesis. Methods: Recombinant bacterial ROR1 protein was used as an immunogen to generate ROR1 monoclonal antibodies. ROR1 transcript levels were detected by RT-qPCR and the protein expression of ROR1 in HCC was assessed by Western blotting by using homemade anti-ROR1 monoclonal antibodies. Apoptosis, cell cycle, trans-well migration, and drug efflux assays were performed in shRNA-ROR1 HCC cell clones to uncover the functional contribution of ROR1 to hepatocarcinogenesis. Results: New ROR1 antibodies specifically detected endogenous ROR1 protein in human and mouse HCC cell lines. ROR1-knockdown resulted in decreased proliferation and migration but enhanced resistance to apoptosis and anoikis. The observed chemotherapy-resistant phenotype of ROR1-knockdown cells was due to enhanced drug efflux and increased expression of multi-drug resistance genes. Conclusions: ROR1 is expressed in HCC and contributes to disease development by interfering with multiple pathways. Acquired ROR1 expression may have diagnostic and prognostic value in HCC.
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Affiliation(s)
- Metin Cetin
- Department of Molecular Biology and Genetics, Gebze Technical University, Kocaeli 41400, Turkey.
| | - Gorkem Odabas
- Department of Molecular Biology and Genetics, Gebze Technical University, Kocaeli 41400, Turkey.
| | - Leon R Douglas
- Protein Core Facility, Cancer Research UK and Experimental Cancer Medicine Centres, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Patrick J Duriez
- Protein Core Facility, Cancer Research UK and Experimental Cancer Medicine Centres, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
| | - Pelin Balcik-Ercin
- Department of Molecular Biology and Genetics, Gebze Technical University, Kocaeli 41400, Turkey.
| | - Irem Yalim-Camci
- Department of Molecular Biology and Genetics, Gebze Technical University, Kocaeli 41400, Turkey.
| | - Abdulkadir Emre Sayan
- Cancer Sciences Unit and Cancer Research UK Centre, University of Southampton, Southampton General Hospital, Somers Cancer Research Building, Mailpoint 824, Southampton SO16 6YD, UK.
| | - Tamer Yagci
- Department of Molecular Biology and Genetics, Gebze Technical University, Kocaeli 41400, Turkey.
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4
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Rotblat B, Agostini M, Niklison-Chirou MV, Amelio I, Willis AE, Melino G. Sustained protein synthesis and reduced eEF2K levels in TAp73 -\- mice brain: a possible compensatory mechanism. Cell Cycle 2018; 17:2637-2643. [PMID: 30507330 DOI: 10.1080/15384101.2018.1553341] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The transcription factor p73 is a member of the p53 family, of which the transactivation domain containing isoform (TAp73) plays key roles in brain development and neuronal stem cells. TAp73 also facilitates homoeostasis and prevents oxidative damage in vivo by inducing the expression of its target genes. Recently, we found that in addition to its role in regulation of transcription, TAp73 also affects mRNA translation. In cultured cells, acute TAp73 depletion activates eEF2K, which phosphorylates eEF2 reducing mRNA translation elongation. As a consequence, there is a reduction in global proteins synthesis rates and reprogramming of the translatome, leading to a selective decrease in the translation of rRNA processing factors. Given the dramatic effects of Tap73 depletion in vitro it was important to determine whether similar effects were observed in vivo. Here, we report the surprising finding that in brains of TAp73 KO mice there is a reduced level of eEF2K, which allows protein synthesis rates to be maintained suggesting a compensation model. These data provide new insights to the role of TAp73 in translation regulation and the eEF2K pathway in the brain.
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Affiliation(s)
- Barak Rotblat
- a MRC Toxicology Unit , University of Cambridge , Rome , UK.,b Department of Life Sciences , Ben Gurion University in the Negev , Beer Sheva , Israel
| | - Massimiliano Agostini
- a MRC Toxicology Unit , University of Cambridge , Rome , UK.,c Department of Experimental Medicine and Surgery, IDI-IRCCS , University of Rome Tor Vergata , Rome , Italy
| | - Maria Victoria Niklison-Chirou
- a MRC Toxicology Unit , University of Cambridge , Rome , UK.,d Blizard Institute of Cell and Molecular Science, Barts and the London School of Medicine and Dentistry , Queen Mary University of London , London , UK
| | - Ivano Amelio
- a MRC Toxicology Unit , University of Cambridge , Rome , UK
| | - Anne E Willis
- a MRC Toxicology Unit , University of Cambridge , Rome , UK
| | - Gerry Melino
- a MRC Toxicology Unit , University of Cambridge , Rome , UK.,c Department of Experimental Medicine and Surgery, IDI-IRCCS , University of Rome Tor Vergata , Rome , Italy
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5
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p73 promotes glioblastoma cell invasion by directly activating POSTN (periostin) expression. Oncotarget 2017; 7:11785-802. [PMID: 26930720 PMCID: PMC4914248 DOI: 10.18632/oncotarget.7600] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 01/18/2016] [Indexed: 12/13/2022] Open
Abstract
Glioblastoma Multiforme is one of the most highly metastatic cancers and constitutes 70% of all gliomas. Despite aggressive treatments these tumours have an exceptionally bad prognosis, mainly due to therapy resistance and tumour recurrence. Here we show that the transcription factor p73 confers an invasive phenotype by directly activating expression of POSTN (periostin, HGNC:16953) in glioblastoma cells. Knock down of endogenous p73 reduces invasiveness and chemo-resistance, and promotes differentiation in vitro. Using chromatin immunoprecipitation and reporter assays we demonstrate that POSTN, an integrin binding protein that has recently been shown to play a major role in metastasis, is a transcriptional target of TAp73. We further show that POSTN overexpression is sufficient to rescue the invasive phenotype of glioblastoma cells after p73 knock down. Additionally, bioinformatics analysis revealed that an intact p73/POSTN axis, where POSTN and p73 expression is correlated, predicts bad prognosis in several cancer types. Taken together, our results support a novel role of TAp73 in controlling glioblastoma cell invasion by regulating the expression of the matricellular protein POSTN.
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6
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Fujitani M, Sato R, Yamashita T. Loss of p73 in ependymal cells during the perinatal period leads to aqueductal stenosis. Sci Rep 2017; 7:12007. [PMID: 28931858 PMCID: PMC5607290 DOI: 10.1038/s41598-017-12105-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Accepted: 09/05/2017] [Indexed: 11/17/2022] Open
Abstract
The p53 family member p73 plays a critical role in brain development. p73 knockout mice exhibit a number of deficits in the nervous system, such as neuronal death, hydrocephalus, hippocampal dysgenesis, and pheromonal defects. Among these phenotypes, the mechanisms of hydrocephalus remain unknown. In this study, we generated a p73 knock-in (KI) mutant mouse and a conditional p73 knockout mouse. The homozygous KI mutants showed aqueductal stenosis. p73 was expressed in the ependymal cell layer and several brain areas. Unexpectedly, when p73 was disrupted during the postnatal period, animals showed aqueductal stenosis at a later stage but not hydrocephalus. An assessment of the integrity of cilia and basal body (BB) patch formation suggests that p73 is required to establish translational polarity but not to establish rotational polarity or the planar polarization of BB patches. Deletion of p73 in adult ependymal cells did not affect the maintenance of translational polarity. These results suggest that the loss of p73 during the embryonic period is critical for hydrocephalus development.
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Affiliation(s)
- Masashi Fujitani
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan. .,Molecular Research Center for Children's Mental Development, United Graduate School of Child Development, Osaka University, 2-2 Yamadaoka, Suita, Osaka, 565-0872, Japan. .,Department of Anatomy and Neuroscience, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan.
| | - Ryohei Sato
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Toshihide Yamashita
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan. .,World Premier International, Immunology Frontier Research Center, Osaka University, 3-1 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan. .,Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan.
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7
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Tonino SH, Mulkens CE, van Laar J, Derks IAM, Suo G, Croon-de Boer F, van Oers MHJ, Eldering E, Wang JY, Kater AP. Induction of TAp73 by platinum-based compounds to overcome drug resistance in p53 dysfunctional chronic lymphocytic leukemia. Leuk Lymphoma 2014; 56:2439-47. [PMID: 25511680 DOI: 10.3109/10428194.2014.996751] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In chronic lymphocytic leukemia (CLL), strategies to overcome drug resistance due to p53 dysfunction are highly needed. Platinum-based compounds such as cisplatinum (CDDP) are active in fludarabine-refractory CLL through a largely unknown mechanism. We analyzed the mechanism of action of CDDP in the context of p53 dysfunctionality. In vitro treatment with CDDP did not induce death in quiescent CLL cells, but did induce apoptosis in CD40-ligand (and CpG) stimulated and proliferating cells, irrespective of p53 function. In the p53 dysfunctional prolymphocytic cell-line MEC1, CDDP treatment resulted in apoptosis, cell cycle arrest and ABL1-dependent expression of TAp73, CDKN1A, PUMA and BID. TAp73 RNA-interference decreased sensitivity to CDDP. Finally, both in vitro stimulated CLL cells and lymph node (LN) derived CLL cells showed increased TAp73 expression in comparison with quiescent peripheral blood derived cells. Activity of CDDP may therefore be mediated by TAp73, especially in the context of activation such as occurs in the LN microenvironment.
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Affiliation(s)
- Sanne H Tonino
- a Department of Hematology , Academic Medical Center , Amsterdam , The Netherlands.,b Lymphoma and Myeloma Center Amsterdam (LYMMCARE) , Amsterdam , The Netherlands
| | - Chantal E Mulkens
- c Laboratory for Experimental Immunology, Academic Medical Center , Amsterdam , The Netherlands
| | - Jacoline van Laar
- c Laboratory for Experimental Immunology, Academic Medical Center , Amsterdam , The Netherlands
| | - Ingrid A M Derks
- c Laboratory for Experimental Immunology, Academic Medical Center , Amsterdam , The Netherlands
| | - Guangli Suo
- d Division of Hematology-Oncology, Department of Medicine , Moores Cancer Center, University of California , San Diego, La Jolla , CA , USA
| | | | - Marinus H J van Oers
- a Department of Hematology , Academic Medical Center , Amsterdam , The Netherlands.,b Lymphoma and Myeloma Center Amsterdam (LYMMCARE) , Amsterdam , The Netherlands
| | - Eric Eldering
- b Lymphoma and Myeloma Center Amsterdam (LYMMCARE) , Amsterdam , The Netherlands.,c Laboratory for Experimental Immunology, Academic Medical Center , Amsterdam , The Netherlands
| | - Jean Y Wang
- d Division of Hematology-Oncology, Department of Medicine , Moores Cancer Center, University of California , San Diego, La Jolla , CA , USA
| | - Arnon P Kater
- a Department of Hematology , Academic Medical Center , Amsterdam , The Netherlands.,b Lymphoma and Myeloma Center Amsterdam (LYMMCARE) , Amsterdam , The Netherlands
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8
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Grespi F, Amelio I, Tucci P, Annicchiarico-Petruzzelli M, Melino G. Tissue-specific expression of p73 C-terminal isoforms in mice. Cell Cycle 2012; 11:4474-83. [PMID: 23159862 PMCID: PMC3552929 DOI: 10.4161/cc.22787] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
p73 is a p53 family transcription factor. Due to the presence in the 5' flanking region of two promoters, there are two N-terminal variants, TAp73, which retains a fully active transactivation domain (TA), and ΔNp73, in which the N terminus is truncated. In addition, extensive 3' splicing gives rise to at least seven distinctive isoforms; TAp73-selective knockout highlights its role as a regulator of cell death, senescence and tumor suppressor. ΔNp73-selective knockout, on the other hand, highlights anti-apoptotic function of ΔNp73 and its involvement in DNA damage response. In this work, we investigated the expression pattern of murine p73 C-terminal isoforms. By using a RT-PCR approach, we were able to detect mRNAs of all the C-terminal isoforms described in humans. We characterized their in vivo expression profile in mouse organs and in different mouse developmental stages. Finally, we investigated p73 C-terminal expression profile following DNA damage, ex vivo after primary cultures treatment and in vivo after systemic administration of cytotoxic compounds. Overall, our study first elucidates spatio-temporal expression of mouse p73 isoforms and provides novel insights on their expression-switch under triggered conditions.
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Affiliation(s)
- Francesca Grespi
- Medical Research Council, Toxicology Unit, Leicester University, Leicester, UK
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9
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Malatesta M, Peschiaroli A, Memmi EM, Zhang J, Antonov A, Green DR, Barlev NA, Garabadgiu AV, Zhou P, Melino G, Bernassola F. The Cul4A-DDB1 E3 ubiquitin ligase complex represses p73 transcriptional activity. Oncogene 2012; 32:4721-6. [PMID: 23085759 DOI: 10.1038/onc.2012.463] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 08/15/2012] [Accepted: 08/22/2012] [Indexed: 11/09/2022]
Abstract
The Cullin4A (cul4A)-dependent ligase (CDL4A) E3 has been implicated in a variety of biological processes, including cell cycle progression and DNA damage response. Remarkably, CDL4A exerts its function through both proteolytic and non-proteolytic events. Here, we show that the p53 family member p73 is able to interact with the CDL4A complex through its direct binding to the receptor subunit DNA-binding protein 1 (DDB1). As a result, the CDL4A complex is able to monoubiquitylate p73. Modification of p73 by CDL4A-mediated ubiquitylation does not affect p73 protein stability, but negatively regulates p73-dependent transcriptional activity. Indeed, genetic or RNA interference-mediated depletion of DDB1 induces the expression of several p73 target genes in a p53-independent manner. In addition, by exploiting a bioinformatic approach, we found that elevated expression of Cul4A in human breast carcinomas is associated with repression of p73 target genes. In conclusion, our findings add a novel insight into the regulation of p73 by the CDL4A complex, through the inhibition of its transcriptional function.
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Affiliation(s)
- M Malatesta
- Department of Experimental Medicine and Surgery, University of Rome 'Tor Vergata', Rome, Italy
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10
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Taebunpakul P, Sayan BS, Flinterman M, Klanrit P, Gäken J, Odell EW, Melino G, Tavassoli M. Apoptin induces apoptosis by changing the equilibrium between the stability of TAp73 and ΔNp73 isoforms through ubiquitin ligase PIR2. Apoptosis 2012; 17:762-76. [PMID: 22484480 DOI: 10.1007/s10495-012-0720-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Apoptin, a protein derived from the chicken anaemia virus, induces cell death in various cancer cells but shows little or no cytotoxicity in normal cells. The mechanism of apoptin-induced cell death is currently unknown but it appears to induce apoptosis independent of p53 status. Here we show that p73, a p53 family member, is important in apoptin-induced apoptosis. In p53 deficient and/or mutated cells, apoptin induced the expression of TAp73 leading to the induction of apoptosis. Knockdown of p73 using siRNA resulted in a significant reduction in apoptin-induced cytotoxicity. The p53 and p73 pro-apoptotic target PUMA plays an important role in apoptin-induced cell death as knockdown of PUMA significantly reduced cell sensitivity to apoptin. Importantly, apoptin expression resulted in a marked increase in TAp73 protein stability. Investigation into the mechanisms of TAp73 stability showed that apoptin induced the expression of the ring finger domain ubiquitin ligase PIR2 which is involved in the degradation of the anti-apoptotic ∆Np73 isoform. Collectively, our results suggest a novel mechanism of apoptin-induced apoptosis through increased TAp73 stability and induction of PIR2 resulting in the degradation of ∆Np73 and activation of pro-apoptotic targets such as PUMA causing cancer cell death.
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Affiliation(s)
- P Taebunpakul
- Head and Neck Oncology Group, King's College London Dental Institute, Floor 28 Tower Wing, Guy's Hospital Campus, London, SE1 9RT, UK
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11
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Conforti F, Yang AL, Agostini M, Rufini A, Tucci P, Nicklison-Chirou MV, Grespi F, Velletri T, Knight RA, Melino G, Sayan BS. Relative expression of TAp73 and ΔNp73 isoforms. Aging (Albany NY) 2012; 4:202-5. [PMID: 22388545 PMCID: PMC3348480 DOI: 10.18632/aging.100441] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The transcription factor p73 belongs to the p53 family of tumour suppressors and similar to other family members, transcribed as different isoforms with opposing pro- and anti-apoptotic functions. Unlike p53, p73 mutations are extremely rare in cancers. Instead, the pro-apoptotic activities of transcriptionally active p73 isoforms are commonly inhibited by over-expression of the dominant negative p73 isoforms. Therefore the relative ratio of different p73 isoforms is critical for the cellular response to a chemotherapeutic agent. Here, we analysed the expression of N-terminal p73 isoforms in cell lines and mouse tissues. Our data showed that the transcriptionally competent TAp73 isoform is abundantly expressed in cancer cell lines compared to the dominant negative ΔNp73 isoform. Interestingly, we detected higher levels of ΔNp73 in some mouse tissues, suggesting that ΔNp73 may have a physiological role in these tissues.
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Affiliation(s)
- Franco Conforti
- University of Southampton, Cancer Sciences Unit, Somers Cancer Research Building, Southampton, UK
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12
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De Cola A, Bongiorno-Borbone L, Bianchi E, Barcaroli D, Carletti E, Knight RA, Di Ilio C, Melino G, Sette C, De Laurenzi V. FLASH is essential during early embryogenesis and cooperates with p73 to regulate histone gene transcription. Oncogene 2011; 31:573-82. [PMID: 21725362 DOI: 10.1038/onc.2011.274] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Replication-dependent histone gene expression is a fundamental process occurring in S-phase under the control of the cyclin-E/CDK2 complex. This process is regulated by a number of proteins, including Flice-Associated Huge Protein (FLASH) (CASP8AP2), concentrated in specific nuclear organelles known as HLBs. FLASH regulates both histone gene transcription and mRNA maturation, and its downregulation in vitro results in the depletion of the histone pull and cell-cycle arrest in S-phase. Here we show that the transcription factor p73 binds to FLASH and is part of the complex that regulates histone gene transcription. Moreover, we created a novel gene trap to disrupt FLASH in mice, and we show that homozygous deletion of FLASH results in early embryonic lethality, owing to arrest of FLASH(-/-) embryos at the morula stage. These results indicate that FLASH is an essential, non-redundant regulator of histone transcription and cell cycle during embryogenesis.
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Affiliation(s)
- A De Cola
- IDI-IRCCS Biochemistry Laboratory, c/o Department of Experimental Medicine, University of Rome Tor Vergata, Roma, Italy
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13
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P73 regulates cisplatin-induced apoptosis in ovarian cancer cells via a calcium/calpain-dependent mechanism. Oncogene 2011; 30:4219-30. [PMID: 21516125 PMCID: PMC3194400 DOI: 10.1038/onc.2011.134] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
P73 is important in drug-induced apoptosis in some cancer cells, yet its role in the regulation of chemosensitivity in ovarian cancer (OVCA) is poorly understood. Furthermore, if and how the deregulation of p73-mediated apoptosis confers resistance to cisplatin (CDDP) treatment is unclear. Here we demonstrate that TAp73α over-expression enhanced CDDP-induced PARP cleavage and apoptosis in both chemosensitive (OV2008 and A2780s) and their resistant counterparts (C13* and A2780cp) and another chemoresistant OVCA cells (Hey); in contrast, the effect of ΔNp73α over-expression was variable. P73α downregulation attenuated CDDP-induced PUMA and NOXA upregulation and apoptosis in OV2008 cells. CDDP decreased p73α steady-state protein levels in OV2008, but not in C13*, although the mRNA expression was identical. CDDP-induced p73α downregulation was mediated by a calpain-dependent pathway. CDDP induced calpain activation and enhanced its cytoplasmic interaction and co-localization with p73α in OV2008, but not C13* cells. CDDP increased the intracellular calcium concentration ([Ca(2+)](i)) in OV2008 but not C13* whereas cyclopiazonic acid (CPA), a Ca(2+)-ATPase inhibitor, caused this response and calpain activation, p73α processing and apoptosis in both cell types. CDDP-induced [Ca(2+)](i) increase in OV2008 cells was not effected by the elimination of extracellular Ca(2+), but this was attenuated by the depletion of internal Ca(2+) store, indicating that mobilization of intracellular Ca(2+]) stores was potentially involved. These findings demonstrate that p73α and its regulation by the Ca(2+)-mediated calpain pathway are involved in CDDP-induced apoptosis in OVCA cells and that dysregulation of Ca(2+)/calpain/p73 signaling may in part be the pathophysiology of CDDP resistance. Understanding the cellular and molecular mechanisms of chemoresistance will direct the development of effective strategies for the treatment of chemoresistant OVCA.
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14
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Gomes CC, Diniz MG, Oliveira CS, Tavassoli M, Odell EW, Gomez RS, De Marco L. Impact of WWOX alterations on p73, ΔNp73, p53, cell proliferation and DNA ploidy in salivary gland neoplasms. Oral Dis 2011; 17:564-71. [PMID: 21332605 DOI: 10.1111/j.1601-0825.2011.01802.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVE WWOX gene is altered in a variety of neoplasms. Wwox is pro-apoptotic through interaction with p73 and may be involved in chromosomal stability by interaction with p73 and p53. The aims of this study were to characterize WWOX transcription, methylation status and immunoexpression in salivary neoplasms and to determine whether these were associated with p73, p53, cell proliferation and DNA ploidy. MATERIALS AND METHODS Seven malignant and 21 benign fresh salivary neoplasms were included. WWOX expression was determined by RT-PCR and sequencing of transcripts, quantitative PCR and immunohistochemistry. Methylation-specific PCR was used to assess the methylation of its first exon. For p73, ΔNp73, p53 and ki67 immunohistochemistry and ploidy analysis, 29 malignant samples from archives were included. RESULTS No consistent pattern of WWOX exon 1 methylation was found, but aberrant and novel transcripts were observed in 17/28 neoplasms; 55% of tumours showed reduced WWOX RNA. WWOX RNA levels were associated with p53 immunopositivity. Immunohistochemical Wwox expression did not correlate with methylation status, p53 or p73 expression or proliferation. p73, proliferation and DNA ploidy were associated with malignant phenotype. CONCLUSION Aberrant WWOX transcription and decreased expression are frequent in salivary neoplasms and WWOX transcription is associated with p53 staining.
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Affiliation(s)
- C C Gomes
- Department of Pathology, Biological Sciences Institute, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
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15
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Nekulová M, Zitterbart K, Sterba J, Veselská R. Analysis of the intracellular localization of p73 N-terminal protein isoforms TAp73 and ∆Np73 in medulloblastoma cell lines. J Mol Histol 2010; 41:267-75. [PMID: 20803057 DOI: 10.1007/s10735-010-9288-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 08/18/2010] [Indexed: 12/13/2022]
Abstract
The protein homologous to the tumor suppressor p53, p73, has essential roles in development and tumorigenesis. This protein exists in a wide range of isoforms with different, even antagonistic, functions. However, there are virtually no detailed morphological studies analyzing the endogenous expression of p73 isoforms at the cellular level in cancer cells. In this study, we investigated the expression and subcellular distribution of two N-terminal isoforms, TAp73 and ΔNp73, in medulloblastoma cells using immunofluorescence microscopy. Both proteins were observed in all cell lines examined, but differences were noted in their intracellular localization between the reference Daoy cell line and four newly established medulloblastoma cell lines (MBL-03, MBL-06, MBL-07 and MBL-10). In the new cell lines, TAp73 and ΔNp73 were located predominantly in cell nuclei. However, there was heterogeneity in TAp73 distribution in the cells of all MBL cell lines, with the protein located in the nucleus and also in a limited non-random area in the cytoplasm. In a small percentage of cells, we detected cytoplasmic localization of TAp73 only, i.e., nuclear exclusion was observed. Our results provide a basis for future studies on the causes and function of distinct intracellular localization of p73 protein isoforms with respect to different protein-protein interactions in medulloblastoma cells.
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Affiliation(s)
- Marta Nekulová
- Department of Experimental Biology, School of Science, Masaryk University, Brno, Czech Republic
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16
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Differential control of TAp73 and DeltaNp73 protein stability by the ring finger ubiquitin ligase PIR2. Proc Natl Acad Sci U S A 2010; 107:12877-82. [PMID: 20615966 DOI: 10.1073/pnas.0911828107] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
p73 is a p53-related transcription factor with fundamental roles in development and tumor suppression. Transcription from two different promoters on the p73 gene results in generation of transcriptionally active TAp73 isoforms and dominant negative DeltaNp73 isoforms with opposing pro- and anti-apoptotic functions. Therefore, the relative ratio of each isoform is an important determinant of the cell fate. Proteasomal degradation of p73 is mediated by polyubiquitination-dependent and -independent processes both of which appear, thus far, to lack selectivity for the TAp73 and DeltaNp73 isoforms. Here, we describe the characterization of another transcriptional target of TAp73; a ring finger domain ubiquitin ligase p73 Induced RING 2 protein (PIR2). Although PIR2 was initially identified a p53-induced gene (p53RFP), low abundance of PIR2 transcript in mouse embryonic fibroblasts of TAp73 KO mice compared with WT mice and comparison of PIR2 mRNA and protein levels following TAp73 or p53 overexpression substantiate TAp73 isoforms as strong inducers of PIR2. Although PIR2 expression was induced by DNA damage, its expression did not alter apoptotic response or cell cycle profile per se. However, coexpression of PIR2 with TAp73 or DeltaNp73 resulted in an increase of the TA/DeltaNp73 ratio, due to preferential degradation of DeltaNp73. Finally, PIR2 was able to relieve the inhibitory effect of DeltaNp73 on TAp73 induced apoptosis following DNA damage. These results suggest that PIR2, by being induced by TAp73 and degrading DeltaNp73, differentially regulates TAp73/DeltaNp73 stability, and, hence, it may offer a therapeutic approach to enhance the chemosensitivity of tumor cells.
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Logotheti S, Michalopoulos I, Sideridou M, Daskalos A, Kossida S, Spandidos DA, Field JK, Vojtesek B, Liloglou T, Gorgoulis V, Zoumpourlis V. Sp1 binds to the external promoter of the p73 gene and induces the expression of TAp73gamma in lung cancer. FEBS J 2010; 277:3014-27. [PMID: 20528922 DOI: 10.1111/j.1742-4658.2010.07710.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The p73 gene possesses an extrinsic P1 promoter and an intrinsic P2 promoter, resulting in TAp73 and DeltaNup73 isoforms, respectively. The ultimate effect of p73 in oncogenesis is thought to depend on the apoptotic TA to antiapoptotic DeltaN isoforms' ratio. This study was aimed at identifying novel transcription factors that affect TA isoform synthesis. With the use of bioinformatics tools, in vitro binding assays, and chromatin immunoprecipitation analysis, a region extending -233 to -204 bp upstream of the transcription start site of the human p73 P1 promoter, containing conserved Sp1-binding sites, was characterized. Treatment of cells with Sp1 RNAi and Sp1 inhibitor functionally suppress TAp73 expression, indicating positive regulation of P1 by the Sp1 protein. Notably Sp1 inhibition or knockdown also reduces DeltaNup73 protein levels. Therefore, Sp1 directly regulates TAp73 transcription and affects DeltaNup73 levels in lung cancer. TAp73gamma was shown to be the only TA isoform overexpressed in several lung cancer cell lines and in 26 non-small cell lung cancers, consistent with Sp1 overexpression, thereby questioning the apoptotic role of this specific p73 isoform in lung cancer.
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Affiliation(s)
- Stella Logotheti
- Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, Athens, Greece
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18
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Sayan AE, D'Angelo B, Sayan BS, Tucci P, Cimini A, Cerù MP, Knight RA, Melino G. p73 and p63 regulate the expression of fibroblast growth factor receptor 3. Biochem Biophys Res Commun 2010; 394:824-8. [PMID: 20298673 DOI: 10.1016/j.bbrc.2010.03.084] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Accepted: 03/12/2010] [Indexed: 11/16/2022]
Abstract
p53, p63 and p73 make a family of transcription factors that play a vital role in development and cancer. All p53 family members have more than one promoter producing Transactivating (TA) and Dominant Negative (DeltaN) isoforms and their mRNAs are subjected to extensive splicing at 3' end to produce multiple protein products. p53 is usually inactivated by point mutations during tumorigenesis, whereas the expression levels and p63 and p73 are modulated to give tumor cells a selective advantage. In this study, aiming to find novel targets of the p53 family members, we identified FGFR3 as a gene transcriptionally controlled by p63 and p73. FGFR3 has been implicated in development and tumor biology as activating mutations of this gene was described in skeletal disorders, non-invasive skin conditions and superficial bladder cancers. We found that TAp73, TAp63 and DeltaNp63 was capable of inducing FGFR3. siRNA mediated downregulation of DeltaNp63 decreased endogenous FGFR3 protein levels. Our findings of this new link between p53 family proteins and FGFR3 may help understanding the transition of superficial bladder cancers to an invasive phenotype.
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Affiliation(s)
- A Emre Sayan
- MRC Toxicology Unit, Lancaster Road, Hodgkin Building, Leicester LE1 9HN, UK.
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19
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Wilhelm MT, Rufini A, Wetzel MK, Tsuchihara K, Inoue S, Tomasini R, Itie-Youten A, Wakeham A, Arsenian-Henriksson M, Melino G, Kaplan DR, Miller FD, Mak TW. Isoform-specific p73 knockout mice reveal a novel role for delta Np73 in the DNA damage response pathway. Genes Dev 2010; 24:549-60. [PMID: 20194434 DOI: 10.1101/gad.1873910] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mice with a complete deficiency of p73 have severe neurological and immunological defects due to the absence of all TAp73 and DeltaNp73 isoforms. As part of our ongoing program to distinguish the biological functions of these isoforms, we generated mice that are selectively deficient for the DeltaNp73 isoform. Mice lacking DeltaNp73 (DeltaNp73(-/-) mice) are viable and fertile but display signs of neurodegeneration. Cells from DeltaNp73(-/-) mice are sensitized to DNA-damaging agents and show an increase in p53-dependent apoptosis. When analyzing the DNA damage response (DDR) in DeltaNp73(-/-) cells, we discovered a completely new role for DeltaNp73 in inhibiting the molecular signal emanating from a DNA break to the DDR pathway. We found that DeltaNp73 localizes directly to the site of DNA damage, can interact with the DNA damage sensor protein 53BP1, and inhibits ATM activation and subsequent p53 phosphorylation. This novel finding may explain why human tumors with high levels of DeltaNp73 expression show enhanced resistance to chemotherapy.
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Affiliation(s)
- Margareta T Wilhelm
- The Campbell Family Institute for Breast Cancer Research, Princess Margaret Hospital, Toronto, Ontario, Canada
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20
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Kühnel F, Gürlevik E, Wirth TC, Strüver N, Malek NP, Müller-Schilling M, Manns MP, Carnero A, Zender L, Kubicka S. Targeting of p53-transcriptional dysfunction by conditionally replicating adenovirus is not limited by p53-homologues. Mol Ther 2009; 18:936-46. [PMID: 20040911 DOI: 10.1038/mt.2009.298] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A hallmark of human tumors is the loss of p53 or its transcriptional functions. In this study, we describe the generation of the conditionally replicating adenovirus Adp53sensor for the treatment of p53-dysfunctional tumors. p53-selective attenuation of viral replication was achieved by using p53-dependent expression of the transcriptional repressor Gal4-KRAB that was directed against the adenoviral E1A locus. Adp53sensor shows efficient replication in p53-dysfunctional, but not in p53-active cells. In p53-dysfunctional cells, p53-analogous transcriptional activity by other p53 family members was not sufficient to compromise replication of Adp53sensor. In comparison with a genetically similar, but p53-insensitive virus, Adp53sensor replication was inhibited after systemic infection of p53-wt-mice, but not in p53-ko-mice thus confirming the correct function of the chosen approach. Adp53sensor showed efficient lytic and replicative properties in all investigated cells with p53-dysfunction and successfully inhibited the growth of subcutaneous xenotransplants in vivo. We further demonstrated that intravenous injection of Adp53sensor lead to significantly reduced liver damage compared to the control virus. Together, our data show that Adp53sensor is an oncolytic, p53-selective adenovirus for efficient treatment of p53-dysfunctional tumors with a favorable toxicity profile. Moreover, Adp53sensor provides a strategy that should be applicable to other transcriptionally regulated DNA viruses.
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Affiliation(s)
- Florian Kühnel
- Department of Gastroenterology, Hepatology and Endocrinology, Medical School Hannover, Hannover, Germany
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21
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Klanrit P, Taebunpakul P, Flinterman MB, Odell EW, Riaz MA, Melino G, Salomoni P, Mymryk JS, Gäken J, Farzaneh F, Tavassoli M. PML involvement in the p73-mediated E1A-induced suppression of EGFR and induction of apoptosis in head and neck cancers. Oncogene 2009; 28:3499-512. [PMID: 19597475 DOI: 10.1038/onc.2009.191] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Epidermal growth factor receptor (EGFR) tyrosine kinase is commonly overexpressed in human cancers; however, the cellular mechanisms regulating EGFR expression remain unclear. p53, p63 and p73 are transcription factors regulating many cellular targets involved in controlling the cell cycle and apoptosis. p53 activates EGFR expression, whereas TAp63 represses EGFR transcription. The involvement of p73 in the regulation of EGFR has not been reported. Here, a strong correlation between EGFR overexpression and increased levels of the oncogenic DeltaNp73 isoform in head and neck squamous cell carcinoma (HNSCC) cell lines was observed. Ectopic expression of TAp73, particularly TAp73beta, resulted in suppression of the EGFR promoter, significant downregulation of EGFR protein and efficient induction of cell death in all six EGFR-overexpressing HNSCC cell lines. EGFR overexpression from a heterologous LTR promoter protected lung cancer cells from TAp73beta-induced EGFR suppression and apoptosis. Expression of TAp73beta efficiently induced promyelocytic leukaemia (PML) protein expression and PML knockdown by shRNA attenuated the downregulation of EGFR and induction of apoptosis by p73 in HNSCC cells. Furthermore, PML was found to be important for E1A-induced suppression of EGFR and subsequent killing of HNSCC cells. Our data therefore suggest a novel pathway involving PML and p73 in the regulation of EGFR expression.
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Affiliation(s)
- P Klanrit
- Head and Neck Oncology Group, King's College London Dental Institute, Guy's Hospital Campus, London SE1 9RT, UK
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22
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Lau LMS, Wolter JK, Lau JTML, Cheng LS, Smith KM, Hansford LM, Zhang L, Baruchel S, Robinson F, Irwin MS. Cyclooxygenase inhibitors differentially modulate p73 isoforms in neuroblastoma. Oncogene 2009; 28:2024-33. [PMID: 19363520 DOI: 10.1038/onc.2009.59] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
p73 encodes multiple functionally distinct isoforms. Proapoptotic TAp73 isoforms contain a transactivation (TA) domain, and like p53, have tumor suppressor properties and are activated by chemotherapies to induce cell death. In contrast, antiapoptotic DeltaNp73 isoforms lack the TA domain and are dominant-negative inhibitors of p53 and TAp73. DeltaNp73 proteins are overexpressed in a variety of tumors including neuroblastoma. Thus, identification of drugs that upregulate TAp73 and/or downregulate DeltaNp73 represents a potential therapeutic strategy. Here, we report that cyclooxygenase (COX) inhibitors induce apoptosis independent of p53, and differentially modulate endogenous p73 isoforms in neuroblastoma and other tumors. COX inhibitor-mediated apoptosis is associated with the induction of TAp73beta and its target genes. COX inhibitors also downregulate the alternative-spliced DeltaNp73(AS) isoforms, Deltaexon2 and Deltaexon2/3. Furthermore, forced expression of DeltaNp73(AS) results in diminished apoptosis in response to the selective COX-2 inhibitor celecoxib. Celecoxib-mediated downregulation of DeltaNp73(AS) is associated with decreased E2F1 levels and diminished E2F1 activation of the p73 promoter. These results provide the first evidence that COX inhibitors differentially modulate p73 isoforms leading to enhanced apoptosis, and support the potential use of COX inhibitors as novel regulators of p73 to enhance chemosensitivity in tumors with deregulated E2F1 and in those with wild-type (wt) or mutant p53.
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Affiliation(s)
- L M S Lau
- Hospital for Sick Children, University of Toronto, Ontario, Canada
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23
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Abstract
The role of various p73 isoforms in tumorigenesis has been controversial. However, as we have recently shown, the generation of TAp73-deficient (TAp73(-/-)) mice reveals that TAp73 isoforms exert tumor-suppressive functions, indicating an emerging role for Trp-73 in the maintenance of genomic stability. Unlike mice lacking all p73 isoforms, TAp73(-/-) mice show a high incidence of spontaneous tumors. Moreover, TAp73(-/-) mice are infertile and produce oocytes exhibiting spindle abnormalities. These data suggest a link between TAp73 activities and the common molecular machinery underlying meiosis and mitosis. Previous studies have indicated that the spindle assembly checkpoint (SAC) complex, whose activation leads to mitotic arrest, also regulates meiosis. In this study, we demonstrate in murine and human cells that TAp73 is able to interact directly with several partners of the SAC complex (Bub1, Bub3, and BubR1). We also show that TAp73 is involved in SAC protein localization and activities. Moreover, we show that decreased TAp73 expression correlates with increases of SAC protein expression in patients with lung cancer. Our results establish TAp73 as a regulator of SAC responses and indicate that TAp73 loss can lead to mitotic arrest defects. Our data suggest that SAC impairment in the absence of functional TAp73 could explain the genomic instability and increased aneuploidy observed in TAp73-deficient cells.
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24
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Specific activation of microRNA106b enables the p73 apoptotic response in chronic lymphocytic leukemia by targeting the ubiquitin ligase Itch for degradation. Blood 2008; 113:3744-53. [PMID: 19096009 DOI: 10.1182/blood-2008-09-178707] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Chronic lymphocytic leukemia (CLL) is characterized by cells that exhibit dysfunctional apoptosis. Here, we show that deacetylase inhibition led to the E2F1- and myc-mediated transcriptional activation of the microRNA miR106b in primary CLL cells. Induction of miR106b was associated with a down-regulation in the levels of the E3-ubiquitin ligase Itch. Decreases in Itch protein levels were associated with a reciprocal accumulation of its proapoptotic substrate, TAp73 (p73), and induction of p53 up-regulated modulator of apoptosis (PUMA) mRNA and protein. This event was accompanied by mitochondrial dysfunction, processing of caspase-9, and apoptosis of CLL cells. Ectopic expression of miR106b in CLL cells demonstrated that Itch was a direct target of miR106b such that miR106b-induced decreases in Itch resulted in an accumulation of p73. Thus, our results identify a novel regulatory mechanism wherein microRNA regulate cell survival by mediating the posttranscriptional down-regulation of an ubiquitin ligase, leading to the induction of a proapoptotic regulator in malignant cells. Silencing of miRNA expression in CLL may selectively suppress proapoptotic pathways, providing such tumors with a survival advantage. Consequently, chemotherapeutic drugs that activate miR106b could initiate a p53-independent mechanism that targets CLL cells.
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25
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Roperch JP, El Ouadrani K, Hendrix A, Emami S, De Wever O, Melino G, Gespach C. Netrin-1 induces apoptosis in human cervical tumor cells via the TAp73alpha tumor suppressor. Cancer Res 2008; 68:8231-9. [PMID: 18922894 DOI: 10.1158/0008-5472.can-08-1483] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Netrins and their receptors deleted in colon cancer (DCC), neogenin, UNC5, and integrins are involved in axon guidance, epithelial morphogenesis, vascular pattering, cancer cell survival, invasion, tumor angiogenesis, and metastasis. Here, we considered the possible contribution of the p53-related apoptosis mediators p63 and p73 in the mechanisms underlying the antagonism between netrin-1 and DCC at the cell death control. We have showed that ectopic expression and external addition of netrin-1 in HeLa and HEK-293 cells with inactive p53 lead to impaired cell viability and induction of apoptosis. These responses were associated with up-regulation of the proapoptotic protein TAp73alpha, decreased Bcl-2/Bax ratio, and caspase-3 cleavage, with no change in protein levels of the antiapoptotic NH(2)-terminal-truncated DeltaNp73alpha isoform, p73 adapter Yap-1 and p73 E3 ubiquitin ligase Itch, and p63, as well as the transcripts encoding p63, TAp73alpha, and DeltaNp73alpha. However, the proteasome inhibitor MG132 potentiated, while DCC counteracted, netrin-1-induced TAp73alpha. Consistently, netrin-1 expression correlated with stabilization of the TAp73alpha protein and lower levels of TAp73alpha ubiquitination that was conversely enhanced by DCC, in a netrin-dependent manner. Our data indicate that netrin-1 selectively up-regulates TAp73alpha by preventing its ubiquitination and degradation. Targeted repression of p73alpha by shRNA reversed TAp73alpha and the apoptosis induced by netrin-1, and exacerbated the growth of HeLa tumor xenografts. Apoptosis induced by cisplatin was markedly enhanced in netrin-1 or DCC-expressing cells. Collectively, our data reveal that the transcriptionally active TAp73alpha tumor suppressor is implicated in the apoptosis induced by netrin-1 in a p53-independent and DCC/ubiquitin-proteasome dependent manner.
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Affiliation(s)
- Jean-Pierre Roperch
- Institut National de la Sante, Recherche Medicale U673 Molecular and Clinical Oncology of Solid Tumors, Université Pierre et Marie Curie-Paris 6, Hôpital Saint-Antoine, Paris, France
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26
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Brn-3a/POU4F1 interacts with and differentially affects p73-mediated transcription. Cell Death Differ 2008; 15:1266-78. [PMID: 18421303 DOI: 10.1038/cdd.2008.45] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The Brn-3a/POU4F1 POU transcription factor is critical for the survival and differentiation of specific sensory neurons during development or upon injury; by regulating expression of target genes, either directly or indirectly upon interaction with other proteins. In this study, we demonstrated the physical interaction of Brn-3a with different p73 isoforms and showed co-localization in sensory neurons arising from the neural crest. The biological effects of p73/ Brn-3a interaction depend on the particular p73 isoform, because co-expression of Brn-3a with TAp73 enhanced cell cycle arrest, whereas Brn-3a and DeltaNp73 cooperated to increase protection from apoptosis. Brn-3a antagonized TAp73 transactivation of pro-apoptotic Bax, but co-operated to increase transcription of the cell cycle regulator p21 CIP1/Waf1. The region 425-494 amino acids within the TAp73 C terminus were critical for Brn-3a to repress Bax transactivation, but not for cooperation on the p21 CIP1/Waf1 promoter. Our results suggest that co-factors binding to the p73 C terminus facilitate maximal activation on the Bax but not p21 CIP1/Waf1 promoter and that Brn-3a modulates this interaction. Thus, the physical interaction of Brn-3a with specific p73 isoforms will be critical for determining cell fate during neuronal development or in injured neurons expressing both factors.
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Sayan AE, Sayan BS, Gogvadze V, Dinsdale D, Nyman U, Hansen TM, Zhivotovsky B, Cohen GM, Knight RA, Melino G. P73 and caspase-cleaved p73 fragments localize to mitochondria and augment TRAIL-induced apoptosis. Oncogene 2008; 27:4363-72. [PMID: 18362891 DOI: 10.1038/onc.2008.64] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The p73 protein, a member of the p53 family, has both developmental and tumorigenic functions. Here we show that p73 is cleaved by caspase-3 and -8 both in vitro and in vivo during apoptosis elicited by DNA-damaging drugs and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor ligation. TAp73 and some of its cleavage products are localized to mitochondria. siRNA-mediated downregulation of p73 expression induced a small but significant change in the susceptibility of HCT116 cells to TRAIL-induced apoptosis. A transcription-deficient mutant of TAp73 enhanced TRAIL-induced apoptosis suggesting that p73 protein has transcription-independent functions during death receptor-mediated apoptosis. Additionally, recombinant p73 protein induced cytochrome c release from isolated mitochondria providing evidence that nonnuclear p73 may have additional functions in the progression of apoptosis.
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Affiliation(s)
- A E Sayan
- MRC Toxicology Unit, University of Leicester, Leicester, UK
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Patel S, Bui TT, Drake AF, Fraternali F, Nikolova PV. The p73 DNA Binding Domain Displays Enhanced Stability Relative to Its Homologue, the Tumor Suppressor p53, and Exhibits Cooperative DNA Binding. Biochemistry 2008; 47:3235-44. [DOI: 10.1021/bi7023207] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Seema Patel
- Department of Biochemistry and Pharamceutical Sciences Research Division, School of Biomedical & Health Sciences, King’s College London, 150 Stamford Street, London SE1 9NH, United Kingdom, and Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, Kingʼs College London, London SE1 1UL, United Kingdom
| | - Tam T.T. Bui
- Department of Biochemistry and Pharamceutical Sciences Research Division, School of Biomedical & Health Sciences, King’s College London, 150 Stamford Street, London SE1 9NH, United Kingdom, and Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, Kingʼs College London, London SE1 1UL, United Kingdom
| | - Alex F. Drake
- Department of Biochemistry and Pharamceutical Sciences Research Division, School of Biomedical & Health Sciences, King’s College London, 150 Stamford Street, London SE1 9NH, United Kingdom, and Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, Kingʼs College London, London SE1 1UL, United Kingdom
| | - Franca Fraternali
- Department of Biochemistry and Pharamceutical Sciences Research Division, School of Biomedical & Health Sciences, King’s College London, 150 Stamford Street, London SE1 9NH, United Kingdom, and Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, Kingʼs College London, London SE1 1UL, United Kingdom
| | - Penka V. Nikolova
- Department of Biochemistry and Pharamceutical Sciences Research Division, School of Biomedical & Health Sciences, King’s College London, 150 Stamford Street, London SE1 9NH, United Kingdom, and Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, Kingʼs College London, London SE1 1UL, United Kingdom
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Zitterbart K, Zavrelova I, Kadlecova J, Spesna R, Kratochvilova A, Pavelka Z, Sterba J. p73 expression in medulloblastoma: TAp73/DeltaNp73 transcript detection and possible association of p73alpha/DeltaNp73 immunoreactivity with survival. Acta Neuropathol 2007; 114:641-50. [PMID: 17912537 DOI: 10.1007/s00401-007-0298-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 09/13/2007] [Accepted: 09/15/2007] [Indexed: 10/22/2022]
Abstract
The human p73 protein is essential for normal morphogenesis and maintenance of neural tissue. Recently, several TP73 transcripts have been revealed in medulloblastoma (MB), the most common malignant brain tumor in children. Here, we performed immunohistochemical analysis on 29 MB specimens using anti-p73alpha and anti-DeltaNp73 antibodies. Real-time PCR quantification was performed to assess TAp73 and DeltaNp73 transcripts in a subset of 13 MB samples. Normal cerebellar tissues and RNA were used for comparison. Pilot clinical-pathological correlations were also provided. We report significant differences for TAp73 and DeltaNp73 mRNA expression between tumor tissues and reference (P = 0.013, P = 0.028). Immunohistochemically, 52 and 29% MB samples were positive for p73alpha and DeltaNp73, respectively. p73alpha expression was found to be in both the nucleus and cytoplasm, whereas DeltaNp73 was localized predominantly in the cytoplasm. In normal cerebellum, positive staining for p73alpha and DeltaNp73 was observed in the Purkinje cells of newborns, not adult samples, which supports the developmental role of TP73 during organogenesis of the human cerebellum. Survival analysis has shown negative relationship of DeltaNp73-immunoreactivity with overall survival (OS) and event free survival (EFS) (P = 0.026 and P = 0.127, respectively). For p73alpha-positive cases, the negative trend in OS (P = 0.149) and EFS (P = 0.216) was also apparent. Our results indicate the involvement of p73 protein in MB tumorigenesis and define TP73 as a potential prognostic and therapeutic target for medulloblastoma.
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Affiliation(s)
- Karel Zitterbart
- Department of Pediatric Oncology, University Hospital Brno and Masaryk University, Cernopolni 9, 613 00, Brno, Czech Republic.
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Klanrit P, Flinterman MB, Odell EW, Melino G, Killick R, Norris JS, Tavassoli M. Specific isoforms of p73 control the induction of cell death induced by the viral proteins, E1A or apoptin. Cell Cycle 2007; 7:205-15. [PMID: 18256531 DOI: 10.4161/cc.7.2.5361] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
A member of the p53 family, p73, has several isoforms and differentially regulates transcription of genes involved in the control of the cell cycle and apoptosis. We have previously shown efficient and p53-independent, tumor-specific cell death induced by the viral proteins E1A and Apoptin. Here, we demonstrate that the induction of apoptosis by these viral proteins involves activation of TAp73. Both E1A and Apoptin induced expression of endogenous TAp73 and the p53/p73 BH3-only pro-apoptotic target, PUMA, independently of the p53 function. Furthermore, exogenous expression of TAp73 isoforms, particularly TAp73beta, sensitized cells to killing by both E1A and Apoptin, while expression of DeltaNp73alpha blocked this activity. Besides, knockout of the p73 regulator, c-Abl, attenuated E1A-induced apoptosis. In accordance with the role of p73 in apoptosis induced by these viral proteins, overexpression of TAp73beta strongly induced apoptosis in p53-deficient cancer cells in vitro and in HNSCC xenografts. Using a doxycycline-inducible system, we provide evidence for target selectivity and significant differences in protein stability for specific p73 isoforms, suggesting a diverse and pivotal role for p73 in response to various genotoxic agents. Collectively, our data show that in the absence of the p53 function, viral proteins E1A and Apoptin utilize the p73 pathway to induce efficient tumor cell death.
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Affiliation(s)
- Poramaporn Klanrit
- Head and Neck Oncology Group, King's College London Dental Institute, London, United Kingdom
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Overexpressed TP73 induces apoptosis in medulloblastoma. BMC Cancer 2007; 7:127. [PMID: 17626635 PMCID: PMC1955450 DOI: 10.1186/1471-2407-7-127] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Accepted: 07/12/2007] [Indexed: 02/02/2023] Open
Abstract
Background Medulloblastoma is the most common malignant brain tumor of childhood. Children who relapse usually die of their disease, which reflects resistance to radiation and/or chemotherapy. Improvements in outcome require a better understanding of the molecular basis of medulloblastoma growth and treatment response. TP73 is a member of the TP53 tumor suppressor gene family that has been found to be overexpressed in a variety of tumors and mediates apoptotic responses to genotoxic stress. In this study, we assessed expression of TP73 RNA species in patient tumor specimens and in medulloblastoma cell lines, and manipulated expression of full-length TAp73 and amino-terminal truncated ΔNp73 to assess their effects on growth. Methods We analyzed medulloblastoma samples from thirty-four pediatric patients and the established medulloblastoma cell lines, Daoy and D283MED, for expression of TP73 RNA including the full-length transcript and the 5'-terminal variants that encode the ΔNp73 isoform, as well as TP53 RNA using quantitative real time-RTPCR. Protein expression of TAp73 and ΔNp73 was quantitated with immunoblotting methods. Clinical outcome was analyzed based on TP73 RNA and p53 protein expression. To determine effects of overexpression or knock-down of TAp73 and ΔNp73 on cell cycle and apoptosis, we analyzed transiently transfected medulloblastoma cell lines with flow cytometric and TUNEL methods. Results Patient medulloblastoma samples and cell lines expressed full-length and 5'-terminal variant TP73 RNA species in 100-fold excess compared to non-neoplastic brain controls. Western immunoblot analysis confirmed their elevated levels of TAp73 and amino-terminal truncated ΔNp73 proteins. Kaplan-Meier analysis revealed trends toward favorable overall and progression-free survival of patients whose tumors display TAp73 RNA overexpression. Overexpression of TAp73 or ΔNp73 induced apoptosis under basal growth conditions in vitro and sensitized them to cell death in response to chemotherapeutic agents. Conclusion These results indicate that primary medulloblastomas express significant levels of TP73 isoforms, and suggest that they can modulate the survival and genotoxic responsiveness of medulloblastomas cells.
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Domínguez G, Bonilla F. In Reply. J Clin Oncol 2007. [DOI: 10.1200/jco.2006.10.4844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Gemma Domínguez
- Department of Medical Oncology, Hospital Universitario Puerta de Hierro, Madrid, Spain
| | - Félix Bonilla
- Department of Medical Oncology, Hospital Universitario Puerta de Hierro, Madrid, Spain
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Cam H, Griesmann H, Beitzinger M, Hofmann L, Beinoraviciute-Kellner R, Sauer M, Hüttinger-Kirchhof N, Oswald C, Friedl P, Gattenlöhner S, Burek C, Rosenwald A, Stiewe T. p53 family members in myogenic differentiation and rhabdomyosarcoma development. Cancer Cell 2006; 10:281-93. [PMID: 17045206 DOI: 10.1016/j.ccr.2006.08.024] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Revised: 06/05/2006] [Accepted: 08/10/2006] [Indexed: 12/20/2022]
Abstract
The p53 family comprises the tumor suppressor p53 and the structural homologs p63 and p73. How the three family members cooperate in tumor suppression remains unclear. Here, we report different but complementary functions of the individual members for regulating retinoblastoma protein (RB) function during myogenic differentiation. Whereas p53 transactivates the retinoblastoma gene, p63 and p73 induce the cyclin-dependent kinase inhibitor p57 to maintain RB in an active, hypophosphorylated state. DeltaNp73 inhibits these functions of the p53 family in differentiation control, prevents myogenic differentiation, and enables cooperating oncogenes to transform myoblasts to tumorigenicity. DeltaNp73 is frequently overexpressed in rhabdomyosarcoma and essential for tumor progression in vivo. These findings establish differentiation control as a key tumor suppressor activity of the p53 family.
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Affiliation(s)
- Hakan Cam
- Molecular Tumor Biology Group, Rudolf-Virchow-Center, DFG Research Center for Experimental Biomedicine, University of Würzburg, 97078 Würzburg, Germany
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Limesand KH, Schwertfeger KL, Anderson SM. MDM2 is required for suppression of apoptosis by activated Akt1 in salivary acinar cells. Mol Cell Biol 2006; 26:8840-56. [PMID: 16982679 PMCID: PMC1636839 DOI: 10.1128/mcb.01846-05] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Chronic damage to the salivary glands is a common side effect following head and neck irradiation. It is hypothesized that irreversible damage to the salivary glands occurs immediately after radiation; however, previous studies with rat models have not shown a causal role for apoptosis in radiation-induced injury. We report that etoposide and gamma irradiation induce apoptosis of salivary acinar cells from FVB control mice in vitro and in vivo; however, apoptosis is reduced in transgenic mice expressing a constitutively activated mutant of Akt1 (myr-Akt1). Expression of myr-Akt1 in the salivary glands results in a significant reduction in phosphorylation of p53 at serine(18), total p53 protein accumulation, and p21(WAF1) or Bax mRNA following etoposide or gamma irradiation of primary salivary acinar cells. The reduced level of p53 protein in myr-Akt1 salivary glands corresponds with an increase in MDM2 phosphorylation in vivo, suggesting that the Akt/MDM2/p53 pathway is responsible for suppression of apoptosis. Dominant-negative Akt blocked phosphorylation of MDM2 in salivary acinar cells from myr-Akt1 transgenic mice. Reduction of MDM2 levels in myr-Akt1 primary salivary acinar cells with small interfering RNA increases the levels of p53 protein and renders these cells susceptible to etoposide-induced apoptosis in spite of the presence of activated Akt1. These results indicate that MDM2 is a critical substrate of activated Akt1 in the suppression of p53-dependent apoptosis in vivo.
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Affiliation(s)
- Kirsten H Limesand
- Department of Pathology, University of Colorado Health Sciences Center at Fitzsimons, Aurora, CO 80045, USA
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Domínguez G, García JM, Peña C, Silva J, García V, Martínez L, Maximiano C, Gómez ME, Rivera JA, García-Andrade C, Bonilla F. ΔTAp73 Upregulation Correlates With Poor Prognosis in Human Tumors: Putative In Vivo Network Involving p73 Isoforms, p53, and E2F-1. J Clin Oncol 2006; 24:805-15. [PMID: 16380414 DOI: 10.1200/jco.2005.02.2350] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Purpose Although full-length TAp73 variants largely mimic p53 suppressor activities, the transactivation-deficient transcripts ΔTAp73 exert an oncogenic effect by inactivating p53 and TAp73 suppressor properties. Additionally, ΔTAp73 may cooperate with oncogenic RAS to induce cell transformation, confer drug resistance, and induce the phosphorylation of phosphorylated Rb. Here, we study the expression of TAp73 and ΔTAp73 variants and assess possible associations with E2F-1, p53 and K-ras status. We address the possible clinical relevance of alterations in these genes. Patients and Methods We determine in 113 colon and 60 breast cancer patients (a) the expression levels of TAp73, ΔTAp73 (ΔEx2p73, ΔEx2/3p73, and ΔNp73), and E2F-1 transcripts by quantitative real-time reverse transcriptase polymerase chain reaction (PCR); (b) mutations in the first exon of K-ras by PCR–single-stranded confirmational polymorphism; and (c) p53 status by immunohistochemistry. Tumor characteristics were examined in each patient. Results Both suppressor and oncogenic isoforms of TP73 were significantly coupregulated in tumor tissues. Associations were observed between (a) p53 wild type status and upregulation of some TP73 variants; (b) overexpression of E2F-1 and some TP73 forms; and (c) upregulation of ΔTAp73 variants and advanced pathologic stage, lymph node metastasis, vascular invasion, presence of polyps, and tumor localization. Conclusion Overexpression of TP73 variants in tumor tissues indicates that they may be involved in colon and breast carcinogenesis. The association between upregulation of ΔTAp73 isoforms and poor prognosis features, specifically advanced tumor stage, suggests that they may be of practical clinical prognostic value. Interestingly, the in vivo associations identified here may indicate a functional network involving p73 variants, p53, and E2F-1.
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Affiliation(s)
- Gemma Domínguez
- Department of Medical Oncology, Hospital Universitario Puerta de Hierro, C/ San Martín de Porres, 4, 28035-Madrid, Spain
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Müller M, Schilling T, Sayan AE, Kairat A, Lorenz K, Schulze-Bergkamen H, Oren M, Koch A, Tannapfel A, Stremmel W, Melino G, Krammer PH. TAp73/Delta Np73 influences apoptotic response, chemosensitivity and prognosis in hepatocellular carcinoma. Cell Death Differ 2005; 12:1564-77. [PMID: 16195739 DOI: 10.1038/sj.cdd.4401774] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
We investigated the mechanisms by which TAp73 beta and dominant-negative p73 (Delta Np73) regulate apoptosis. TAp73 beta transactivated the CD95 gene via the p53-binding site in the first intron. In addition, TAp73 beta induced expression of proapoptotic Bcl-2 family members and led to apoptosis via the mitochondrial pathway. Endogenous TAp73 was upregulated in response to DNA damage by chemotherapeutic drugs. On the contrary, DeltaNp73 conferred resistance to chemotherapy. Inhibition of CD95 gene transactivation was one mechanism by which DeltaNp73 functionally inactivated the tumor suppressor action of p53 and TAp73 beta. Concomitantly, DeltaNp73 inhibited apoptosis emanating from mitochondria. Thus, DeltaNp73 expression in tumors selects against both the death receptor and the mitochondrial apoptosis activity of TAp73 beta. The importance of these data is evidenced by our finding that upregulation of DeltaNp73 in hepatocellular carcinoma patients correlates with reduced survival. Our data indicate that Delta Np73 is an important gene in hepatocarcinogenesis and a relevant prognostic factor.
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Affiliation(s)
- M Müller
- Department of Internal Medicine IV, Hepatology and Gastroenterology, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
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Munarriz E, Bano D, Sayan AE, Rossi M, Melino G, Nicotera P. Calpain cleavage regulates the protein stability of p73. Biochem Biophys Res Commun 2005; 333:954-60. [PMID: 15975558 DOI: 10.1016/j.bbrc.2005.05.188] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Accepted: 05/24/2005] [Indexed: 10/25/2022]
Abstract
The function of p73, a transcription factor belonging to the p53 family, is finely regulated by its steady-state protein stability. p73 protein degradation/stabilization can be regulated by mechanisms in part dependent on the ubiquitin proteasome system (UPS): (i) Itch/NEDD4-like UPS degradation, (ii) NEDD8 UPS degradation, and (iii) NQO1 20S proteasome-dependent (but ubiquitin-independent) breakdown. Here, we show that, in vitro, Calpain I can cleave p73 at two distinct sites: the first proline-rich region and within the oligomerization domain. Consequently, different p73 isoforms can be degraded by calpains, i.e., both N-terminal isoforms (TAp73 and DeltaNp73) as well as the C-terminal isoforms (alpha, beta, gamma, delta). Moreover, overexpression of the specific endogenous calpain inhibitor, calpastatin, in cultured cells increased the steady-state p73 level. This suggests that calpains may play a physiological role in the regulation of p73 protein stability.
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Affiliation(s)
- Eliana Munarriz
- Medical Research Council, Toxicology Unit, University of Leicester, Leicester LE1 9HN, UK
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