title: HDM2 antagonist Nutlin-3 disrupts p73-HDM2 binding and enhances p73 function.
abstract: Nutlin-3, a small molecule inhibitor, activates p53 by disrupting p53-HDM2 association. In this study, we found that Nutlin-3 suppressed cell growth and induced apoptosis in the absence of wild-type p53, suggesting a p53-independent mechanism for Nutlin-3-induced cell death. Like p53, its homolog p73 transactivates proapoptotic genes and induces cell death. Since HDM2, a key negative regulator of p53, also binds to and inhibits p73, we asked whether p73 could mediate Nutlin-3-induced apoptosis. We demonstrate that Nutlin-3 inhibits endogenous binding between the proapoptotic p73 isoform TAp73alpha and HDM2 in p53-null cells. Dissociation of p73 and HDM2 leads to increased p73 transcriptional activity with upregulation of p73 target genes noxa, puma and p21, as well as enhanced apoptosis. p73 knockdown by siRNA results in rescue of Nutlin-3-treated cells, indicating that Nutlin-3-induced apoptosis is, at least in part, p73 dependent. In addition, Nutlin-3 treatment increases TAp73alpha protein levels with prolongation of p73 half-life. These results provide the first evidence that Nutlin-3 disrupts endogenous p73-HDM2 interaction and enhances the stability and proapoptotic activities of p73 and thus, provides a rationale for the use of Nutlin-3 in the large number of human tumors in which p53 is inactivated.
authors: Division of Hematology/Oncology, Department of Paediatrics, Hospital for Sick Children, University of Toronto, Ontario, Canada.
authors: L M S
authors: LM
authors: Lau
authors: J K
authors: JK
authors: Nugent
authors: X
authors: X
authors: Zhao
authors: M S
authors: MS
authors: Irwin
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001859:Bone Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D045325:HCT116 Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D015151:Immunoblotting; D047468:Immunoprecipitation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology*; D011485:Protein Binding; D014176:Protein Biosynthesis; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors*; D034741:RNA, Small Interfering / Q000494:pharmacology; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; D007093:Imidazoles; D009687:Nuclear Proteins; C498702:PMAIP1 protein, human; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C482205:nutlin 3; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2