Stabilization of p53 by CP-31398 inhibits ubiquitination without altering phosphorylation at serine 15 or 20 or MDM2 binding.
CP-31398, a styrylquinazoline, emerged from a high throughput screen for therapeutic agents that restore a wild-type-associated epitope (monoclonal antibody 1620) on the DNA-binding domain of the p53 protein. We found that CP-31398 can not only restore p53 function in mutant p53-expressing cells but also significantly increase the protein level and promote the activity of wild-type p53 in multiple human cell lines, including ATM-null cells. Cells treated with CP-31398 undergo either cell cycle arrest or apoptosis. Further investigation showed that CP-31398 blocks the ubiquitination and degradation of p53 but not in human papillomavirus E6-expressing cells. Of note, CP-31398 does not block the physical association between p53 and MDM2 in vivo. Moreover, unlike the DNA-damaging agent adriamycin, which induces strong phosphorylation of p53 on serines 15 and 20, CP-31398 exposure leads to no measurable phosphorylation on these sites. We found that CP-31398 could also stabilize exogenous p53 in p53 mutant, wild-type, and p53-null human cells, even in MDM2-null p53(-/-) mouse embryonic fibroblasts. Our results suggest a model wherein CP-31398-mediated stabilization of p53 may result from reduced ubiquitination, leading to high levels of transcriptionally active p53. Further understanding of this mechanism may lead to novel strategies for p53 stabilization and tumor suppression in cancers, even those with absent ARF or high MDM2 expression.
Wang
Wenge
W
Laboratory of Molecular Oncology and Cell Cycle Regulation, Howard Hughes Medical Institute, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Takimoto
Rishu
R
Rastinejad
Farzan
F
El-Deiry
Wafik S
WS
D000230:Adenocarcinoma / Q000473:pathology; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology; D018797:Cell Cycle Proteins; D003110:Colonic Neoplasms / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D004249:DNA Damage; D004268:DNA-Binding Proteins; D004317:Doxorubicin / Q000494:pharmacology; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D016158:Genes, p53; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral / Q000037:antagonists & inhibitors / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000473:pathology; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2; D011743:Pyrimidines / Q000494:pharmacology*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000172:deficiency / Q000187:drug effects* / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin / Q000378:metabolism*
C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; C052603:E6 protein, Human papillomavirus type 18; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D012097:Repressor Proteins; C505639:TNFRSF10B protein, human; C505640:Tnfrsf10b protein, mouse; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D010768:Phosphoserine; D004317:Doxorubicin; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases; C402665:CP 31398