title: TAT-RasGAP317-326 requires p53 and PUMA to sensitize tumor cells to genotoxins.
abstract: Although chemotherapy has revolutionized cancer treatment, the associated side effects induced by lack of specificity to tumor cells remain a challenging problem. We have previously shown that TAT-RasGAP(317-326),a cell-permeable peptide derived from RasGAP, specifically sensitizes cancer cells to the action of genotoxins. The underlying mechanisms of this sensitization were not defined however. Here, we report that TAT-RasGAP(317-326) requires p53, but not the Ras effectors Akt and extracellular signal-regulated kinase, to mediate its tumor sensitization abilities. The TAT-RasGAP(317-326) peptide, although not modulating the transcriptional activity of p53 or its phosphorylation and acetylation status, nevertheless requires a functional p53 cellular status to increase the sensitivity of tumor cells to genotoxins. Genes regulated by p53 encode proapoptotic proteins, such as PUMA, and cell cycle control proteins, such as p21. The ability of TAT-RasGAP(317-326) to sensitize cancer cells was found to require PUMA but not p21. TAT-RasGAP(317-326) did not affect PUMA levels, however, but increased genotoxin-induced mitochondrial depolarization and caspase-3 activation. These results indicate that TAT-RasGAP(317-326) sensitizes tumor cells by activating signals that intersect with the p53 pathway downstream of, or at the level of, proapoptotic p53 target gene products to increase the activation of the mitochondrial death pathway.
authors.affiliation: Department of Physiology, Lausanne University, Rue du Bugnon 7/9, 1005 Lausanne, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Michod
authors.forename: Christian
authors.initials: C
authors.lastname: Widmann
mesh_terms: D000107:Acetylation / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015696:Gene Products, tat / Q000737:chemistry / Q000494:pharmacology*; D045325:HCT116 Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D009153:Mutagens / Q000494:pharmacology*; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology*; D010455:Peptides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D013816:Thermodynamics; D014158:Transcription, Genetic / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D020703:ras GTPase-Activating Proteins / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D015696:Gene Products, tat; D009153:Mutagens; D010455:Peptides; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D020703:ras GTPase-Activating Proteins; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D002945:Cisplatin