title: Chemotherapy-mediated p53-dependent DNA damage response in clear cell renal cell carcinoma: role of the mTORC1/2 and hypoxia-inducible factor pathways.
abstract: The DNA-damaging agent camptothecin (CPT) and its analogs demonstrate clinical utility for the treatment of advanced solid tumors, and CPT-based nanopharmaceuticals are currently in clinical trials for advanced kidney cancer; however, little is known regarding the effects of CPT on hypoxia-inducible factor-2α (HIF-2α) accumulation and activity in clear cell renal cell carcinoma (ccRCC). Here we assessed the effects of CPT on the HIF/p53 pathway. CPT demonstrated striking inhibition of both HIF-1α and HIF-2α accumulation in von Hippel-Lindau (VHL)-defective ccRCC cells, but surprisingly failed to inhibit protein levels of HIF-2α-dependent target genes (VEGF, PAI-1, ET-1, cyclin D1). Instead, CPT induced DNA damage-dependent apoptosis that was augmented in the presence of pVHL. Further analysis revealed CPT regulated endothelin-1 (ET-1) in a p53-dependent manner: CPT increased ET-1 mRNA abundance in VHL-defective ccRCC cell lines that was significantly augmented in their VHL-expressing counterparts that displayed increased phosphorylation and accumulation of p53; p53 siRNA suppressed CPT-induced increase in ET-1 mRNA, as did an inhibitor of ataxia telangiectasia mutated (ATM) signaling, suggesting a role for ATM-dependent phosphorylation of p53 in the induction of ET-1. Finally, we demonstrate that p53 phosphorylation and accumulation is partially dependent on mTOR activity in ccRCC. Consistent with this result, pharmacological inhibition of mTORC1/2 kinase inhibited CPT-mediated ET-1 upregulation, and p53-dependent responses in ccRCC. Collectively, these data provide mechanistic insight into the action of CPT in ccRCC, identify ET-1 as a p53-regulated gene and demonstrate a requirement of mTOR for p53-mediated responses in this tumor type.
authors.affiliation: Division of Biomedical Sciences, St George's University of London, Cranmer Terrace, London, SW17 0RE, UK.
authors.forename: J
authors.initials: J
authors.lastname: Selvarajah
authors.forename: K
authors.initials: K
authors.lastname: Nathawat
authors.forename: A
authors.initials: A
authors.lastname: Moumen
authors.forename: M
authors.initials: M
authors.lastname: Ashcroft
authors.forename: V A
authors.identifier: 0000000169852664
authors.initials: VA
authors.lastname: Carroll
mesh_terms: D047310:Apigenin / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D002166:Camptothecin / Q000494:pharmacology; D002292:Carcinoma, Renal Cell / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology*; D015687:Cell Hypoxia / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000235:genetics; D019332:Endothelin-1 / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D007680:Kidney Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D047310:Apigenin; D051792:Basic Helix-Loop-Helix Proteins; D002166:Camptothecin; D019332:Endothelin-1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes; D012333:RNA, Messenger; D058570:TOR Serine-Threonine Kinases; D016159:Tumor Suppressor Protein p53; D000099162:Endothelial PAS Domain-Containing Protein 1