title: Regulation of Bax activation and apoptotic response to microtubule-damaging agents by p53 transcription-dependent and -independent pathways.
abstract: Microtubule-damaging agents (MDA) are potent antineoplastic drugs that are widely used in clinical treatment for a variety of cancers. However, the precise mechanisms underlying MDA-induced cell death are largely unknown. Here, we report that both p53 and Bax are central participants in the MDA-mediated cell death machinery in HCT116 human colon cancer cells. MDA, including epothilone B analogue (BMS-247550) and vinblastine, induced apoptosis of Bax-positive HCT116 cells in a p53-dependent manner; p53 was required for MDA-induced Bax conformational change. In response to MDA treatment, the BH3-only proapoptotic protein PUMA was up-regulated in p53-positive but not in p53 knockout HCT116 cells. Moreover, PUMA knockout HCT116 cells were resistant to MDA-induced Bax conformational change and apoptosis. In addition, introducing p53 plasmid DNA into p53-deficient HCT116 cells restored PUMA expression and apoptotic response to MDA treatment. However, ectopic expression of the p53 point mutation L22Q/W23S, but not the proline-rich domain deletion mutants 83-393 and DeltaProAE, could also sensitize p53 knockout HCT116 cells to MDA-induced Bax activation and apoptosis, although all mutants failed to restore PUMA expression. Together, these findings suggest that p53 acts upstream of Bax to promote MDA-mediated cell death in a proline-rich domain-dependent manner through both transcription-dependent (by up-regulating PUMA expression) and -independent mechanisms in human colon cancer HCT116 cells.
authors.affiliation: Drug Discovery Program, H. Lee Moffitt Cancer Center and Research Institute, Department of Interdisciplinary Oncology, University of South Florida College of Medicine, Tampa, Florida 33612, USA.
authors.forename: Hirohito
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Jiandong
authors.initials: J
authors.lastname: Chen
authors.forename: Kapil
authors.initials: K
authors.lastname: Bhalla
authors.forename: Hong-Gang
authors.initials: HG
authors.lastname: Wang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D045744:Cell Line, Tumor / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D003110:Colonic Neoplasms; D034261:Epothilones / Q000494:pharmacology; D017353:Gene Deletion; D006801:Humans; D008870:Microtubules / Q000187:drug effects*; D008928:Mitochondria / Q000378:metabolism; D016296:Mutagenesis; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D014158:Transcription, Genetic / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; C438378:BBC3 protein, human; D034261:Epothilones; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C430592:ixabepilone