Akt-mediated cisplatin resistance in ovarian cancer: modulation of p53 action on caspase-dependent mitochondrial death pathway.
Akt is a determinant of cisplatin [cis-diammine-dichloroplatinum (CDDP)] resistance in ovarian cancer cells, and this may be related to the regulation of p53. Precisely how Akt facilitates CDDP resistance and interacts with p53 is unclear. Apoptotic stimuli induce second mitochondria-derived activator of caspase (Smac) release from mitochondria into the cytosol, where it attenuates inhibitor of apoptosis protein-mediated caspase inhibition. Whereas Smac release is regulated by p53 via the transactivation of proapoptotic Bcl-2 family members, it is unclear whether p53 also facilitates Smac release via its direct mitochondrial activity. Here we show that CDDP induces mitochondrial p53 accumulation, the mitochondrial release of Smac, cytochrome c, and HTR/Omi, and apoptosis in chemosensitive but not in resistant ovarian cancer cells. Smac release was p53 dependent and was required for CDDP-induced apoptosis. Mitochondrial p53 directly induced Smac release. Akt attenuated mitochondrial p53 accumulation and Smac/cytochrome c/Omi release and conferred resistance. Inhibition of Akt facilitated Smac release and sensitized chemoresistant cells to CDDP in a p53-dependent manner. These results suggest that Akt confers resistance, in part, by modulating the direction action of p53 on the caspase-dependent mitochondrial death pathway. Understanding the precise etiology of chemoresistance may improve treatment for ovarian cancer.
Yang
Xiaokui
X
Reproductive Biology Unit and Division of Gynaecology Oncology, Department of Obstetrics and Gynaecology and Cellular and Molecular Medicine, University of Ottawa, Ontario, Canada.
Fraser
Michael
M
Moll
Ute M
UM
Basak
Ajoy
A
Tsang
Benjamin K
BK
D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D020169:Caspases / Q000378:metabolism*; D002945:Cisplatin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D005260:Female; D000074923:High-Temperature Requirement A Serine Peptidase 2; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D016159:Tumor Suppressor Protein p53; D051057:Proto-Oncogene Proteins c-akt; D012697:Serine Endopeptidases; C000615914:HTRA2 protein, human; D000074923:High-Temperature Requirement A Serine Peptidase 2; D020169:Caspases; D002945:Cisplatin