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Cancer Res. 2002 Feb 1;62(3):924-31.

Dysfunctional apoptosome activation in ovarian cancer: implications for chemoresistance.

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  • 1Department of Obstetrics and Gynecology, University of Michigan Medical School, L4000 Women's Hospital, 1500 East Medical Center Drive, Ann Arbor, MI 48109, USA.


Alterations in the regulation of apoptosis may contribute to the pathogenesis of cancer and resistance of tumor cells to chemotherapy. In mammalian cells, nonreceptor-mediated apoptosis occurs predominantly via assembly of a cytochrome c-dependent apoptosome complex containing caspase-9 and apoptotic protease-activating factor-1 (Apaf-1). We show here that cytosolic extracts from human ovarian carcinoma cell lines and primary ovarian tumor samples are deficient in their ability to activate procaspase-9 in the presence of cytochrome c and dATP when compared with control extracts. SKOV3, a human ovarian carcinoma cell line with diminished apoptosome activity, was significantly more resistant to chemotherapy-induced apoptosis than cell lines with functional Apaf-1 activity. This dysfunctional apoptosome activity was not explained by reduced expression levels of caspase-9 or Apaf-1. Moreover, expression levels of known inhibitors of the apoptosome, including heat shock protein 70, heat shock protein 90, or X-linked inhibitor of apoptosis, did not correlate with functional activity of the apoptosome. SKOV3, an ovarian cancer cell line with dysfunctional apoptosome activity, retains the ability to form the Apaf-1 oligomer; however, there is a diminished amount of caspase-9 in the apoptosome. The reduction in the amount of caspase-9 in the apoptosome in the SKOV3 cell line was associated with diminished caspase-3 activity. Dysfunctional apoptosome activation may contribute both to the pathogenesis of ovarian carcinoma and to chemoresistance.

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