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Apaf‐1 overexpression partially overcomes apoptotic resistance in a cisplatin‐selected HeLa cell line
Author(s) -
Kamarajan Pachiyappan,
Sun Nian-Kang,
Sun Chun-Ling,
Chao Chuck C.-K
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02817-4
Subject(s) - apoptosis , cytochrome c , hela , caspase , cisplatin , caspase 3 , microbiology and biotechnology , dna fragmentation , caspase 9 , programmed cell death , cell culture , biology , activator (genetics) , xiap , chemistry , cell , biochemistry , gene , genetics , chemotherapy
Inhibition of caspase‐3‐mediated apoptosis has been hypothesized to be associated with chemoresistance. Investigations of apoptosis revealed that cytosolic cytochrome c is associated with a complex of apoptotic protease activating factor‐1 (Apaf‐1), an adapter molecule, and caspase‐9 to activate caspase‐3. However, whether these apoptotic molecules are involved in acquired cisplatin resistance is not understood. The present work shows reduced activation of caspase‐3 and apoptosis in a cisplatin‐selected HeLa cell line. Ac‐DEVD‐CHO, a caspase‐3 inhibitor, inhibited cisplatin‐induced apoptosis about 60–70% in both cell lines. Ac‐LEHD‐CHO, a caspase‐9 inhibitor or Ac‐IETD‐CHO, a caspase‐8 inhibitor, inhibited cisplatin‐induced caspase‐3 activation and apoptosis similarly in both cell lines. In addition, cisplatin induced the activation of caspase‐9, the upstream activator of caspase‐3, in a dose‐dependent manner, and the activation of caspase‐9 was less induced in resistant cells. The accumulation of cytosolic cytochrome c , an activator of caspase‐9, and the induction of the mitochondrial membrane‐associated voltage‐dependent anion channel were also reduced in cisplatin‐resistant cells. However, the concentration of Bcl‐2 family proteins in cisplatin‐resistant cells was normal. The concentration of Apaf‐1 was unaltered in both cell lines. Increasing the cellular concentration of Apaf‐1 through the transient expression of the gene increased the induction of apoptosis in resistant cells, associated with enhanced activation of caspase‐9, caspase‐3 and DNA fragmentation factor. Regression analysis reveals that the modification factor, the ratio of the slope in the linear range of the dose–response curve with Apaf‐1 to the slope without Apaf‐1, is 1.5 and 4.75 in the HeLa and cisplatin‐resistant HeLa cells, respectively. These results indicate that apoptosis and caspases are less induced in cisplatin‐selected HeLa cells. They also suggest that ectopic overexpression of Apaf‐1 may partially reverse the acquired cisplatin resistance.