Etoposide (VP-16) sensitizes p53-deficient human non-small cell lung cancer cells to caspase-7-mediated apoptosis.
Human non-small-cell-lung-cancer (NSCLC) cells of (p)53-null genotype were exposed to low-dosage topoisomearse II inhibitor etoposide (VP-16). The cellular proliferation rate could be effectively inhibited by VP-16 in dose-dependent manner. The effective drug concentration for growth inhibition could be as low as 0.5 microM and the apoptotic phenotype became evident 48 h later. In H1299 cells, VP-16-induced cytotoxic effect was demonstrated associated with apoptosis that disappeared when restored with wild-type p53. Cell cycle analysis revealed that, upon VP-16 induction, cell death began with growth arrest by accumulating cells at the G(2)-M phase. The cells at sub-G(1) phase increased at the expense of those at G(2)-M transition state. To assess the regulation of cell cycle modulators, western blot analysis of H1299 cell lysates showed the release of apoptosis initiator, cytochrome c and apaf-1 hours following drug induction. The cleavage of downstream effectors, procaspase-9 and procaspase-7, but not procaspase-3, was accompanied with proteolysis of poly-(ADP-ribose) polymerase (PARP). VP-16-activated procaspase-7 cleavage was abrogated in cells with ectopically expressed p53. On the other hand, the inhibited procaspase-7 fragmentation by caspase-specific inhibitor reversed apoptotic phenotype caused by drug induction. Thus, VP-16-induced apoptotic cell death was contributed by caspase-7 activation in(p)53-deficient human NSCLC cells.
Chiu
C-C
CC
Department of Biological Science, National Taiwan Normal University, Taipei, Taiwan.
Lin
C-H M Y
CH
Fang
K
K
D017209:Apoptosis / Q000187:drug effects*; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology*; D053179:Caspase 7; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003374:Coumarins / Q000378:metabolism; D053938:DNA Fragmentation; D005047:Etoposide / Q000494:pharmacology*; D016158:Genes, p53; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D015854:Up-Regulation
D061945:Caspase Inhibitors; D003374:Coumarins; D009842:Oligopeptides; D016159:Tumor Suppressor Protein p53; C108637:aspartyl-glutamyl-valyl-aspartal; C115495:aspartyl-glutamyl-valyl-aspartyl-7-amino-4-trifluoromethylcoumarin; D005047:Etoposide; D011065:Poly(ADP-ribose) Polymerases; C505520:CASP7 protein, human; D053179:Caspase 7; D020169:Caspases