Mitomycin C induces apoptosis in a caspases-dependent and Fas/CD95-independent manner in human gastric adenocarcinoma cells

We investigated the mechanism of mitomycin C (MMC)-induced apoptosis in SNU -16 human gastric adenocarcinoma cells. Caspase-8 and caspase-3 were activa ted in MMC-treated cells whereas caspase-1 was not activated, and cytochrom e c was released from mitochondrial membrane to cytosol suggesting that cas pase-9 was activated during the MMC-induced apoptotic process. Protein kina se C (PKC) delta was cleaved to its characteristic 40 kDa fragment in a cas pase-3-dependent manner: on the other hand PKC zeta was cleaved to approxim ately 40 kDa independently of caspase-3 in the drug-induced apoptosis of th e cells. Incubation with z-DEVD-fmk; and benzyloxycarbonyl-Val-Ala-Asp-fluo romethylketone (z-VAD-fmk) almost completely abrogated MMC-induced DNA frag mentation, indicating that activation of these caspases was crucially invol ved in MMC-induced apoptosis. Activation of caspase-8 in response to Fas tr iggering by recruitment of caspase-8 to the Fas has also been found, howeve r, MMC did not induce FasL and Fas expression, as evidenced by reverse tran scriptase-polymerase chain reaction and Western blotting. Taken together, t hese findings indicate that MMC-induced apoptosis in SNU-16 cells was media ted by caspase-8, caspase-9, and caspase-3 activation independently of FasL /Fas interactions. (C) 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.