PURPOSE: Protein kinase C (PKC) is a family of phospholipid dependent serine/threonine protein kinases that have important role in differentiation, development and tumor promotion.
PKC also has been reported to be implicated in the induction of apoptosis in a number of studies, but the efforts to define a role for PKC in the induction of apoptosis have been complicated by conflicting reports.
MATERIALS AND METHODS: To determine the effect of phorbol 12-myristate 13-acetate (PMA) on the induction of apoptosis, DNA fragmentation was detected by agarose gel electrophoresis and morphological changes of apoptotic cells were detected by Hoechst 33258 staining. For the detection of caspase-3/CPP32 activity, we used the enzyme substrate Ac-DEVD-pNa and anti- D4-GDI antibody.
RESULTS: In the present study, PMA, a PKC activator, induced apoptosis in SNU-16 human gastric cancer cell line, whose apoptosis was significantly inhibited by the PKC inhibitor, chelerythrine chloride. The caspase-3/CPP32 protease activity was increased in PMA-induced apoptosis. Furthermore, 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF), a serine profease inhibitor, also significantly suppressed PMA-induced cell death in an upstream of caspase-3/CPP32.
CONCLUSION: These findings indicate that PMA induces apoptotic cell death in the SNU-16 adenocarcinoma cells through PKC activation, which activates AEBSF-sensitive serine proteases and caspase-3/CPP32. Therefore, our results suggest that PKC would be a potential target for induction of apoptosis.
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