Role of protein kinases in the ethanol-induced apoptosis of cultured humangastric carcinoma cells

To investigate the role of protein kinase family in intracellular pathways leading to apoptosis, three human gastric carcinoma cell lines (MKN-74, MKN -45 and TMK-1) were induced with ethanol. Apoptosis was confirmed by positi ve TUNEL signal, typical morphological features including fragmented nuclei , activation of caspase-3 and cleavage of poly (ADP-ribose) polymerase. Wes tern blot analysis confirmed higher expression of protein kinase C (PKC) in MKN-74 and MKN-45, and lower expression in TMK-1. The expression levels di d not change with ethanol treatment. In MKN-74 and MKN-45, ethanol-induced apoptosis was partially, but significantly suppressed by H7 treatment (an i nhibitor of PKC, protein kinase A (PKA), and protein kinase G (PKG)) and ca lphostin C (an inhibitor of PKC). On the contrary, H7 and HA1004 (an inhibi tor of PKA and PKC), significantly enhanced ethanol-induced apoptosis in TM K-1. Inhibitory effect of calmodulin antagonists was not detected in the et hanol-induced apoptosis of the three cell lines, suggesting that calmodulin is not involved in this signal pathway. These results might suggest that s ignal transduction leading to apoptosis is partially mediated by PKC, while not by PKA and PKG which might play a role in the signal transduction apop tosis inhibition of human gastric carcinoma cells.