Ethanol Induces Apoptosis in Human Gastric Carcinoma Cells: The Role of Apoptosis-Related Molecules

Ethanol triggers apoptosis in a variety of mammalian cultured cells. Here, ethanol-induced apoptosis in five human gastric carcinoma cell lines was examined. Trypan blue-positive cells were detected in more than 77% of 10% ethanol treated cells at 6 h in all the cell lines. The apoptosis, which had a typical morphology and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) signals were induced with 3% and 5% ethanol treatments. The apoptotic cells were detected in 36% of MKN-74, 54% of MKN-45 which have wild-type p53, and 37% of TMK-1 cells at 48 h with 5% ethanol, in contrast to less than 18% of MKN-28 and KATO-III cells. The DNA ladder appeared in the MKN-74, MKN-45 and TMK-1, but not in the MKN-28 and KATO-III. The expression of apoptosis-associated molecules p53, Bcl-2, Bax and c-Myc proteins was analyzed in the ethanol-treated cells. The levels of p53, Bcl-2 and Bax proteins were not changed in the ethanol-induced apoptosis. MKN-28 and KATO-III showed higher expressions of Bcl-2 protein compared to the other cell lines, and the down-regulation of c-Myc protein after 1.5 h of ethanol treatment. Calcium antagonists verapamil or nifedipine decreased apoptotic cells in ethanol treated MKN-74, MKN-45 and TMK-1. These results suggest: i) 3% and 5% ethanol induced apoptosis via the influx of extracellular calcium, but were not changed the expression levels of p53 and c-Myc protein, while 10% ethanol provoked necrosis in these cell lines, and ii) the apoptosis resistance by ethanol might be implicated in the higher expression of Bcl-2 protein and down-regulation of c-Myc protein as shown in MKN-28 and KATO-III.