Induction of the apoptosis-promoting protein Bak by perillyl alcohol in pancreatic ductal adenocarcinoma relative to untransformed ductal epithelial cells

Perillyl alcohol has antitumor activity toward pancreas and other cancers with low toxicity. Here, we have investigated the mechanism of action responsible for the differential sensitivity of malignant versus non-malignant pancreatic cells to the drug. We report that the rate of apoptosis is over 6-fold higher in perillyl alcohol-treated pancreatic adenocarcinoma cells than in untreated cells, and that the effect of perillyl alcohol on pancreatic tumor cells is significantly greater than its effect on non-malignant pancreatic ductal cells. Moreover, the perillyl alcohol-induced increase in apoptosis in all of the pancreatic tumor cells is associated with a 2- to 8-fold increase in the expression of the proapoptotic protein Bak, but Bak expression is not affected by perillyl alcohol in non-malignant cells. Thus, the antitumor activity of perillyl alcohol toward pancreatic cancers may be due to preferential stimulation of Bak-induced apoptosis in malignant versus normal cells. Bak may, therefore, be a useful biomarker for the chemopreventive and therapeutic effects of perillyl alcohol.