NAC Protects Against Benzyl Isothiocyanate Induced G2/M Arrest and Apoptosis in Human Pancreatic Cancer Cells.

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Previously, we showed that benzyl isothiocyanate (BITC), a naturally occurring anti-cancer agent present in cruciferous vegetables, inhibits the proliferation of Capan-2 human pancreatic cancer cells by causing cell cycle arrest and apoptosis. However, the exact mechanisms of growth suppressive effects of BITC were not clear. Here we demonstrate that BITC treatment of Capan-2 cells resulted in the significantly increased expression of cyclin dependent kinase (cdk) inhibitor p21 in a dose-dependent manner concomitant with decreased expression of cdk1. Treatment of these cells with growth suppressive concentration of BITC for 24h resulted in significant accumulation of cells in G2/M phase and induction of apoptosis as measured by flow cytometery. Interestingly, pretreatment of cells with N-acetyl cysteine (NAC), a common antioxidant, significantly protected Capan-2 cells from BITC-induced G2/M arrest as well as apoptosis. NAC treatment also prevented BITC-mediated up regulation of the expression of p21, suggesting the involvement of reactive oxygen species (ROS). We next demonstrated that BITC-treatment causes significant generation of ROS, as measured by DCF fluorescence and that NAC almost completely blocked the generation of BITC-mediated ROS. We therefore, conclude that generation of ROS may be the key factor in BITC-mediated increased p21 expression, which in turn may be responsible for G2/M arrest and apoptosis in these cells. [Supported in part by RO1 grant CA 106953 (to S.K.S.) awarded by the National Cancer Institute].