Norcantharidin (NCTD), a demethylated form of cantharidin, is now in used as a routine anticancer drug. However, the detailed mechanisms underlying this process are generally unclear. The aims of this study were to evaluate the apoptotic effects and molecular mechanisms of NCTD. MTT assay was used to determine the cell growth inhibitory rate. Flow cytometry were used to detect the apoptosis and the loss of mitochondrial membrane potential (Δψm) induced by NCTD. Caspase detection kit were used to detect the activity of caspase-3 -9. Western-blot was used to detect the expression of Bcl-2, Bax and cytochrome C (cyt C). Our results indicated that, treatment of NCTD resulted in significant decrease in cell viability in a dose-and time-dependent manner. A dose-dependent apoptosis was also observed by flow cytometery analysis. Molecular mechanistic studies of apoptosis revealed that, NCTD treatment resulted in a significant loss of Δψm, release of cyt C, enhanced expression of pro-apoptotic protein Bax and suppression of anti-apoptotic protein Bcl-2. These were followed by activation of caspases-9 and -3, subsequently leading to cell apoptosis. These results indicate that, NCTD induced cytotoxicity in HepG2 cells by apoptosis, which is mediated through mitochondrial pathway.Key words: Norcantharidin, apoptosis, caspase, Bax/Bcl-2, cyto C, HepG2 cells
