The triterpenoid 3-acetoxylanosta-8,24-dien-21-oic acid (FPOA) is isolated from the fruiting body of Fomitopsis pinicola. The present study reports that FPOA exerts cytotoxic activity and describes the molecular mechanism of FPOA-induced apoptosis on human HepG2 hepatoma cells. FPOA exhibited significant cytotoxic effects against HepG2, MCF-7 and HeLa cells. However, FPOA was particularly cytotoxic towards HepG2 cells, with a half maximal inhibitory concentration value of 42.10 µM, thus these cells were taken forward for further analysis. Flow cytometry results demonstrated that FPOA significantly increased the apoptotic rate of HepG2 cells in a dose-dependent manner, explaining its potent cytotoxicity. In addition, western blot analysis revealed that FPOA significantly increased the B-cell lymphoma 2 (Bcl-2)-associated X/Bcl-2 ratio, and cytochrome c, caspase-9 and caspase-3 release, in addition to significantly decreasing poly(ADP) ribose polymerase levels. These observations indicate that FPOA induces the apoptosis of HepG2 cells by activating members of the caspase protein family and triggering the mitochondrial apoptosis signaling pathway. Based on these results, FPOA is a potential agent for the treatment of cancer.
Keywords: 3-acetoxylanosta-8,24-dien-21-oic acid; Fomitopsis pinicola; HepG2 cells; apoptosis; cytotoxicity.