Andrographolide-induced Cell Cycle Arrest and Apoptosis in Hormone-refractory Prostate Cancer Cell DU145

Cell cycle regulation and apoptosis are two important control mechanisms of cell proliferation. A lot of natural products have been suggested to have the property of inducing cell cycle arrest, cell differentiation and apoptosis in cancer cells. Andrographolide (Andro) is the main bioactive component form Andrographis paniculate (穿心莲) and has been reported to have anti-proliferative effect on several tumor cell lines.Results showed that Andro inhibits cell proliferation of hormone-refractory prostate cancer cell line DU145 time and dose-dependently, with the IC50 value (48h) of 13.04μM. At relatively low concentration (≤40μM), it was shown that Andro-treated DU145 cell accumulate at G2/M phase dose-dependently. Furthermore, immunoblot of Du145 is caused by mitotic arrest. On the other hand, high concentration (80μM) of Andro directly induced cell death without marked cell cycle distribution alteration. Additionally, microtube network was visualized by immunostaining of tubulin, which revealed that Andro treatment leads to formation of abnormal spindle-chromosome structure resulting in cell arrest at prometaphase. Western blotting analysis showed that Andro exposure trigger several cell cycle regulation pathways including up-regulation of cyclin B1 and p21 (Wafl/Cip1) activity, dephosphorylation on Tyr15 of Cdk1 and phosphorylation of Cdc25C. Andro-induced apoptosis was assoiated with activation of caspase-7, PRAP, but not caspase-9 and caspase-3.