Taxifolin Enhances Andrographolide-induced Cell Cycle Arrest and Apoptosis in Prostate Cancer Cell Line DU145

Taxifolin (Taxi), a dihydroflavonol, together with its glycosides are commonly found in many medical plants. Lots of flavonoids have been suggested to suppress cancer cell proliferation through various mechanisms. Whereas, the cytotoxity effect of Taxi on cancer cell lines is relatively low. Results showed that Taxi has low anti-proliferative effect on DU145 cell line (IC50＞500μM, 48h), however, low concentration of (100μM) Taxi treatment significantly enhances the growth inhibition of Andro-treated DU145 cell. It was found that combination treatment of 100μM Taxi and Andro (10-40μM) induce cell G2/M accumulation rate significantly higher than that induced by Andro alone, which is caused by raising mitotic index. In addition, quantification of apoptosis by double staining with Annexin V-FITC/PI revealed that Andro-induced apoptosis rate is also increased distinctly by synchromous treatment of Andro and Taxi. While treatment with Taxi alone did not show marked effect on either cell cycle or cell viability. Western blotting analysis revealed that combination treatment up-regulate cyclin B1 and p21 (Waf1/Cip1) compared to Andro alone; and capspase-7 and PARP expression related to apoptosis increase in the combined treatment. Therefore, low cytotoxic taxifolin might be a promising component in combined drug treatment of tumor.