18α-glycyrrhetinic acid targets prostate cancer cells by down-regulating inflammation-related genes

Glycyrrhetinic acid is an active triterpenoid metabolite of glycyrrhizin abundantly present in licorice roots. Glycyrrhetinic acid exists as a and p stereo-isomeric forms. Both stereo-isomeric forms are known to have anti-inflammatory and anticancer activity. However, the effects and anticancer mechanism of a glycyrrhetinic acid in prostate cancer cells has not yet been evaluated. Therefore, we investigated the growth inhibition, induction of apoptosis and the anticancer mechanisms of 18 alpha-glycyrrhetinic acid (AGA), on the androgen-independent metastatic prostate cancer cell line DU-145. Our results showed that AGA inhibited proliferation and growth of these cells by inducing apoptosis as determined by Annexin V and flow cytometry analyses. Our studies also showed that HUVEC tube formation was drastically reduced when cultured in conditioned medium of AGA-treated DU-145 cells. In addition, AGA treatment prevented the invasion of DU-145 prostate cancer cells on matrigel coated transwells via down-regulation of NF-kappa B (p65), VEGF and MMP-9 expression. Furthermore, AGA treatment also downregulated the expression of pro-inflammatory cytokine/growth factor genes HMGB1, IL-6 and IL-8 in DU-145 cells. Interestingly, AGA simultaneously upregulated the expression of non-steroidal anti-inflammatory gene-1 (NAG-1) in DU-145 cells suggesting its anti-inflammatory activity on prostate cancer cells. Taken together, the results of this study suggest that AGA may be a promising anticancer agent that merits further investigation for the chemoprevention and treatment of prostate cancer.