Effect of curcumin on the interaction between androgen receptor and Wnt/β-catenin in LNCaP xenografts

PURPOSE Curcumin is a nontoxic, chemopreventive agent possessing multifaceted functions. Our previous study showed that curcumin inhibits androgen receptor (AR) through modulation of Wnt/β-catenin signaling in LNCaP cells. Therefore, we investigated the in vivo effects of curcumin by using LNCaP xenografts. MATERIALS AND METHODS LNCaP cells were subcutaneously inoculated in Balb/c nude mice. When the tumor volume reached greater than 100 mm(3), either curcumin (500 mg/kg body weight) or vehicle was administered through oral gavage three times weekly for 4 weeks. The expression of AR and intermediate products of Wnt/β-catenin were assessed. RESULTS Curcumin had an inhibitory effect on tumor growth during the early period, which was followed by a slow increase in growth over time. Tumor growth was delayed about 27% in the curcumin group. The mean prostate-specific antigen (PSA) doubling time in the curcumin group was approximately twice that in the untreated group. Curcumin significantly decreased AR expression at both the mRNA and protein level. The PSA levels tended to be reduced in the curcumin group. However, there were no significant changes in expression of Wnt/β-catenin pathway intermediates. CONCLUSIONS This study revealed that curcumin initially interferes with prostate cancer growth by inhibiting AR activity and possibly by reducing PSA expression. Further research is needed to investigate the plausible mechanism of the antiandrogenic action of curcumin.