Androgen depletion up-regulates cadherin-11 expression in prostate cancer

Men with castration-resistant prostate cancer (PCa) frequently develop metastasis in bone. The reason for this association is unclear. We have previously shown that cadherin-11 (also known as OB-cadherin), a homophilic cell adhesion molecule that mediates osteoblast adhesion, plays a role in the metastasis of PCa to bone. Here, we report that androgen-deprivation therapy up-regulates cadherin-11 expression in PCa. In human PCa specimens, immunohistochemical staining showed that 22/26 (85%) primary PCa tumours from men with castrationresistant PCa expressed cadherin-11. In contrast, only 7/50 (14%) androgen-dependent PCa tumours expressed cadherin-11. In the MDA-PCa-2b xenograft animal model, cadherin-11 was expressed in the recurrent tumours following castration. In the PCa cell lines, there is an inverse correlation between expression of cadherin-11 and androgen receptor (AR), and cadherin-11 is expressed in very low levels or not expressed in AR-positive cell lines, including LNCaP, C4-2B4 and VCaP cells. We showed that AR likely regulates cadherin-11 expression in PCa through an indirect mechanism. Although re-expression of AR in the AR-negative PC3 cells led to the inhibition of cadherin-11 expression, depletion of androgen from the culture medium or down-regulation of AR by RNA interference in the C4-2B4 cells or VCaP cells only produced a modest increase of cadherin-11 expression. Promoter analysis indicated that cadherin-11 promoter does not contain a typical AR-binding element, and AR elicits a modest inhibition of cadherin-11 promoter activity, suggesting that AR does not regulate cadherin-11 expression directly. Together, these results suggest that androgen deprivation up-regulates cadherin-11 expression in prostate cancer, and this may contribute to the metastasis of PCa to bone. Our study suggests that therapeutic strategies that block cadherin-11 expression or function may be considered when applying androgen-ablation therapy.