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 castration‐resistant 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. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.