SMAD4 and prostate neoplasm: Smad4 knockdown mediated by siRNA did not block the increase in N-cadherin of BM-MSCs in response to hormone-insensitive prostate tumor cells (unpublished), although the increase in N-cadherin expression was significantly downregulated in response to hormone-insensitive prostate tumor cells by inhibiting TGF-β with either TGF-β type I receptor inhibitors or TGF-β type I receptor knockdown.