SMAD4 and prostate cancer: Oncogenic microRNA miR-1260b targets both Smad4 and secreted frizzled-related protein 1 (sFRP1, an endogenous Wnt pathway inhibitor) [13], suggesting that there is a population of prostate cancer patients in which the Wnt pathway is up-regulated while the BMP and TGFβ pathways are inactivated.