TGFB1 and prostate cancer: Methylation silencing of TGFBR2 was found in rat prostate cancers [15], further studies also proved AR/miRNA-21 or AR/miR-2909 positive feedback loop down-regulated the expression of TGFBR2, leading to attenuation of TGF-β mediated Smad2/3 activation and subsequent tumor-suppressive activity [16, 17].