Elf5 Inhibits TGF-β-Driven Epithelial-Mesenchymal Transition in Prostate Cancer by Repressing SMAD3 Activation

BACKGROUNDThe epithelial-mesenchymal transition (EMT) has been associated with the acquisition of migration, invasiveness, and metastasis traits. During tumor progression, EMT can be induced by transforming growth factor- (TGF-) signal that epithelial cells receive from their microenvironment. However, the master regulatory controls on TGF--EMT axis are not understood. METHODSThe protein expression in human specimens was measured by immunohistochemical staining. E74-like factor 5 (Elf5) was silenced by short interfering RNAs in LNCaP cells and stably overexpressed by HA-tagged Elf5 cDNAs in 22Rv1 cells. These cells were used to study migration and anchorage-independent growth. RESULTSOur data reveal that Elf5 results in the failure of mesenchymal morphogenesis, upregulation of EMT markers, spheres formation, and migration in the presence of TGF-. Furthermore, Elf5 blocks TGF- signaling, through decreasing drosophila mothers against decapentaplegic protein (SMAD3) activation by binding to it, one of the major effector of TGF--induced EMT. Moreover, Elf5 can serve as a prognostic marker of metastasis-free survival in patients with TGF--positive prostate cancer. CONCLUSIONSElf5 expression is inversely correlated with EMT. Elf5 inhibits TGF--driven EMT via repressing SMAD3 phosphorylation in prostate cancer cells. In addition, Elf5 can be used as a biomarker of metastasis-free survival in patients with TGF--positive prostate cancer. Prostate 75:872-882, 2015. (c) 2015 Wiley Periodicals, Inc.