Tumor metastasis suppressor functions of Ets transcription factor through integrin β3-mediated signaling pathway

Prostate-derived Ets transcription factor (PDEF) is a member of the Ets transcription factor family originally identified in prostate tissue. PDEF functions like a tumor metastasis suppressor. Although the underlying mechanism is not very clear. In this study, a significantly higher expression level of integrin β3 was observed in aggressive prostate cancer (PCa) cells; PC3, that lack the expression of PDEF, was confirmed by quantitative real-time polymerase chain reaction and the immunoblot analysis. Dual immunofluorescence studies have confirmed the lower expression of PDEF and higher expression level of integrin β3 in PCa cells compared with non-tumorigenic prostate epithelial RWPE-1 cells. Then, it was attempted to identify integrin β3-mediated downstream signaling pathways that modulate actin cytoskeleton remodeling in PCa cells. Inhibition of PDEF by RNA interference (PDEF_KD ) in DU145 cells confirmed by transcript and western blot analysis, exhibited significantly higher expression level of integrin β3 and its downstream signaling molecules talin and paxillin, associated with promoting migration and invasion of cells. Given the involvement of integrin-mediated invasion of cells, PDEF_KD DU145 cells were treated with Echistatin, a potent integrin β3-specific antagonist and found that the cells significantly reduced the transcript and protein expression levels of talin and paxillin; and reduced the invasion of cells. Overall, the cytoskeleton remodeling by integrin β3, modulated by PDEF, may represent a novel molecular link with cell adhesion and migration leading to the suppression of metastasis in PCa cells.