TMPRSS2 and Familial prostate cancer: It remains unclear whether expression of the TMPRSS2-ERG fusion mRNA in a prostate cancer cell serves as a major driver for its tumorigenic features [33], or whether the fusion event occurs as a result of an androgen-responsive tumor cell state, as suggested by induction of the fusion event in normal prostate epithelial cells in response to androgen [35], [36].