Genetic interaction between Tmprss2-ERG gene fusion and Nkx3.1-loss does not enhance prostate tumorigenesis in mouse models..     ///     Gene fusions involving ETS family transcription factors (mainly TMPRSS2-ERG and TMPRSS2-ETV1 fusions) have been found in ~50% of human prostate cancer cases.     ///    "In Tmprss2-ERG;Nkx3.1+/- (or -/-) male mice, although we observed a slight but significant upregulation of Tmprss2-ERG fusion expression upon Nkx3.1 loss, we did not detect any significant cooperation between these two genetic events to enhance prostate tumorigenesis in vivo. "    ///    "Although expression of TMPRSS2-ERG or TMPRSS2-ETV1 fusion alone is insufficient to initiate prostate tumorigenesis, they appear to sensitize prostate epithelial cells for cooperation with additional oncogenic mutations to drive frank prostate adenocarcinoma. "    ///    "We recently generated knockin mouse models for TMPRSS2-ERG and TMPRSS2-ETV1 fusions, utilizing the endogenous Tmprss2 promoter. "    ///    "Previous studies have shown that deletions at 8p21 (harboring NKX3.1) and 21q22 (resulting in TMPRSS2-ERG fusion) were both present in a subtype of prostate cancer cases, and that ERG can lead to epigenetic silencing of NKX3.1 in prostate cancer cells, whereas NKX3.1 can in turn negatively regulate TMPRSS2-ERG fusion expression via suppression of the TMPRSS2 promoter activity. "