NKX3-1 and prostate cancer: 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.