TET enzymes oxidize 5 mC–5 hmC, and the TET family of proteins promotes site-specific DNA demethylation in normal cells, but in prostate cancer, its tumor suppressor TET family proteins are inhibited, such as TET2, which is involved in Androgen Receptor (AR) signaling, and its down-regulation is associated with prostate cancer progression, TET proteins can inhibit tumor progression and invasion by down-regulating the methylation of key genes, and it is considered as a new prognostic biomarker along with 5 hmC (90–92). Here, TET2 is linked to Familial prostate cancer.