There are five members in the DNMT family, including DNMT1, DNMT2, DNMT3a, DNMT3b, and DNMT3L, the most common mutation of DNMT in cancer is the DNMT3a mutation, while DNMT3b is a pro-carcinogenic gene in endometrial, lung and prostate cancer, and a tumor suppressor gene (TSG) in lymphoma. The gene discussed is DNMT3B; the disease is Familial prostate cancer.