MAPK1 and Familial prostate cancer: Histone deacetylase inhibitors inhibit the growth of prostate cancer cells by inhibiting ERK activity and downregulating DNMT1 protein levels, and were found to reverse promoter hypermethylation and gene silencing of three tumor suppressor genes in an LNCaP prostate cancer cell line; these three genes included retinoic acid receptor B2 (RARB2) and cycle-dependent kinase inhibitors p21 and p16 [22].