Inhibition of methyltransferase Repressive Complex 2 Subunit(EZH2)and acetyltransferase Histone Deacetylase(HDAC), which are involved in regulating histone modifications, can lead to tumor regression in AT-Rich Interaction Domain 1A (ARID1A) mutant ovarian cancer mouse models. The gene discussed is EZH2; the disease is ovarian cancer.