DNMT1 and neoplasm: Furthermore, ROS can induce hypermethylation of tumor suppressor genes by the upregulation of DNMT1 and histone deacetylase 1, enzymes involved in gene silencing through promoter methylation and histone deacetylation [75], and by the formation and relocalization of a silencing complex, composed of DNMT1, DNMT3B, SIRT1, and members of polycomb repressive complex 4, stimulating cancer-specific hypermethylation [76].