MEG3, which is downregulated in multiple cancer cell lines, is epigenetically activated upon the methylation of histone H3 at lysine 4 (H3K4me3) by MEN1 (multiple endocrine neoplasia type 1), a component of the MLL complex that functions as a tumor suppressor [78,193,269]. This evidence concerns the gene KMT2A and multiple endocrine neoplasia type 1.