To address the mechanism involved in the epigenetic regulation of ID4, we first analyzed the expression of genes involved in the DNA methylation including DNMTs (DNMT1, DNMT3A and DNMT3B) and constituents of PRC2 (EZH2, Suz12, EED) and PRC1 (RING1) complex in The Cancer Genome Atlas (TCGA) [31] prostate cancer adenocarcinoma (PRAD) gene expression (IlluminaHiseq) database (Fig. 1A). Here, EED is linked to prostate adenocarcinoma.