CBX1 (HP1α) is a member of the heterochromatin protein 1 family (HP1s) that plays a role in the formation and maintenance of heterochromatin. This gene encodes a non-histone protein that is able to bind to histone proteins via methylated lysine residues. Genome-wide localization analysis reveals H3K27me3 binding at CBX1 promoter regions and thus points to heterochromatin formation corresponding to gene silencing in prostate cancer. It has already been shown that CBX1 is downregulated in invasive breast cancer cells , and our findings show that a novel epigenetic mechanism might involve CBX1 in transcriptional regulation, thus providing new insight for further elucidation of the molecular mechanisms causing the CBX1 downregulation in cancer cells.