These processes may collaborate to regulate gene expression, and studies have shown that multiple hypermethylated genes can be robustly reactivated by a combination of DNA-methyltransferase-1 (DNMT1) and HDAC inhibition, suggesting that DNMT1 and HDAC are both essential in the silencing of gene expression in cancer cells [3], [5]. The gene discussed is HDAC9; the disease is cancer.