CASP3 and cancer: Recent findings have shown that HDACi increases the cytotoxicity potency of 5-FU (Okada et al., 2016; Minegaki et al., 2018) using mechanisms such as thymidylate synthase (TS) downregulation in human cancer cells, upregulation of major histocompatibility complex (MHC) class II and p21 (CDKNIA) genes, and apoptosis induction by activating caspase-3/7.