CDKN1A and malignant colon neoplasm: HDAC inhibitors such as depsipeptide and valproic acid (VPA) for instance, are capable of potentiating the antitumor activity of 5-FU in colon cancer via the induction of caspase-3/7 activation, MHC class II gene expression, cell cycle arrest by cyclin-dependent kinase inhibitor 1A (CDKN1A) upregulation, and extensive TYMS downregulation [275,276].