CDKN1A and hepatocellular carcinoma: The HDAC inhibitor SAHA has a key role in promoting sensitivity to 5-FU and irinotecan via triggering proapoptotic signals in hepatocellular carcinoma cells through overcoming MDR-mediated drug efflux, suppressing SN-38 glucuronidation and synchronization of the cell cycle by upregulation of CDK-inhibitor p21cip1/waf1 (173).