TRAIL-induced apoptosis was chiefly promoted in colon cancer WiDr cells by pre-exposure to Entinostat, an HDAC1, 2, and 3 inhibitors, and in colon cancer DLD-1 cells by RGFP966, an HDAC3-specific inhibitor, or PCI34051, an HDAC8-specific inhibitor. Here, HDAC1 is linked to colonic neoplasm.