CASP3 and colorectal carcinoma: Additionally, caspase-9 which is reported to play a key role in intrinsic apoptosis has been activated by the release of cleaved caspase-3 product after FAC-pretreated/5-FU-treated CRC cells, and 5-FU alone compared to untreated control and FAC alone treatment (Fig. 4D, G, H).