FAS and colorectal carcinoma: Houghton and co-workers showed that different CRC cell lines varied in the efficiency of Fas upregulation in response to 5-FU/LV treatment and this correlated with the efficiency of thymidine reversal, indicating 5-FU’s DNA-directed effects were cell line dependent and correlated with Fas upregulation and activation of extrinsic apoptosis[116].