Indeed, we found that the Flag-tagged CAD protein, when ectopically expressed in GC and CRC cells, could still be probed under 5-FU treatment using the anti-Flag antibody for immunoblotting, albeit at a lower molecular weight (Fig. 2a and Supplementary Fig. 2e), suggesting that CAD is cleaved in these cells. Here, CAD is linked to colorectal carcinoma.