Subsequently, in colorectal carcinoma cell lines, expressing neither constitutive nor inducible CYP1A1,14 CYP2W1 was found to bioactivate 5F 203 and structurally related 2‐(3,4‐dimethoxyphenyl)‐5‐fluorobenzothiazole (GW 610); stable knockdown of CYP2W1 gene led to significant loss of benzothiazole (GW 610, 5F 203) activity in KM12 and HCC 2998 CRC cell lines.22 This evidence concerns the gene CYP1A1 and colorectal carcinoma.