An analysis of the antitumor activity of GW-610 (2-(3,4-dimethoxyphenyl)-5-fluorobenzothiazole) and 5F-203 (2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole) in breast cancer cell lines selectively depleted of CYP1A1, CYP2S1, and CYP2W1 showed that, in contrast to CYP1A1 and CYP2W1, CYP2S1 mediates the inactivation of these drugs [13,62]. The gene discussed is CYP2S1; the disease is breast carcinoma.