CYP1A1 and adenoma: Consequently, no tumors were observed in wild-type mice under this treatment regime, while both VillinCreAhrfl/fl and VillinCreR26LSL-Cyp1a1 mice developed numerous tumors throughout the colon (Figures 4A–4C, top row), ranging in severity from low-grade adenoma to adenocarcinoma (Figure 4D).