AHR and neoplasm: Since LEF and TCF are essential transcription factors in the Wnt/β-catenin pathway and mediators of tumor formation induced by Apc deficiency in the intestine 29, 35, we examined the localization and expression of LEF and TCF in the tumor tissues from the ApcMin/+ mice and ApcMin/+ AhR -/- mice by IHC (Figure 5B).