No significant differences were found in tumor size (Figure 6B), tumor inhibition rate (Figure 6C), or AhR, β-catenin and TCF1/LEF4 expression (Figure 6D) between the DLD-1/AhR-/- control group and the DLD-1/AhR-/- + Tryptophan group. This evidence concerns the gene AHR and neoplasm.