To further assess the effects of Trp/AhR-mediated activation of Wnt/β-catenin pathway on colorectal tumor growth, DLD-1 cells were transfected with AhR over-expression plasmid and inoculated into the nude mice, followed by gavaged with Tryptophan (0.8%) for 4 weeks as previous described 45. The gene discussed is AHR; the disease is colorectal neoplasm.