Kynurenic acid (KYNA), an important tryptophan‐derived metabolite, inhibits tumor proliferation by decreasing the phosphorylation of ERK1/2 and p38 kinases in colon cancer cells.[66] However, LCA activates ERK1/2 in colon cancer cells and stimulates the secretion of IL‐8, accelerating carcinogenesis. This evidence concerns the gene CXCL8 and neoplasm.