Levels of P. anaerobius are higher in human colon tumor tissues and adenomas compared with nontumor tissues; this bacterium increases colon dysplasia in a colorectal cancer mouse model. P. anaerobius interacts with TLR2 and TLR4 in colon cells to increase the abundance of reactive oxidative species, which promotes cholesterol synthesis and cell proliferation. This evidence concerns the gene TLR4 and colorectal cancer.