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. Here, TLR4 is linked to colonic neoplasm.