TLR2 and colorectal carcinoma: In one preclinical study, however, Lee et al. showed that B. fragilis colonization protected mice from colitis-associated CRC through a mechanism dependent on polysaccharide A production and toll-like receptor 2 (TLR2) signaling and associated with inhibition of C–C motif chemokine receptor 5 (CCR5) in the colon [13].