TLR4 and colorectal cancer: F. nucleatum promotes colorectal cancer cell proliferation and tumorigenesis by activating Toll-like receptor 4(TLR4) signaling, which upregulates nuclear factor-κB, as indicated by increased MicroRNA-21 expression or the TLR4/p-PAK1/p-β-catenin S675-cascade signaling pathway (Yang et al., 2017; Wu et al., 2018).