TLR4 and neoplasm: PAUF has been shown to be an endogenous ligand for TLR2 and TLR4, it activates the canonical signaling pathways of TLR2-tumor progression locus 2 (TPL2)/mitogen-activated ERK kinase (MEK)/extracellular signal-regulated kinase (ERK), but it fails to mediate TLR2-induced NF-κB activation [103].