TLR2 and neoplasm: TLR2 KD not only markedly blocked the Pam3Cys-stimulated expression and phosphorylation of Stat3, but also significantly reduced the constitutive expression and phosphorylation of Stat3 compared to the basal level of Stat3 in B16 cells (P<0.001, Fig. 2C), suggesting the basal activity of TLR2 is critical for the constitutive activation of Stat3 in the tumor cells.