Gram-positive and negative bacteria can stimulate bronchial epithelial TLR2 or TLR4 respectively, thereby enhancing the adhesion of NSCLC cells to liver sinusoids via IL-6 secretion, ultimately promoting liver metastasis.346,347 Activation of epithelial TLR4 also fosters the recruitment of PMN-MDSCs, setting the stage for pre-metastatic niches.348 Furthermore, activation of TLR4 in M2 TAMs can induce EMT in pancreatic cancer cells partially through IL-10 signaling.349 In lung epithelial cells, TLR3 can be activated by RNA from exosomes derived from primary tumors. This evidence concerns the gene TLR4 and non-small cell lung carcinoma.