TLR9 and lung cancer: Jiang et al. showed that CpG ODN is a specific agonist of TLR9, activating the TLR9 pathway by upregulating transcription of TLR9 to play immunoregulatory effects.56 Di et al.57 found that using the specific ligand of TLR9, CpG ODN, to stimulate the A549 lung cancer cell line can produce resistance to apoptosis induced by TNF-α.