TLR9 and neoplasm: However, there is evidence that tumor-induced down-regulation of TLR9 in pDCs was observed within the tumor environment (108), and simultaneously various cytokines in the tumor microenvironment such as VEGF, TGF-β and IL-10 inhibit the maturation and activation of TIpDCs (109), resulting in a significant decrease in the expression of IFN-α, indicating TIpDCs dysfunction (108, 110).