Fig. 6.

The TLR activation and induction of PD-L1/PL-D expression in GBM cell. In GBM TME, the PD-1/PD-L1 axis promotes tumor invasion through infiltration of MDSCs and Treg and exhaustion of cytotoxic T-cells. TLR recognizes ligand to elevate PD-L1 expression in three ways, the early-phase MyD-dependent NF-κB signaling, the late-phase MyD-independent NF-κB signaling, and IFN secretion which activates IFNAR signaling to induce further expression of PD-L1. TLR agonist combined with checkpoint inhibitor potentiates antitumor response by T-cell attraction, IFN production, PD-L1 upregulation and blockade of PD-1/PD-L1 axis