Figure 3.

Poly(I:C) mediates its effect on PD-L1 and PD-L2 expression in primary human glioblastoma cells primarily via the TLR3-TICAM1 pathway. (A) Poly(I:C) upregulates mRNA expression of TLR3 adaptor molecule TICAM1 but not MAVS, the adaptor molecule for the cytosolic receptor pathway, in primary human glioblastoma cells. mRNA expression following poly(I:C) treatment is shown relative to the basal, naïve condition (dashed line at 1); n = 8; Wilcoxon Signed Ranks test. (B) Patient-specific presentation of the proportional PD-L1 and PD-L2 expression in the naïve setting (white) versus poly(I:C) treatment with (light grey) and without (dark grey) the TLR3 inhibitor chloroquine. TLR3 inhibition clearly diminishes the effect of poly(I:C) on both PD-1 ligands. (C) Relative upregulation (ΔMFI) of PD-L1 and PD-L2 by poly(I:C) when TLR3 signaling is blocked with chloroquine. Data are normalized to naïve (baseline) and poly(I:C) treatment (100%, dashed line) as to show the percentage of upregulation by poly(I:C) not accounted for by TLR3; n = 5; Wilcoxon Signed Ranks test. Bar represents median. Symbols depict primary glioblastoma cells derived from different glioblastoma patients. CQ: chloroquine; *, p < 0.05; **, p < 0.01.