Fig. 6. STINGVAX can up-regulate PD-L1.

(A) STINGVAX treatment induces up-regulation of PD-L1 on tumors, correlating with increased infiltration of IFNγ⁺CD8⁺ T cells. Scale bars, 100 μm. Harvested tumor tissues from treated mice were probed with CD8, IFNγ, and PD-L1 conjugates, followed by DAPI counter-stain. Colocalized CD8 and IFNγ costaining positive cells are shown in yellow; CD8, green (FITC); IFNγ, red [phycoerythrin (PE)]. PD-L1–PE conjugate (red) was used for the right panel. DAPI (blue) was used as a counterstain. The absolute number of CD8⁺IFNγ⁺ and PD-L1⁺ cells per mass of tumor tissue is shown in the right panels. Data are means ±SEM from five samples. (B) Combination of STINGVAX (with CDA) and PD-1–blocking antibody slightly improved the antitumor response of established B16 tumors compared to the STINGVAX, but did not reach statistical significance (top panel). However, the combination of STINGVAX (RR-S2 CDA) + anti–PD-1 significantly improved the antitumor response when compared against the combination of STINGVAX (CDA) + anti–PD-1. The smaller panels on the bottom right are volume plots of individual mice (overlapping curves represent multiple mice with regression). Each group had 10 mice, and data represent means ± SEM. The graph is representative of five experiments. n.s., not significant.