Sequential Administration of Anti-PD-1 and Anti-Tim-3 Combined with an SA-GM-CSF-anchored Vaccine Overcomes Adaptive Immune Resistance to Reject Established Bladder Cancer

Program death receptor-1 (PD-1) and T-cell immunoglobulin and mucin domain-containing protein-3 (Tim-3) play an important role in tumor immune evasion. PD-1 blockade could produce an effective anti-tumor effect but the response rate was low due to lacking of tumor infiltrating lymphocytes (TILs) and existing of other negative regulatory pathways. Streptavidin(SA)-GM-CSF surface-anchored tumor cells vaccine could induce specific anti-tumor immune response. However, this vaccine failed to induce regression of established tumor because it also up-regulated PD-1 expression on tumor cells dependent on IFNγ and up-regulated PD-1/Tim-3 expression on CD8 TILs. Subsets of CD8 TILs assay showed that PD-1 expression was closely associated with CD8 TILs exhaustion, and Tim-3 expression was closely correlated with secretion function but not proliferation of CD8 TILs. Sequential administration of anti-PD-1 and anti-Tim-3 could further improve the efficacy of SA-GM-CSF-anchored vaccine therapy, and tumor regression was noted in over 50%. This triple therapy improves the specific cytotoxic activity and decreased the apoptosis of CD8 TILs. These findings indicated that this triple therapy could induce a more robust anti-tumor immune response.