Immune checkpoint inhibitors (ICIs), including
programmed cell death protein 1 (PD-1)/
programmed death-ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated
protein 4 have shown promising
cancer clinical outcomes. However, IC
therapy has low patient response rates (10%-15%). Thus, ICIs and sufficient
antigen combinations into the tumor microenvironment (TME) is important to produce strong
tumor-specific adaptive immune responses. Mice were treated with
cisplatin, and human
cancer cells were exposed to inflammatory
cytokines, to confirm increased PD-L1 and major histocompatibility complex (MHC) I expression by
tumor cells or dendritic cells. TC-1, CT26, B16-F1, or B16-F10
tumor cells, and bone marrow-derived dendritic cells, were treated with
interferon (IFN)-β, IFN-γ, or
tumor necrosis factor-α to identify the molecular mechanisms underlying
tumor PD-L1 and MHC I upregulation, and to examine MHC I, CD40, CD80, CD86, or PD-L1 levels, respectively. For synergistic combination
therapy, αPD-L1
monoclonal antibody (mAb) covalently linked to the long E7
peptide was generated.
Chemotherapy shifted the TME to express high PD-L1 and MHC I, resulting in targeted ICI cargo delivery and enhanced generation and activation of
tumor antigen-specific T cells. Synergistic effects of vaccination and IC blockade in the TME were demonstrated using an anti-PD-L1 mAb covalently conjugated to the E7 long
peptide.