Adenoviruses harboring the herpes simplex virus thymidine kinase (HSVtk) gene under the regulation of a trans-splicing ribozyme targeting human telomerase reverse transcriptase (hTERT-TR) show marked and specific antitumor activity. In addition to inducing tumor cell death by direct cytotoxicity, it is becoming clear that HSVtk also induces antitumor immunity. Programmed death ligand 1 (PD-L1) expressed on tumor cell surfaces mediates tumor-induced immunoresistance by inhibiting PD1-expressing tumor-infiltrating T cells. Here, we explored whether a soluble form of PD1 (sPD1-Ig), which blocks PD-L1, could synergize with TERT-TR-regulated HSVtk to enhance the adenoviral therapeutic efficacy by boosting antitumor immunity. Tumor antigen released by HSVtk-transduced tumors successfully primed tumor antigen-specific CD8 T cells via dendritic cells (DC). Regression of murine tumors was markedly enhanced when sPD1-Ig was incorporated into the adenovirus as compared with a single-module adenovirus expressing only HSVtk. This effect was abolished by CD8 T-cell depletion. Consistent with this, following adoptive transfer of tumor antigen-specific CD8 T cells into tumor-bearing Rag1-/- mice, dual-module adenovirus significantly enhanced CD8 T cell-mediated tumor rejection. In addition, secondary tumor challenge at a distal site was completely suppressed in mice treated with a dual-module adenovirus. These results suggest that a dual-targeting strategy to elicit both tumor antigen priming and tumor-induced immunoresistance enhances CD8 T cell-mediated antitumor immunity.
Bibliographical noteFunding Information:
This work was supported by grants from the Innovative Research Institute for Cell Therapy (A062260) and the Global Core Research Center grant (No.20110030678)), Republic of Korea.
All Science Journal Classification (ASJC) codes
- Molecular Medicine
- Molecular Biology
- Drug Discovery