Improving immunotherapeutic efficacy against metastatic tumors in a pre-clinical model of murine renal cell carcinoma.

Abstract

Renal and pelvic cancers are the ninth most common cancer in the U.S., and although five-year survival rates for localized renal tumors are >90%, those for metastasized tumors are <12%. Metastatic renal cell carcinoma (RCC), the most common type of renal neoplasm, is resistant to radio- and chemotherapies. Immune-based therapies, including checkpoint blockade, are being pursued in an attempt to amplify protective adaptive immunity but overall response rates remain at 20–30%. We hypothesized that a therapeutic strategy employing T cell priming plus checkpoint blockade would result in improved clearance of renal tumors verses checkpoint alone. Utilizing our previously described in vivo T cell priming therapy, adenovirus-encoded tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) (AdTRAIL) with class B oligonucleotides (CpG), we evaluated therapeutic effects on primary tumor outgrowth and metastatic burden in a pre-clinical model of orthotopic murine RCC. We report here that administration of intra-renal AdTRAIL/CpG in combination with α-CTLA-4, but not α-PD-1, causes significant decreases in primary tumor burdens. Strikingly, we observed that this therapeutic strategy caused significant reductions in metastatic lung burdens – equating to a 98% reduction over no therapy controls. Flow cytometric analysis revealed increases in CD8⁺ T cells in AdTRAIL-treated groups over no therapy/checkpoint alone; results were further supported by immunosuppressive CD4⁺ to CD8⁺ T cell ratios that were in favor of anti-tumoral responses. Our results suggest AdTRAIL/CpG can be used as an effective upstream therapeutic approach to enhance the efficacy of α-CTLA-4 checkpoint blockade in a pre-clinical model of murine RCC.