RESUMO
OBJECTIVES: With the poorest 5-year survival of all cancers, improving treatment for pancreatic cancer is one of the biggest challenges in cancer research. We sought to explore the potential of combining both priming and activation of the immune system. To achieve this, we combined a CD40 agonist with interleukin-15 and tested its potential in pancreatic cancer. METHODS: Response to this combination regimen was assessed in pancreatic ductal adenocarcinoma mouse models, and a thorough analysis of the tumor microenvironment was performed. RESULTS: We demonstrated profound reduction in tumor growth and increased survival of mice with the majority of mice being cured when both agents were combined, including an unprecedented 8-fold dose reduction of CD40 agonist without losing any efficacy. RNAseq analysis showed involvement of natural killer (NK) cell- and T-cell-mediated anti-tumor responses and the importance of antigen-presenting cell pathways. This combination resulted in enhanced infiltration of tumors by both T cells and NK cells, as well as a striking increase in the ratio of CD8+ T cells over Tregs. We also observed a significant increase in numbers of dendritic cells (DCs) in tumor-draining lymph nodes, particularly CD103+ DCs with cross-presentation potential. A critical role for CD8+ T cells and involvement of NK cells in the anti-tumor effect was highlighted. Importantly, strong immune memory was established, with an increase in memory CD8+ T cells only when both interleukin-15 and the CD40 agonist were combined. CONCLUSION: These novel preclinical data support initiation of a first-in-human clinical trial with this combination immunotherapy strategy in pancreatic cancer.
RESUMO
Prognosis of glioblastoma remains dismal, underscoring the need for novel therapies. Immunotherapy is generating promising results, but requires combination strategies to unlock its full potential. We investigated the immunomodulatory capacities of poly(I:C) on primary human glioblastoma cells and its combinatorial potential with programmed death ligand (PD-L) blockade. In our experiments, poly(I:C) stimulated expression of both PD-L1 and PD-L2 on glioblastoma cells, and a pro-inflammatory secretome, including type I interferons (IFN) and chemokines CXCL9, CXCL10, CCL4 and CCL5. IFN-ß was partially responsible for the elevated PD-1 ligand expression on these cells. Moreover, real-time PCR and chloroquine-mediated blocking experiments indicated that poly(I:C) triggered Toll-like receptor 3 to elicit its effect. Cocultures of poly(I:C)-treated glioblastoma cells with peripheral blood mononuclear cells enhanced lymphocytic activation (CD69, IFN-γ) and cytotoxic capacity (CD107a, granzyme B). Additional PD-L1 blockade further propagated immune activation. Besides activating immunity, poly(I:C)-treated glioblastoma cells also doubled the attraction of CD8+ T cells, and to a lesser extent CD4+ T cells, via a mechanism which included CXCR3 and CCR5 ligands. Our results indicate that by triggering glioblastoma cells, poly(I:C) primes the tumor microenvironment for an immune response. Secreted cytokines allow for immune activation while chemokines attract CD8+ T cells to the front, which are postulated as a prerequisite for effective PD-1/PD-L1 blockade. Accordingly, additional blockade of the concurrently elevated tumoral PD-L1 further reinforces the immune activation. In conclusion, our data proposes poly(I:C) treatment combined with PD-L1 blockade to invigorate the immune checkpoint inhibition response in glioblastoma.