Abstract B130: Induced lymphangiogenesis enhances antigen-specific T-cell response in anticancer vaccination

Abstract

Tumor-associated lymphatic vessels play multiple and complex roles in the regulation of antitumor immunity. In both mouse and human melanomas, lymphatic markers correlate with increased tumor immune infiltrates and enhanced responsiveness to immunotherapy. Despite the immune-promoting functions of lymphatics in cancer immunotherapy, manipulation of lymphatic vessels directly within the tumor site appears controversial as a therapeutic strategy, due to the correlation of tumor lymphatic growth (lymphangiogenesis) with cancer cell dissemination and metastasis. Here, we sought to manipulate and exploit lymphatic vessels remotely from the tumor by developing and characterizing a lymphangiogenic cancer vaccine. Lymphangiogenic whole-cell vaccines were formulated using lethally irradiated tumor cells overexpressing the pro-lymphangiogenic growth factor VEGF-C in combination with topically retained immune adjuvants (VEGFC vax). In the B16F10 and B16F10-OVA mouse melanoma models, VEGFC vax induced extensive lymphatic growth at the cutaneous injection site, as assessed by both flow cytometry and histologic analysis. Induced lymphangiogenesis increased the rate of fluorescent microbead transport from the skin to the draining lymph nodes, suggesting an enhanced antigen trafficking. In addition, VEGF-C overexpression drove the recruitment in the vaccine injection site of naive T-cells (responsive to lymphatic-derived CCL21), which could be primed in situ. Compared to a control VEGF-C-free vaccine formulation, VEGFC vax induced a broader T-cell response targeting multiple mouse melanoma antigens (including tumor neoantigens), as assessed by IFNγ ELISPOT following antigen-specific stimulation. In a prophylactic setting, VEGFC vax provided complete protection against B16F10 melanoma challenge, outperforming both the control vaccine and a GM-CSF-secreting whole-cell vaccine (GVAX). Overall this study provides a proof of concept for the use of VEGF-C as an immunostimulatory agent in cancer vaccines, based on its ability to activate and expand lymphatic vessels and consequently promote local immune cell trafficking, antigen transport and T-cell activation. In addition, we here developed and characterized a whole-cell VEGF-C vaccine formulation with potential for clinical translation. Citation Format: Maria Stella Sasso, Sylvie Hauert, Priscilla Briquez, Yue Wang, Jun Ishihara, Jeffrey A. Hubbell, Melody A. Swartz. Induced lymphangiogenesis enhances antigen-specific T-cell response in anticancer vaccination [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B130.