Abstract 5389: Development of T-cell exclusion in melanoma

Abstract Immune checkpoint inhibitors (ICIs), which prevent immune cell exhaustion and boost an antitumor response, have shown remarkable treatment efficacy in patients with advanced melanoma. However, its efficacy is limited by the emergence of resistance associated with an immunosuppressive tumor microenvironment (TME). The contribution of abnormal tumor vasculature to limited immune cell infiltration into the tumor core has been reported but the mechanisms of its development are still elusive. We analyzed how tumor angiogenesis affects the immune cell exclusion at different time points of primary melanoma using syngeneic murine melanomas. The spatial distribution of various immune cell populations and vascular integrity were analyzed in whole tumor cross-sections via multiplex immunofluorescence staining. We found that the exclusion pattern of CD8+ T cells was less evident with a balanced distribution across the whole tumor regions at the early stage. However, as the tumor grows, there is a pronounced accumulation of CD8+ T cells at the tumor periphery with a conspicuous absence in the core. Tumor blood vessels were structurally uniform and functionally stable in the early developmental tumor but became unstable and leaky as the tumor progressed, which was associated with the development of CD8+ T-cell exclusion. To understand the mechanism underlying vascular regulation of immune exclusion during tumor progression, we will investigate the expression of genes related to tumor angiogenesis using spatial transcriptomic analysis and RNA sequencing of endothelial cells (CD45+CD31-) sorted from the murine melanomas. These results highlight the contribution of spatial tumor vascular destabilization to the T-cell exclusion development, implying the potential of targeting tumor vasculature to enhance immune activation and the therapeutic efficacy of ICI in melanoma. Citation Format: Ha-Ram Park, Hee Won Yang, Minah Kim. Development of T-cell exclusion in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5389.