Abstract A019: The role of tumor transcriptional variability in evading acute CD8+ T cell exposure in melanoma

Abstract

Abstract Throughout melanoma progression and immunotherapy treatment, melanoma cells often develop an ability to evade the immune system. Thus, there is a pressing need to identify and target the melanoma cell-intrinsic mechanisms underlying immune evasion. Our laboratory has pioneered the identification of transcriptional pathways that underlie melanoma progression. We have found that within even clonal melanoma cell populations, subclones of cells demonstrate tremendous heterogeneity in their transcriptional state. We previously demonstrated that these varying transcriptional states correspond to varying sensitivities of melanoma cells to stressors such as targeted therapies, and that these states can be stable across multiple cell divisions. We hypothesize that varying transcriptional states also correspond to cells that have differing abilities to evade CD8+ T cells, which are major effector cells against melanoma. To study the interactions between melanoma cells and CD8+ T cells, we engineered an ovalbumin antigen and OT-I T cell receptor system using mouse melanoma cell lines. We combined this system with DNA barcoding, which enables us to track subclones of cells undergoing immune selection. When cocultured together in vitro, ovalbumin-expressing melanoma cells are effectively killed by OT-I cells. However, we find that subclones of melanoma cells consistently possess different sensitivity to OT-I cells, and these differences are not due to their genetic background nor their ability to express and present ovalbumin. We then leveraged our DNA barcoding system with single cell RNA sequencing (scRNA-seq) to link the lineage and transcriptional state of single melanoma cells that persist through OT-I coculture. By expanding on these preliminary results, we aim to identify novel melanoma cell targets to decrease immune evasion. Citation Format: Raymond W.S. Ng, Sydney M Shaffer. The role of tumor transcriptional variability in evading acute CD8+ T cell exposure in melanoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Cancer Evolution and Data Science: The Next Frontier; 2023 Dec 3-6; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_2):Abstract nr A019.