Immunoediting restricts clonal neoantigens in primary human tumors 2606

Abstract Description Evidence consistent with immunoediting in human cancer has been identified through associative studies. To provide direct evidence that differences in the neoantigen profile are immune-mediated, we compared the neoantigen profiles of cutaneous squamous cell carcinoma (cSCC) from immunocompetent and immunosuppressed patients. Despite consistency in the overall mutational burden and signature, immunocompetent patients have a lower clonal mutational burden compared to immunosuppressed patients. Furthermore, clonal mutations in cSCC from immunocompetent patients have a lower proportion of neoantigens predicted to bind MHC class I, supporting the role of the immune system in shaping the neoantigen profile. In single-cell RNA sequencing of intratumoral CD8+ T cells from a separate cohort of cSCC from immunocompetent and immunosuppressed patients, we observe an increase in exhausted CD8+ T cells in tumors from immunocompetent patients, suggesting an explanation for the persistence of binding neoantigens subclonally. Finally, we compare clonal and subclonal neoantigens as an unbiased screen for characteristics associated with neoantigen immunogenicity. Neoantigens with a large increase in predicted MHC class I binding relative to the normal peptide are enriched in subclonal neoantigens in immunocompetent patients. Overall, this work supports the immune system’s role in sculpting the neoantigen profile of cSCC. Funding Sources Supported by American Cancer Society - Simone Charitable Foundation - Discovery Boost Grant, AZ-DBG-23-1151311-01-IBCD; NIH F30CA281056; R35GM149235 Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)