Abstract 5093: Chemically inducible splice-neoantigens for cancer immunotherapy

Abstract

Abstract Although immune checkpoint blockade therapies have dramatically improved the survival rate of patients with cancer compared with other treatment approaches, a substantial number of patients show poor response or resistance to these therapies. Meta-analyses for programmed cell death 1 (PD-1) blockade responses highlight the importance of neoantigens, derived from non-synonymous mutations in cancer cells, for antitumor immune responses. Intriguingly, recent transcriptome and genomics studies predict the presence of putative neoantigens as a result of an irregular pre-mRNA splicing regulation in cancer cells, indicating that alterations in RNA splicing in cancer cells might induce antitumor immune responses. Here, we report that induction of serine/arginine-rich splicing factor (SRSF)-dependent splicing boosts the production of splicing-associated neoantigens (splice-neoantigens) and potentiates the response to PD-1 blockade. Administration of a synthetic SRSF activator RECTAS suppressed tumor growth in a host CD8+ T cell- and tumor major histocompatibility complex class I-dependent manner and promoted the antitumor effect of anti-PD-L1 antibody without detectable autoimmunity. Subsequent transcriptome analysis and validation for immunogenicity identified six splice-neoantigen candidates whose expression was induced by RECTAS treatment. Importantly, vaccination of the identified neoepitopes elicited T cell responses capable of killing cancer cells in vitro, in addition to suppression of tumor growth in vivo upon sensitization with RECTAS. Collectively, these results provide support for the further development of splice variant-inducing treatments for cancer immunotherapy. Citation Format: Shingo Matsushima, Masahiko Ajiro, Kei Iida, Kenji Chamoto, Tasuku Honjo, Masatoshi Hagiwara. Chemically inducible splice-neoantigens for cancer immunotherapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5093.