Abstract 636: Comprehensive analysis of T cells responsive to neoantigens derived from tumor-specific genetic mutations

Abstract

Neoantigens derived from tumor-specific genetic mutations can be recognized as foreign by the host immune system, and might be suitable as target for cancer immunotherapy possibly due to their higher immunogenicity. In this study, to really know the immunogenicity of tumor-specific neoantigens, we comprehensively investigated T cell responses against neoantigens derived from genetic mutations in gastric cancer. Using next-generation sequencing, 156 missense mutations were identified in tumor cells from two gastric cancer patients. From them, we selected 30 potentially immunogenic amino acid sequences, which were derived from the mutations and predicted to potentially bind to HLA-class I (A*0201, A*0206, or A*2402) by an epitope prediction server, IEBD. We synthesized 30 kinds of 27mer long peptides, in which the mutated sequences were located in the center, and then cultured peripheral blood mononuclear cells (PBMC) from healthy donors in the presence of the synthetic peptides to evaluate whether they could really induce antigen-specific T cell responses. In the analysis with PBMC from 18 healthy donors, 27/30 (90%) synthetic peptides showed an ability to induce antigen-specific T cell responses in at least one donor, assessed by cytokine production assay. Among them, 15 peptides were immunogenic in more than one donor. The antigen-specific T cell responses were detected more frequently in CD4+ T cells (70%) than in CD8+ T cells (43%). The specificity of T cell responses to mutated sequences, but not to the corresponding wild type sequences, were confirmed in 5 of 8 (63%) peptides examined. In addition, antigen-specific T cell responses induced by mutated peptides were shown to be much higher than those induced by the corresponding wild type peptides. These findings clearly demonstrated high immunogenicity and specificity of neoantigens derived from tumor-specific genetic mutations. Further studies would be recommended to develop a novel immunotherapeutic approach, “personalized cancer vaccination”, targeting mutation-derived neoantigens. Citation Format: Tetsuro Sasada, Junya Ohtake, Satoshi Wada, Erika Yada, Shintaro Yoshida. Comprehensive analysis of T cells responsive to neoantigens derived from tumor-specific genetic mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 636. doi:10.1158/1538-7445.AM2017-636