[Current Topics of Cancer Antigen]

Cancer antigens are classified into shared antigens and tumor-specific antigens based on their expression pattern or immunogenicity. Neo-antigens are defined as a subset of tumor-specific antigens generated by non-synonymous mutations, Indel gene mutation or gene fusions, presented by major histocompatibility complex molecules that were recognized by effector CD8+ T cells. Cancer cells with inherent genetic instability form abnormal proteins that have not been previously recognized by the immune system and these proteins become highly immunogenic antigens(neo-antigens)that can spontaneously trigger CD8+ T cell responses. Cancer cells that present extremely immunogenic neo-antigens are eliminated from the host through the process of carcinogenesis. Therefore, recognition of neo-antigens could be an important subject of the clinical utility of both neo-antigen cancer vaccine and adoptive TCR-T cell therapy as cancer immunotherapies. Furthermore, monitoring the quantity and quality of the neo-antigen derived in each patient could deduce the clinical response to immune checkpoint inhibitors such as anti-PD-1 therapy in various cancers. Here we review the evidence for the relevance of tumor neo-antigens and host immune response. We discuss the utility as a biomarker for cancer immunotherapy using the neoantigen expression in tumor tissues and the development of neo-antigen-targeted cancer vaccine and T cell mediated therapies.