HLA-C and neoplasm: Importantly, tumor antigens can be categorized into two main groups: tumor-associated antigens (TAAs), which are self-antigens that are abnormally expressed in cancer cells but also expressed in normal cells, and tumor neoantigens, which are the repertoire of peptides that are expressed in the surface of tumor cells but are not expressed in normal tissues and are recognized by antigen-specific T cell receptors (TCRs) through the cooperation of major histocompatibility complex (MHC) molecules [23].