Abstract B018: Landscape of natural HLA class I ligand peptides of cancer cells

HLA class I ligand repertoire on cancer cells directly influences immune surveillance system against cancer. We performed large-scale mass spectrometric profiling of the natural HLA-A*2402 ligand peptides and unveiled the landscape of natural HLA class I ligand peptides derived from various cancer cells including colon cancer cells (SW480, Colo320, HCT15) and lung cancer cells (LHK2, Sq-1). Known A24-binding anchors (Y/F at P2 and F/L/I at P9) were largely conserved among the ligands; however, a subset of peptides had an unusual anchor (K/R at the C-terminal P9 or P10), suggesting diverse usage of anchors in certain types of cancer cells. Moreover, a certain amino acid residue had significantly low frequency in the N-terminal flanking sequence, suggesting that it might inhibit processing of the peptides. Profiling of the natural HLA ligands of cancer cells revealed "neoantigen" peptides derived from mutated genome DNA and "aberrant antigen" peptides derived from long noncoding RNAs as well as "cancer-germ cell antigen" peptides. Among the natural HLA ligands derived from cancer cells, immunogenicity of the "neoantigen" peptide was the highest. The landscape clarified immunogenic peptide repertoire that might be suitable for cancer vaccine as well as as-yet-unknown rules for antigen processing. Citation Format: Yasuhiro Kikuchi, Takayuki Kanaseki, Ayumi Hongo, Serina Tokita, Toshihiko Torigoe, Kochin Vitaly. Landscape of natural HLA class I ligand peptides of cancer cells [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B018.