Identification and enhancement of HLA-A2.1-restricted CTL epitopes in a new human cancer antigen-POTE

• Published in: PloS one Vol. 8; no. 6; p. e64365
• Main Authors: Huang, Yi-Hsiang, Terabe, Masaki, Pendleton, C David, Stewart Khursigara, Deborah, Bera, Tapan K, Pastan, Ira, Berzofsky, Jay A
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04-06-2013; Public Library of Science (PLoS)
• Subjects: Affinity; Amino Acid Sequence; Amino acids; Animals; Antigenic determinants; Antigens; Antigens, Neoplasm - chemistry; Antigens, Neoplasm - immunology; Binding; Biology; Cancer; Cancer therapies; Cancer vaccines; CD8 antigen; Cell Line, Tumor; Colon; Cross Reactions; Cytotoxicity; Development and progression; Epitopes; Epitopes, T-Lymphocyte - immunology; Hepatitis; Histocompatibility antigen HLA; HIV; HLA antigens; HLA-A2 Antigen - immunology; Human immunodeficiency virus; Humans; Immunogenicity; Immunological tolerance; Immunotherapy; Laboratories; Ligands; Lung cancer; Lung diseases; Lymphocytes; Lymphocytes T; Medical research; Medicine; Metastasis; Mice; Mice, Transgenic; Molecular biology; Non-small cell lung cancer; Non-small cell lung carcinoma; Pancreas; Peptides; Phenylalanine; Placenta; Prostate; Prostate cancer; Protein Structure, Tertiary; Receptors, Antigen, T-Cell - metabolism; T cells; T-Lymphocytes, Cytotoxic - immunology; Transgenic animals; Tumor cells; Tumors; Tyrosine; Vaccines; Valine; United States > US; Maryland
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0064365

Identification of CD8(+) T cell epitopes that can induce T cells to kill tumor cells is a fundamental step for development of a peptide cancer vaccine. POTE protein is a newly identified cancer antigen that was found to be expressed in a wide variety of human cancers, including prostate, colon, lung, breast, ovary and pancreas. Here, we determined HLA-A2.1-restricted cytotoxic T lymphocyte (CTL) epitopes in the POTE protein, and also designed enhanced epitopes by amino acid (AA) substitutions. Five 9-mer peptides were first selected and their binding affinity to HLA-A2 molecules was measured by the T2 binding assay. POTE 272-280 and POTE 323-331 showed the strongest HLA-A2 binding affinity. AA substituted peptides POTE 252-9V (with valine at position 9), POTE 553-1Y (with tyrosine at position 1) and POTE 323-3F (with phenylalanine at position 3) conferred higher affinity for HLA-A2, and induced CTL responses cross-reactive with wild type antigens. While POTE 252-9V was the strongest in this respect, POTE 323-3F had the greatest increase in immunogenicity compared to wild type. Importantly, two modified epitopes (POTE-553-1Y and POTE-323-3F) induced CTLs that killed NCI-H522, a POTE-expressing HLA-A2(+) human non-small cell lung cancer cell line, indicating natural endogenous processing of these epitopes. In conclusion, the immunogenicity of POTE epitopes can be enhanced by peptide modification to induce T cells that kill human cancer cells. A combination of POTE 553-1Y and POTE 323-3F epitopes might be an attractive vaccine strategy for HLA-A2 cancer patients to overcome tolerance induced by tumors and prevent escape.