title: Identification and enhancement of HLA-A2.1-restricted CTL epitopes in a new human cancer antigen-POTE.
abstract: 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.
authors.affiliation: Institute of Clinical Medicine, Infection and Immunity Research Center, National Yang-Ming University, Division of Gastroenterology, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Yi-Hsiang
authors.initials: YH
authors.lastname: Huang
authors.forename: Masaki
authors.initials: M
authors.lastname: Terabe
authors.forename: C David
authors.initials: CD
authors.lastname: Pendleton
authors.forename: Deborah
authors.initials: D
authors.lastname: Stewart Khursigara
authors.forename: Tapan K
authors.initials: TK
authors.lastname: Bera
authors.forename: Ira
authors.initials: I
authors.lastname: Pastan
authors.forename: Jay A
authors.initials: JA
authors.lastname: Berzofsky
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm / Q000737:chemistry / Q000276:immunology*; D045744:Cell Line, Tumor; D003429:Cross Reactions; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D015789:HLA-A2 Antigen / Q000276:immunology*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D017434:Protein Structure, Tertiary; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D000951:Antigens, Neoplasm; D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D011948:Receptors, Antigen, T-Cell