title: A ras-mutated peptide targeted by CTL infiltrating a human melanoma lesion.
abstract: Ags derived from commonly mutated oncogenic proteins seem ideally suited as targets for tumor immunotherapy. Nonetheless, only a few mutated epitopes efficiently presented by human tumors have thus far been identified. We describe here an approach to identify such epitopes. This approach involves: 1) identifying tumors expressing a ras mutation and isolating the tumor-infiltrating lymphocytes (TIL); 2) transfecting COS cells to induce expression of unknown mutated peptides in the context of a patient's HLA class I molecules; and 3) screening epitope recognition by using TIL from the tumors expressing a ras mutation. By using this approach, there appeared to be a N-ras mutation (a glutamine-to-arginine exchange at residue 61 (Q61R)), detected in a melanoma lesion, which was recognized specifically by the autologous TIL in the HLA-A*0101 context. The ras peptide 55-64(Q61R) was the epitope of these TIL and was regularly presented by Q61R-mutated HLA-A*0101(+) melanoma cell lines. This peptide and its wild-type homolog (55-64(wt)) bound to HLA-A*0101 with similar affinities. However, only the mutated peptide could induce specific CTL expansion from PBL. All the CTL clones specific to the mutated peptide, failed to recognize the wild-type sequence on both COS and melanoma cells. These data thus show that oncogenic protein mutations can create shared tumor-specific CTL epitopes, efficiently presented by tumor cells, and that screening for oncogene-transfected COS cell recognition by TIL (from tumors containing mutations) is a powerful approach for the identification of these epitopes.
authors.affiliation: Institut de Biologie, Institut National de la Santé et de la Recherche Médicale, Unité 463, and Faculté des Sciences et Techniques de Nantes, Nantes, France. blinard@nantes.inserm.fr
authors.forename: Boris
authors.initials: B
authors.lastname: Linard
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bézieau
authors.forename: Houssem
authors.initials: H
authors.lastname: Benlalam
authors.forename: Nathalie
authors.initials: N
authors.lastname: Labarrière
authors.forename: Yannick
authors.initials: Y
authors.lastname: Guilloux
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Diez
authors.forename: Francine
authors.initials: F
authors.lastname: Jotereau
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics / Q000276:immunology*; D019556:COS Cells; D002478:Cells, Cultured; D002999:Clone Cells; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D015234:HLA-A Antigens / Q000378:metabolism; D006801:Humans; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology*; D008545:Melanoma / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D015689:Oncogene Protein p21(ras) / Q000235:genetics / Q000276:immunology*; D010455:Peptides / Q000276:immunology; D017354:Point Mutation; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D018984:Epitopes, T-Lymphocyte; D015234:HLA-A Antigens; D010455:Peptides; D015689:Oncogene Protein p21(ras)