title: Identification of immunodominant HLA-B7-restricted CD8+ cytotoxic T cell epitopes derived from mammaglobin-A expressed on human breast cancers.
abstract: Mammaglobin-A (MGBA), a 10-kD protein, is over expressed in 80% of primary and metastatic human breast cancers. Breast cancer patients demonstrate high frequencies of CD8(+) cytotoxic T lymphocytes (CTL) specific to MGBA. Defining CD8(+) CTL responses to HLA class I-restricted MGBA-derived epitopes assumes significance in the context of our ongoing efforts to clinically translate vaccine strategies targeting MGBA for prevention and/or treatment of human breast cancers. In this study, we define the CD8(+) CTL response to MGBA-derived candidate epitopes presented in the context of HLA-B7, which has a frequency of 17.7% in Caucasian and 15.5% in African American populations. We identified seven MGBA-derived candidate epitopes with high predicted binding scores for HLA-B7 using a computer algorithm. Membrane stabilization studies with TAP-deficient T2 cells transfected with HLA-B7 indicated that MGBA B7.3 (VSKTEYKEL), B7.6 (KLLMVLMLA), B7.7 (NPQVSKTEY), and B7.1 (YAGSGCPLL) have the highest HLA-B7 binding affinities. Further, two CD8(+) CTL cell lines generated in vitro against T2.B7 cells individually loaded with MGBA-derived candidate epitopes showed significant cytotoxic activity against MGBA B7.1, B7.3, B7.6, and B7.7. In addition, the same CD8(+) CTL lines lysed the HLA-B7(+)/MGBA(+) human breast cancer cell line DU-4475 but had no significant cytotoxicity against HLA-B7(-) or MGBA(-) breast cancer cell lines. Cold-target inhibition studies strongly suggest that MGBA B7.3 is an immunodominant epitope. In summary, our results define HLA-B7-restriced, MGBA-derived, CD8(+) CTL epitopes with all of the necessary features for developing novel vaccine strategies against HLA-B7 expressing breast cancer patients.
authors.affiliation: Department of Surgery, Washington University School of Medicine, Box 8109, 3328 CSRB, 660 South Euclid Avenue, Saint Louis, MO 63110, USA.
authors.forename: Haseeb
authors.initials: H
authors.lastname: Ilias Basha
authors.forename: Venkataswarup
authors.initials: V
authors.lastname: Tiriveedhi
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Fleming
authors.forename: William E
authors.initials: WE
authors.lastname: Gillanders
authors.forename: T
authors.initials: T
authors.lastname: Mohanakumar
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000915:Antibody Affinity / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D001943:Breast Neoplasms / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D005260:Female; D015793:HLA-B7 Antigen / Q000276:immunology*; D006801:Humans; D060785:Mammaglobin A; D009363:Neoplasm Proteins / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014598:Uteroglobin / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D018984:Epitopes, T-Lymphocyte; D015793:HLA-B7 Antigen; D060785:Mammaglobin A; D009363:Neoplasm Proteins; C556448:SCGB2A2 protein, human; D014598:Uteroglobin