Identification of HLA-A24 restricted CD8+ Cytotoxic T-Cell Epitopes Derived from Mammaglobin-A A Human Breast Cancer Associated Antigen

摘要

Human breast cancer associated antigen, Mammaglobin-A (Mam-A), potentially offers a novel therapeutic target as breast cancer vaccines. In this study, we define the CD8⁺ CTL response to Mam-A derived candidate epitopes presented in the context of HLA-A24 (A*2402). HLA-A24 has a frequency of 72% in Japanese, 27% in Asian-Indian and 18% in Caucasian populations. Using HLA-binding prediction algorithm we identified seven HLA-A24 restricted Mam-A-derived candidate epitopes (MAA24.1–7). Membrane stabilization studies with TAP-deficient T2 cells transfected with HLA-A2402 (T2.A24) indicated that MAA24.2 (CYAGSGCPL) and MAA24.4 (ETLSNVEVF) have the highest HLA-A24 binding affinity. Further, two CD8⁺ CTL cell lines generated in vitro against T2.A24 cells individually loaded with Mam-A-derived candidate epitopes showed significant cytotoxic activity against MAA24.2 and MAA24.4. In addition, the same CD8⁺ CTL lines lysed the HLA-A24⁺/Mam-A⁺ stable transfected human breast cancer cell line AU565 and MDA-MB-361. However, these CTLs had no cytotoxicity against HLA-A24⁻/Mam-A⁺ and HLA-A24⁺/Mam-A⁻ breast cancer cell lines. In summary, our results define HLA-A24-restriced, Mam-A-derived, CD8⁺ CTL epitopes which can potentially be employed for Mam-A-based breast cancer vaccine therapy to breast cancer patients with HLA-A24 phenotype.