Abstract
Background: A novel breast cancer–associated antigen, mammaglobin-A, is expressed in 80% of primary breast tumors. The characterization of immune responses against this highly expressed breast cancer–specific antigen would be of value in the development of new therapeutic strategies for breast cancer. Methods: We developed an in vivo model using human leukocyte antigen-A*0201/human CD8+ (HLA-A2+/hCD8+) double-transgenic mice to define the epitopes and to study the level of protection acquired by mammaglobin-A cDNA vaccination toward mammaglobin-A+/HLA-A2+ breast cancer cell lines. Mammaglobin-A epitopes were identified using an HLA class I peptide binding prediction computer program, and their activity was verified using gamma interferon ELISPOT and cytotoxicity assays. Results: We identified seven mammaglobin-A–derived candidate epitopes that bind the HLA-A*0201 molecule (Mam-A2.1–7). CD8+ cytotoxic T lymphocytes (CTLs) from HLA-A2+/hCD8+ mice reacted to the Mam-A2.1 (amino acids [aa] 83–92, LIYDSSLCDL), Mam-A2.2 (aa 2–10, KLLMVLMLA), Mam-A2.4 (aa 66–74, FLNQTDETL), and Mam-A2.6 (aa 32–40, MQLIYDSSL) epitopes. CD8+ CTLs from breast cancer patients also recognized a similar epitope pattern as did those in the HLA-A2+/hCD8 mice and reacted to the Mam-A2.1, Mam-A2.2, Mam-A2.3, Mam-A2.4, and Mam-A2.7 epitopes. Passive transfer of mammaglobin-A–reactive CTLs into SCID (severe combined immunodeficient) beige mice with actively growing mammaglobin-A+ tumors resulted in statistically significant regression (P<.001) in the growth of the tumors. Conclusions: The HLA-A2+/hCD8+ mouse represents a valuable animal model to characterize the HLA-A*0201–restricted CD8+ CTL immune response to mammaglobin-A in vivo, and the data reported here demonstrate the immunotherapeutic potential of mammaglobin-A for the treatment and/or prevention of breast cancer.