Characterization of novel breast carcinoma–associated BA46-derived peptides in HLA-A2.1/Db-β2mtransgenic mice

The human milk fat globule membrane protein BA46 (lactadherin) is highly overexpressed in human breast tumors, making it a potential target for tumor immunotherapy. We have identified BA46derived peptides that contain the motif recognized by the MHC class I molecule HLA-A2.1 and that are processed and presented by human breast carcinoma cells. In mice lacking normal class I molecules but expressing an HLA-A2.1/D b -2 microglobulin single chain (HHD mice), three peptides elicited specific CTL activity. Two of these peptides also stimulated cytotoxic activity in peripheral blood lymphocytes from HLA-A2.1-positive breast carcinoma patients. Adoptive transfer of HHDderived bulk CTLs to nude mice bearing human breast carcinoma transplants reduced tumor growth. These peptides therefore represent naturally processed BA46-derived CTL epitopes that can be used in peptide-based antitumor vaccines.