Ovarian cancer-associated lymphocyte recognition of folate binding proteinpeptides

Background: Tumor-associated lymphocytes (TAL) isolated from ovarian cancer patients contain cytotoxic T lymphocytes (CTL) capable of recognizing spec ific HLA/peptide complexes on tumor cells leading to tumor cell lysis. Curr ently, HER2/neu, overexpressed in only 30% of breast and ovarian cancers, i s the only known source of CTL-recognized peptides in epithelial cancers. T herefore, we have investigated peptides derived from folate binding protein (FBP), which is over-expressed in more than 90% of ovarian cancers and in the majority of other epithelial tumors. Methods: TAL were isolated from the malignant ascites of four consecutive H LA-A2(+) ovarian cancer patients and incubated in IL-2. Initial chromium-re lease assays were performed within 1 week. T2 cells, incubated with peptide , were used to reconstitute T cell epitopes. The FBP sequence was interroga ted for HLA-A2 binding peptides, and five were synthesized (E37-41). Results: Freshly cultured, unstimulated ovarian TAL recognize peptides deri ved from FBP. These peptides are presented in the context of HLA-A2, and ar e specifically recognized in a HLA class I-restricted fashion. TAL recognit ion of these reconstituted T cell epitopes is concentration dependent. Furt hermore, the FBP peptides are shown by cold target inhibition studies to be naturally processed and presented antigens. Conclusions: FBP peptides are recognized by freshly isolated TAL from ovari an cancer patients, suggesting in vivo expression and sensitization. Becaus e FBP is over-expressed 20-fold in most adenocarcinomas, these peptides may be used in a widely applicable peptide-based vaccine for epithelial tumors .