Identification And Functional Study Of HLA-A～*0201-restricted CD8～+ CTL Epitopes Derived From Human Phosphatidylethanolamine-binding Protein 4(hPEBP4)

Human phosphatidylethanolamine-binding protein 4 (hPEBP4) is a novel molecule cloned by us from the cDNA library of human bone marrow stromal cells using large-scale random sequencing. We previously demonstrated that hPEBP4 is highly expressed in human breast cancer cell lines such as MCF-7 cells and clinical breast cancer specimens but not in normal breast tissues by RT-PCR and immunohistochemical analysis. hPEBP4 has been found to promote cellular resistance to TNF-a-induced apoptosis of breast cancer cells. In this study, using a computer-assisted analysis and T2 binding assay, we selected three peptides with high affinity to HLA-A*0201 molecules and then test the capability of three peptides with high affinity to induce antigen-specific CTL in vivo in HLA-A2.1/K^b transgenic mice and in vitro in peripheral blood of HLA-A2.1-positive breast cancer individuals. Immunogenicity of candidate peptides was detected by IFN- Y ELISPOT, ⁵¹Cr cytotoxicity assay and intracellular staining assay. Results demonstrate that P40-48(TLFCQGLEV, residues:40-48) is naturally processed CTL epitope with immunotherapeutic potentials from endogenous hPEBP4 protein as a tumor rejection antigen, and therefore it may be a candidate for peptide vaccines or targeted T-cell therapies for treating breast carcinoma or other carcinoma overexpressing hPEBP4 protein.