RESUMEN
AIM:To observe whether modified epitopes from pancreatic tumor antigen mucin 4 (MUC4) have HLA-A2-restricted antitumor ability.METHODS:RT-PCR and Western blot were used to identify the expression of MUC4 in the pancreatic tumor cell lines CAPAN-2 and ASPC-1.HLA-A2 epitopes from MUC4 protein were predicted by the software of NetCTL 1.2, BIMAS, SYFPEITHI and IEDB.The modified peptides from MUC4 containing HLA-A2 were obtained by replacing anchor residues of the binding anchor motifs.The peptides were synthesized by standard solid-phase methods.The binding affinity of the peptides to HLA-A2 molecule was evaluated by T2 binding assay.ELISPOT assay was used to investigate the ability of the peptide to induce specific restricted cytotoxic T-lymphocytes (CTLs) and release of IFN-γ.The ability of the peptides to induce T-cell response was investigated by cytotoxicity assay in vitro.RESULTS:The expression of MUC4 was observed in the CAPAN-2 cells and ASPC-1 cells.The candidate peptides P1944-1Y, P1944-2L, P1944-1Y2L, P2004 and P2004-1Y9V showed moderate affinity toward HLA-A2 molecule.T2 binding assay showed that P1944-1Y2L and P2004-1Y9V had significantly higher affinity for HLA-A2 than the native peptides.ELISPOT assay showed P1944, P1944-1Y2L, P2004 and P2004-1Y9V were able to induce specific CTLs and more amounts of IFN-γ were released.ELISPOT assay showed that significantly more amounts of IFN-γ released by P1944-1Y2L and P2004-1Y9V were observed than the native peptides.The CTLs induced by P1944, P1944-1Y2L, P2004 and P2004-1Y9V lyzed the CAPAN-2 cells.P1944-1Y2L and P2004-1Y9V peptide-specific CTLs showed higher cytotoxicity against pancreatic tumor cell line CAPAN-2 than the native peptide-specific CTLs.CONCLUSION:Compared with the native peptides, modified epitopes P1944-1Y2L and P2004-1Y9V have higher binding affinity with HLA-A2 and retain immunogenecity.In addition, the anti-tumor immunity of modified epitopes P1944-1Y2L and P2004-1Y9V is stronger than that of the native peptides.The peptides P1944-1Y2L and P2004-1Y9V are excellent HLA-A2-restricted CTL epitopes from tumor antigen MUC4, which could serve as new candidates towards antitumor peptide vaccines.