ABSTRACT
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.
ABSTRACT
AIM: To identify the human leucocyte antigen A2 (HLA-A2) restricted cytotoxic T lymphocyte (CTL) epitopes from tumor antigen PIWIL2.METHODS:RT-PCR and Western blot was used to determine the expres-sion of PIWIL2 in cancer cell lines MCF-7, SW480 and HT-29.HLA-A2 epitopes from PIWIL2 protein were predicted by the software of BIMAS, RankPep, NetMHC, NetCTL1.2 and IEDB.The peptides were synthesized by standard solid-phase methods.The binding affinity of the peptides to HLA-A2 molecules was evaluated by T2 cells binding assay.ELISPOT as-say was used to investigate the levels of IFN-γ.The cytotoxicity assay in vitro was also used to determine the ability of indu-cing T cell response by the peptides.RESULTS:The expression of PIWIL2 was observed in MCF-7, SW480 and HT-29. The candidate peptide P485, P493 and P965 showed moderate affinity toward HLA-A2 molecule.ELISPOT assay showed P485 and P965 induced CTLs of IFN-γrelease form CTLs.The CTLs induced by P485 and P965 lysed the MCF-7 cells. CONCLUSION:The peptides P485 and P965 are excellent HLA-A2 restricted cytotoxic T lymphocyte epitopes from the tumor antigen PIWIL2, which could serve as new candidates towards antitumor peptide vaccines.