Mesothelin (MSLN) is an attractive candidate as a molecular target for pancreatic cancer immunotherapy. The purpose of this study was to demonstrate that cytotoxic T lymphocytes (CTLs) generated from peripheral blood mononuclear cells (PBMCs) by stimulation with genetically-modified dendritic cells (DCs) expressing MSLN could produce specific anti-tumor immunity against pancreatic cancer cells endogenously expressing MSLN. MSLN-specific CTLs were generated from PBMCs of healthy donors by in vitro stimulation with DCs adenovirally-transduced with the full-length MSLN gene (DC-AxCAMSLN). The cytotoxic activity was tested using a 4-h (51)Cr-release assay. The pancreatic cancer cell lines (PK1, CfPAC1, AsPC1), a lymphoblastoid cell lines (LCL) transduced with the MSLN gene, and LCL pulsed with MSLN-epitope peptides were used as target cells. MSLN-specific CTLs induced by in vitro stimulation with DC-AxCAMSLN killed pancreatic cancer cell lines expressing MSLN in an HLA-restricted fashion. These CTLs also showed cytotoxic activity against autologous LCL pulsed with multiple MSLN-derived epitope peptides. In addition, CD8(+) T cells, as well as CD4(+) T cells, sorted from these CTLs showed significant production of interferon-γ when stimulated with DC-AxCAMSLN. The in vitro stimulation of PBMCs with DCs transduced with the full-length MSLN gene elicited a potent MSLN-specific cytotoxic activity against pancreatic cancer cell lines endogenously expressing MSLN by recognizing multiple MSLN epitopes and activating both CD8(+) T cells and CD4(+) helper T cells. These results therefore suggest the potential of developing future clinical applications of the vaccines using genetically-modified DCs expressing MSLN.
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