An experimental study on cancer vaccine therapy using dendritic cells genetically transduced with the tumor antigen gene and the ubiquitin gene

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Cancer immunotherapy using dendritic cells (DCs) adenovirally transduced with the whole tumor-associated antigen (TAA) gene is an effective approach. In this study, we established the carcinoembryonic antigen (CEA) -specific cytotoxic T lymphocytes (CTLs) using an in vitro stimulation with adenovirally modified human DCs that express CEA. Moreover, DCs were transduced with the fusion gene of the CEA gene and the ubiquitin gene, and we showed the more potent cytotoxic activity against CEA-expressing targets (A24). Streptococcal preparation OK-432 is useful for stimulating DCs in terms of the maturation. To augment therapeutic antitumor effect, we investigated whether the OK-432 stimulation would be more effective on inducing CEA-specific CTLs compared with the other typical stimuli. DCs were cultured under various conditions, tumor necrosis factor (TNF) -a, lipopolysaccharide (LPS) or OK-432. A cytotoxic assay using peripheral blood mononuclear cells (PBMCs) -derived CTLs was performed in a 4h^<-51>Cr release assay. OK-432 stimulated immature DCs to acquire mature phenotype and to produce significant amounts of T-helper 1 cytokines. In all groups (immature DCs, TNF-a/DCs, LPS/DCs, OK-432/DCs), CEA-specific CTLs were generated. OK-432-stimulated DCs (HLA-A24) induced the most potent cytotoxic activity against CEA-expressing targets (A24), and not against controls. OK-432/DCs could induce markedly potent CTLs specific to the target cells pulsed with CEA652 peptide (HLA-A24-restricted peptide), although others failed to induce potent CTLs. In conclusion, the CTLs induction protocol using adenovirally modified DCs transduced with the fusion gene of the CEA gene and the ubiquitin gene or after maturation with OK-432 showed a potent antitumor activity against CEA-expressing target cells, and is therefore promising for clinical applications as a cancer vaccine therapy.