Coculturing Dendritic Cells with Zoledronate Acid Efficiently Enhance the Anti-Tumor Effects of Cytokine-Induced Killer Cells

Introduction Dendritic cells (DCs) have greater stimulating activity on innate and adaptive immunity following short-term sensitization with zoledronate acid (DCs Zol ). We identified the phenotype, cytotoxicity, and mechanisms of killing of cytokine-induced killer (CIK) cells which were cocultured with DCs Zol . Methods Adherent and nonadherent cells of peripheral blood mononuclear cell from myeloma patients were incubated for DCs and CIK cells. Then, the CIK cells were cocultured with DCs Zol (DCs Zol -CIK). Expression of markers for DCs Zol -CIK cells was measured using flow cytometry. Cytotoxicity was evaluated by against human myeloma cell lines and mechanisms of killing were tested by selectively blocking NKG2D receptor. The anti-tumor activity of these effector cells was further evaluated using a nude mice tumor model. Results γδ TCR expression of CIK cells significantly increased after coculture with immature or mature DCs Zol (iDCs/mDCs Zol -CIK) and these cells aggressively lysed myeloma cells compared with mDCs-CIK and zoledronate acid pulsed CIK cells (CIK Zol ; 50.8 ± 7.9% and 48.2 ± 4.7% versus 31.9 ± 5.1% and 20.5 ± 3.6%, effector versus target ratio was 60:1). Both αβ T and γδ T cells in the iDCs Zol -CIK cells performed the majority of lysis. The iDCs/mDCs Zol -CIK cells greatly increased NKG2D expression compared with mDCs-CIK and CIK Zol during culture (71.5 ± 11.3% and 67.7 ± 9.3% versus 51.3 ± 6.2% and 47.1 ± 5.7%). iDCs Zol -CIK cell-mediated lysis dropped 69.21% when the NKG2D receptor was blocked and the cytotoxicity correlated with NKG2D ligand–MICA expression on the target cells. In a human myeloma bearing nude mice model, iDCs Zol -CIK and mDCs Zol -CIK cells treatment groups obtained 75% and 62.5% long-term survival (>120 days) respectively, as compared with none of the control animals or 37.5% treated with mDCs-CIK cells. Conclusion Large numbers of CIK cells with greater anti-tumor activities are rapidly generated by Zol-treated iDCs/mDCs. This strategy is worthy of further investigation to improve adoptive cell therapy against tumors.