Cytokine-induced killer cells showing multidrug resistance and remaining cytotoxic activity to tumor cells after transfected with mdr1 cDNA

BACKGROUND: Routine treatment of cancer such as surgery, radiation or chemotherapy is sometimes unable to eradicate metastatic malignant cells. So we tried a new method and increased the adoptive immunotherapy of Cytokine-induced killer (CIK) cells in tumor patients and the multidrug resistance (mdr1) cDNA was transfected into CIK cells. METHODS: CIK cells were obtained from peripheral blood and induced by IFN-gamma, anti-CD3 monoclonal antibody, IL-2 and IL-1. CIK cells were transfected with plasmid PHaMDR containing human mdr1 cDNA by electroporation. RT-PCR was used to detect mdr1 mRNA in transfected CIK cells. P-glycoprotein (P-gp) expressed on surface of CIK cells was assayed by FITC-conjugated anti-P-gp monoclonal antibody and flow cytometry. Multidrug resistance to doxorubicin and colchicine and cytotoxic activity to human breast cancer cell line MCF7 were performed using MTT method. RESULTS: mdr1 mRNA was detected in transfected CIK cells. P-gp was expressed on the surface of the transfected CIK cells, and the P-gp positive cells reached 21% - 37% of the total CIK cells after transfection. The IC50 to doxorubicin increased to 22.3 - 45.8 times, and that to colchicines to 6.7 - 11.35 times, as compared to those of untransfected CIK cells. However, the cytotoxic activity to MCF7 cell line remained unaltered. CONCLUSIONS: CIK cells were successfully transfected with mdr1 cDNA by using electroporation. The transfected CIK cells had the characteristics of multidrug resistance without change in their cytotoxic activity to tumor cells.