Induction of γδT Cells Using Zoledronate Plus Interleukin-2 in Patients with Metastatic Cancer
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A loss of human leukocyte antigen (HLA) expression in clinical tumors is one of their escape mechanisms from immune attack by HLA-restricted effector cells. In this study, the induction of HLA-unrestricted effector cells, γδT cells, using zoledronate (ZOL) and interleukin (IL)-2 in vitro was investigated in patients with metastatic cancer. Peripheral blood mononuclear cells (PBMCs) from 10 cancer patients (8 colorectal and 2 esophageal) with multiple metastases and ascites lymphocytes from 3 cancer patients (1 gastric and 2 colorectal) were stimulated with varied concentrations of ZOL plus 100 U/ml IL-2 for 48 hr followed by culturing with IL-2 alone for 12 days. Lymphocyte proliferative responses were determined using 3H-TdR uptakes and interferon (IFN)-γ production was evaluated using enzyme-linked immunosorbent assay. Surface phenotyping was performed using flow cytometry. Cytotoxic activity of effector cells was determined using 51Cr-releasing assay.
It was found that proliferative responses of PBMCs were significantly stimulated with ZOL plus IL-2 when compared with IL-2 alone, showing 200 to 500-fold expansions for 2 weeks, although ZOL alone induced no response. The optimal concentration of ZOL was 1-5 μM. Ascites lymphocytes could also be stimulated with ZOL plus IL-2. The proliferative responses were remarkable in patients whose PBMCs could produce high levels ofIFN-γ during an initial 48-hr stimulation using ZOL plus IL-2. Removal of an adherent cell fraction before the induction augmented the proliferative responses in patients who otherwise had low-grade proliferative responses. Generated cells comprising approximately 90 or 20% in PBMCs from healthy donors or cancer patients, respectively, expressed γδ-type T-cell receptor. γδT cells showed high cytotoxic activity against CD166-positive TE12 and TE13 cancer cells but not against CD166-negative MKN45 cells. The cytotoxic activity against TE13 cells was augmented when target cells were pre-treated overnight with ZOL.
These results suggest that ZOL in the presence of IL-2 can efficiently stimulate the proliferation of γδT cells, which have cytotoxic properties against cancer cells. The use of zoledronate-activated killer (ZAK) cells should be encouraged in possible adoptive immunotherapy trials for patients with incurable cancer.
Hiroshima Journal of Medical Sciences
Hiroshima University Medical Press
(c) Hiroshima University Medical Press.