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Background: The antibody-dependent cellular cytotoxicity (ADCC) is a cell-mediated immune defense mechanism in which effector immune cells actively lyse antibody-coated target cells. The ADCC of tumor cells is employed in the treatment of various cancers overexpressing unique antigens, and only natural killer (NK) cells are known to be major effectors of antibody mediated ADCC activity. Canine NK cells are still defined as non-B, non-T large granular lymphocytes because of the lack of information regarding the NK cell-restricted specific marker in dogs, and it has never been demonstrated that canine NK cells have ADCC ability against tumor cells. In the present study, we investigated whether canine non-B, non-T NK cells have ADCC ability against target antibody-coated tumor cells, using cetuximab and trastuzumab, the only human antibodies reported binding to canine cancer cells., Results: Activated canine non-B, non-T NK cells (CD3 - CD21 - CD5 - TCRαβ - TCRγδ - ) for 13~17 days ex vivo showed ADCC ability against trastuzumab- or cetuximab-coated target tumor cells expressing various levels of human epidermal growth factor receptor 2 (HER-2) and epidermal growth factor receptor (EGFR). Trastuzumab and cetuximab induced significant ADCC responses of canine NK cells even in CMT-U334 and CF41.Mg cells expressing low levels of HER-2 and/or EGFR, as well as in SKBR3 and DU145 cells overexpressing HER-2 and/or EGFR. The trastuzumab-mediated ADCC activity of NK cells was significantly enhanced by treatment with rcIL-21., Conclusions: The results of this study suggest that canine non-B, non-T NK lymphocytes have a potential ADCC function and that combinational strategies of monoclonal antibodies with either cytokines, which activate NK cells in vivo, or adoptive transfer of NK cells may be a feasible method for amplifying the efficacy of immunotherapy against malignant cancers even with very low expression of target molecules in dogs.

Background/aim: The inhibition of a disintegrin and metalloproteinase (ADAM) has the potential to become a novel approach for natural killer (NK) cell-based cancer immunotherapy. Thus, the aim of this study was to investigate the influence of ADAM10 and ADAM17 inhibitors on expanded NK cell to enhance antibody-dependent cellular cytotoxicity (ADCC) in breast cancer cell lines., Materials and Methods: NK cells were expanded in medium supplemented with an ADAM10 or ADAM17 inhibitor to prevent the shedding of soluble CD16/FcγRIII. The expression level of CD16 and production of interferon-gamma (IFN-γ) was detected by flow cytometry using specific antibodies. ADCC activity of expanded NK cells was estimated in trastuzumab treated breast cancer cell lines such as MCF-7, MDA-MB-231, SKBR3, and BT-474 cells., Results: The ADAM17 inhibitor increased the purity of expanded NK cells to 90% after 14 days at 5 and 10 μM in vitro (p=0.043). However, the expansion rate of NK cells was decreased at 10 μM of the ADAM 17 inhibitor (p=0.043). Inhibition of ADAM10 suppressed the expansion of NK cells, although the NK purity was increased at 1 μM of the inhibitor. The expression of CD16 was significantly increased at 1 and 5 μM of the ADAM17 inhibitor (p=0.046, 0.028, respectively) during the culturing period. Inhibition of ADAM10 reduced the expression of CD16 on NK cells. The cytotoxic activity of the ADAM17 inhibitor treated NK cells against MCF-7 (p=0.039) and BT-474 (p=0.027) cells was significantly elevated. The ADCC activity of NK cells treated with 5 μM of ADAM17 inhibitor was significantly increased against SKBR-3 and BT-474 (p=0.027). Inhibition of ADAM17 increased the production of IFN-γ in expanded NK cells., Conclusion: The inhibition of ADAM17 enhanced the purity of expanded NK cells and the ADCC activity of these cells against trastuzumab treated breast cancer cell lines., (Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)