Rescuing lymphocytes from HLA-G immunosuppressive effects mediated by the tumor microenvironment.
Oncotarget 2016;
6:37385-97. [PMID:
26460949 PMCID:
PMC4741936 DOI:
10.18632/oncotarget.6044]
[Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Accepted: 09/17/2015] [Indexed: 11/25/2022] Open
Abstract
Several studies have demonstrated that the antitumor activities of both T and natural killer (NK) effector populations are limited by the immunosuppressive strategies of tumors. In several malignant transformations, the expression of HLA-G by tumor cells rises dramatically, rendering them strongly immunosuppressive. In this study, we postulated that the absence of HLA-G receptors would prevent the immunosuppressive effects of both soluble and membrane-bound HLA-G. Thus, we investigated the therapeutic potential of effector NK cells genetically modified to downregulate the expression of ILT2 (HLA-G receptor) on their cell surfaces. We have shown that the proliferation of modified NK is still dependent on stimulation signals (no malignant transformation). ILT2− NK cells proliferate, migrate, and eliminate HLA-G negative targets cells to the same extent parental NK cells do. However, in the presence of HLA-G positive tumors, ILT2− NK cells exhibit superior proliferation, conjugate formation, degranulation, and killing activities compared to parent NK cells. We tested the effectiveness of ILT2− NK cells in vivo using a xenograft cancer model and found that silencing ILT2 rescued their anti-tumor activity.
We believe that combining ILT2− NK cells with existing therapeutic strategies will strengthen the antitumor response in cancer patients.
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