MicroRNA-mediated down-regulation of NKG2D ligands contributes to glioma immune escape

Abstract

Malignant gliomas are intrinsic brain tumors with a dismal prognosis. They are well-adapted to hypoxic conditions and poorly immunogenic. NKG2D is one of the major activating receptors of natural killer (NK) cells and binds to several ligands (NKG2DL).Here we evaluated the impact of miRNA on the expression of NKG2DL in glioma cells including stem-like glioma cells. Three of the candidate miRNA predicted to target NKG2DL were expressed in various glioma cell lines as well as in glioblastomas in vivo: miR-20a, miR-93 and miR-106b. LNA inhibitor-mediated miRNA silencing up-regulated cell surface NKG2DL expression, which translated into increased susceptibility to NK cell-mediated lysis. This effect was reversed by neutralizing NKG2D antibodies, confirming that enhanced lysis upon miRNA silencing was mediated through the NKG2D system. Hypoxia, a hallmark of glioblastomas in vivo, down-regulated the expression of NKG2DL on glioma cells, associated with reduced susceptibility to NK cell-mediated lysis. This process, however, was not mediated through any of the examined miRNA. Accordingly, both hypoxia and the expression of miRNA targeting NKG2DL may contribute to the immune evasion of glioma cells at the level of the NKG2D recognition pathway. Targeting miRNA may therefore represent a novel approach to increase the immunogenicity of glioblastoma.

Engineering NK Cells Modified With an EGFRvIII-specific Chimeric Antigen Receptor to Overexpress CXCR4 Improves Immunotherapy of CXCL12/SDF-1α-secreting Glioblastoma

“…This could imply that other therapeutic interventions designed to synergize with redirected CAR-modified NK cells may be needed to achieve a better killing efficiency when targeting glioblastoma cells. Some examples of these approaches include: Aurora B and Survivin inhibitors that can increase the expression of TRAIL-R2/DR5 death receptors on glioblastoma cells and therefore increases killing efficiency of TRAIL + - NK cells, 60, 61 locked nucleic acids (LNAs) constraining tumor miRNAs and increasing expression of NKG2D ligands on glioma cells which can activate NK cells, 62 maintaining NK cell cytotoxicity by applying TGFβRI-inhibitors or soluble TGFβRII molecules to overcome the immunosuppressive milieu of glioblastomas. 63, 64 …”

Biological activity of tumor-treating fields in preclinical glioma models

“…The GIC lines T-269, T-325, S-24, ZH-161 and ZH-305 were established from freshly resected tumors and cultured in phenol red-free neurobasal medium with B-27 supplement (20  μ l/ml), glutamax (10  μ l/ml) (Invitrogen), fibroblast growth factor-2 and epidermal growth factor (20 ng/ml each; Peprotech, Rocky Hill, PA, USA). 31 Cells were authenticated routinely at the Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany by short tandem repeat analysis, LTC lastly in 2013 and GIC in 2016. Accutase was purchased from PAA.…”

The therapeutic potential of natural killer cells to target medulloblastoma

“…These data suggest that adoptive NK cell therapy could play an important role in the treatment of patients with MB, as has been proposed for other CNS tumors, such as glioblastoma [21,22]. However, conditions in the tumor microenvironment, such as hypoxia, and glioma cell secretion of substances such as lactate dehydrogenase or the beta-galactoside-binding lectin, galectin-1, should downregulate the expression of NKG2DL [23][24][25]. These mechanisms and others might contribute to the immunoevasion of CNS tumor cells at the level of the NKG2D recognition pathway [23].…”