Evaluation of Comprehensive Gene Expression and NK Cell-Mediated Killing in Glioblastoma Cell Line-Derived Spheroids

SIMPLE SUMMARY: Glioblastoma (GBM) is the most aggressive primary malignant brain tumor in adults. Despite standard treatment, including surgery, chemotherapy, and radiotherapy, it is associated with poor survival. Immunotherapy is a promising alternative for patients with GBM. Natural killer (NK) cells are possible promising targets in GBM treatment because of their potent cytotoxic effect. We previously reported that highly activated and ex vivo-expanded NK cells, or genuine induced NK cells (GiNK), exert a greatly cytotoxic effect on GBM cells. In this study, we investigated the potential of NK cell-based immunotherapy for GBM, which we evaluated using an ex vivo three-dimensional GBM cell-derived spheroid model. Our results indicated that the NK cells had an anti-tumor effect on the spheroid models. Our findings could lead to the development of future NK cell-based immunotherapies for GBM. ABSTRACT: Glioblastoma (GBM) is the most common and aggressive primary brain tumor, with a dismal prognosis. Natural killer (NK) cells are large granular lymphocytes with natural cytotoxicity against tumor cells, and they should be established for the novel treatment of patients with GBM. We previously reported highly activated, and ex vivo-expanded NK cells derived from human peripheral blood, designated genuine induced NK cells (GiNK), which were induced by specific culture conditions and which exerted a cytotoxic effect on GBM cells via apoptosis. Here, we comprehensively summarize the molecular characteristics, especially focusing on the expression of stem cell markers, extracellular matrix markers, chemokines, chemokine receptors, and NK receptor ligands of spheroids derived from GBM cell lines as compared with that of two-dimensional (2D) adherent GBM cells via microarray. The spheroid had upregulated gene expression of stem cell markers, extracellular matrix markers, chemokines, chemokine receptors, and NK cell inhibitory receptor ligands compared with the 2D adherent GBM cells. Preclinical evaluation of the NK cells was performed via an ex vivo 3D spheroid model derived from GBM cell lines. In the model, the NK cells accumulated and infiltrated around the spheroids and induced GBM cell death. Flow cytometry-based apoptosis detection clearly showed that the NK cells induced GBM cell death via apoptosis. Our findings could provide pivotal information for NK cell-based immunotherapy for patients with GBM.