Natural Product 4-Acetylantroquinonol B Enhances NK Cell-Mediated Immunity Against Glioblastoma.

Glioblastoma (GBM) recurs rapidly despite surgery and radiochemotherapy and is associated with profound natural killer (NK) cell dysfunction. Adoptive NK cell transfer has emerged as a plausible immunotherapy for GBM and is being tested clinically; however, its efficacy is limited by the suppressive tumor microenvironment, low NK infiltration, and metabolic exhaustion. 4-Acetylantroquinonol B (4-AAQB), a ubiquinone derivative purified from Antrodia cinnamomea, has demonstrated antitumor and anti-inflammatory properties. These properties suggest that 4-AAQB may rescue or enhance NK cell activity against GBM cells. Therefore, we evaluated the effects of 4-AAQB on the cytotoxicity of NK-92 cells against human GBM cells using NK cell cytotoxicity assays. Treatment with 4-AAQB significantly enhanced the cytotoxicity of NK-92 cells against GBM cells, without affecting normal MRC5 fibroblasts. Additionally, in a GBM xenograft mouse model, 4-AAQB and NK-92 cells individually suppressed tumor growth, whereas their combination produced a synergistic antitumor effect without inducing liver or kidney toxicity. Bulk RNA sequencing of excised tumors revealed distinct differentially expressed genes in the combination group that were not shared with either monotherapy. Notably, the combined therapy upregulated immune effector genes involved in apoptotic cell clearance and NK cell maturation, while simultaneously downregulating key survival and resistance pathways. Furthermore, pathway analysis revealed suppression of autophagy and mitophagy, suggesting that 4-AAQB sensitizes GBM cells to immune-mediated apoptosis by disrupting intrinsic survival circuits. These findings support 4-AAQB as an orally administered adjuvant that enhances NK cell immunotherapy for GBM and warrant further translational development.