Natural Killer Cell‐Derived Extracellular Vesicle Preparations Demonstrate Potent Antitumor Activity Against Human Glioblastoma In Vitro and In Vivo

ABSTRACT Extracellular vesicles (EVs) derived from activated natural killer (NK) cells represent a promising cell‐free immunotherapy for cancer. However, the use of primary expanded human NK cell‐derived EVs (NK‐EVs) for intractable brain tumours is underexplored. Here, we evaluated common EV isolation methods including precipitation for bulk EVs and size exclusion chromatography (SEC) to obtain both NK‐EVs and proteins. Precipitated NK‐EVs demonstrated potent dose‐dependent cytotoxicity against multiple glioblastoma (GBM) cell lines, including those resistant to conventional NK cell therapy. They suppressed tumour growth in subcutaneous GBM xenograft models and, following intravenous administration, significantly inhibited orthotopic brain tumour progression and prolonged survival. SEC‐NK‐EVs expressed high levels of activating receptors (NKG2D, DNAM‐1, NKp30) and effector proteins (perforin, granzyme B) with lower inhibitory receptors (TIGIT, TIM‐3, CD96 and LAG3) compared to parental cells. Importantly, both SEC‐NK‐EVs and proteins exhibited antitumor activity, revealing complementary therapeutic mechanisms within the NK cell secretome. Collectively, these findings establish NK‐EVs as an effective cell‐free immunotherapy strategy for GBM that has the potential to evade key limitations of adoptive NK cell therapy, including the immunosuppressive tumour microenvironment.