Abstract A019: Timed intracranial therapy with NK cells and NK cell-derived extracellular vesicles following temozolomide exhibits curative potential in mesenchymal glioblastoma model

Abstract Glioblastoma (GBM) is an incurable brain cancer driven by tumor-initiating glioma stem cells (GSCs). GSCs are heterogenous in that they exhibit transcriptomes resembling either proneural (PN) or mesenchymal (MES) subtypes of GBM. Residual deposits of GSCs are thought to trigger inevitable relapse of GBM following surgery, radiation and temozolomide (TMZ) chemotherapy in the absence of robust immune infiltration and surveillance. Here we explore and exploit our observation that GSC subtypes differ dramatically in their sensitivity to NK mediated killing. Thus, MES-GSCs (unlike PN-GSCs) are enriched in ligands for NKG2D receptors (MICA, MICB, ULBP2-5) and are efficiently killed by NK92MI human NK cells in vitro. Markers of NK cell sensitivity also correlate with the MES subtype of GBM in large transcriptomic datasets (TCGA). While neither endogenous NK cells, nor exogenously injected intracranial NK92MI cells eradicate MES-GSC tumors, pre-treatment of tumor bearing mice with TMZ and the resulting onset of tumor repopulation renders subsequent NK therapy curative in the case of MES-GSC xenografts, but not in their PN-GSC counterparts. These curative effects of NK92MI cells are retained following their irradiation, which also results in complete growth arrest and gradual elimination of these cells from the site of their intracranial inoculation. Delay in injection of NK92MI cells beyond 14 days post TMZ administration erodes their curative potential in MES-GSC tumors due to the onset of post chemotherapy tumor regrowth. Notably, the NK effector expression and tumor killing activity in vitro and in vivo is retained in preparations of extracellular vesicle (EV)-enriched supernatants (VES) from NK92MI cell cultures. Thus, our data suggest that timed chemotherapy may have a potential to modify effector:target ratio in GBM tumors in vivo rendering the NK-sensitive tumor subtypes susceptible to immunological eradication. Moreover, NK cell derived EVs (or VES preparations) may present themselves as potential off-the-shelf therapeutics to treat currently incurable cancers, such as GBM. Citation Format: Brian G. Meehan, Lata Adnani, Xianbing Zhu, Nadim G. Tawil, Victoria Yip, Fang Cheng Wong, Delphine Garnier, Ichiro Nakano, Sidong Huang, Janusz Rak. Timed intracranial therapy with NK cells and NK cell-derived extracellular vesicles following temozolomide exhibits curative potential in mesenchymal glioblastoma model [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Mechanisms of Cancer Immunity and Cancer-related Autoimmunity; 2025 Sep 24-27; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(9 Suppl):Abstract nr A019.