Therapeutic antibodies targeting immune checkpoints have shown limited efficacy in clinical trials in glioblastoma (GBM) patients. Ultrasound-mediated blood-brain barrier opening (UMBO) using low-intensity pulsed ultrasound improved drug delivery to the brain. We explored the safety and the efficacy of UMBO plus immune checkpoint inhibitors in preclinical models of GBM. A Blood-brain barrier (BBB) opening was performed using a 1 MHz preclinical ultrasound system in combination with 10µl/g microbubbles. Brain penetration of immune checkpoint inhibitors was determined, and immune cell populations were evaluated using flow cytometry. The impact of repeated treatments on survival was determined. In syngeneic GL261-bearing immunocompetent mice, we showed that UMBO safely and repeatedly open the BBB. BBB opening was confirmed visually and microscopically using Evans’s blue dye and magnetic resonance imaging. UMBO plus anti-PDL-1 was associated with a significant improvement of the overall survival compared to anti-PD-L1 alone. Using mass spectroscopy, we showed that the penetration of therapeutic antibodies can be increased when delivered intravenously compared to non-sonicated brains. Furthermore, we observed an enhancement of activated microglia percentage when combined with anti-PD-L1. Here, we report that the combination of UMBO and anti-PD-L1 dramatically increases GL261-bearing mice's survival compared to their counterparts treated with anti-PD-L1 alone. Our study highlights the BBB as a limitation to overcome to increase the efficacy of anti-PD-L1 in GBM and supports clinical trials combining UMBO and in GBM patients.

Glioblastoma (GBM) is the most aggressive brain cancer. To model GBM in research, orthotopic brain tumor models, including syngeneic models like GL261 and genetically engineered mouse models like TRP, are used. In longitudinal studies, tumor growth and treatment response are typ-ically tracked with in vivo imaging, including bioluminescence imaging (BLI), which is quick, cost-effective, and easily quantifiable. However, BLI requires luciferase-tagged cells, and recent studies indicate that the luciferase gene can elicit an immune response, leading to tumor rejection and experimental variation. We sought to optimize the engraftment of two luciferase-expressing GBM models, GL261 Red-FLuc and TRP-mCherry-FLuc, showing differences in tumor take, with GL261 Red-FLuc cells requiring immunocompromised mice for 100% engraftment. Immuno-histochemistry and MRI revealed distinct tumor characteristics: GL261 Red-FLuc tumors were well-demarcated with densely packed cells, high mitotic activity, and vascularization. In con-trast, TRP-mCherry-FLuc tumors were large, invasive, and necrotic, with perivascular invasion. Quantifying tumor volume using the HALO® AI analysis platform yielded results comparable to manual measurements, providing a standardized and efficient approach for reliable high-throughput analysis of luciferase-expressing tumors. Our study highlights the importance of considering tumor engraftment when using luciferase-expressing GBM models, providing in-sights for preclinical research design.

Radiation therapy is employed in treating various cancer types. However, depending on the type and stage of cancer, its benefits can be limited, and it may cause serious side effects that detrimentally affect the quality of life (QOL) for the patient. Preventing the side effects of radiation therapy can enhance the response to cancer treatment and improve the patient’s QOL. Independently, vitamin C and hydrogen have demonstrated potential in reducing the side effects of anticancer drugs and radiation therapy. Furthermore, both have been postulated to possess direct anticancer properties. However, the effects of their combined therapy remain underexplored. This study investigates the hypothesis that combining vitamin C and hydrogen efficiently prevents radiation-induced injuries. Survival rates were investigated in cancer cell lines (MDA-MB231 and GL261) and normal cells (HUVEC) treated with hydrogen, vitamin C and irradiation. Apoptosis was assessed using the FLICA test, and EMT gene expression was elucidated via the qPCR technique. In the normal cell line, the introduction of vitamin C and hydrogen to the culture medium boosted survival rates, exhibiting a radioprotective effect upon irradiation. In contrast, cancer cells showed a decreased survival rate with the introduction of vitamin C and hydrogen, which was further diminished with irradiation. Treated cancer cells showed signs of apoptosis. Caspase activity in viable cells was reduced by the combination treatment with vitamin C and hydrogen. Additionally, glioblastoma cells treated with this combination showed reduced EMT gene expression. This study reveals that a combined therapy of hydrogen and vitamin C offers radioprotective effects on normal cells and exerts direct anticancer effects on cancer cells, while also amplifying the anticancer effects of radiation. Importantly, this combined therapy attenuated the radiation-induced EMT signature in the GL261 murine glioma cell line, suggesting potential in diminishing treatment resistance and tumor invasion.