Abstract
Diffuse Intrinsic Pontine Glioma (DIPG) is a high-grade pediatric brainstem glioma afflicting children 7–9 years old. The anatomic and diffuse characteristics of DIPG prevent surgical removal, and the blood-brain barrier impedes chemotherapy, while radiation, the current standard treatment, does not improve survival. Intranasal delivery (IND) of mesenchymal stem cells (MSC) can potentially overcome these obstacles and transport therapeutics directly to DIPG. We utilized a patient-derived xenograft model of DIPG implanted in the brainstem of nude mice to assess the viability of IND of MSCs for targeting DIPG. Magnetic resonance imaging (MRI) was used for tumor detection and longitudinal tracing and quantification of superparamagnetic iron nanoparticle-labeled MSCs. Whole brain scans were acquired using a T2-weighted MR sequence in 3 dimensions with isotropic spatial resolution (150-micron), and were performed before and at multiple time-points after (1h, 24h, 48h, and 120h) IND of MSCs. All images were realigned for accurate comparison between time-points. Concentrated hypointense signals, indicative of iron-labelled MSCs, were observed in the brainstem 2 days post-IND, which became more diffuse 5 days post-IND. Prussian Blue (PB) staining confirmed the presence of iron nanoparticles in the brainstem. Immunocytochemistry (ICC), using antibodies against MSC marker CD105, and DIPG-specific mutation H3-K27M, identified MSCs surrounding the tumor at 5 days post-IND. Additionally, PB staining detected iron nanoparticles in the trigeminal nerve, confirming the route of MSC migration to the brain. Fractionated brain irradiation (0.5 Gy delivered 3 times/week for 2 weeks), significantly improved MSC migration and targeting of DIPG, as determined by MRI, PB, and ICC. Cytokine array analysis of irradiated DIPG tumors revealed a significant upregulation of MIP-3-beta and TRAIL R4, potentially promoting MSC migration to irradiated DIPG tumors. Our findings demonstrate the potential for stem cell-based therapeutics to target DIPG and warrants further investigation. Supported by the Robert H. Lurie Comprehensive Cancer Center.