ID #1039 An NF1-Deficient Brain Organoid Microenvironment Enhances Glioma Progression via Cytokines

Abstract

Neurofibromatosis type 1 (NF1) is a tumor-predisposition syndrome affecting 1 in 3,000 people. NF1 patients develop benign neurofibromas, and 15–20% eventually develop gliomas. NF1 encodes neurofibromin, a negative Ras regulator; its loss hyperactivates Ras/MAPK signaling. While NF1 inactivation is linked to low-grade gliomas, the drivers of malignant progression remain unclear. Current preclinical models, such as glioma cell lines and xenografts, fail to replicate the NF1 tumor microenvironment, necessitating more physiologically relevant systems to study tumor–host interactions. We hypothesized that an NF1-deficient microenvironment may promote glioma growth and affect therapy responses.

We generated 3D cerebral organoids from NF1 wild-type and NF1-mutant (NF1+/−, NF1−/−) hiPSCs derived from patient tumors. Organoid development was assessed using immunofluorescence and RNA sequencing. We co-cultured fluorescently labeled high-grade glioma cells with organoids to measure proliferation, cytokine secretion, and response to the CDK4/6 inhibitor abemaciclib.

At day 30, NF1-mutant organoids retained larger neural progenitor pools and more immature neurons than controls, despite similar Ki-67 indices. This suggests reduced apoptosis, consistent with NF1’s role in restraining progenitor expansion. Transcriptomic profiling showed elevated Ras GTPase activity and enrichment of pathways related to ion channels, axon guidance, and synapse formation, indicating a hyperexcitable neuronal state.

In co-culture, NF1-mutant organoids supported increased glioma proliferation and secreted higher levels of pro-inflammatory cytokines. Notably, they released more GM-CSF and IL-18—cytokines known to promote glioma proliferation. Treatment of an NF1-derived glioma cell line with exogenous GM-CSF or IL-18 validated the cytokine-driven proliferation observed in the organoid co-cultures, confirming a tumor-supportive microenvironment.

To assess therapeutic response, NF1-mutant co-cultures were treated with abemaciclib. This preliminary result showed a modest reduction in tumor proliferation and invasion, supporting the platform’s utility for testing drug responses, particularly in CDKN2A/B-mutant contexts.

Overall, NF1 loss fosters a tumor-permissive neural microenvironment. This platform offers a valuable ex vivo model for studying NF1-driven glioma genesis and guiding therapy