NFS-22. Investigating Malignant Transformation in Nf1 Pediatric Gliomas Using an Ipscs-Derived Cerebral Organoid Model

Abstract BACKGROUND Neurofibromatosis Type 1 (NF1) is an autosomal dominant tumor predisposition syndrome affecting 1 in 3000 children around the world. Although NF1 inactivation is recognized as the cause of low-grade glioma (LGG) development, little is known about subsequent genetic alterations that lead to malignant transformation. One of the limitations in understanding the molecular events underlying the malignant transformation of NF1 gliomas is the lack of appropriate NF1 preclinical models for its comprehensive profiling. OBJECTIVE Brain organoids have emerged as powerful in vitro models for studying the interaction between tumor cells and the tumor microenvironment. In this study, we present a novel cerebral organoid model, developed to investigate the molecular events leading to malignant transformation in NF1 pediatric gliomas. METHODS Induced pluripotent stem cells (iPSCs)-derived cerebral organoids were generated using NF1wt and NF1mut iPSCs, the latter reprogrammed from patients with plexiform neurofibromas (Carlos III Health Institute, Spain). Immunofluorescence analysis was performed at four different developmental stages to confirm their correct cytoarchitectural development and differentiation into heterogeneous cell populations. Furthermore, four mCherry-labelled isogenic glioma cells lines, RES 186 wild type, NF1-/-, CDKN2a-/-,NF1-/-/CDKN2a-/- were co-cultured with the developed cerebral organoids and their migration potential and invasiveness were compared using two-photon microscopy. RESULTS/DISCUSSION NF1mut cerebral organoids display ventricular-like zone at early stages of development (d15-d30), characterized by luminal Sox2+ neural stem cells surrounded by Tuj1+ immature neuron. These organized structures disappear at later stages, while progenitor cells start to differentiate into fully mature neurons and glial cells (d45-d60). Additionally, after 10 days of co-culture, all four RES186 isogenic cell lines infiltrated the organoid structure with different invasion patterns. The established organoid model will provide a platform for evaluating the impact of sequential mutational events on LGG transformation, taking into consideration the role exerted by the tumor microenvironment in supporting tumor cell invasion and migration.