The development and validation of a novel patient-derived 3D meningioma cell culture model

Meningiomas are the most frequent intracranial brain tumours. Current treatment options of surgery and radiotherapy are sometimes insufficient and effective systemic therapies remain unestablished. The development of accurate in vitro systems to model the complexity of meningioma pathology is essential for predicting drug response and developing novel therapeutics. Therefore, in this study, I established an easy-to-use in vitro patient-derived meningioma spheroid model that maintained the morphological and molecular features of the parental tumours, including tissue histology, the tumour microenvironment, and the mutational profile. Comprehensive characterisation of the global transcriptomes of the novel patient-derived spheroids with traditional meningioma monolayer cultures and parental tissues revealed an enhanced Notch1-mediated mesenchymal gene expression signature in the spheroids compared to traditional 2D monolayer cultures. These features were confirmed by the presence of other mesenchymal traits such as invasion capacity, demonstrating this spheroid model as the first meningioma 3D culture method capable of studying functional invasion, and indicating its relevance for studying the molecular mechanisms associated with invasion and the related oncogenic process of epithelial-tomesenchymal transition (EMT). The suitability of this model for use as a tool for research questions, including pre-clinical drug testing, was demonstrated by studying the effect of Notch1 shRNA targeting, and by treatment using several inhibitors. Concomitantly, this proof-of-concept study allowed for the development of a novel effective combination therapy of MER tyrosine kinase (MERTK) and histone deacetylase (HDAC) inhibition, which in addition to having a synergistic inhibitory effect on spheroid viability, also decreased spheroid proliferation, expression of EMT-associated proteins and spheroid invasion capacity. Hence, I propose this meningioma spheroid model as novel preclinical drug screening tool to assess the efficacy of drug compounds targeting EMT and brain invasion of meningiomas and the combination of HDAC and MERTK inhibitors as a promising therapeutic strategy