MBRS-28. EXOSOMES DRIVE MEDULLOBLASTOMA METASTASIS IN A MMP2 AND EMMPRIN DEPENDENT MANNER

INTRODUCTION: Recurrent/metastatic medulloblastoma (MB) is a devastating disease with an abysmal prognosis of less than 10% 5-year survival. The secretion of extracellular vesicles (EVs) has emerged as a pivotal mediator for communication in the tumour microenvironment during metastasis. The most investigated EV’s are exosomes, nanovesicles secreted by all cell types and able to cross the blood-brain-barrier. Matrix metalloproteinases (MMPs) are enzymes secreted by tumour cells that can potentiate their dissemination by modification of the extracellular matrix. We hypothesise that exosomal MMP2 and its inducer EMMPRIN could enhance metastasis of MB. METHODS: Proliferation, invasion and migration assays were used to evaluate the phenotypic behaviour of primary cell lines pre-treated with metastatic tumour cell-derived exosomes. Gelatin zymography and western blotting were performed to confirm MMP2 functional activity in cell lines and exosomes. Nanoscale flow cytometry was used to measure surface exosomal EMMPRIN levels. Exosomal MMP2 and EMMPRIN were modulated at the RNA level. RESULTS: Number of exosomes is directly related to the migratory behaviour of parental MB cell lines (p<0.01). Notably, functional exosomal MMP2 and EMMPRIN levels also correlate with this. Furthermore, exosomes from metastatic cell lines conferred enhanced migration and invasion on their matched isogenic primary (non-metastatic) cell line pair by ~3.8-fold (p<0.01). Exosomes from metastatic cell lines also conferred increased migration on poorly migratory foetal neuronal stem cells. CONCLUSION: Together this data suggests that exosomal MMP2 and EMMPRIN may promote medulloblastoma metastasis and supports analysis of exosomal MMP2 and EMMPRIN levels in patient cerebral spinal fluid samples.