AQP4 and neoplasm: Therefore, in the present study, the size, nature and cargo of the major subclasses of EVs generated by GBM cells, expressing either M1-AQP4 (forming AQP4-tetramers) or M23-AQP4 (forming AQP4-OAPs), have been analysed for their ability to activate the invasiveness or apoptotic pathways of recipient tumour cells.