AQP4 and glioblastoma: Glioblastomas also cause alterations in AQP4 protein distribution and polarization, instead of concentrating in astrocytic endfeet, polarized AQP4 starts redistributing throughout the entire astrocyte cell membrane, suffers upregulation and results in a disorganized polarization which leads to an augmentation of the hematoencephalic barrier permeability and exacerbation of vasogenic edema [4].