AQP4 and glioblastoma: As the extracellular matrix (ECM) plays an important role in the polarized localization of OAPs, AQP4 delocalization probably in turn depends on modification of ECM: it has indeed reported that, besides AQP4, dystroglycan, agrin and the matrix metalloproteinases (MMP) 2, 3 and 9 also undergo altered expression in human primary glioblastomas [140].