AQP4 and brain neoplasm: AQP1 is capable of transporting oxygen as well as water across cell membranes which is an important function of being mostly expressed in red blood cells and in the choroid plexus In brain tumors like ependymomas AQP4 as well as AQP1 are found but AQP4 was only expressed in ependymomas when tumors grow in the fossa inferior of the brain, but not in supratentorial regions [25].