Expression of the Aquaporin-1 Water Channel in Human Glial Tumors

Abstract

Malignant glial tumors are associated with cerebral edema. The aquaporins (AQPs) are a family of membrane proteins that provide a major pathway for water transport in mammals. In the central nervous system, AQP1 is selectively expressed in the choroid plexus and thought to participate in cerebrospinal fluid production. Prior studies have suggested that AQP1 may be up-regulated in glial tumors, potentially contributing to tumor-associated edema. The objective of this study was to investigate the expression of AQP1 in a large series of human glial tumors. Thirty-six human glial tumors were obtained from the University of California, San Francisco Neurosurgery Tissue Bank. AQP1 expression was evaluated by reverse transcriptase polymerase chain reaction, complementary deoxyribonucleic acid gene array, Western blot analysis, and immunohistochemical analyses. AQP1, normally restricted to choroid epithelia, was highly expressed in glioblastomas. Complementary deoxyribonucleic acid array, Western blot analysis, and immunohistochemical analysis revealed intense up-regulation of AQP1 expression in all glioblastomas studied. The abnormal up-regulation of AQP1 in glial tumors suggests a potential pathological role for this membrane water channel and raises the possibility that selective AQP1 inhibition might offer a new therapeutic target for treatment of tumor-associated edema.