Altered expression of alpha-dystroglycan subunit in human gliomas

Dystroglycan (DG) is an integral membrane receptor of extracellular matrix proteins, composed of two subunits alpha and beta derived from a common precursor. In brain DG is expressed in neurons, glia limitans, astrocytic endfeet around vessels and endothelial cells. We investigate whether DG may play a role in brain tumors. Western blot and immunofluorescence analysis showed that, while beta-DG subunit was present, the highly glycosylated alpha-DG subunit was strongly reduced in surgically derived human glioblastoma biopsies, in low passage patient-derived cultures and in glioma cell lines, U87MG and A172MG, but not in all glioma cell lines tested. Immunohistochemistry of tumor frozen sections revealed that the loss of alpha-DG was confined in the tumor area but not around blood vessels. Overexpression of DG decreased the growth rate of the glioma cell lines lacking the highly glycosylated a-DG subunit and the colony-forming efficiency. Clonogenic assay in presence of temozolomide showed an additive effec...