Location-dependent role of the human glioma cell peripheral-type benzodiazepine receptor in proliferation and steroid biosynthesis.

We examined the localization and function of the peripheral-type benzodiazepine receptor (PBR), a protein highly expressed in steroidogenic tissues and aggressive tumor cells, in cell lines derived from glioblastoma multiforme tumors. In MGM-1 cells, PBR is located in the nucleus, and cells proliferate in response to PBR ligands but do not synthesize steroids de novo. In MGM-3 cells, PBR is located in mitochondria and the cells synthesize steroids, but do not proliferate in response to PBR ligands. In glioblastoma biopsies, PBR is expressed in the nuclei of cells, while it is found in the cytosol of astrocytomas, and is absent from meningioma and medulloblastoma tumor biopsies. These data suggest that the subcellular localization of PBR defines its function.