Increased expression of diazepam binding inhibitor in human brain tumors.

Benzodiazepines, which are in extensive clinical use, can regulate neoplastic growth via benzodiazepine receptors. We have studied the expression of the diazepam binding inhibitor (DBI) polypeptide, a putative endogenous ligand for benzodiazepine receptors in normal and pathological human brain. In normal brain, DBI immunoreactivity (IR) and mRNA were detected in all brain areas, with the highest levels in the cerebellum, amygdala, and hippocampus. In light and electron microscope immunohistochemistry, DBI-IR was only detected in glial and ependymal cells. In brain tumors, such as astrocytomas, glioblastomas and medulloblastomas, a much higher content of DBI-IR and -mRNA was found in normal tissues. The highest level of DBI expression was found in the most anaplastic tumors. DBI-IR was virtually undetectable in meningiomas and pituitary adenomas. The high expression of DBI in brain tumors might play a role in the neoplastic growth of glial cells via the mitochondrial benzodiazepine receptor, or it may be involved in the regulation of the high energy consumption of these tumors via acyl-CoA metabolism.