Blood-brain barrier and treatment of central nervous system tumors

The blood-brain barrier (BBB) separates the central nervous system (CNS) from systemic blood circulation by a continuous capillary network. The barrier's capillary endothelium has interendothelial tight junctions which prevent passage of large molecular weight, water soluble, highly polar molecules. The barrier protects the brain from toxic substances and also prevents therapeutic drugs from CNS entry. Its permeability within brain tumors is different with fenestrated endothelium resembling that of normal brain regions outside the BBB. Despite capillary changes within CNS tumors, their effect on improved therapies has not been shown. Combined chemotherapy with surgery and radiation does not significantly prolong glioma patients' survival. Discussed are new therapeutic approaches which include: osmotic, transient blood-brain barrier disruption followed by chemotherapy or immunotherapy, drug "tailoring" to render them more effective in barrier entry, and genetic glioma manipulation to make it the target of antiviral drugs which may penetrate the barrier.