Blood brain barrier: a challenge for effectual therapy of brain tumors

Abstract

Brain tumors are one of the most formidable diseases of mankind. They have only a fair to poor prognosis and high relapse rate. One of the major causes of extreme difficulty in brain tumor treatment is the presence of blood brain barrier (BBB). BBB comprises different molecular components and transport systems, which in turn create efflux machinery or hindrance for the entry of several drugs in brain. Thus, along with the conventional techniques, successful modification of drug delivery and novel therapeutic strategies are needed to overcome this obstacle for treatment of brain tumors. In this review, we have elucidated some critical insights into the composition and function of BBB and along with it we have discussed the effective methods for delivery of drugs to the brain and therapeutic strategies overcoming the barrier.

Figure 1

A pictorial representation of the BBB and its tight junction structure. The figure shows an irrigated blood vessel in the brain which forms the BBB. The BBB is constituted by endothelial cells with tight junctions, surrounded by pericytes and astrocytic end-feet. The tight junction is further established by the interaction of proteins like claudins, occludin, junction adhesion molecules, and cytoplasmic accessory proteins (ZO1, ZO2, and ZO3) of adjacent endothelial cells. The details of each component of the BBB are mentioned in the text of this review.

Figure 2

Schematic classification of transporters of human BBB. Two main classes of drug transporters are ATP-binding cassette (ABC) transporters and solute carrier transporters. Each of them is further classified into several other transporters mentioned in the flowchart. More information about each of the transporters is mentioned in the text.