Emerging molecular mechanisms of brain tumour oedema

A common property of brain rumours is their ability to cause oedema in the surrounding brain. Oedema forms as a result of a leaky blood-tumour barrier and persists when the brain fails to clear the excess fluid. It is a signi ficant source of morbidity and mortality. The principal anatomical componen t of the blood-brain barrier is the endothelial tight junction which opens in glioma microvessels. Multiple tight junction proteins have recently been identified, such as occludin, claudin, ZO-1, ZO-2 and ZO-3. We propose a m odel to explain tight junction opening in gliomas based on vascular endothe lial growth factor secretion and loss of tight junction inducing factor pro duction by tumour cells. The level of expression of the water channel aquap orin-4 in peritumoural astrocytes may determine the rate of oedema fluid cl earance. The identification of the molecular mechanisms of brain tumour oed ema may allow the design of never anti-oedema medications.