Significance of blood vessel leakiness in cancer

Despite major advances in the field of tumor angiogenesis, relatively little attention has been paid to the permeability of blood vessels in tumors. The leakiness of tumor vessels is well documented in experimental tumor models and in human cancer, but the mechanism is poorly understood, as are the implications to the rate of cancer growth, predisposition to metastasis, and delivery of macromolecular therapeutics to tumor cells. Sixteen experts in the fields of cancer biology and vascular biology gathered at the William Guy Forbeck "Focus on the Future" Conference to discuss this topic. The meeting was the first of its kind focused on the significance of blood vessel leakiness in tumors. The participants discussed the cellular basis of tumor vessel leakiness, endothelial barrier function of blood vessels, monitoring tumor vessel leakiness, mediators of endothelial leakiness, consequences of tumor vessel leakiness, genomic analysis of vascular targets, targeting drugs to tumor vessels, and therapeutic manipulation of tumor vessels. The group concluded that a more complete understanding of the basic biology of tumor vessels will be necessary to fully appreciate the consequences of vessel leakiness in cancer. New research tools such as intravital measurements of tumor blood flow and vessel leakiness, in vivo phage display, magnetic resonance imaging, and use of selective angiogenesis inhibitors will contribute to this understanding.