Figure 6.

The mechanism of the enhanced permeability and retention (EPR) effect. Substances (10–100 nm in diameter) such as monoclonal antibodies (mAbs) or nanoparticles spontaneously penetrate into solid tumor stroma or parenchyma through the capillary endothelial fenestration, ranging from 200 to 2000 nm, in neovasculature, caused by vascular endothelial growth factor (VEGF) secreted from cancer cells, due to wall fluid shear stress (FSS) (approximately 0.4 Pa), and, subsequently, remain there because of an underdeveloped lymphatic system in solid tumor parenchyma and high-pressure interstitial fluid in deep cancer tissue.