Ricky T. Tong

Elevated interstitial fluid pressure, a hallmark of solid tumors, can compromise the delivery of therapeutics to tumors. Here we show that blocking vascular endothelial growth factor (VEGF) signaling by DC101 (a VEGF-receptor-2 antibody) decreases interstitial fluid pressure, not by restoring lymphatic function, but by producing a morphologically and functionally "normalized" vascular network. We demonstrate that the normalization process prunes immature vessels and improves the integrity and function of the remaining vasculature by enhancing the perivascular cell and basement membrane coverage. We also show that DC101 induces a hydrostatic pressure gradient across the vascular wall, which leads to a deeper penetration of molecules into tumors. Thus, vascular normalization may contribute to the improved survival rates in tumor-bearing animals and in colorectal carcinoma patients treated with an anti-VEGF antibody in combination with cytotoxic therapies.

Preclinical and clinical evidence shows that antiangiogenic agents can decrease tumor vessel permeability and interstitial fluid pressure (IFP) in a process of vessel "normalization." The resulting normalized vasculature has more efficient perfusion, but little is known about how tumor IFP and interstitial fluid velocity (IFV) are affected by changes in transport properties of the vessels and interstitium that are associated with antiangiogenic therapy. By using a mathematical model to simulate IFP and IFV profiles in tumors, we show here that antiangiogenic therapy can decrease IFP by decreasing the tumor size, vascular hydraulic permeability, and/or the surface area per unit tissue volume of tumor vessels. Within a certain window of antiangiogenic effects, interstitial convection within the tumor can increase dramatically, whereas fluid convection out of the tumor margin decreases. This would result in increased drug convection within the tumor and decreased convection of drugs, growth factors, or metastatic cancer cells from the tumor margin into the peritumor fluid or tissue. Decreased convection of growth factors, such as vascular endothelial growth factor-C (VEGF-C), would limit peritumor hyperplasia, and decreased VEGF-A would limit angiogenesis in sentinel lymph nodes. Both of these effects would reduce the probability of lymphatic metastasis. Finally, decreased fluid convection into the peritumor tissue would decrease peritumor edema associated with brain tumors and ascites accumulation in the peritoneal or pleural cavity, a major complication with a number of malignancies.