Normalizing Tumor Microenvironment to Treat Cancer: Bench to Bedside to Biomarkers

For almost four decades, my work has focused on one challenge: improving the delivery and efficacy of anticancer therapeutics. Working on the hypothesis that the abnormal tumor microenvironment—characterized by hypoxia and high interstitial fluid pressure—fuels tumor progression and treatment resistance, we developed an array of sophisticated imaging technologies and animal models as well as mathematic models to unravel the complex biology of tumors. Using these tools, we demonstrated that the blood and lymphatic vasculature, fibroblasts, immune cells, and extracellular matrix associated with tumors are abnormal, which together create a hostile tumor microenvironment. We next hypothesized that agents that induce normalization of the microenvironment can improve treatment outcome. Indeed, we demonstrated that judicious use of antiangiogenic agents—originally designed to starve tumors—could transiently normalize tumor vasculature, alleviate hypoxia, increase delivery of drugs and antitumor immune cells, and improve the outcome of various therapies. Our trials of antiangiogenics in patients with newly diagnosed and recurrent glioblastoma supported this concept. They revealed that patients whose tumor blood perfusion increased in response to cediranib survived 6 to 9 months longer than those whose blood perfusion did not increase. The normalization hypothesis also opened doors to treating various nonmalignant diseases characterized by abnormal vasculature, such as neurofibromatosis type 2. More recently, we discovered that antifibrosis drugs capable of normalizing the tumor microenvironment can improve the delivery and efficacy of nano- and molecular medicines. Our current efforts are directed at identifying predictive biomarkers and more-effective strategies to normalize the tumor microenvironment for enhancing anticancer therapies.