Donald M. McDonald, MD, PhD, a professor in the Department of Anatomy and an investigator in the Cardiovascular Research Institute at the University of California, San Francisco Comprehensive Cancer Center, discusses the recent discovery of novel resistance to therapies that inhibit angiogenesis, particularly in breast cancer.

The underlying mechanisms of anti-angiogenesis resistance are being investigated in pre-clinical trials. Angiogenesis inhibitors prune the blood vessels feeding a tumor causing intratumoral hypoxia. It is believed it is this mechanism that can activate systems that promote invasions and metastasis from the tumor.

At this stage all observations into mechanisms of resistance are from pre-clinical models and it is still unclear how to generalize these studies in human cancers.