LA JOLLA, CA--Glioblastoma, the most common and lethal form of brain cancer and the disease that killed Massachusetts Senator Ted Kennedy, resists nearly all treatment efforts, even when attacked simultaneously on several fronts. One explanation can be found in the tumor cells' unexpected flexibility, discovered researchers at the Salk Institute for Biological Studies.
When faced with a life-threatening oxygen shortage, glioblastoma cells can shift gears and morph into blood vessels to ensure the continued supply of nutrients, reports a team led by Inder Verma, Ph.D., in a feature article in this week's issue of the Proceedings of the National Academy of Sciences.
Their study not only explains why cancer treatments that target angiogenesis--the growth of a network of blood vessels that supplies nutrients and oxygen to cancerous tissues--routinely fail in glioblastoma, but the findings may also spur the development of drugs aimed at novel targets.
"This surprising effect of anti-angiogenic therapy with drugs such as Avastin tells us that we have to rethink glioblastoma combination therapy," says senior author Verma, a professor in the Laboratory of Genetics and holder of the Irwin and Joan Jacobs Chair in Exemplary Life Science. "Disrupting the formation of tumor blood vessels is not enough; we also have to prevent the conversion of tumor cells into blood vessels cells."
To grow beyond one to two millimeters in diameter--roughly the size of a pinhead--tumors need their own independent blood supply. To recruit new vasculature from existing blood vessels, many tumors overexpress growth factors, predominantly vascular endothelial growth factor, or VEGF. This led to the development of Avastin, a monoclonal antibody that intercepts VEGF.
"In a recent phase II clinical trial, 60 percent of patients with glioblastoma responded to a combination of Avastin and Irinotecan, which directly interferes with the growth
|Contact: Gina Kirchweger|