Hijacking the Body’s Controls
Twenty-five years ago, Li did his research training in the lab of Dr. Judah Folkman. If that name sounds familiar, there’s a good reason; Folkman was a pioneer in the field of cancer research, and his theory of the role of angiogenesis in tumor development forever changed cancer treatment.
Angiogenesis is a big word for a simple concept: it’s the process through which our bodies create new blood vessels. In normal, healthy individuals, new blood vessels grow only under specific circumstances: as part of the healing process for an injury, for instance, or during pregnancy. Our bodies contain a natural system of checks and balances to regulate the growth of blood vessels, known to scientists as angiogenesis stimulators and inhibitors. “The stimulators act as natural fertilizers to get vessels to grow, and the inhibitors prune back extra vessels when they’re no longer needed,” Li explains.
Without blood vessels to supply them with the nutrients necessary for expansion, microscopic cancers have nothing to do and nowhere to go. But as cancer cells mutate, they can hijack the body’s system of checks and balances, using angiogenesis stimulators to create the blood supply they need. A microscopic tumor, given a steady influx of blood, can grow to up to 16,000 times its original size in as little as two weeks. And, of course, what goes in must come out; the blood feeding the tumor is circulated back through the body, now bearing cancer cells that can take up residence in distant organs, leading to metastasis. “This is the turnkey step that converts a harmless cancer into a deadly one,” says Li.
Folkman’s theory was that a growing tumor could be “starved to death,” so to speak, by cutting off its blood supply. Forty years ago, he presented his thesis in the New England Journal of Medicine and was met with skepticism, ridicule and dismissal. Today there are 12 antiangiogenic drugs on the market for cancer treatment, with 26 more in the final stages of human testing and another 100-plus behind them in human trials. Every major pharmaceutical company has an angiogenesis program, and the first FDA-approved antiangiogenic cancer drug, Avastin, is practically a household name.