The FDA revoked approval of Avastin for breast cancer last year after further assessing the relative risks and benefits to women taking it. Blocking VEGF seemed to slow tumor growth for awhile, but the FDA determined that it did not significantly improve or extend the lives of most women taking it.
“It was not clear why some tumors responded and others did not. It was also unclear why some tumors would respond initially and then would stop responding," said McDonald, who has studied blood vessels in tumors and the effect of cancer drugs for years in his UCSF laboratory.
Two years ago former UCSF professor Douglas Hanahan and colleagues found in laboratory experiments that Avastin-like drugs would shrink tumors but unexpectedly did something else as well. The drugs also morphed tumors from roundish blobs into highly irregular growths with tendrils that penetrated surrounding tissues and even spread to other organs—suggesting that the VEGF blockade could also make tumors more aggressive, invasive and metastatic.
McDonald’s group confirmed Hanahan’s findings and discovered that c-MET was involved. In their latest research, Barbara Sennino, PhD, with other investigators in his group set out to determine whether c-MET drove tumor aggressiveness during anti-VEGF therapy. What their paper shows is that blocking c-MET and VEGF together in mice is more powerful than blocking either alone because it not only slows tumor growth but also reduces invasion and metastasis.