Researchers working on a new approach to cancer that starves tumours by cutting off their blood supply have identified another naturally produced compound to add to the arsenal.
The new compound, anti-angiogenic anti-thrombin III (aaAT), is easily produced from goat milk and should be ready to test on people quickly, said Dr Judah Folkman of Children's Hospital in Boston, who led the research.
In work with colleague Dr Michael O'Reilly, it was confirmed that the compound, when tested in mice, worked at least as well as two proteins their laboratory developed last year.
When injected into specially bred mice infected with cancer, aaAT caused their tumours to wither and die.
But Dr Folkman warned that it must be tested in humans first - and many compounds that "cure" cancer in mice do not work in people.
Tumours are started by cancerous cells growing out of control. Once they reach a certain size, they have to create a blood supply to feed themselves in a process called angiogenesis.
But the Folkman team have found that tumours also secrete other substances that stop other tumours from forming and competing with them.
Their latest breakthrough has been outlined in the latest issue of Science journal. These are the compounds they are working to develop as cancer drugs.
Angiostatin and endostatin are now being developed by Maryland biotechnology company EntreMed Inc.
Dr Folkman's team has since turned to human tumours to see if they can find something there. By growing two human lung cancer tumours side by side in a laboratory dish, they found a compound was being secreted by one that interfered with the other.
It stopped the growth of endothelial cells - the cells that line blood vessels and that are required for the growth of new blood vessels.