NOTE: See our updated article, "The Flap
Over Angiostatin and Endostatin" (1998). Little did we realize
when we wrote this article in 1996 the worldwide hysteria that would soon
be generated about Dr. Folkman's work.
A prominent Boston-area researcher believes he has found a way to stop
malignancies in their tracks by injecting an agent that normally occurs
in the body. Judah Folkman, MD and his colleagues at Harvard Medical School
reported their finding in late February in the British journal, New Scientist.
They have called this agent angiostatin. It is based upon work that Folkman
and colleagues did starting in the 1970s: it reputedly stops blood vessels
in cancer tumors from developing, thereby halting their growth and preventing
the development of metastases.
The team injected the new agent into mice with lung cancer. "We
injected the mice every day," Folkman said, "a bit like insulin
injections for people with diabetes, and the tumors were held in check —
preventing any further deterioration.''
Folkman has shown that tumors which cannot sprout new blood vessels are
unable to grow bigger than a pea. But whether or not new vessels actually
form depends on the balance between stimulators and inhibitors in the blood
stream. This process is called angiogenesis.
Angiostatin, which is a fragment of a blood-clotting protein, is an angiogenesis
inhibitor. The scientists inserted the gene that codes for the manufacture
of angiostatin into cancer cells that were then implanted into mice. It
was found that cells altered in this way did indeed produce a higher than
normal level of angiostatin.
"They ended up behaving more like slow-growing warts than tumors,
and after three months the mouse was still going strong, which is the equivalent
of six years in human terms,'' said Dr. Folkman. He warned that producing
the agent for human patients still faces major obstacles. It takes almost
a gallon of blood plasma and a week of laboratory work to produce just 0.005
ounce of the precious substance. And attempts to grow the gene in bacteria
have failed so far.
Folkman has not found universal acceptance for his claims. James Pluda
of the NCI threw some cold water on the idea. "A few years ago we were
very excited about a number of agents which seemed to prevent new vessel
growth in the laboratory,'' he said in response to Folkman's article, "but
when it came to clinical trials, the substances did not fulfill their promise."
The principle of blocking angiogenesis is familiar to many from the book
Sharks Don't Get Cancer. In it, I. William Lane, PhD claims that shark
cartilage does the same thing as angiostatin. Folkman vigorously disputes
such claims, stating that an insufficient amount of the key ingredients
could possibly reach the tumors.
