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Prevention of Cancer by increased Blood Flow

Prevention of Cancer by increased Blood Flow

The first detailed analysis of an organ-forming protein, a natural

chemical that induces the body to sprout blood vessels, could open

new approaches to fighting cancer, heart disease and other ailments,

researchers say.

The protein, named angiogenin, was discovered and studied by

researchers at Harvard Medical School, who published their findings

in the latest issue of the journal Biochemistry. They also isolated

the gene that oversees production of the protein.

“It is the first time that a specific substance has been clearly

related to the creation of a type of organ,” said Dr. Hans Neurath,

editor of Biochemistry. “That is really a first.”

Cancers secrete angiogenin — and probably other, similar,

substances — to promote the growth of tiny blood vessels called

capillaries. This provides the blood supply that allows the tumor to

enlarge and eventually spread.

Some experts theorize that if some way could be found to block

angiogenin and its chemical cousins, then cancers could be stopped.

“I would fondly hope that this will prove possible,” said Dr. Bert

L. Vallee, who directed the research. “I think this should

facilitate it.”

Experts say the work represents a major step in the study of

angiogenesis, or blood vessel formation, which was pioneered two

decades ago by Dr. Judah Folkman, another Harvard researcher.

“It’s a stunning achievement,” Folkman said. “I think it’s very

important for the whole field, because it will enlarge everyone’s

thinking about how tumors send the signal to keep blood vessels

growing in toward them.”

Dr. James F. Riordan, another member of the research team, said one

logical cancer strategy will be to try to produce antibodies that

will neutralize angiogenin.

The researchers said they were surprised to find that angiogenin

holds about a 35 percent similarity to another well-known enzyme

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called ribonuclease. This, too, could be turned to their advantage

in finding ways to defeat the protein.

Comparing angiogenin to ribonuclease “gives us a clue as to its

three- dimensional structure,” Riordan said. “If you know the

structure, you can try to design drugs that will specifically bind

to the protein” and deactivate it.

The blood vessel growth promoters also probably play a role in

diseases besides cancer. For instance, experts believe that they are

responsible for the proliferation of blood vessels that leads to

blindness in victims of diabetes as well as the overabundance

of capillaries in rheumatoid arthritis.

Neurath said it may be possible to use the substance to promote the

growth of new blood vessels in victims of heart disease.

Vallee said much more work remains to understand the workings of the

gene and the chemical it produces.

“What turns it on?” he said. “What turns it off? How is it made?

How is it excreted? It is enough to keep people busy a long time.”

The scientists derived angiogenin from a human colon cancer and

showed that it would promote capillary growth in chicken eggs and

rabbits.

Normal tissues also produce similar hormones. They are part of the

female menstrual cycle and fetal growth in the womb, and they are

released to repair wounds and heart attacks.

Folkman said the angiogenesis factors released by cancers are

probably extremely similar to those produce in the body’s day-to-day

housekeeping.

“The big difference is timing,” said Folkman. “Normal tissues rarely

put these factors out. They are normally turned off. In the tumor,

they are turned on and stay on continuously.”