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.”
