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On cancer - causes, prevention, etc
US
CANCER
Scientists study growth gene
===========================================
BOSTON (AP) -- 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 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."
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