US  
 CANCER
 Scientists study growth gene
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 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."