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." a19 9820 95-06-30 The Shooting at Ruby Ridge 19/21 RUBY.020 31960 95-06-30 The Shooting at Ruby Ridge 20/21 RUBY.0