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Researchers discover human virus that can target, kill cancer cells in mice WASHINGTON (November 12, 1998 6:51 p.m. EST http://www.nandotimes.com) - Scientists have discovered a human virus that can target and kill cancer cells, researchers said Thursday. Reovirus normally causes mild upper respiratory infections in humans, but when targeted to certain cell functions in laboratory mice it infected and destroyed tumors, said Peter Forsyth, a neural oncologist at the University of Calgary, who worked on a study of the virus. "This virus selectively attacks tumor cells and leaves normal ones intact," Forsyth said in a telephone interview. "In some ways it can be thought of as a magic bullet." The reovirus uses the Ras pathway in the cells of the mice, the researchers wrote in a report in the journal Science. The Ras pathway normally regulates cell growth but becomes highly active in about 75 percent of tumors, including breast, pancreatic and brain cancers, Forsyth said. "This is one of the most common pathways that is activated in human cancers," Forsyth said. "This pathway is used for a broad range of cancer and isn't specific." When the pathway begins signaling tumors to grow out of control, it acts like a telephone line going from the outside of the cell to the inside. The reovirus tunes right in on this line, Forsyth said. It uses the signaling pathway to attack tumors by activating an enzyme that allows viral proteins to be made, and these kill the cancer cells. Previous research has identified other tumor-killing viruses and early results from one study that has reached clinical trials in humans indicate they can shrink tumors, particularly when used in conjunction with other therapies, according to a related article in the journal Science. But this is the first virus that uses the Ras signaling pathway, said Patrick Lee, a virologist and cancer biologist at the University of Calgary, who led the study. "This is the pathway everyone wants to target," he said in a telephone interview. "The treatment is very effective." The researchers said a single dose of reovirus caused tumors to shrink or disappear in 65 to 80 percent of mice bred to have weak immune systems. In healthy mice, multiple doses of the virus made the tumors completely disappear without damaging normal tissue, unlike treatments like chemotherapy, surgery and radiation. And because reovirus does not seem to affect noncancerous cells, the researchers say the treatment could have potential for attacking metastatic tumors, which have spread to other parts of the body. In some cases, after the team injected the reovirus it moved through the body and eliminated tumors in different areas, Lee said. "This offers the hope of being able to treat metastatic cancer," Forsyth added. While the results in mice were promising, Forsyth pointed out that testing reovirus as an anti-cancer agent in humans could be a lengthy process. "The steps involved in taking this into the clinic are complicated and will take some time," he said. By Michael Kahn, Reuters News Service Copyright 1998 Nando Media Copyright 1998 Reuters News Service janet paterson - 51/41/37 - almonte/ontario/canada http://www.newcountry.nu/pd/members/janet/ [log in to unmask]