Virus linked to mesothelioma
A Hawaii cancer researcher and his team said they are unraveling the mystery of why some workers heavily exposed to asbestos develop cancer, while most do not.
Dr. Michele Carbone, director of the Thoracic Oncology Program, Cancer Research Center of Hawaii, said in an interview, "It's not just a case of good vs. bad luck, but a combination of the mineral fibers and viruses that's responsible."
"Those factors work together to cause malignant mesothelioma, an aggressive cancer of membranes lining the chest and abdominal cavities", he said.
People work in shipyards have high incidence of mesothelioma. Five percent of those with more than 10 years' exposure will die of cancer. Carbone said, "That's a lot, but it also tells you 95 percent of them equally loaded with asbestos do not get it. So the issue is, why?"
Carbone has been studying thoracic cancers, specifically malignant mesothelioma, for more than 10 years.
In the latest paper, Carbone reported finding a link between asbestos fibers and a monkey virus called SV40. Low amounts of asbestos believed insufficient to cause mesothelioma will cause the disease more often among humans infected with the virus, the researchers reported.
Carbone's team had previously discovered the monkey virus in some human mesotheliomas. He said he was surprised to find that the virus and asbestos co-operate to cause human cancer.
Monkey cells were used to develop polio vaccines. Some prepared from 1954 to 1961 were contaminated with infectious SV40. "But it was believed all polio vaccines after 1962 were SV40-free", Carbone said. A study he headed, however, found that vaccines produced in the former Soviet Union remained contaminated with the monkey virus until 1978. "That means supposedly safe levels of asbestos exposure might not be safe for the millions of people exposed to SV40-contaminated polio vaccines", Carbone said.
"About 2,000 to 3,000 Americans die annually from mesothelioma, and cases have been increasing, associated with widespread asbestos use in the past century", researchers said. "The virus doesn't cause a lot of cancer in humans, most likely because their immune systems are stronger than those of animals", Carbone said. "But some people are less resistant, and mesothelioma cells harbor the virus better than other cells", he explained. "In the presence of asbestos, transformation of human cells increased 10 times or more. What it shows is if you are infected with the virus and also exposed to asbestos, probably your risk to the disease is much higher."
