Virus not linked to type of lung cancer

Infection with simian virus 40 (SV40) plays little or no role in the development of mesothelioma, a cancer affecting the lining of the lungs that has been linked to asbestos exposure, according to a report in The Lancet.

In the 1950s and 1960s, several hundred thousand military recruits in the US received a vaccine contaminated with SV40. Since then, concerns have been raised that SV40 may cause cancer after researchers noticed the presence of its DNA in various tumor specimens.

However, the new results indicate that the SV40 DNA seen in these specimens may have simply resulted from contamination in the lab - the virus was not actually present in the tumor before it was removed from the patient.

The current findings are just the latest in a series of reports that have failed to show a link between SV40 and various cancers, such as mesothelioma, lymphoma, and brain tumors.

In the study, Dr. Marc Ladanyi and colleagues, from Memorial Sloan-Kettering Cancer Center in New York, looked for SV40 DNA in 71 mesothelioma samples.

The authors found no evidence of genuine SV40 DNA in the tumor specimens. They did, however, find SV40 DNA that came from circular molecules called plasmids, not from the virus itself. The researchers suggest that these plasmids were probably introduced as contaminants in the lab.

"Because SV40 appears unlikely to have a major role, if any, in human mesotheliomas, (doctors) should continue to consider asbestos exposure as the most likely and most thoroughly established (cause) in individuals with this cancer," the researchers conclude.

SOURCE: The Lancet, September 25, 2004.