The findings shed light on a possible cause of a group of lymph node cancers that has become increasingly more common in the last 30 years, and simultaneously casts a disturbing shadow on the long-term effects of a contaminated batch of polio vaccine made more than 40 years ago.

The research teams, from Baylor University Medical School in Houston and the University of Texas Medical School in Dallas published their findings in the March 9 issue of The Lancet.

Dr. Janet Butel of Baylor says the findings offer hope for better treatment and the potential of preventing a significant number of the approximately 287,000 new non-Hodgkin lymphoma cases are diagnosed worldwide every year.

"This is an important finding because cancers with a viral cause offer the possibility of developing new and better ways of treating and diagnosing and ultimately preventing the tumor," said Dr. Janet Butel, chairman of the department of molecular virology and microbiology at Baylor.

At the same time she says their finding suggests monkey viruses once introduced into humans may be transmitted to others. The virus named simian virus 40 (SV40) usually infects rhesus monkeys. However, in the 1950s and early 1960s, some batches of polio vaccine became accidentally infected with the virus. The vaccine was then given to millions of people worldwide.

Because some patients with SV40-positive tumors were born after 1963 and would not have been exposed to the contaminated vaccine, it appears that SV40 continues to spread among humans in ways that are not yet clear.

"This study further demonstrates that humans can be infected by SV40, an infection that was not suspected in the past," she said. Recently, evidence of SV40 infection has also been found in human brain tumors, tumors of the lining of the chest and abdomen (mesothelioma), and osteosarcomas.

In their study, Butel and Dr. Regis Vilchez, an assistant professor of medicine and first author, analyzed samples from 154 patients who had lymphomas and found 42 percent positive for SV40 DNA, whereas many control samples were negative.

In a similar study at the University of Texas Southwestern led by Dr. Adi Gazdar, researchers examined nearly 400 cancerous and healthy blood samples, and found the viral footprint for SV40 in the tumors of 43 percent of the non-Hodgkin lymphoma patients.

The virus was present in only 9 percent of patients with Hodgkin’s lymphoma, a different form of the disease that affects primarily a type of immune system cell, called B cells. This type of lymphoma is highly curable.

By comparison, zero percent of healthy subjects and patients with other types of adult or pediatric cancers, other than bone tumors showed any evidence of the SV40 virus.

While the findings of both studys hold great promise, there is a long way to go before any clinical applications of the data are developed. It is more likely that they will lead to screening and early detection techniques before yielding vaccines or therapies.

“We have some clues, but it’s not going to be fast,” Gazdar said. “The first thing is for scientists around the world to duplicate our research. Fortunately, Dr. Janet Butel, a noted virologist from Baylor College of Medicine in Houston, has independently obtained almost identical data. These two extensive and carefully done studies present a powerful one-two punch against skeptics.”

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