Virus tied to breast cancer: study

By JEREMY LAURANCE

A virus may play a role in causing breast cancer, say American researchers, suggesting that the disease could be spread through populations.

They found traces of the virus, which is similar to one known to cause breast cancer in mice, in up to three-quarters of tumour samples taken from women worldwide.

Nine out of 10 of the samples that contained the virus were from aggressive breast cancers, suggesting it may cause a more virulent form of the disease.

Paul Levine and colleagues from the George Washington University School of Public Health say in the online edition of the journal Cancer: "These findings provide increasing evidence for a human breast cancer virus with geographic differences in prevalence".

But the findings were dismissed by British expert Rob Newton, of the Cancer Research UK epidemiology unit at Oxford, who said the virus that caused breast cancer in mice had been identified in 1936, and researchers had spent decades looking unsuccessfully for a human equivalent.

"The evidence [for a human equivalent] remains deeply unconvincing and deeply contentious," he said.

The American research involved analysis of 38 tissue samples taken from Tunisian women with breast cancer. The tissue samples were tested in two independent US laboratories.

The results showed 74 per cent of the samples tested positive for viral sequences from the mouse mammary tumour virus (MMTV), a much higher proportion than found in tissue samples from breast cancer patients in other parts of the world.

Previous studies have shown MMTV virus present in 36 per cent of American women with breast cancer, in 38 per cent from Italy, 42 per cent from Australia and 31 per cent from Argentina.

The researchers say: "MMTV may be spread by a species of house mouse that is extremely common in North Africa but less so in the US. Studies show that some colonies of these mice are commonly infected with MMTV."

Cancer experts believe the study of viruses is one of the most important areas of research because infections are second only to tobacco as a cause of cancer and, once identified, vaccines can be developed.

But Dr Newton said the geographical variations in breast cancer could be due to differences in the average age of first birth, start of menstruation and menopause.

Last year, University of New South Wales researchers said men who developed breast cancer could also carry the MMTV virus.


Herald Feature: Health

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