SUMMARY OF RESEARCH ON THE MOUSE MAMMARY TUMOR VIRUS


Scientists have proven that the human papilloma virus (“HPV”) causes cervical cancer. In fact, Dr. Van Hausen, the scientist who first made this discovery, won the Nobel Prize for medicine in 2008 for his groundbreaking research.
But HPV is not the only virus known to cause cancer. At least six other viruses are proven cancer agents and scientists now believe that as much as 15-20% of all human cancers are of viral origin. Of all of the potential tumor viruses presently under investigation the one with the greatest potential impact on women is the mouse mammary tumor virus (“MMTV”) a virus found in mice that causes breast cancer in 95% of the animals it infects.
Although MMTV was first discovered in 1936, research proceeded slowly at first, primarily because scientists lacked the technology to study it well. But as technology improved, and as other viruses were shown to cause other cancers, there was renewed interest in MMTV and its relation to human breast cancer.
In the 19990’s Dr. Beatriz Pogo of Mt. Sinai University found a DNA “fingerprint” that was 98% similar to MMTV in 38% of the breast cancer tissues she examined. She also discovered that the DNA fingerprint contained elements that responded to hormonal stimulation, as does MMTV.
During this same time, another researcher, Dr. Polly Etkind, found viral sequences similar to MMTV in patients who had both breast cancer and lymphoma, Interestingly, these sequences were not found in the normal breast tissue of these patients.
To date, at least seven groups of researchers have found viral gene sequences in human breast cancer tissue and have reported their findings in ten separate studies. One group has reported that the virus, that they now refer to as human mammary tumor virus, HMTV, can infect and rapidly spread to normal human breast cells.
Dr. Paul Levine of George Washington University discovered that 74% of Tunisian women with breast cancer had evidence of MMTV compared to only 36% of women in the United States. But, interestingly, 75% of women in the United States who have inflammatory breast cancer show evidence of MMTV.
To prove that MMTV/HMTV causes human breast cancer we must know exactly where and how the virus infects humans and we must determine exactly how the virus alters the DNA of normal breast cells and transforms them into cancer cells.
The question remains open: Does a virus cause breast cancer in women? The lines of inquiry have not yet converged to answer that question, but Pogo, Levine, Holland, Etkind and others, here in the United States and around the world, continue their quest to answer the question and solve the puzzle.
If researchers can confirm a causal connection between MMTV and human breast cancer, then the implications for the treatment and prevention of breast cancer would be dramatic. Another 1.3 million new cases of breast cancer will be diagnosed around the world by the end of 2009, and hundreds of thousands more women will die this year of the disease. Millions of lives and billions of dollars are at stake: it is a question that needs to be answered…as soon as possible.