Virus Linked to Breast Cancer

November 18, 1999

Judith Zwolak

Virus linked to breast cancer By Judith Zwolak Tulane researchers have identified a virus that exists in about 90 percent of the tumor cells of women who have breast cancer. This human mammary tumor virus is not contagious, but is part of the genetic code that a person inherits, says Robert Garry, professor of microbiology and immunology and the studys lead investigator.

He presented the research at the International Congress of Virology in Sydney, Australia, last month. Its not a virus like the one that causes the common cold, Garry says. Its more like a set of genes that are inherited. The virus is genetically similar to one known to cause cancer in mice-the mouse mammary tumor virus.

Researchers have known about the mouse virus for nearly 50 years and have long searched for a human version, Garry says. The technologies have evolved over the last 10 years so that we have much more sensitive techniques to study genetic material, Garry says. The discovery of the human virus was made possible by the development of new research tools, such as polymerase chain reaction, a technique by which a small fragment of DNA can be rapidly duplicated many times.

In examining 30 samples of breast cancer tissue, Garry found the virus in about 90 percent of the tumors. He also studied 70 samples of tissue from healthy women and found that 20 to 30 percent of these women also carried the virus. Garry says he intends to expand his sample base in future research to clarify the meaning of the results.

These numbers are admittedly small, he says. Well have to establish that this virus is not just a marker. The mouse version is known to cause cancer in mice. We still have to prove that with the human virus. The virus Garry identified is part of a family of retroviruses, which, unlike most viruses, become part of a persons genetic makeup.

Although the bodys natural defenses have a tough time fighting retroviruses, Garry says that researchers have made progress in detection and treatment of viruses that cause cancer, such as the human papillomavirus, which can lead to cervical cancer, and the human T-cell leukemia virus, which is linked to T-cell lymphomas. With the human papillomavirus, researchers have the potential to improve diagnosis by developing techniques directly targeting the virus, he says.

They are also developing a vaccine against the virus and the trials look promising. Garry says the mouse mammary tumor virus similarity to the human version makes it an ideal model for researchers to use to develop diagnostic tools and, eventually, perhaps a vaccine. With this mouse model already in existence, we have a lot going for us, he says.

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