Scientists Identify Genetic Link to Breast Cancer

The key to unlocking the cure for breast cancer is to gain a better understanding of how and why the disease develops and spreads. Knowing the risk factors and being aware that you may have inherited a high risk of breast or other types of cancers is only the beginning.

Better methods of detection, including the use of magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), breast-specific gamma imaging (BSGI) and positron emission mammography (PEM) , are another step forward in conquering the deadly disease. The MRI identifies breast lumps, and MRS measures specific molecules known to accumulate in cancer cells. BSGI and PEM rely on the use of radiotracers to detect cancer cells instead of the X-rays used in mammograms. All are non-invasive and can significantly improve the ability to distinguish between cancerous and non-cancerous tumors.

While surgery, chemotherapy, radiation treatments, and new drug combinations have proven successful in the battle against breast cancer, researchers continue to search for ways to advance in the fight by working to understand the genetic factors surrounding the disease.

Cancer occurs when abnormal cells in the body grow out of control. They are named after the part of the body where abnormal cell growth begins. Therefore, breast cancers are cancer cells originating from the breast. Breast cancer cells that spread to other parts of the body are called metastases.

A new discovery that could lead to further advancement in the battle against breast cancer is the identification of a gene linked to poor-prognosis breast cancer. The gene was detected by genomic profiling studies and may lead the way to a new course of treatment for the disease. The discovery confirms beliefs in the possibility that such a gene may exist in the body’s 8q22 region of chromosome 8. Although researchers have known for some time that an increased number of copies of 8q22 creates a poor prognosis for a breast cancer patient since it promotes the spread of cancer cells, the reason for this had remained unclear until now.

Yibin Kang, Ph.D., of Princeton University, and colleagues conducted a study of the metastasis gene metadherin (MTDH) that showed the gene promotes both chemoresistance and metastasis in 30 to 40 percent of breast cancers. Although most normal DNA sequences contain only two copies of a gene, the researchers found in studies on lab mice, that some breast tumors had as many as eight copies of this gene segment. The team then studied human breast tumor samples taken from 250 patients to search for these genetic abnormalities and found the gene MTDH was overly active or expressed in aggressive tumors. The full report can be found in the January 6th issue of Cancer Cell.

Another important result of the study is the possibility that drugs capable of blocking the gene could prevent local tumors from spreading, thereby increasing a breast cancer patient’s chances for survival. In a statement, Dr. Kang said, “Inhibiting this gene in breast cancer patients will simultaneously achieve two important goals: reduce the chance of recurrence, and, at the same time, decrease the risk of metastatic dissemination.” He went on to explain, “Clinically, these are the two major reasons why breast cancer patients die from the disease.”

According to the CDC, second only to non-melanoma skin cancer, breast cancer is the most common form of cancer in women and is the number one cause of cancer death in Hispanic women. It is also the second most common cause of cancer death in white, black, Asian/Pacific Islander, and American Indian/Alaska Native women.

The most recent statistics compiled from 2004 reveal that 186,772 women and 1,815 men were diagnosed with breast cancer and that 40,954 women and 362 men died from the disease. Projections by the National Cancer Institute for 2008 estimated 182,460 new cases in women and 1990 cases in men with expected deaths of 40,480 women and 450 men. These estimates show a decrease in the number of deaths in women while projecting an increase in the number of deaths for men.

Although more than 98 percent of breast cancer patients whose cancer cells do not spread live five years or more, there is only a 27 percent survival rate for those patients whose cancer does spread to other organs. Halting the spread of cancer cells is crucial to the chance for survival. Kang is hopeful that the discovery of the gene linked to the spread of cancer will lead to drugs that will not prevent breast cancer from spreading, but also make the cancer more responsive to treatment. In addition, Kang said that the gene could also be significant in other types of cancers, including prostate cancer.