All about Breast Cancer Genes
BRCA-1
Recently, scientists have begun to isolate genes responsible for hereditary breast cancer. In 1994 the gene, named Breast Cancer 1 (BRCA-1), was finally isolated in Chromosome #17, one of the 23 pairs of chromosomes found in most human cells. An altered BRCA-1 has been linked to the development of breast and ovarian cancer.
In 1995, scientists developed experimental tests for detecting several recently discovered cancer genes, including BRCA-1. However preliminary studies have shown that testing positive for an altered BRCA-1 gene does not necessarily mean a woman will develop breast cancer. At least 15% of the women who carry the altered gene will never develop the disease. Scientists have no way of knowing yet which women fall into that category. In addition, because BRCA-1 alterations occur in many different places scattered throughout the gene, developing an accurate test will be very difficult to do.
The altered BRCA-1 gene appears in only 5% of the 182,000 breast cancer cases that develop. If a woman tests negative (that is, she does not have the altered gene), this does not necessarily mean she will be free of breast cancer during her lifetime.
BRCA-2
Scientists also have recently located the gene BRCA-2 on Chromosome #13. Like BRCA-1, BRCA-2 appears to be a cancer-causing gene when altered. BRCA-2 appears to account for as many cases of breast cancer as does BRCA-1. BRCA-2 apparently triggers breast cancer in males as well as in females.
P53
There are specific genes in the cells of our bodies that normally help to prevent tumors from forming. One of these tumor-suppressor genes , called P53 ("p" for protein and "53" for its weight) was recently named "Molecule of the Year" by the editors of the journal Science . This protein plays a major role in cell growth. The job of P53 is to prevent (suppress) cells from growing. When it has been damaged or altered, P53 loses its ability to block cell growth. Changes to the gene result in an increased risk of cancer. Almost 50% of all human cancer cells contain a P53 mutation. These cancers are more aggressive and more often fatal. Since P53 is so important for normal cell growth in humans, researchers are continuing to look for ways to diagnose, prevent, and treat cancer associated with P53.
ATM
After more than a decade of intensive searching, researchers have isolated a recessive gene that increases the risk for people to develop some kinds of cancer (as well as a rare genetic disease). The gene, ataxia telangiectasia mutated (ATM) may be involved in many cancers, including breast cancer. The normal role of the ATM gene is to control cell division. Although researchers do not know why an altered ATM causes cancer, 1% of Americans (more than 2 million people) carry at least one copy of the defective form of the gene. By examining the role of altered ATM genes, scientists are hoping to shed some light on what makes cells live, grow, and die.
Besides being associated with cancers, the ATM gene may also identify those individuals who are sensitive to radiation. The altered form of the ATM gene is closely linked to a childhood disorder of the nervous system called Ataxia Telangiectasia, or AT. AT afflicts 1 in 40,000 children in the U.S. and 1 in 200,000 worldwide each year.
P65
With the recent discovery of the gene called P65, scientists are hoping to develop a blood test to detect cancers of the breast and prostate at a much earlier stage than is now possible. The altered form of P65 is linked to the overproduction of certain hormones that may help to cause both breast and prostate cancers. The new blood test, called the tumor blood marker , hopefully will allow doctors to monitor a patient's response to cancer treatment. The level of the P65 protein marker in the blood decreases as tumors are destroyed during therapy. A study is being performed to determine if the tumor marker blood test is suitable for widespread use.
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