When cells become cancerous they divide rapidly and lose their normal function. The genes regulating cell division have stopped working properly. The mammogram shown here on the left shows normal breast tissue; the whitish area in the tissue on the right is cancerous.  It is also important to remember that having a defective gene does not mean that you are definitely going to get cancer -- it means that you have a higher risk of developing cancer.

Normal vs. Cancerous Breast. Courtesy of the National Cancer Institute

A breast cancer cell as seen through an electron microscope. Courtesy of the National Cancer Institute

In October 1990, Dr. Mary-Claire King's team at the University of California at Berkeley announced that chromosome 17 carried the breast cancer gene called BRCA1. Their discovery set off a scramble to find the specific section of DNA containing the gene. In September 1994, a team led by Dr. Mark Skolnick of the University of Utah Medical Center, which included a group led by National Institute of Environmental Health Sciences scientist Dr. Roger Wiseman, announced the discovery of the BRCA1 gene.

Knowing the BRCA1 gene allows scientists to study the protein whose structure and function the gene governs. Is it not as active as it should be? Is it too active? Are necessary receptors not being formed? BRCA1 contributes only to 5%-10% of inherited breast cancers and may have a role in noninherited breast cancer when the BRCA1 protein somehow gets located in the wrong place. Other genes also are involved in breast cancer and need to be studied. The best way to detect breast cancer early is still regular mammograms.

Woman having mammogram. Courtesy of the National Cancer Institute

"No Cancer" button. Courtesy of the National Heart, Lung, and Blood Institute

Gene therapy trials for all types of cancer are trying three different ideas: correcting the genes that normally prevent tumors but have mutated, increasing the body's immune defense to tumors, and altering normal cells to withstand higher doses of chemotherapy or altering cancer cells to become more sensitive to the drugs. For more on gene therapy see this page.

BRCA1 is a dominant mutation linked to breast cancer.