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Scientists have also discovered the next defective gene to contribute to an increase in breast cancer susceptibility, which they naturally called BRCA-2. The incidence of BRCA-2 appears to be slightly less than BRCA-1. BRCA-2 is autosomal dominant also and resides on the thirteenth chromosome. Initially, it was believed that the presence of the BRCA-2 gene defect did not appear to increase risk for ovarian cancer. However, it is now clear that these mutations do, in fact, increase the risk of ovarian cancer, perhaps by as much as 20 to 25 percent. This is not as high as with the mutations in BRCA-1, but significant nonetheless. It also appears that men with the defect have an increased incidence of breast cancer.

Our understanding of the genetics of cancer will most likely increase tremendously in the next few years. Current research will be outdated in only months because of how much and how rapidly data are now accumulating.

Here are some general principles that may help you understand cancer at the cellular level and that won’t change over time. Genes are responsible for the production of proteins. Cancer is caused by the production of proteins that, in excess, stimulate uncontrolled cellular replication or the abnormal function of specific proteins that guard against cells going out of control. Gene defects that produce either type of protein in abnormal quantities or with deficits in function can lead to cancer.

There are three types of gene defects that appear to lead to cancer:

1. Oncogene production. This type of mutation leads to the production of proteins giving rise to the malignant transformation of the cell. An example is the Her-2/neu oncogene.
2. Tumor suppressor gene defect. This type of gene functions normally to produce proteins that protect cells against malignant transformation. When the gene gives rise to defective or absent proteins, cancers occur. This defect occurs only when both chromosomes are affected. An example is the P53 gene. The P53 gene is interesting because when a cell’s genetic material is threatened, for example, by a virus or radiation, the P53 gene is activated and makes a protein that prevents the cell from dividing. Any defects in the genes resulting from the “attack” are repaired. Only then can the cell divide again; otherwise, it goes on to die without passing on the faulty genes. When no proteins are produced, however, a mutation can occur and run its course through to the development of cancer.
3. Mutator genes. These abnormal genes accelerate the production of oncogenes or defective tumor suppressor genes.

While we wait for more breakthroughs, doctors obtain information continuously from individual women’s cancers and blood. Commercial genetic testing for breast cancer genes is now available as well. There are some ethical, legal, social, and medical issues created by this newly available genetic information that we all should address. Once armed with this patient information, the medical community must be prepared to counsel women on strategies of surveillance, prevention, and interventions. To give women critical information about increased breast cancer risks without action plans would only be an anxiety-provoking injustice. This new information availability raises concerns about confidentiality involving employers, the insurance industry, and the government.

At a recent national meeting for breast cancer researchers, a true story was told of a young woman who was a member of a possible BRCA-1 family that had been studied by researchers. Since this was a research study, it was not clear if and when she would receive results of the testing, so she had decided to have prophylactic bilateral mastectomies based on her family history alone. While getting preoperative blood work at the hospital, she stopped by the research lab. She explained to the research assistant about her upcoming surgery. The assistant promptly looked up her family file and told the woman that she was BRCA-1 negative. You can imagine her response—first relief, then elation, then guilt for not having what others in her family had. Finally, she was angry; angry at not being informed of her BRCA-1 negativity.

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