The Gene Factor:
Gene BRCA1

Breast cancer awareness postage stamp.

One in eight women in the United States develops breast cancer every year. In 1990, Mary-Claire King determined that in 5–10% of those women the cancer is the result of a mutation to a gene on the long arm of chromosome 17, the BRCA1 (Breast Cancer 1) gene. BRCA2, a first cousin to BRCA1, is found on chromosome 13. Both BRCA genes are tumor suppressor genes, and mutations to them allow breast tumors to begin to grow. The BRCA1 gene is made up of more than 1800 amino acids with a molecular mass of 220,000 atomic mass units, which makes it a very large gene. BRCA2 is twice its size. Genes of that magnitude have increased chances for mutations to occur in them.

A great deal has been researched and written about a genetic mutation (in BRCA1) that affects directly only 5–10% of all breast cancers. Since the discovery of BRCA1, it has become clear, however, that most, if not all cancers, are the result of multiple mutations in the genetic structure of cell. Central to this argument is the work of Alfred Knudson of the Fox Chase Cancer Center in Philadelphia, who advanced the so-called "two-hit hypothesis": There must be more than a single genetic mutation for a person to develop cancer.

The importance of BRCA1 increased in 1995 with the finding that although produced inside the cell, BRCA1 actually seems to protect cells walls against cancer. This research is still in progress.

The presence of BRCA1 and BRCA2 can be determined by genetic testing at a cost of more than $2000 per test. This ability raises a number of issues not related to science but to psychology, ethics, and law. Who should be tested? Should the tests be subsidized by government? Should children be tested? Who has a right to know the results of any given test? Presented with the opportunity, how should women decide whether to be tested and if so, what should they do with the results? There are many issues, scientific and otherwise, to be decided where cancer and genetics meet.

For more information, at other Web sites...

Alfred G. Knudson, Jr., M.D. Ph.D. — professional information from the Fox Chase Cancer Center.

Fox Chase Cancer Center — home page of the Philadelphia cancer treatment center.