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US Researchers Discover New Breast Cancer Gene - 2003-01-21

U.S. researchers have discovered another breast cancer gene that may provide a new point of attack against the disease. The molecule is common to many types of breast cancer.

Scientists at the U.S. government's National Cancer Institute found the gene while looking in test tubes at cells extracted from different types of breast cancers. They were on a genetic fishing expedition, not knowing what they would catch. Their goal was to find any proteins produced in abundance in breast cancer cells, but absent in healthy tissues.

Proteins are the product of genes and carry out the functions of life. A protein found in cancer but not in normal tissue is seen as a clear sign of a cancer gene at work.

The laboratory probe of breast cancer cells yielded 3,000 proteins unrelated to any known genes. Research leader Ira Pastan says one gene in particular caught researchers attention because it was present in many types of breast cancer, both local tumors and those that had metastasized, or spread.

"We examined how frequently the gene is expressed in breast cancer and it is expressed in about half of the samples we analyzed," he said. "The only other place we found the gene to be expressed besides breast cancer is salivary gland. I guess that is not entirely surprising since in development of organs, salivary gland and breast glands have a common origin."

The function of the gene, called BASE, is not yet known, but the researchers' study published in the Proceedings of the U.S. National Academy of Sciences says its structure suggests it is secreted from breast cancer cells into the blood rather than working only within cells. This is useful because it could be detected by a simple blood test, helping diagnose many different types of breast cancer. Mr. Pastan's group is developing such a test.

"The second importance of the finding is since the protein is made by lots of breast cancers, it could be used as a target for new vaccines to treat breast cancer," he said. "The side effect might be dryness of the mouth or some other response related to salivary gland damage, but that would be an acceptable side effect, we think, if we could do something to treat metastatic breast cancer." The researchers say this is not the type of breast cancer gene that is inherited and which creates a predisposition to breast cancer. Rather, it is found in the far more common sporadic, or random, breast cancers in which cells mutate in response to some environmental factor.

Although scientists have discovered hundreds of genes involved in breast cancer, some are more influential in development of the disease than others. BASE, the newly discovered gene, appears to be one of them, according to breast cancer treatment physician Lyndsay Harris of the Dana Farber Cancer Institute in Boston.

"What sets certain genes apart is that they appear to drive the process," he said. "verything flows from them. The BASE gene has characteristics like that. It is on the surface of the cells. It's a receptor. These are things that make it a little more likely to be important at driving the process of carcinogenesis."

At the National Cancer Institute, the researchers say their next goal now that they have found the new gene is to figure out how to attack it with drugs or a vaccine.