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Breast cancer gene identified
Edward R. Winstead

Scientists have identified a new breast cancer gene. The gene makes a protein that is found in breast cancer cells and the salivary gland, but not in other parts of the body.

The protein, called BASE, appears to be secreted from cells and it may enter the bloodstream. If so, a simple blood test could be developed to detect breast cancer. Proteins secreted from prostate cancer cells have been used to diagnose that disease.

"We are excited by the idea that this protein may get into the bloodstream and could be a marker for detecting breast cancer," says Ira Pastan of the National Cancer Institute in Bethesda, Maryland, who led the study.

The protein was found in 30 to 40 percent of the breast cancer cells the researchers tested. But it was not present in 'essential' tissues, such as the brain, liver, kidneys and lungs.

"The goal of this project is to find proteins that are made in breast cancer cells only," says Kristi A. Egland, also of the National Cancer Institute and a member of the research team. BASE is one of about three thousand novel genes identified during the study, and other genes are now being analyzed.

The researchers are looking for proteins that could be diagnostic markers or drug targets. These include molecules that are secreted from cells or that reside on the membranes of cells.

The research is still in the initial stages. It will take a year to make an antibody for detecting the protein in blood, then another year to analyze blood from patients and healthy individuals. If all goes well clinical trials would follow.

The BASE protein appears to be a distant relative of a protein found in horse sweat.

"Salivary glands and breast glands are related," says Pastan. "This protein may have a function in the secretion of breast milk during lactation, for instance. We only looked in normal, non-lactating breasts, which are quite different from lactating breasts."

At the start of the project, Pastan had predicted that the team would definitely find something but it might not be exactly what they were looking for. "In this case," says Egland, "we found one protein we were looking for, and we're hoping to find many more."

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Egland, K.A. et al. Discovery of the breast cancer gene BASE using a molecular approach to enrich for genes encoding membrane and secreted proteins. Proc Natl Acad Sci USA Published online January 21, 2003.

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