Protein Found to Halt Breast Cancer Cells

Researchers said Thursday that they had isolated a human protein that in the laboratory was found to stop the growth of breast cancer cells without affecting other types of human cells.

The scientists said the discovery may mark a significant advance in the search for a breast cancer treatment and may ultimately help lead to a strategy for prevention of the malignancy, which now strikes one American woman in 10.

A team of University of Michigan scientists led by Dr. Max S. Wicha, writing in Friday’s Science magazine, said it had isolated a human protein that it believes plays a key role in the body’s own system for controlling cell growth.

The team has dubbed the protein mammastatin and is now trying to produce it in sufficient quantities to test it in laboratory animals and ultimately in humans, Wicha said in a telephone interview.

“Mammastatin, which is produced by normal breast cells, is a potent inhibitor of breast cancer cells growing in the laboratory,” Wicha said.

“It specifically stops the growth of breast cancer cells but not cells from other tissues.”

Wicha said he and his colleagues were now using genetic engineering techniques to try to clone the human gene responsible for producing the protein.

Achieving this would enable them to make relatively large amounts of the compound in the laboratory, but it may take several years to accomplish this, he said.

About 142,000 American women will be diagnosed with breast cancer and an estimated 43,000 will die of the disease this year, according to the American Cancer Society.

In normal breast tissue, cell growth appears to be controlled by a balance between growth inhibitors and growth stimulators, the researchers said.

In cancerous tissues, abnormal cell growth may occur because a stimulator overpowers its inhibitor, creating an imbalance, they said.

The scientists said they had developed a test to measure mammastatin in blood and found it to be present in all women, though at widely varying levels.