Protein could help detect aggressive breast cancer

By Amy Norton

NEW YORK (Reuters Health) - Scientists have identified a cellular protein that could eventually help diagnose and manage a particularly aggressive form of breast cancer.

The protein, called nestin, has been known to exist in adult stem cells in the central nervous system. Stem cells are primitive cells that can develop into mature, specialized cells.

The new study, published in the journal Cancer Research, found that cells in normal breast tissue express nestin. But more importantly, extremely high levels of nestin exist in basal epithelial breast tumors -- an especially aggressive type of breast cancer that's most common in younger black women.

The findings are consistent with past research has suggested about basal epithelial breast tumors -- that they arise from breast stem cells that have gone genetically awry. The tumors are more deadly than other forms of breast cancer, as they progress quickly and have a high rate of recurrence.

A key problem in battling the disease is that, at the molecular level, basal epithelial tumors have none of the markers that aid in treating other forms of breast cancer.

That is, they have neither receptors for the hormones estrogen or progesterone, nor a protein called HER2. This means that women with basal epithelial tumors cannot be helped by drugs that target estrogen and progesterone -- including tamoxifen and aromatase inhibitors -- or by the anti-HER2 therapy Herceptin.

This lack of molecular markers also complicates diagnosis.

There's no definitive test for basal epithelial breast cancer, Dr. James DiRenzo, the lead author of the new study, told Reuters Health. It's only recognized once a woman's cancer appears to be a "triple negative," he explained -- no receptors for estrogen or progesterone, and no HER2.

A "definitive and selective marker" for basal epithelial tumors could help doctors diagnose them more quickly, according to DiRenzo, an assistant professor of pharmacology at Dartmouth Medical School in Hanover, New Hampshire.

It could also aid in monitoring cancer recurrence after a woman is treated, researchers say. Basal epithelial tumors are notorious for recurring within a short period.

But more research is still needed to prove whether nestin is that definitive marker, DiRenzo said. The current findings are based on an analysis of a small number of breast tumor samples, 16 of which were basal epithelial tumors.

Fourteen of those samples were found to have high levels of nestin, whereas tumors with hormone receptors or HER2 showed no evidence of the protein.

The next step, DiRenzo said, is to confirm the findings with a similar, but much larger, study.

What's more, he noted, the findings raise questions about the role nestin might play in the development of basal epithelial tumors -- and whether the protein could become a target for new therapies.

SOURCE: Cancer Research, January 15, 2007.