Radiation Empowers Breast Cancer Stem Cells

Breast cancer radiation generates breast cancer stem cells

(RxWiki News) Radiation therapy following breast cancer surgery is common, because it's clinically proven to help kill any remaining cancer cells in the area. A recent laboratory study discovered this powerful energy empowers other cancer cells as well.

New research has found that in addition to killing tumor cells, radiotherapy turns other cancer cells into breast cancer stem cells that tend to evade both radiation and chemotherapy. And breast cancer stem cells are believed to be the only cause for tumors to return.

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Researchers with the University of California Los Angeles (UCLA) Jonsson Comprehensive Cancer Center uncovered that these stem cells actually work against radiation treatment. Knowing this will help scientists find what's behind this transformation to prevent it from ever happening.

Such a discovery would make breast cancer radiation treatment even more effective, according to study senior author, radiation treatment for breast cancer could become even more effective, said study senior author Dr. Frank Pajonk, an associate professor of radiation oncology and Jonsson Cancer Center researcher.

To understand more about what this means, dailyRx spoke with Wendy Woodward, M.D., Ph.D., section chief of breast radiation oncology at The University of Texas MD Anderson Cancer Center, who began by saying that "first and foremost it does not imply that radiation is not safe or appropriate for women with breast cancer who are at high risk of in-breast or chest wall recurrence without radiation."

"Numerous clinical studies have repeatedly shown that radiation improves breast cancer specific survival for appropriately selected women with breast cancer, and we have even published a study in collaboration with the British Columbia Cancer Agency showing that women who experience a recurrence after radiation, have outcomes that are equivalent to women who recur but have never had radiation," said Dr. Woodward, who was not involved in this research.

In the laboratory, Dr. Pajonk and his team traced the formation so-called induced breast cancer stem cells (iBCSC) in mice models. Researchers exposed these breast cancer cells to radiation and placed them in mice, after eliminating a smaller pool of breast cancer stem cells.

Pajonk and his team used imaging technology they had developed to look at cancer stem cells. So they were able to observe how the iBCSC formed after being exposed to radiation.

They found that these cells were "remarkably similar to breast cancer stem cells found in tumors that had not been irradiated," Pajonk said. Researchers learned these iBCSC were 30 times more capable of forming new tumors than the breast cancer cells from which they had originated and that had not been irradiated.

The team also found that the iBCSC had a more than 30-fold increased ability to form tumors compared to the non-irradiated breast cancer cells from which they originated.

Dr. Woodward explained, "This [study] suggests that the way radiation is given in the clinic is safe and effective and does not make cancer more aggressive. The reason this laboratory based paper is so important then is because we know that some breast cancers are very aggressive and resistant to treatment, and this work shows us another way that under specific conditions in the laboratory the tumors we aren’t curing are evading our best therapies," Dr. Woodward said.

She concludes, "Hopefully this better understanding will lead to new therapies to make these tumors sensitive to radiation. This knowledge cannot only help select targets to promote radiation sensitivity but also guide our use of them in designing clinical trials."

The study appears Feb. 13, 2012 in the early online edition of the peer-reviewed journal Stem Cells.

This study was funded by the National Cancer Institute, the California Breast Cancer Research Program and the Department of Defense.