Wilmington, DE, February 24, 2020 -- While radiation is successfully used to treat breast cancer by killing cancer cells, inflammation caused as a side-effect of radiation can have a contrary effect by promoting the survival of triple-negative breast cancer cells, according to research published online in the International Journal of Radiation Biology by Jennifer Sims-Mourtada, Ph.D., director of Translational Breast Cancer Research at ChristianaCare's Helen F. Graham Cancer Center & Research Institute.
Accounting for 15-20% of all breast cancers, triple-negative breast cancer is faster growing than other types of breast cancers.
Dr. Sims-Mourtada's latest study, "Radiation induces an inflammatory response that results in STAT3-dependent changes in cellular plasticity and radioresistance of breast cancer stem-like cells," brings scientists closer to understanding the mechanisms behind this aggressive and hard-to-treat cancer. It shows that inflammation caused by radiation can trigger stem-cell-like characteristics in non-stem breast cancer cells.
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"This is the good and the bad of radiation," Dr. Sims-Mourtada said. "We know radiation induced inflammation can help the immune system to kill tumor cells -- that's good -- but also it can protect cancer stem cells in some cases, and that's bad."
She added, "What's exciting about these findings is we're learning more and more that the environment the tumor is in - its microenvironment - is very important. Historically, research has focused on the genetic defects in the tumor cells. We're now also looking at the larger microenvironment and its contribution to cancer."
The term triple-negative breast cancer refers to the fact that the cancer cells don't have estrogen or progesterone receptors and also don't make too much of the protein called HER2. The cells test "negative" on all 3 tests. These cancers tend to be more common in women under age 40, who are African-American, Latina or who have a BRCA1 mutation.
"My work focuses on cancer stem cells and their origination," Dr. Sims-Mourtada said. "They exist in many cancers, but they're particularly elusive in triple-negative breast cancer. Their abnormal growth capacity and survival mechanisms make them resistant to radiation and chemotherapy and help drive tumor growth."
She and her team applied radiation to triple-negative breast cancer stem cells and to non-stem cells. In both cases, they found radiation induced an inflammatory response that activated the Il-6/Stat3 pathway, which plays a significant role in the growth and survival of cancer stem cells in triple-negative breast cancers. They also found that inhibiting STAT3 blocks the creation of cancer stem cells. Still unclear is the role IL-6/STAT3 plays in transforming a non-stem cell to a stem-cell.