Vitamin D Holds Promise in Battling a Deadly Breast Cancer, SLU Researchers Say

In research published in the Jan. 17 issue of The Journal of Cell Biology, a team led by Susana Gonzalo, Ph.D., assistant professor of biochemistry and molecular biology at Saint Louis University, has discovered a molecular pathway that contributes to triple-negative breast cancer, an often deadly and treatment resistant form of cancer that tends to strike younger women. In addition, Gonzalo and her team identified vitamin D and some protease inhibitors as possible new therapies and discovered a set of three biomarkers that can help to identify patients who could benefit from the treatment.

In the recent breakthrough, which was funded in part by a $500,000 Department of Defense grant, Gonzalo’s lab identified one pathway that is activated in breast cancers with the poorest prognosis, such as those classified as triple-negative. These cancers often strike younger women and are harder to treat than any other type of breast cancer. Women who are born with BRCA1 gene mutations are at increased risk for developing breast and ovarian cancers within their lifetime, and the tumors that arise are frequently the triple-negative type. Although chemotherapy is the most effective treatment for triple-negative breast cancer, it has profound secondary effects. Understanding the biology of triple-negative breast cancers will help to develop less toxic therapeutic strategies.

Experiments performed in Gonzalo's laboratory, in collaboration with the laboratories of Xavier Matias-Guiu and Adriana Duso (IRBLleida, Spain), showed that activation of this novel pathway not only allows tumor cells to grow unchecked, but also explains the reduced sensitivity of these types of tumors to current therapeutic strategies. Importantly, vitamin D plays a role in turning off this pathway, providing a safe and cost-effective strategy to fight these types of tumors.

THE SCIENCE

For molecular biologists like Gonzalo who look for answers below the cellular level to discover why some people develop cancer, the search often involves tracing a chain of events to try to understand cause and effect of the behavior between several genes and the proteins which they express. In order to understand these complex pathways, researchers often turn levels of proteins on or off by expressing one gene or suppressing another. Part of a researcher’s challenge is determining what the function of each component of a pathway is.

The cell employs a complex mechanism to protect genetic information and ensure that damaged DNA is not passed on to daughter cells. Cells have built in checkpoints and fail safes to ensure the accuracy of their DNA code and are able to slow or stop their own proliferation if the information is compromised. Loss of these checkpoints and the accumulation of damaged DNA often leads to cancer.

The Pathway
BRCA1 is a well-established tumor suppressor gene. Women who carry mutations in this gene have a high risk of developing breast and ovarian cancer. Tumors that arise often lack expression of three receptors: estrogen, progesterone and HER2 (thus, “triple-negative”), and do not respond to hormone therapy.