Vitamin D may be a breast cancer therapy UPI 1/23/2013 4:08:18 AM ST. LOUIS, Jan. 22 (UPI) -- Vitamin D may be involved in a possible new breast cancer therapy, U.S. and Spanish researchers say. Susana Gonzalo, an assistant professor of biochemistry and molecular biology at Saint Louis University, and her team identified one pathway 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, 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, Gonzalo said. Experiments performed in Gonzalo's laboratory, in collaboration with the laboratories of Xavier Matias-Guiu and Adriana Duso in Spain, showed activation of this novel pathway not only allowed 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, Gonzalo said. The findings were published in The Journal of Cell Biology.