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Triple negative breast cancer
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ER+ and HER2+ breast cancers are often treated with targeted therapy, but no such treatment is available for triple-negative breast cancer (TNBC). Early laboratory research suggests that vitamin D and androgen receptors might be potential targets for new treatment for TNBC. However, many more studies are needed before these targets can be tested against human breast cancer (7/5/16).
Learning whether researchers can utilize vitamin D and/or androgen receptors as targets for triple-negative breast cancer treatments.
Researchers have developed treatments that target estrogen receptor positive (ER+) breast cancer and human epidermal growth factor receptor 2-positive (HER2+) breast cancers, which are approved and used clinically. Treatment development for triple-negative breast cancer (TNBC) has not been as successful because these cancers do not have the same targets.
This is early research. The researchers used these treatments on breast cancer cells grown in the lab, not in mice or humans. This means researchers do not know if these treatments are effective or safe for breast cancer patients. While some of the drugs used in the study are FDA approved for treatment of castration-resistant prostate cancer, others have not been used in humans. Clearly, much more work needs to be done before drugs targeting vitamin D or androgen receptors can be used to treat breast cancer. For now, this is an interesting new line of research that may one day lead to new therapy for triple-negative breast cancer.
Oncology Nurse Advisor
Sylvester Comprehensive Cancer Center
Triple-negative breast cancers (TNBC) do not have receptors for estrogen, progesterone, or human epidermal growth factor receptor 2 (HER2). Patients diagnosed with TNBC typically have a poorer prognosis than patients with other breast cancers. However, the researchers previously noted that about two of three triple-negative breast cancers have vitamin D receptors, androgen receptors, or both. Ankita Thakkar and colleagues at the University of Miami, Miller School of Medicine, published a study in the journal Breast Cancer Research and Treatment that looked at using drugs that target the vitamin D receptor and/or the androgen receptor to kill breast cancer cells in the laboratory.
Can vitamin D and androgen receptors be used as drug targets for triple-negative breast cancer treatments?
This research study used human breast cancer cells grown in the lab. Researchers grew the cells in a laboratory environment that provided all of the nutrients the cells needed to grow and divide. The breast cancer cells were considered triple negative, in other words, they did not have estrogen receptors (ER-), progesterone receptors (PR-), or human epidermal growth factor receptors 2 (HER2-). They did, however, have vitamin D and androgen receptors. The researchers treated these cells with various agents to determine whether the vitamin D and androgen receptors might be targets for triple-negative breast cancer treatment. Two of the drugs they used for the androgen receptor, Enzalutamide and Bicalutamide, are FDA approved for castration-resistant prostate cancer but have not been used for breast cancer.
This research found that drugs targeting the androgen receptor drugs stopped breast cancer cells from growing, regardless of how many androgen receptors the cell had. This is different from what the researchers found in human prostate cancer cells grown in the lab, where the extent of the drug’s success depended on how much androgen receptor was present in the cancer cell. These are new drugs, and it is not known if they can be safely used in humans. Even though some of the drugs used are approved for castration-resistant prostate cancer, more laboratory research and subsequent clinical trials are needed before we know whether or not these drugs are safe and effective for women with breast cancer. For now, it is an interesting observation that may or may not lead to new treatment.
This research suggests that it is possible that vitamin D and androgen receptors may be used someday to target triple-negative breast cancers that have those receptors. However, this is early work using breast cancer cells grown in the lab. It will be some time before these drugs can be tested in a clinical trial for potential use in the clinic.
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Thakkar A, Wang B, Picon-Ruiz M, et al. “Vitamin D and androgen receptor-targeted therapy for triple-negative breast cancer.” Breast Cancer Research and Treatment. Published online first on April 27, 2016.
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