A class of drugs already approved for the treatment of estrogen receptor-positive breast cancer may also have the potential to halt the spread of hard-to-treat, triple-negative breast cancer, a new study finds.
Published in the journal Nature Communications, the study reveals that drugs that block an enzyme pathway called CDK 4/6 – known as CDK 4/6 inhibitors – prevented the spread of triple-negative breast cancer in a number of models.
After skin cancer, breast cancer is the most common cancer among women in the United States. In 2017, approximately 252,710 new cases of invasive breast cancer will be diagnosed in the U.S., and around 40,610 women will die from the disease.
Estrogen receptor-positive (ER-positive) breast cancer is the most common form of breast cancer, whereby the breast cancer cells contain receptors for the hormone estrogen. When these receptors receive signals from the hormone, this can promote cancer cell growth.
Similarly, in progesterone receptor-positive (PR-positive) breast cancer, cancer cells contain receptors for the hormone progesterone that can promote cancer cell growth, while in HER2-positive breast cancer, the cells possess too many receptors for the HER2 gene, which can exacerbate the disease.
Thankfully, there are a number of hormonal therapies and other medications that can target estrogen, progesterone, and HER2 receptors in order to treat breast cancer, and CDK 4/6 inhibitors fall into this category. This class of drugs has been approved for the treatment of ER- and HER2-positive breast cancers.
Now, study co-author Dr. Matthew Goetz, leader of the Women’s Cancer Program at Mayo Clinic in Rochester, MN, and colleagues suggest that CDK 4/6 inhibitors may also be effective for the treatment of triple-negative breast cancer.
Triple-negative breast cancer accounts for around 10-20 percent of breast cancers.
In triple-negative breast cancer, cancer cells are absent of estrogen, progesterone, and HER2 receptors. As such, the cancer does not respond to therapies that target these receptors, making it more difficult to treat.
According to Dr. Goetz and colleagues, previous research has shown that CDK 4/6 inhibitors are ineffective in reducing the growth of cancer cells in triple-negative breast cancer.
While the new study confirmed these findings, the team found that CDK 4/6 inhibitors may be effective for halting the spread of cancer cells to other areas of the body – otherwise known as cancer metastasis – in triple-negative breast cancer.
The researchers came to their findings by testing CDK 4/6 inhibitors in a number of triple-negative breast cancer models, including “patient-derived xenografts,” which are immunodeficient mouse models implanted with human tumor tissue.
The team found that while CDK 4/6 inhibitors did not halt the growth of triple-negative breast cancer cells, the drugs significantly reduced the spread of cancer cells to distant organs by targeting a protein called SNAIL, which is known to promote cancer metastasis.
According to the researchers, their study results indicate that CDK 4/6 inhibitors may be beneficial for patients with triple-negative breast cancer.
“These findings may provide a new treatment for the prevention of cancer metastasis. Mayo Clinic is now developing new studies that will focus on the role of CDK 4/6 inhibitors and their potential to inhibit cancer metastasis in women with triple-negative breast cancer who are at highest risk for cancer metastasis.”
Dr. Matthew Goetz