Posted on July 31st, 2012 by
A subset of triple-negative breast cancers contains a genetic change that contributes to cancer growth and may be possible to target with drugs. These results were published in Nature.
Each year, more than 220,000 women are diagnosed with breast cancer in the United States. For these women, tests to identify certain characteristics of the tumor play an important role in treatment selection. Cancers that are hormone receptor-positive, for example, are commonly treated with hormonal therapies such as tamoxifen or an aromatase inhibitor. Similarly, cancers that overexpress a protein known as HER2 tend to respond to treatment with a HER2-targeted drug such as Herceptin® (trastuzumab).
Triple-negative breast cancer refers to breast cancer that is estrogen receptor-negative, progesterone receptor-negative, and HER2-negative. This type of breast cancer currently has fewer treatment options than other types of breast cancer because if doesn’t respond to hormonal therapy or HER2-targeted therapy. Ongoing research into the biologic underpinnings of triple-negative breast cancer may provide clues about how to target this type of breast cancer.
A study recently published in the journal Nature sought to identify genetic changes that may contribute to certain types of breast cancer, including triple-negative breast cancer. The study collected tumor samples from 103 breast cancer patients from Mexico and Vietnam. The DNA from the tumor samples was compared with DNA from normal tissue.
A genetic change that was identified in a triple-negative sample involved a fusion of two genes: MAGI3 and AKT3. The protein produced by this fusion gene is thought to contribute to cancer growth. When the researchers looked for this fusion gene in another set of tumor samples, they found it in 7% of triple-negative samples (5 out of 72).
Drugs that target this biological pathway are already being investigated for other purposes, and may eventually prove to be useful for triple-negative breast cancers that contain the fusion gene. If researchers are able to find a targeted drug that is effective against these cancers, it would be an important advance in the treatment of triple-negative breast cancer. Only a subset of triple-negative breast cancers contain the genetic change identified in this study, but ongoing research may identify additional targets.
Reference: Banerji S, Cibulskis K, Rangel-Escareno C et al. Sequence analysis of mutations and translocations across breast cancer subtypes. Nature;2012;486:405-409.
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