Treatment with three drugs that inhibit the human epidermal growth factor receptor (HER) stops HER2-positive breast cancer tumor growth in mice better than treatment with just one or two of the drugs.
Grazia Arpino, M.D., Ph.D., of Baylor College of Medicine in Houston, and colleagues measured tumor growth in mice with human breast cancer tumors that overexpress HER2. Some mice received one of three HER inhibitors - pertuzumab, trastuzumab, or gefitinib - or a combination of two or three of the drugs. The mice also received different combinations of hormonal therapy, including estrogen supplements, estrogen withdrawl, and tamoxifen.
A combination of all three HER inhibitors was more effective at slowing tumor growth than a single drug or combination of two drugs. The tumors grew after 49 days in mice that received all three drugs, compared with 21 days for mice in the estrogen-only group and 28 days for mice that got estrogen and pertuzumab. The addition of tamoxifen to any of the three drugs also inhibited tumors growth in the mice, but after two months the tumors grew resistant to the treatment. In mice treated with all three HER inhibitors plus tamoxifen or estrogen withdrawal, most tumors completely disappeared and did not progress for more than 189 days after treatment.
"These results support the hypothesis that acquired resistance to the individual agents is the result of [an] incomplete blockade of this complex network at the receptor level and not activation of a different survival pathway," the authors write.
Contact: Kimberlee Barbour
Other highlights in the May 2 JNCI
Note: The Journal of the National Cancer Institute is published by Oxford University Press and is not affiliated with the National Cancer Institute. Attribution to the Journal of the National Cancer Institute is requested in all news coverage. Visit the Journal online at jnci.oxfordjournals/.
Contact: Liz Savage
Journal of the National Cancer Institute
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