For years, clinicians have known that the breast cancer drug tamoxifen works by blocking the effects of estrogen in breast tissue. But they could only guess why the drug was effective for just about 5 years.
In the July 30 issue of Science, researchers from Duke University Medical Center and Novalon Pharmaceutical Corp offer an explanation. In laboratory studies, they found that tamoxifen causes estrogen receptors in the breast to change shape. The receptors form a unique pocket shape where proteins inside the cell begin to bind to the receptor. The binding action causes the cells to respond differently to tamoxifen, viewing the drug as if it were an estrogen rather than an antiestrogen, and cancer growth recurs.
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