Dioxins are widespread by-products of many industrial processes. Exposure to these environmental contaminants can cause cancer and infertility. In particular, dioxins are known to either promote or antagonize the effects of estrogens—steroid hormones that regulate the function of reproductive tissues and other organs—although the molecular details of these estrogen-related actions remain unclear. In the May 29 Nature, Fumiaki Ohtake and colleagues at the University of Tokyo describe how dioxins alter cellular responses to estrogens in cultured cells and mice (Nature, 423:545-550, May 29, 2003).

Ohtake et al. first looked at dioxin estrogen-related action in cultured breast and uterine cancer cells. Estrogens act by binding to specific receptors present in the cell nucleus: ER-α and ER-β, The activated receptors in turn dock to control regions of target genes and trigger their transcription, initiating a cascade of molecular and cellular events.

Dioxins and related pollutants normally bind to another...

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