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Cross talk between hormone receptors has unexpected effects

One of the first clues pathologists look for in tissue from a newly diagnosed breast cancer patient is the estrogen receptor, a nuclear protein that converts hormonal messages in the bloodstream into instructions for the cell about how to behave. They also look for the presence of progesterone receptors, primarily to confirm that the estrogen receptor is active.

In the June 24 issue of Science Advances, however, researchers radically upgrade the significance of the progesterone receptor. They show that when exposed to estrogens and progestins, these receptor proteins interact with different sets of binding sites in the cell’s chromosomes, with the progesterone receptor dramatically altering how estrogen receptors interact with the cell’s DNA.

Chart illustrating that tumor cells in the placebo-treated mice grew rapidly
Tumor cells in the placebo-treated mice grew rapidly. Tamoxifen prevented the tumors from growing. CDB4124 initially caused the tumors to regress, but after 35 days, the tumors began growing again. The combination of tamoxifen and CDB4124 caused tumors to shrink 70 percent by day 60
Image Credit: The Greene Laboratory