Mapping Ignorance: Cut the stem off to fight breast cancer
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Estrogens are steroid hormones affecting several organs including mammary glands. More precisely, these glands exert their action by means of estrogens through the estrogen receptor (ER), a transcription factor belonging to the family of nuclear receptors. So far, two types of ERs have been identified: alpha and beta. ER-beta is expressed in all mammary cells while ER-alpha is found in some particular cells (specifically, it is expressed in 20% of luminal cells, which form the lumen of the conducts and the mammary lobules). Experiments with mice have proved that if one of these genes is “removed”, this has an effect on the development of the gland. Thus, mice lacking the alpha receptor exhibit an anomalous breast epithelium, composed of rudimentary ducts. Mice lacking beta receptor show a normal morphology. In light of these results, ER-alpha must be the receptor intervening in the formation of the mammary gland.