Tamoxifen

**Semantic type:** Organic Chemical|Pharmacologic Substance

**Definition:** An antineoplastic nonsteroidal selective estrogen receptor modulator (SERM). Tamoxifen competitively inhibits the binding of estradiol to estrogen receptors, thereby preventing the receptor from binding to the estrogen-response element on DNA. The result is a reduction in DNA synthesis and cellular response to estrogen. In addition, tamoxifen up-regulates the production of transforming growth factor B (TGFb), a factor that inhibits tumor cell growth, and down-regulates insulin-like growth factor 1 (IGF-1), a factor that stimulates breast cancer cell growth.

**Synonyms:** - 1-p-beta-dimethylamino-ethoxyphenyl-trans-1,2-diphenylbut-1-ene - TAMOXIFEN - TMX - tamoxifen