4-Hydroxyestradiol

**Semantic type:** Organic Chemical

**Definition:** A metabolite formed during the metabolism of 17beta-estradiol by hydroxylation of the carbon at position 4 by cytochrome P450 1B1, with potential carcinogenic activity. The mechanism of action for the tumor promoting activity of 4-hydroxyestradiol (4-OHE2) is not entirely known but this metabolite undergoes metabolic redox cycling with its oxidized quinoid form, estradiol 3,4-quinone, and generates reactive oxygen species (ROS), which induce oxidative DNA damage. 4-OHE2 also activates nuclear factor-kappaB (NF-kB) and extracellular signal-regulated kinase/mitogen-activated protein kinase pathways, and induces the expression of certain genes through activation of the estrogen receptor (ER), which stimulates cellular proliferation in susceptible cells.

**Synonyms:** - 3,4,17beta-Estriol - 3,4,17beta-Trihydroxy-1,3,5[10]-Estratriene - 4-HYDROXYESTRADIOL - 4-Hydroxy-17-Beta-Estradiol - 4-Hydroxyestradiol-17beta - 4-OH-Estradiol - 4-OHE2 - 4OHE2 - Estra-1,3,5(10)-Triene-3,14,17beta-Triol