Estrone sulfate

Estrone sulfate (E1S), or estrone 3-sulfate, is a natural, endogenous steroid and an estrogen ester and conjugate. In addition to its role as a natural hormone, estrone sulfate is used as a medication, for instance in menopausal hormone therapy; for information on estrone sulfate as a medication, see the estrone sulfate (medication) article. E1S itself is biologically inactive, with less than 1% of the relative binding affinity of estradiol for the ERα and ERβ. However, it can be transformed by steroid sulfatase (also known as estrogen sulfatase) into estrone, an estrogen. Simultaneously, estrogen sulfotransferases, including SULT1A1 and SULT1E1, convert estrone to E1S, resulting in an equilibrium between the two steroids in various tissues. Estrone can also be converted by 17β-hydroxysteroid dehydrogenases into the more potent estrogen estradiol. E1S levels are much higher than those of estrone and estradiol, and it is thought to serve as a long-lasting reservoir for estrone and estradiol in the body. In accordance, E1S has been found to transactivate the estrogen receptor at physiologically relevant concentrations. This was diminished with co-application of irosustat (STX-64), a steroid sulfatase inhibitor, indicating the importance of transformation of estrone sulfate into estrone in the estrogenicity of E1S. Unlike unconjugated estradiol and estrone, which are lipophilic compounds, E1S is an anion and is hydrophilic. As a result of this, whereas estradiol and estrone are able to readily diffuse through the lipid bilayers of cells, E1S is unable to permeate through cell membranes. Instead, estrone sulfate is transported into cells in a tissue-specific manner by active transport via organic-anion-transporting polypeptides (OATPs), including OATP1A2, OATP1B1, OATP1B3, OATP1C1, OATP2B1, OATP3A1, OATP4A1, and OATP4C1, as well as by the sodium-dependent organic anion transporter (SOAT; SLC10A6). E1S, serving as a precursor and intermediate for estrone and estradiol, may be involved in the pathophysiology of estrogen-associated diseases including breast cancer, benign breast disease, endometrial cancer, ovarian cancer, prostate cancer, and colorectal cancer. For this reason, enzyme inhibitors of steroid sulfatase and 17β-hydroxysteroid dehydrogenase and inhibitors of OATPs, which prevent activation of E1S into estrone and estradiol, are of interest in the potential treatment of such conditions. E1S, also known as estrone 3-sulfate or as estra-1,3,5(10)-trien-17-one 3-sulfate, is a naturally occurring estrane steroid and a derivative of estrone. It is an estrogen conjugate or ester, and is specifically the C3 sulfate ester of estrone. Related estrogen conjugates include estradiol sulfate, estriol sulfate, estrone glucuronide, estradiol glucuronide, and estriol glucuronide, while related steroid conjugates include dehydroepiandrosterone sulfate and pregnenolone sulfate. E1S is produced via estrogen sulfotransferases from the peripheral metabolism of the ovarian estrogens estradiol and estrone. Estrogen sulfotransferases are expressed minimally or not at all in the gonads. In accordance, E1S is not secreted from the ovaries in humans. The elimination half-life of estrone sulfate is 10 to 12 hours. Its metabolic clearance rate is 80 L/day/m2.