Sulfation of tibolone and tibolone metabolites by expressed human cytosolic sulfotransferases.

Tibolone is an important therapeutic agent used in the treatment of menopausal symptoms in many countries and has beneficial effects on menopausal and postmenopausal vasomotor, bone, vaginal and mood symptoms without affecting the endometrial, breast or cardiovascular systems. The rapid metabolism of tibolone to active metabolites including 3alpha-OH-tibolone, 3beta-OH-tibolone and Delta(4)-tibolone may be important in its tissue-specific effects. Sulfation also has a major role in the metabolism and regulation of the tissue-specific activity of tibolone and its metabolites.

Regulation of MCF-7 breast cancer cell growth by beta-estradiol sulfation.

Estrogen stimulation is an important factor in human breast cancer cell growth and development. Metabolism of beta-estradiol (E2), the major endogenous human estrogen, is important in regulating both the level and activity of the hormone in breast tissues. Conjugation of E2 with a sulfonate moiety is an inactivation process since the sulfate ester formed by this reaction can not bind and activate the estrogen receptor.