Estrogen Sulfotransferase Induction Inhibits Breast Cancer Cell Line MCF-7 Proliferation.

Estrogens are known for their proliferative effects, resulting in tumorigenesis and causing cancers. The majority of breast cancers are estrogen-dependent. Estrogenb-locking drugs developed for treating estrogen-dependent breast cancers include antagonists of estrogen receptors (ERs) and inhibitors of estrogen synthesis enzymes such as aromatase and steroid sulfatase (STS). However, drugs targeting estrogen inactivation enzyme, estrogen sulfotransferase (SULT1E1), have not been developed for estrogen-dependent cancer treatment or prevention. Estrogens must be inactivated after their actions in vivo by SULT1E1, uncontrolled estrogen activity in certain tissues will cause cancers. The majority of human breast cancer cell lines are known to express very low levels of SULT1E1 compared to normal mammary cells. Therefore, gene up-regulation of SULT1E1 could provide novel possibilities for the treatment of estrogen-dependent breast and endometrial cancers. Our data suggest that certain nutritional flavonoids induce SULT1E1 and inhibit cell proliferation in estrogen-dependent breast cancer MCF-7 cells. Our results also suggest that SULT1E1 inducer has an additive or synergistic effect on the inhibition of MCF-7 cell proliferation when combined with other known breast cancer drugs. Naturally occurring flavonoids are safe and inexpensive; they could be used for the prevention of certain breast cancers and/or used as co-drug for the treatment of estrogen-dependent cancers. These results may lead to creating innovative approaches for the treatment or prevention of estrogen-dependent cancers and may lead to the discovery of novel drugs or co-drugs.