Metabolic fate of estradiol in human mammary cancer cells in culture: estrogen sulfate formation and cooperativity exhibited by estrogen sulfotransferase.
The metabolism of 17 beta-estradiol in both estrogen receptor positive and negative human breast cancer cell lines has been compared. Initial experiments in which confluent cells were exposed to 1 nM [3H]17 beta-estradiol for 24 h, revealed that the main metabolites formed by estrogen receptor positive MCF-7 and ZR-75-1 cells were 17 beta-estradiol-3-sulfate (together with lesser amounts of estrone sulfate) and estrone. In estrogen receptor negative cell lines, production of estrogen sulfates was either significantly lower (MDA-MB-231 cells) than receptor positive cells, or failed to be produced at all (MDA-MB-330 cells). In both these receptor negative cell lines, production of estrone was significantly higher than in receptor positive cells. Accumulation of estrogen sulfates resulted from attainment of a steady state between synthesis catalysed by estrogen sulfotransferase and degradation catalysed by estrogen sulfatase. The former was present in the cytosol and showed a very high affinity for 17 beta-estradiol and estrone (low nM range). Complex initial velocity versus estrogen substrate curves were obtained with enzyme purified 106-fold by affinity chromatography. Such curves were consistent with a rate equation of degree 3 or 4 and suggest the presence of cooperatively linked dependent binding sites.
Adams
J B
JB
School of Biochemistry, University of New South Wales, Sydney, Australia.
Phillips
N S
NS
Hall
R
R
D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D002460:Cell Line; D004958:Estradiol / Q000031:analogs & derivatives / Q000378:metabolism*; D004970:Estrone / Q000378:metabolism; D005260:Female; D006801:Humans; D011960:Receptors, Estrogen / Q000032:analysis; D015238:Sulfotransferases; D013466:Sulfurtransferases / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure
D011960:Receptors, Estrogen; D004970:Estrone; C028628:estradiol-3-sulfate; D004958:Estradiol; D013466:Sulfurtransferases; D015238:Sulfotransferases; C020122:estrone sulfotransferase