Determination of estradiol 2- and 16-alpha-hydroxylase activities in MCF-7 human breast cancer cells in culture using radiometric analysis.
Using a radiometric assay the effects of estradiol upon the activity of estradiol 2- and 16 alpha-hydroxylases in MCF-7 human breast cancer cells in culture were studied. After 5 days of treatment and 36 h of withdrawal, incubation in the presence of either 2- or 16 alpha-tritiated substrate was carried out. Estradiol (10 nM) significantly increased 16 alpha-hydroxylase activity (21%, P less than 0.01), while no effects on 2-hydroxylase activity was observed. Treatment for 6 weeks caused a major increase in 16 alpha-hydroxylation (65%, P less than 0.001) and a significant reduction in 2-hydroxylation (21%, P less than 0.05). These effects were not observed in estrogen receptor-negative MDA-MB-231 human breast cancer cells. Our observations suggest that these two metabolic pathways in MCF-7 cells are independently regulated and that this regulation is affected via the estrogen receptor.
Niwa
T
T
Laboratory of Biochemical Endocrinology, Rockefeller University Hospital, 1230 York Avenue, New York, New York 10021.
Bradlow
H L
HL
Fishman
J
J
Swaneck
G E
GE
D001189:Aryl Hydrocarbon Hydroxylases; D001943:Breast Neoplasms / Q000201:enzymology*; D019363:Cytochrome P-450 CYP1A1; D065727:Cytochrome P-450 CYP2C8; D065729:Cytochrome P-450 CYP2C9; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006801:Humans; D011874:Radiometry; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C450259:CYP2C8 protein, human; D019363:Cytochrome P-450 CYP1A1; D065727:Cytochrome P-450 CYP2C8; D039181:Steroid 16-alpha-Hydroxylase; C020120:estrogen 2-hydroxylase