Formation and turnover of long-chain fatty acid esters of 5-androstene-3 beta, 17 beta -diol in estrogen receptor positive and negative human mammary cancer cell lines in culture.
Microsomal preparations derived from bovine placenta cotyledons, previously investigated as a convenient source of fatty acyl coenzyme A: estradiol-17 beta-acyl transferase, have been shown to acylate other steroids bearing 3 beta- or 17 beta-hydroxyl groups. In the presence of 0.1 mM oleoyl CoA, the apparent Km values for dehydroepiandrosterone, testosterone, and 5-androstene-3 beta,17 beta-diol (delta 5-DIOL) were 45, 67, and 20 microM, respectively. Acylation of delta 5-DIOL occurred at either the 3 beta- or 17 beta-positions to give monoesters. Testosterone, estradiol-17 beta, and delta 5-DIOL acted as competitive inhibitors for the acylation of the 3 beta-hydroxyl group of dehydroepiandrosterone (Ki values 71, 75, and 41 microM, respectively). Such data indicate that a single enzyme of wide substrate specificity may be involved in these acylation reactions. When estrogen receptor (ER) positive and negative human mammary cancer cell lines were incubated with 10 nM [3H]delta 5-DIOL, intracellular accumulation of delta 5-DIOL long-chain fatty acid esters occurred; rates being higher (p less than 0.001) in ER negative cells (MDA-MB-231 and MDA-MB-330) compared to MCF-7 cells (ER positive), and higher (P less than 0.005) in MDA-MB-231 cells compared to ZR-75-1 cells (ER positive). After exposure to 10 nM [3H]delta 5-DIOL for 16 h, the total labeled steroid fatty acid fraction was composed predominantly of delta 5-DIOL-3 beta- and 17 beta-monoesters (approximately 85%), the remainder containing approximately equal amounts of delta 5-DIOL-diesters and dehydroepiandrosterone-3 beta-esters. Subsequent transfer to medium lacking delta 5-DIOL was accompanied by a breakdown of the labeled esters, which was more rapid in the ER positive cell lines. During this period, intracellular free delta 5-DIOL levels rapidly declined in MDA-MB-330 cells but were maintained in MCF-7 cells, presumably by binding to ER. This behavior parallels that of estradiol-17 beta previously observed in these cell lines and further emphasizes the potential importance of the adrenal-derived estrogen delta 5-DIOL in consideration of a hormone-based etiology of human breast cancer.
Adams
J B
JB
School of Biochemistry, University of New South Wales, Sydney, Australia.
Martyn
P
P
Smith
D L
DL
Nott
S
S
D015114:Androstenediol / Q000031:analogs & derivatives / Q000378:metabolism*; D000734:Androstenediols / Q000378:metabolism*; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism*; D002417:Cattle; D004952:Esters; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D006801:Humans; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D011960:Receptors, Estrogen / Q000032:analysis*; D014407:Tumor Cells, Cultured / Q000378:metabolism
D000734:Androstenediols; D004952:Esters; D005227:Fatty Acids; D011960:Receptors, Estrogen; D015114:Androstenediol