Inhibition of Oestrone Sulphatase Activity by Tibolone and its Metabolites

Abstract

Tibolone is a 19-nortestosterone derivative commonly used in hormone replacement therapy. Although tibolone and its 3α/β-hydroxy metabolites exert oestrogenic effects on bone and the vasomotor system, they do not appear to stimulate breast tissue proliferation. It has been proposed that the lack of an oestrogenic effect on breast tissues may result from the inhibition of oestrone sulphatase (E1-STS) in this tissue by tibolone and its metabolites. In this study we have examined the ability of tibolone and its metabolites to inhibit E1-STS activity in intact breast cancer cells, its effect on E1-STS activity in placental microsomes and also the expression of E1-STS mRNA in more detail. As the major proportion of hydroxytibolone metabolites circulate in a sulphated form, the ability of the 3α-sulphate and 3α, 17β-disulphate metabolites to inhibit E1-STS activity was also examined. In MCF-7 cells, tibolone and its 3β-hydroxylated metabolite were relatively potent inhibitors; they inhibited activity by 48 % and 46 %, respectively. In these cells, the 3α-sulphate and 3α, 17β-disulphate metabolites of tibolone inhibited E1-STS activity by 95 % and 79 % at 10 µM, respectively. No effects of tibolone or its metabolites on the expression of E1-STS mRNA in MCF-7 cells were detected. Using T-47D breast cancer cells, evidence was obtained that the sulphated metabolites of tibolone could continue to inhibit E1-STS activity after removal of the drugs and extensive washing of cells. In placental microsomes, however, the 3β-hydroxy metabolite was the most potent inhibitor with an IC₅₀ of 20.5 µM; the sulphated metabolites were less potent. Neither tibolone nor its metabolites had any inhibitory effect on the conversion of oestrone to oestradiol in breast cancer cells. Results from this study have confirmed that tibolone and its metabolites can inhibit E1-STS activity. This may explain the absence of breast stimulation as observed in clinical studies.

Key words

Hormone Replacement Therapy - Oestrogens - Steroid Sulphates - Enzymes

References

• 1 Kloosterboer H L, Sands R. Intracrinology: the secret of the tissue-specificily of tibolone.  J Brit Menopause Soc. 2000;  6 Suppl. 2 23-27
• 2 Tax L, Goorissen E M, Kicovic P M. Clinical profile of Org OD14.  Maturitas. 1987;  1 Suppl. 3-13
• 3 de Aloysio D, Fabiani A G, Mauloni M, Bottiglioni F. Use of Org OD14 for the treatment of climacteric complaints.  Maturitus. 1987;  1 Suppl. 49-65
• 4 Markiewicz L, Gurpide E. In vitro evaluation of estrogenic, estrogen antagonistic and progestagenic effects of a steroidal drug (Org OD14) and its metabolites on human endometrium.  J Steroid Biochem. 1990;  35 535-541
• 5 Tang B, Markiewicz L, Kloosterboer H J, Gurpide E. Human endometrial 3β-hydroxysteroid dehydrogenase/isomerase can locally reduce intrinsic estrogenic/progestagenic activity ratios of a steroidal drug (Org OD14).  J Steroid Biochem Molec Biol. 1993;  45 345-351
• 6 Kloosterboer H J, Schoonen W GEJ, Deckers G H, Klijn J GM. Effects of progestagens and Org OD14 in in vitro and in vivo tumor models.  J Steroid Biochem Molec Biol. 1994;  49 311-318
• 7 Chetrite G, Kloosterboer H J, Pasqualini J R. Effect of tibolone (Org OD14) and its metabolites on estrone sulphatase activity in MCF-7 and T-47D mammary cancer cells.  Anticancer Res. 1997;  17 135-140
• 8 Delbressine L, de Gooyer M, Kloosterboer H L. Sulphated metabolites of tibolone show sulphatase inhibiting activity. Program ENDO 2000 Abstr. 1639: 396
• 9 Santner S J, Feil P D, Santen R J. In situ estrogen production via estrone sulfatase pathway in breast tumors: relative importance versus aromatase pathway.  J Clin Endocrinol Metab. 1984;  59 29-33
• 10 Sanker B R, Maran R RM, Sudha S, Govindarajulu P, Balasubramanian K. Chronic corticosterone treatment impairs Leydig cell 11β-hydroxysteroid dehydrogenase activity and LH- stimulated testosterone production.  Horm Metab Res. 2000;  32 142-146
• 11 Purohit A, Reed M J. Oestrogen sulphatase activity in hormone-dependent breast cancer cells: Modulation by steroidal and non-steroidal therapeutic agents.  Int J Cancer. 1992;  50 901-905
• 12 Singh A, Reed M J. Insulin-like growth factor type I and insulin-like growth factor type II stimulate oestradiol 17β-hydroxysteroid dehydrogenase (reductive) activity in breast cancer cells.  J Endocrinol. 1991;  129 R5-R8
• 13 Duncan L J, Purohit A, Howarth N M, Potter B VL, Reed M J. Inhibition of estrone sulfatase activity by estrone-3-O-methylthiophosphonate: a potential therapeutic agent in breast cancer.  Cancer Res. 1993;  53 298-303
• 14 Carlstrom K, Doberl A, Gershagen S, Rannevik G. Peripheral plasma levels of dehydroepiandrosterone sulphate, dehydroepiandrosterone, androstenedione and testosterone following different doses of danazol.  Acta Obstet Gynec Scand. 1984;  123 Suppl. 125-129
• 15 Carlstrom K, Doberl A, Pousette A, Rannevik G, Wilking N. Inhibition of steroid sulphatase activity by danazol.  Acta Obstet Gynec Scand. 1984;  123 Suppl. 107-111
• 16 Chetrite G S, Kloosterboer H J, Philippe J-C, Pasqualini J R. Effects of Org OD14 (Livial) and its metabolites on 17β-hydroxysteroid dehydrogenase activity in hormone-dependent MCF-7 and T-47D breast cancer cells.  Anticancer Res. 1999;  19 261-268
• 17 Purohit A, Vernon K A, Wagenaar-Hummelinck A E, Woo L WL, Hejaz , HAM , Potter B VL, Reed M J. The development of A-ring modified analogues of oestrone-3-O-sulphamate as steroid sulphatase inhibitors with reduced oestrogenicity.  J Steroid Biochem Molec Biol. 1998;  64 269-275
• 18 Ciobanu L C, Boivin R P, Luu-The V, Labrie F, Poirier D. Potent inhibition of steroid sulfatase activity by 3-O-sulfamate 17α benzyl (or 4′-tert-butyl-benzyl) estra-1,3,5(10)-trienes: combinations of two substituents at position C3 and C17α of estradiol.  J Med Chem. 1999;  42 2280-2286
• 19 Purohit A, Williams G J, Roberts C J, Potter B VL, Reed M J. In vivo inhibition of oestrone sulphatase and dehydroepiandrosterone sulphatase by oestrone-3-O-sulphamate.  Int J Cancer. 1995;  62 106-111
• 20 Purohit A, Dauvois S, Parker M G, Potter B VL, Williams G J, Reed M J. The hydrolysis of oestrone sulphate and dehydroepiandrosterone sulphate by human steroid sulphatase expressed in transfected COS-1 cells.  J Steroid Biochem Molec Biol. 1994;  50 101-104
• 21 Poulin R, Labrie F. Stimulation of cell proliferation and estrogenic response by adrenal C19-delta-5-steroids in the ZR-75 - 1 human breast cancer cell line.  Cancer Res. 1986;  46 4933-4937
• 22 Dauvois S, Labrie F. Androstenedione and androst-5-ene-3β, 17β-diol stimulate DMBA-induced mammary tumours - role of aromatase.  Breast Cancer Res Treat. 1989;  13 61-69