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Nomegestrol acetate (NOMAC), a 17alpha-hydroxy-nor-progesterone derivative (17alpha-acetoxy-6-methyl-19-nor-4,6-pregnadiene-3,20-dione, the active substance in Lutenyl), is a potent and useful clinical synthetic progestin for the treatment of menopausal complaints and is under current development for oral contraception. Previous studies in this laboratory demonstrated that NOMAC can block sulfatase and 17beta-hydroxysteroid dehydrogenase, the enzymes involved in the biosynthesis and transformation of estradiol (E2) in hormone-dependent MCF-7 and T-47D breast cancer cells. In the present study, the effect of NOMAC on sulfatase activity using total breast cancer tissue, compared to the effect in normal breast tissue, was explored. Slices of tumoral or normal breast tissues (45-65 mg) were incubated in buffer (20 mM Tris-HCl, pH 7.2) with physiological concentrations of [3H]-estrone sulfate (5x10(-9) M), alone or in the presence of nomegestrol acetate (5x10(-5) - 5x10(-7) - 5x10(-9) M), for 4 h at 37 degrees C. Estrone sulfate (E1S), estrone (E1) and E2 were characterized by thin layer chromatography and quantified using the corresponding standard. It was observed that [3H]- E1S was only converted to [3H]- E1 and not to [3H]- E2, in normal or cancerous breast tissues, which suggests a low or no 17beta-HSD activity under these experimental conditions. The sulfatase activity was more intense with breast cancer tissue than normal tissue, since the concentrations of E1 were 42.5 +/- 3.4 and 27.2 +/- 2.5 pg/mg tissue, respectively. NOMAC, at the concentration of 5x10(-5) M, inhibited this conversion by 49.2% and 40.8% in cancerous and normal breast tissues, respectively. The sulfatase inhibition at low concentration (5x10(-7) M) was 32.5% and 22.8%, respectively. It is concluded that sulfatase activity is almost twice as potent in cancerous breast tissues than in normal tissues. Nomegestrol acetate is a strong anti-sulfatase agent, in particular with cancerous breast tissues. The inhibition of estrone sulfatase activity by NOMAC in total normal or cancerous breast tissues can open attractive perspectives for future clinical trials.

Estradiol (E2) is one of the main factors which control the growth and evolution of breast cancer. Consequently, to block the formation of E2 inside cancer cells has been an important target in recent years. Breast cancer cells possess all the enzymatic systems (e.g. sulfatase, aromatase, 17beta-hydroxysteroid dehydrogenase [17beta-HSD]) involved in the conversion of estrogen precursors into E2. Sulfotransferase, which converts estrogen to its sulfate, is also present in this tumoral tissue. Duphaston is a synthetic progestogen with properties similar to the natural progesterone. In the present study we examined the effect of Duphaston and its 20-dihydro-metabolite on the sulfatase and 17beta-HSD activities in MCF-7 and T-47D breast cancer cells. The cells were incubated with estrone sulfate (E1S) (5x10(-9)M) in the absence or presence of Duphaston or its 20-dihydro-metabolite (5x10(-5) to 5x10(-9)M) for 24h at 37 degrees C. In another series of experiments, estrone (E1) (5x10(-9)M) was incubated with T-47D cells in the absence or presence of the two progestogens (5x10(-5) to 5x10(-9)M) for 24h at 37 degrees C. E1S, E1 and E2 were characterized by thin layer chromatography and quantified using the corresponding standard. Duphaston and its 20-dihydro-metabolite, at concentrations of 5x10(-7) and 5x10(-5)M, inhibited the conversion of E1S to E2 by 14% and 63%, 65% and 74%, respectively, in MCF-7 cells; the values were 15% and 48% and 31% and 51%, respectively, in T-47D cells. In another series of experiments it was observed that, after 24-h incubation, E1 (5x10(-9)M) was converted in a great proportion to E2 in the T-47D cells and that this transformation was significantly inhibited by Duphaston and its 20-dihydro-metabolite. The IC50 value, corresponding to 50% of the inhibition in the conversion of 1 to E2, was 9x10(-6)M for 20-dihydro-metabolite in this cell line. It was concluded that the progestogen Duphaston and its 20-dihydro-metabolite are potent inhibitory agents on sulfatase and 17beta-HSD activities in breast cancer cells. Duphaston is a progestogen with properties similar to the endogenous progesterone. The data open interesting perspectives to study the biological responses of these progestogens in clinical trials of patients with breast cancer.

Breast cancer cells possess all the enzymes involved in the last steps of estradiol (E2) bioformation, as well as in its transformation (e.g. sulfotransferases) for the conversion to estrogen sulfates (ES). As ES are biologically inactive, the formation of these conjugates is an important transformation pathway in the control of the hormone. In the present study, we explored the effect of nomegestrol acetate on the sulfotransferase activity in the hormone-dependent MCF-7 and T-47D human breast cancer cells. After 24-h incubation at 37 degrees C of physiological concentrations of estrone ([3H]-E1: 5 x 10(-9) mol/l), it was observed that the sulfotransferase activity was present in both cell lines, since the concentrations of estrogen sulfates found were 9.40 +/- 1.10 in MCF-7 cells and 6.65 +/- 0.72 in the T-47D cells. The presence of ES was found exclusively in the culture medium, which suggests that as soon as the sulfate is biosynthesized it is secreted into the medium. Nomegestrol acetate has a stimulatory effect on sulfotransferase activity: at low doses (5 x 10(-8) and 5 x 10(-7) mol/l) this compound strongly increases the activity of this enzyme by 60.6% and 83%, respectively, in the MCF-7 cells and by 69.2% at 5 x 10(-7) mol/l in T-47D cells. At a high concentration (5 x 10(-5) mol/l) the stimulatory effect of nomegestrol acetate on the sulfotransferase activity was only 5.4% and 6.1%, respectively, in MCF-7 and T-47D cells. In conclusion, the stimulation provoked at low doses by nomegestrol acetate on the estrogen sulfotransferase activity involved in the biosynthesis of the biologically inactive estrogen sulfates in hormone-dependent breast cancer cells is an important effect of this progestin and can open attractive clinical applications.