Steroid modulation of aromatase activity in human cultured breast carcinoma cells

Benign Metastasizing Leiomyomatosis to the Skin and Lungs, Intravenous Leiomyomatosis, and Leiomyomatosis Peritonealis Disseminata: A Series of Five Cases

Benign metastasizing leiomyomatosis (BML) is a rare disease that typically occurs in women with a history of uterine leiomyomatosis. Benign metastasizing leiomyomatosis occurs more frequently in the lungs but may also develop in other organs and tissues. Other unusual variants of extra-uterine leiomyomatosis include intravenous leiomyomatosis (IVL) and leiomyomatosis peritonealis disseminata (LPD). In this article, three cases of BML are presented. One case, in a premenopausal woman, presented cutaneous metastases. We also present a case of IVL and a case of LPD, which occurred in postmenopausal women. Given the rarity of BML, IVL, and LPD, the authors reviewed the literature and herein discuss the implications for treatment in all five cases. Evidence for treating BML, IVL, and LPD is still scarce, and data available from our series and other small series seem to point to the patient’s hormonal status playing a fundamental part in the treatment plan. Furthermore, a collecting bag when performing excision of uterine leiomyomas may help avoid the potential spreading of leiomyomatosis. Hysterectomized patients with chronic cough, frequent respiratory infections, abdominal discomfort, right heart failure, or non-specific symptoms should be actively screened for BML, IVL, and LPD. Treatment should be individualized according to each patient’s hormonal status and desires.

Adding the phytoestrogen Cimicifugae Racemosae to clomiphene induction cycles with timed intercourse in polycystic ovary syndrome improves cycle outcomes and pregnancy rates - a randomized trial

BACKGROUND

Owing to their potential to act as estrogen receptor modulators and interfere with aromatase enzyme in animal studies, phytoestrogens (PE) may be useful as part of ovulation induction for polycystic ovary syndrome (PCOS).

PATIENTS AND METHODS

Patients <35 years, presenting with infertility and PCOS, were included and randomly allocated to either group I (clomiphene citrate; CC) or group II (CC plus Cimicifugae racemosae; CR). Primary outcome was pregnancy rate. Secondary outcomes included ovulation, midcycle serum estradiol and luteinizing hormone (LH) as well as mid-luteal serum progesterone.

RESULTS

Analysis included 98 patients in group I versus 96 patients in group II. Both groups were matched regarding demographics and basic data. Significant differences were elicited when comparing days until HCG injection (15.0 ± 1.7 versus 12.0 ± 1.9, p=0.91), endometrial thickness (mm) (8.5 ± 1.9 versus 12.5 ± 1.9, p<0.001), serum levels of mid-luteal and midcycle estradiol (p<0.001; Figure 2), LH (IU/ml) (p<0.001) as well as mid-luteal progesterone (p<0.001). PE plus CC group had significantly higher clinical pregnancies per cycle (33/192 (17.2%) versus 71/204 (34.8%), p<0.01), compared to the CC only group.

CONCLUSIONS

Adding CR to clomiphene-induction cycles with timed intercourse in polycystic ovarian syndrome improves cycle outcomes and pregnancy rates.

Novel hormone treatment of benign metastasizing leiomyoma: an analysis of five cases and literature review

OBJECTIVE

To evaluate novel hormonal therapies in patients with unresectable benign metastasizing leiomyoma (BML) disease.

DESIGN

Case series.

SETTING

National Institutes of Health (NIH).

PATIENT(S)

Five subjects with the diagnosis of BML based on imaging and/or histopathologic diagnosis.

INTERVENTION(S)

Four patients were treated with single or combination therapy of leuprolide acetate and/or an aromatase inhibitor. One patient was treated with an antiprogestin (CDB-2914).

MAIN OUTCOME MEASURE(S)

Response to therapy was measured by tumor burden on cross-sectional imaging employing RECIST (Response Evaluation Criteria in Solid Tumors) 1.1 guidelines.

RESULT(S)

Four patients treated with single or combination therapy of leuprolide acetate and/or an aromatase inhibitor demonstrated stable disease with reduction in tumor burden. The fifth patient treated with antiprogestin (CDB-2914) had degeneration of her tumor, progression of its size, and an improvement in symptoms.

CONCLUSION(S)

Hormone treatment with GnRH agonist and/or aromatase inhibition may be a therapeutic option to reduce tumor burden in unresectable BML disease or for those patients who wish to avoid surgical intervention. RECIST 1.1 guidelines, while traditionally used to evaluate tumor response to cancer therapeutics, may be useful in evaluating BML tumor burden response to hormone therapy.

Nomegestrol acetate is an anti-aromatase agent in human MCF-7aro breast cancer cells

: The progestogen nomegestrol acetate (NOMAC), a 17α-hydroxy-nor-progesterone derivative (LUTENYL

: Cells were incubated with physiological concentrations of androgen substrates [

: Aromatase activity levels are high in MCF-7aro cells because the [

: The MCF-7aro cell line shows high aromatase activity and NOMAC can act as an anti-aromatase agent by inhibiting this activity. This is an important new effect of this progestogen. Because NOMAC can also inhibit sulfatase activity in breast cancer cells, we suggest that this dual effect of NOMAC has attractive possibilities for clinical trials.

Inhibition of aromatase activity in MCF-7aro human breast cancer cells by the natural androgens testosterone and androstenedione

: The human breast contains all the enzymes responsible for local bioformation of estradiol (E

: The cells were incubated with physiological concentrations of [

: The MCF-7aro cells have a very high aromatase activity because conversion of [

: In breast cancer cells, the natural androgens testosterone and androstenedione, have the capacity to control bioformation of estradiol by blocking aromatase activity. The data can provide important information on the control mechanism of estrogen intratumoral levels and open new possibilities in breast cancer treatment.

Effects of tibolone on estrogen biosynthesis in the mammary tissue of postmenopausal monkeys

OBJECTIVE

To evaluate the long-term effects of tibolone on estrone sulfate (E1S)-sulfatase activity in breast tissue in a primate model (Macaca fascicularis) in comparison with conventional hormone therapies.

DESIGN

Ovariectomized female animals (n = 112) were randomized into five groups and treated for 2 years. Treatment included tibolone at 0.05 mg/kg (LoTib, n = 23) or 0.2 mg/kg (HiTib, n = 23), conjugated equine estrogens at 0.042 mg/kg (CEE, n = 24), CEE + medroxyprogesterone acetate at 0.167 mg/kg (CEE+MPA, n = 21), or placebo (controls, n = 21). E1S-sulfatase activity was evaluated by incubating homogenized breast tissue with [H]-E1S. Thin-layer chromatography was performed to separate the products estrone (E1) and estradiol (E2). Histomorphometry was performed to measure the amount of epithelial and fat tissue in the mammary gland.

RESULTS

Significantly more E2 than E1 was produced in all groups. E1S-sulfatase activity did not differ among the groups. E1S-sulfatase activity was highest in HiTib animals with less fatty breasts (5.9 fmol total estrogen/mg of protein/min; P < or =0.05) and lowest in HiTib animals with more fatty breasts (2.8 fmol total estrogen/mg of protein/min; P = 0.004 relative to less fatty breasts).

CONCLUSIONS

We conclude that tibolone had a differential effect on local estrogen biosynthesis in animals with high and low breast fat content. Therefore, breast tissue composition affects the steroidogenic response to hormonal treatment.

Lack of dehydroepiandrosterone in type I and II hereditary angioedema and role of danazol in steroid hormone conversion

BACKGROUND

Hereditary angioedema (HAE) is successfully treated with danazol, a therapeutic steroid compound. To investigate hormones of the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axis in patients with HAE with and without danazol.

METHODS

We included 16 patients with type I HAE, nine patients with type II HAE, and 16 healthy subjects. Serum levels of adrenocorticotropic hormone (ACTH), cortisol, androstenedione, dehydroepiandrosterone (DHEA), free testosterone, and 17beta-oestradiol were measured.

RESULTS

Serum levels of ACTH were markedly decreased in patients with type II HAE compared to the other groups (P < 0.001). Serum cortisol was similar between groups but danazol treatment decreased cortisol levels, particularly in women (P = 0.019). Serum levels of DHEA were significantly decreased in all patients with type I and II HAE compared to controls (P < 0.05), which was only partly dependent on prior danazol therapy as patients without danazol had also decreased serum levels of DHEA (P < 0.05). Furthermore, free testosterone serum levels were markedly increased in patients under danazol (P < 0.005) and the ratio of 17beta-oestradiol/free testosterone was significantly decreased in these patients (P < 0.005).

CONCLUSIONS

This study demonstrated decreased DHEA in patients with type I and II HAE independent of danazol therapy, which was particularly evident in women. It also demonstrates that danazol induced a marked up-regulation of free testosterone in relation to precursors and downstream 17beta-oestradiol. In HAE, there seems to be a primary lack of the adrenal androgen DHEA.

Progestins and breast cancer

Progestins exert their progestational activity by binding to the progesterone receptor (form A, the most active and form B, the less active) and may also interact with other steroid receptors (androgen, glucocorticoid, mineralocorticoid, estrogen). They can have important effects in other tissues besides the endometrium, including the breast, liver, bone and brain. The biological responses of progestins cover a very large domain: lipids, carbohydrates, proteins, water and electrolyte regulation, hemostasis, fibrinolysis, and cardiovascular and immunological systems. At present, more than 200 progestin compounds have been synthesized, but the biological response could be different from one to another depending on their structure, metabolism, receptor affinity, experimental conditions, target tissue or cell line, as well as the biological response considered. There is substantial evidence that mammary cancer tissue contains all the enzymes responsible for the local biosynthesis of estradiol (E(2)) from circulating precursors. Two principal pathways are implicated in the final steps of E(2) formation in breast cancer tissue: the 'aromatase pathway', which transforms androgens into estrogens, and the 'sulfatase pathway', which converts estrone sulfate (E(1)S) into estrone (E(1)) via estrone sulfatase. The final step is the conversion of weak E(1) to the potent biologically active E(2) via reductive 17beta-hydroxysteroid dehydrogenase type 1 activity. It is also well established that steroid sulfotransferases, which convert estrogens into their sulfates, are present in breast cancer tissues. It has been demonstrated that various progestins (e.g. nomegestrol acetate, medrogestone, promegestone) as well as tibolone and their metabolites can block the enzymes involved in E(2) bioformation (sulfatase, 17beta-hydroxysteroid dehydrogenase) in breast cancer cells. These substances can also stimulate the sulfotransferase activity which converts estrogens into the biologically inactive sulfates. The action of progestins in breast cancer is very controversial; some studies indicate an increase in breast cancer incidence, others show no difference and still others a significant decrease. Progestin action can also be a function of combination with other molecules (e.g. estrogens). In order to clarify and better understand the response of progestins in breast cancer (incidence, mortality), as well as in hormone replacement therapy or endocrine dysfunction, new clinical trials are needed studying other progestins as a function of the dose and period of treatment.

Effects of black cohosh on estrogen biosynthesis in normal breast tissue in vitro

OBJECTIVES

To investigate the effect of black cohosh on the estrogen biosynthesis in the breast in vitro.

METHODS

Steroid sulfatase (STS) activity was studied in normal breast tissue obtained from pre- and postmenopausal women undergoing reduction mammoplasty. STS protein expression was studied by immunohistochemistry and western blotting. Breast tissue was incubated in vitro without or with black cohosh (iCR) at concentrations ranging from 0.1mg/ml to 1 ng/ml. STS activity was evaluated by incubating homogenized breast tissue with [3H]-estrone sulfate, separating the formed products, estrone (E1) and estradiol (E2), by thin layer chromatography and measuring the amounts of E1 and E2 by scintillation counting.

RESULTS

STS protein expression and enzymatic activity were detected in all specimens investigated. In all groups, significantly more E1 than E2 was produced. Local estrogen formation was decreased in premenopausal breast tissue by treatment with iCR at 0.1mg/ml (p<or=0.05).

CONCLUSIONS

iCR decreases local estrogen formation in normal human breast tissue in vitro. This may contribute to the lack of hormonal effects of black cohosh in breast tissue observed in previous studies.

Differential effect of hormone therapy on E1S-sulfatase activity in non-malignant and cancerous breast cells in vitro

Breast tissue possesses the enzymes for local estrogen biosynthesis. We measured the effect of Estradiol (E2), Tibolone (OrgOD14) and its metabolite Org4094 on estrone sulfate (E1S)-sulfatase (STS) using breast cancer (MCF-7) and non-malignant breast cells (HBL-100). Cells were cultured in 5% steroid depleted fetal calf serum for 3 days and subsequently incubated with each steroid for either 24 h or directly in cell extracts. STS mRNA and protein expression, and its subcellular localization were determined by semi-quantitative RT-PCR, immunoblotting, and confocal immunofluorescence microscopy. STS activity was evaluated by incubating homogenized breast cells with [(3)H]-E1S. The products E1 and E2 were separated by thin layer chromatography. STS was co-localized with the Golgi marker protein GM130 and the endoplasmic reticulum marker protein calnexin. Treatment did not significantly alter STS mRNA expression. STS protein expression was increased by each steroid in HBL-100 cells but by E2 only in MCF-7 cells. 24 h incubation with OrgOD14 and Org4094 did not alter STS activity in both cell lines. However, STS activity was significantly diminished in HBL-100 but slightly increased in MCF-7 cells by 24 h treatment with E2. "Direct" incubation of cell extracts, eliminating cellular regulation of metabolism, reduced estrogen biosynthesis regardless of cell line and treatment. In conclusion, the immediate reduction of estrogen biosynthesis by OrgOD14 is counteracted by an increased STS protein expression. On the contrary, E2 exerts a differential effect on STS in HBL-100 and MCF-7 cells. The transition from normal to malignant breast cells may be accompanied by an abolished autoregulation of local estrogen formation.

A novel steroidal selective steroid sulfatase inhibitor KW-2581 inhibits sulfated-estrogen dependent growth of breast cancer cells in vitro and in animal models

We screened a series of 17beta-(N-alkylcarbamoyl)-estra-1,3,5(10)trine-3-O-sulfamate derivatives, and describe here a potent and selective steroid sulfatase (STS) inhibitor with antitumor effects in breast cancer models in vitro and in vivo. In biochemical assays using crude enzymes isolated from recombinant Chinese hamster ovary cells expressing human arylsulfatses (ARSs), one of the best compounds, KW-2581, inhibited STS activity with an IC(50) of 4.0 nM, while > 1000-fold higher concentrations were required to inhibit the other ARSs. The failure to stimulate the growth of MCF-7 human breast cancer cells as well as in uteri in ovariectomized rats indicated the lack of estrogenicity of this compound. In MCF-7 cells transfected with the STS gene, termed MCS-2 cells, KW-2581 inhibited the growth of cells stimulated by estrone sulfate (E1S) but also 5-androstene-3beta, 17beta-diol 3-sulfate (ADIOLS) and dehydroepiandrostenedione 3-sulfate. We found that oral administration of KW-2581 inhibited both E1S- and ADIOLS-stimulated growth of MCS-2 cells in a mouse hollow fiber model. In a nitrosomethylurea-induced rat mammary tumor model, KW-2581 induced regression of E1S-stimulated tumor growth as effectively as tamoxifen or another STS inhibitor, 667 Coumate. Dose-response studies in the same rat model demonstrated that more than 90% inhibition of STS activity in tumors was necessary to induce tumor shrinkage. STS activity in tumors has well correlated with that in leukocytes, suggesting that STS activity in leukocytes could be used as an easily detectable pharmacodynamic marker. These findings demonstrate that KW-2581 is a candidate for development as a therapeutic agent for the treatment of hormone receptors-positive breast cancer.

Inhibition of steroid sulfatase activity and cell proliferation in ZR-75-1 and BT-474 human breast cancer cells by KW-2581 in vitro and in vivo

In the present study, we found that two hormone receptor-positive human breast cancer cell lines, ZR-75-1 and BT-474, naturally expressed steroid sulfatase (STS) protein and had catalytic activity to produce estrone from estrone sulfate (E1S) with a comparable level to those in human breast cancer tissues. E1S at physiological concentrations stimulated the growth of those cells. A novel steroidal STS inhibitor, KW-2581 inhibited the STS activity of ZR-75-1 cells with an IC(50) of 13 nM, a potency equal to or higher than that of the non-steroidal STS inhibitor, 667 COUMATE. The inhibitory effect of KW-2581 was enhanced by pre-incubation with STS enzyme, suggests being irreversible inhibition. KW-2581 inhibited the E1S-stimulated growth of ZR-75-1 cells with an IC(50) of 0.18 nM, but failed to inhibit the growth stimulated by 17beta-estradiol. Expression of E1S-induced progesterone receptors in ZR-75-1 cells was reduced by treatment of KW-2581 at concentrations as low as 0.1 nM. Oral administration of KW-2581 for 4 weeks caused tumor shrinkage in a mouse xenograft model. Tumor STS activity had been completely (>95%) eliminated by 24 hours after the last administration. These findings suggest that KW-2581 has considerable potential for therapeutic development as a novel anti-hormonal drug for treatment of breast cancer.

Effects of Prenatal Stress on the Activity of an Enzyme Involved in Neurosteroid Synthesis During the “Critical Period” of Sexual Differentiation of the Brain in Male Rats

The effects of daily immobilization stress applied to female rats on days 15 to 18 of pregnancy on the activity of the enzyme 5 alpha-reductase (isoform I), involved in the synthesis of brain neurosteroids were studied in male offspring. The results demonstrated a decrease in enzyme activity in the cerebral cortex and hypothalamus of male fetuses one day after the last session of stress, while enzyme activity was elevated in the cortex of neonates. Increases in 5 alpha-reductase activity in the cortex, hippocampus, and hypothalamus were also seen in prenatally stressed males on day 5 of life. There were reductions in plasma testosterone and progesterone levels in experimental animals on day 19 of embryonic life and in neonatal rats, the blood progesterone level in prenatally stressed rats remaining decreased at age five days. The possible involvement of neurosteroids in the actions of prenatal stress on sexual differentiation of the brain is discussed.

Effect of nomegestrol acetate on estrogen biosynthesis and transformation in MCF-7 and T47-D breast cancer cells

Although ovaries serve as the primary source of estrogen for pre-menopausal women, after menopause estrogen biosynthesis from circulating precursors occurs in peripheral tissues by the action of several enzymes, 17beta-hydroxysteroid dehydrogenase 1 (17beta-HSD1), aromatase and estrogen sulfatase. In the breast, both normal and tumoral tissues have been shown to be capable of synthesizing estrogens, and this local estrogen production can be implicated in the development of breast tumors. In these tissues, estradiol (E(2)) can be synthesized by three pathways: (1) estrone sulfatase transforms estrogen sulfates into bioactive estrogens, (2) 17beta-HSD1 converts estrone (E(1)) into E(2), (3) aromatase which converts androgens into estrogens is also present and contributes to the in situ synthesis of active estrogens but to a far lesser extent than estrone sulfatase. Quantitative assessment of E(2) formation in human breast tumors indicates that metabolism of estrone sulfate (E(1)S) via the sulfatase pathway produces 100-500 times more E(2) than androgen aromatization. Breast tissue also possesses the estrogen sulfotransferase involved in the conversion of estrogens into their sulfates that are biologically inactive. In the present review, we summarized the action of the 19-nor-progestin nomegestrol acetate (NOMAC) on the sulfatase, 17beta-HSD1 and sulfotransferase activities in the hormone-dependent MCF-7 and T47-D human breast cancer cell lines. Using physiological doses of substrates NOMAC blocks very significantly the conversion of E(1)S to E(2). It inhibits the transformation of E(1) to E(2). NOMAC has a stimulatory effect on sulfotransferase activity in both cell lines, with a strong stimulating effect at low doses but only a weak effect at high concentrations. The effects on the three enzymes are always stronger in the progesterone-receptor rich T47-D cell line as compared with the MCF-7 cell line. Besides, no effect is found for NOMAC on the transformation of androstenedione to E(1) in the aromatase-rich choriocarcinoma cell line JEG-3. In conclusion, the inhibitory effect provoked by NOMAC on the enzymes involved in the biosynthesis of E(2) (sulfatase and 17HSD pathways) in estrogen-dependent breast cancer, as well as the stimulatory effect on the formation of the inactive E(1)S, can open attractive perspectives for future clinical trials.

Progestins and breast cancer

The relationship between the use of menopausal hormone therapy (ERT, unopposed estrogen therapy; HRT, combined estrogen and progestin therapy) and the development of breast cancer remains controversial. Mechanistic studies examining progestins in human breast cancer cell lines have demonstrated a biphasic cellular response to progesterone; initial exposure to hormone results in a proliferative burst with sustained exposure resulting in growth inhibition. To date, there is no definitive evidence that progestins act in the pathogenesis of breast cancer. Epidemiologic studies have produced inconsistent results, and data from randomized, placebo-controlled trials are limited. Although recent results from the continuous combined therapy arm of the Women's Health Initiative trial showed a small increase in the risk of invasive breast cancer in women on therapy for 5 years or more, a clear consensus regarding the relationship between HRT and breast cancer risk cannot yet be drawn from existing data. Studies have consistently documented that HRT use is associated with improved mortality and survival rates for women with breast cancer. Large-scale, randomized studies on different progestin regimens are needed to critically assess the effect of progestin on breast cancer.

Tibolone is not converted by human aromatase to 7alpha-methyl-17alpha-ethynylestradiol (7alpha-MEE): analyses with sensitive bioassays for estrogens and androgens and with LC-MSMS

To exclude that aromatization plays a role in the estrogenic activity of tibolone, we studied the effect tibolone and metabolites on the aromatization of androstenedione and the aromatization of tibolone and its metabolites to 7alpha-methyl-17alpha-ethynylestradiol (7alpha-MEE) by human recombinant aromatase. Testosterone (T), 17alpha-methyltestosterone (MT), 19-nortestosterone (Nan), 7alpha-methyl-19-nortestosterone (MENT) and norethisterone (NET) were used as reference compounds. Sensitive in vitro bioassays with steroid receptors were used to monitor the generation of product and the reduction of substrate. LC-MSMS without derivatization was used for structural confirmation. A 10 times excess of tibolone and its metabolites did not inhibit the conversion of androstenedione to estrone by human recombinant aromatase as determined by estradiol receptor assay whereas T, MT, Nan, and MENT inhibited the conversion for 75, 53, 85 and 67%, respectively. Tibolone, 3alpha- and 3beta-hydroxytibolone were not converted by human aromatase whereas the estrogenic activity formed with the Delta4-isomer suggests a conversion rate of 0.2% after 120 min incubation. In contrast T, MT, Nan, and MENT were completely converted to their A-ring aromates within 15 min while NET could not be aromatized. Aromatization of T, MT, Nan and MENT was confirmed with LC-MSMS. Structure/function analysis indicated that the 17alpha-ethynyl-group prevents aromatization of (19-nor)steroids while 7alpha-methyl substitution had no effect. Our results with the sensitive estradiol receptor assays show that in contrast to reference compounds tibolone and its metabolites are not aromatized.

Conversion of dehydroepiandrosterone sulfate at physiological plasma concentration into estrogens in MCF-7 cells

Metabolism of dehydroepiandrosterone (DHEA), its sulfate (DHEAS), and androstene-3,17-dione (delta(4)) was performed at their physiological plasma concentrations in MCF-7 cell cultures (1 microM, 10 and 2 nM, respectively). Final metabolic products of these steroids were separated by HPLC-radioactive flow detection and identified by LC/MS or MS/MS. Typical and specific mass fragmentation spectra identified the presence of estrone (E(1)), 17beta-estradiol (E(2)), delta(4), DHEA, 5-androstene-3beta,17beta-diol (delta(5)), and testosterone as principal DHEAS metabolites. Other steroids, such as androstenedione, androsterone, and DHEA fatty acid esters at very low concentrations (from pM to nM), were also obtained after steroid incubation. This highly specific method allowed us to conclude whether a metabolite and enzymatic activity of interest were present in MCF-7 cells or not. We also showed that DHEAS at its physiological plasma concentration may be converted into estrogens and estrogen-like compounds in breast cancer cells. The estrogenic action of DHEAS on breast cancer cells was also measured by bioluminescence in a stably transfected human breast cancer MCF-7 cell line with a reporter gene that allowed expression of the firefly luciferase enzyme under the control of an estrogen regulatory element.

Effect of tibolone (Org OD14) and its metabolites on aromatase and estrone sulfatase activity in human breast adipose stromal cells and in MCF-7 and T47D breast cancer cells

Tibolone (Org OD14) is a synthetic steroid used for post-menopausal hormone replacement therapy (HRT). Since HRT might increase breast cancer risk, it is important to determine the possible effects of tibolone on breast tissues. Tibolone and its metabolites Org 4094, Org 30126 and Org OM38 have been reported to inhibit estrone sulfatase activity in MCF-7 and T47D breast cancer cell lines, which suggest beneficial effects on hormone dependent breast cancer by reducing local production of free estrogens. Breast adipose stromal cells (ASCs) contain aromatase activity-an obligatory step in the biosynthesis of estrogens-and possibly contain sulfatase activity. We investigated the effects of tibolone, its metabolites and the pure progestin Org 2058 on PGE(2)-stimulated aromatase activity and on sulfatase activity in human ASC primary cultures and on sulfatase activity in MCF-7 and T47D cell lines. In MCF-7, tibolone and metabolites, but not Org 2058, were found to inhibit sulfatase activity. In T47D, tibolone inhibited sulfatase only at 10(-6)M, although weakly. ASC had high sulfatase activity, which was inhibited by 10(-6)M of tibolone, Org 4094 and Org 30126, but not by Org OM38 or Org 2058. Surprisingly, aromatase activity in ASC was increased by both tibolone and Org 2058 at 10(-6)M. As ligand binding assay results and immunohistochemistry indicated the absence of progesterone and estrogen receptors in ASC, these effects on aromatase and sulfatase activity in ASC likely take place by other routes. Because tibolone and its metabolites inhibit sulfatase activity, and because tibolone only increases aromatase activity at a high concentration, we conclude that effects of tibolone on the breast are probably safe.

Biological effects of progestins in breast cancer

The action of progestins is derived from many factors: structure, affinity for the progesterone receptor or for other steroid receptors, the target tissue considered, the biological response, the experimental conditions, the dose and metabolic transformation. The proliferative response to progestins in human breast cancer cells is contradictory: some progestins inhibit, others stimulate, have no effect at all, or have a dual action. For instance, medroxyprogesterone acetate has a stimulatory effect on breast cancer cells after a short period of treatment, but this effect becomes inhibitory when treatment is prolonged. It has been demonstrated that, in hormone-dependent breast cancer cells, various progestins (nomegestrol acetate, medrogestone, promegestone) are potent sulfatase inhibitory agents. The progestins can also involve the inhibition of the mRNA expression of this enzyme. In another series of studies it was also demonstrated that some progestins are very active in inhibiting 17beta-hydroxysteroid dehydrogenase for the conversion of estrone to estradiol. More recently it was observed that the progestins promegestone and medrogestone stimulate sulfotransferase for the formation of estrogen sulfates. Consequently, the action of progestins in blocking estradiol formation via sulfatase, or in stimulating the effect on sulfotransferase activity, can open interesting and new possibilities in clinical applications in breast cancer.

Involvement of up-regulation of 17beta-hydroxysteroid dehydrogenase type 1 in maintenance of intratumoral high estradiol levels in postmenopausal breast cancers

Estradiol (E2) and estrone (E1) levels as well as mRNA expression levels of aromatase, sulfatase and 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1) in breast cancer tissues were studied to elucidate the mechanism involved in the maintenance of the intratumoral high E2 levels in postmenopausal patients with very low serum E2 levels. Intratumoral E2 levels of postmenopausal patients (127.2 +/- 17.5 pg/g) (mean +/- SE) were not significantly different from those of premenopausal patients (110.1 +/- 10.1 pg/g) (p = 0.36). The mRNA expression levels of aromatase and sulfatase, determined by a quantitative real-time PCR, were not significantly different between premenopausal and postmenopausal breast cancers, but 17beta-HSD1 mRNA expression levels were significantly higher in postmenopausal than premenopausal breast cancers (p < 0.05). Intratumoral E2/E1 ratios were significantly higher in postmenopausal than premenopausal breast cancers (p < 0.01). These results demonstrate that the increased conversion from E1 to E2 catalyzed by 17beta-HSD1 may play an important role in the maintenance of the intratumoral high E2 levels in postmenopausal patients.

Regulation of aromatase by nuclear receptors

We investigated the effects of a nuclear receptor system constituted by retinoid X receptor (RXR) and its heterodimer partner on the aromatase activity in a cultured MCF-7 human breast cancer cell line and also in human ovarian granulosa cells, using each selective ligand for retinoic acid receptor, RAR (TTNPB), retinoid X receptor, RXR (LG100268), PPARgamma (troglitazone), and vitamin D3 receptor (cholecalciferol). In MCF-7 cells, the combined treatment with TTNPB and LG100268 caused a dramatic stimulation of the aromatase activity. The combined treatment with other ligand and LG100268 had little or no effect on the aromatase activity. The increase in the aromatase activity by TTNPB plus LG100268 was accompanied by an increase in the P450arom mRNA levels, which was also found to be related to the specific usage of promoter 1a of the CYP19 gene. These results suggest that a nuclear receptor system constituted by a RAR:RXR heterodimer is involved in the regulation of aromatase activity in MCF-7 breast cancer cells. In cultured human ovarian granulosa cells obtained from patients who underwent in vitro fertilization, troglitazone or LG100268 alone decreased the aromatase activity, while the combined treatment caused an even greater reduction in this activity. Little effect of other specific ligands for RXR heterodimer partners may support the notion that the effects of troglitazone and/or LG100268 in human granulosa cells may be mediated through the specific activation of PPARgamma:RXR heterodimer system. Since similar manners of effects of several PPARgamma ligands and/or LG100268 on the aromatase activity were observed in a newly established human ovarian granulosa cancer cell line, KGN, we performed the detailed analysis of the mechanisms of these effects using this cell line. As a result, the inhibitory effect of aromatase activity by troglitazone plus LG100268 was accompanied by the decrease of P450arom mRNA level. Furthermore, the loss of P450arom expression was considered to be due to both the decreased transcription and rapid degradation of its RNA based on the studies of nuclear run-on assay and RNA stability assay. In conclusion, RAR:RXR and PPARgamma:RXR heterodimer nuclear receptor systems may be other important modulators of estrogen production in human breast cancer cells and ovarian granulosa cells, respectively.

The selective estrogen enzyme modulator (SEEM) in breast cancer

Human breast cancer tissue contains all the enzymes (estrone sulfatase, 17beta-hydroxysteroid dehydrogenase, aromatase) involved in the last steps of estradiol biosynthesis. This tissue also contains sulfotransferase for the formation of the biologically inactive estrogen sulfates. In the last years, it was demonstrated that various progestins (promegestone, nomegestrol acetate, medrogestone), as well as tibolone and its metabolites are potent inhibitors of sulfatase and 17beta-hydroxysteroid dehydrogenase activities. It was also shown that medrogestone, nomegestrol acetate, promegestone or tibolone can stimulate the sulfotransferase activity for the local production of estrogen sulfates. All these data, in addition to numerous agents, which can block the aromatase action, lead to the new concept of selective estrogen enzyme modulators (SEEM), which can largely apply to breast cancer tissue. The exploration of various progestins and other active agents in trials with breast cancer patients, showing an inhibitory effect on sulfatase and 17beta-hydroxysteroid dehydrogenase, or a stimulatory effect on sulfotransferase, will provide a new possibility in the treatment of this disease.

A nuclear receptor system constituted by RAR and RXR induces aromatase activity in MCF-7 human breast cancer cells

Estrogen is the most important endocrine hormone that stimulates the growth of hormone-dependent breast cancer. The biosynthesis of estrogens in breast tissue is catalyzed by cytochrome P450 aromatase (P450arom). The expression of P450arom is controlled by the tissue- or cell-specific promoters of CYP 19 gene. The roles of nuclear receptor systems for the aromatase activity in breast cancer cells have not yet been fully investigated. In the present study, we investigated the effects of a nuclear receptor system constituted by retinoid X receptor (RXR) and its heterodimer partner on the aromatase activity in a cultured MCF-7 human breast cancer cell line, using each selective ligand for retinoic acid receptor (RAR) (TTNPB), RXR (LG100268), PPARgamma (troglitazone), and vitamin D(3) receptor (vitamin D(3)). The treatment of the cells with TTNPB or LG100268 alone for 2 days increased slightly the aromatase activity, but the increases were not statistically significant in comparison to the control. However, the combined treatment with TTNPB (10(-7) M) and LG100268 (10(-7) M) caused a dramatic stimulation of the aromatase activity. The treatment with other ligands had little or no effect on the aromatase activity. The stimulation of the aromatase activity by TTNPB plus LG100268 was dose-dependent, and a maximum stimulation was observed at 10(-7) M in both compounds. In addition, the increase in the aromatase activity was accompanied by an increase in the P450arom mRNA levels determined by RT-PCR in MCF-7 cells. The increase in the P450arom transcript was also found to be related to the specific usage of promoter 1a of the CYP 19 gene based on the analysis using RT-PCR. This is the first demonstration that a nuclear receptor system constituted by a RAR:RXR heterodimer is involved in the regulation of aromatase activity in MCF-7 breast cancer cells.

Effects of pinostrobin on estrogen metabolism and estrogen receptor transactivation

The interaction between the estrogen receptor and 5-hydroxy-7-methoxyflavanone (pinostrobin) was studied in the presence or absence of estradiol or dehydroepiandrosterone sulfate (DHEAS), respectively, using a stably transfected human breast cancer cell line (MVLN). We also evaluated its action on the proliferation in estrogen-dependent (MCF-7) human breast cancer cells in the same conditions than the estrogen receptor assay. On the other hand pinostrobin was evaluated for their effects on the human placental aromatase, 3beta-hydroxysteroid dehydrogenase Delta(4)/Delta(5) isomerase and 17beta-hydroxysteroid dehydrogenase activities. Pinostrobin did not possess antiestrogenic activity but presented anti-aromatase activity and decreased the growth of MCF-7 cells induced by DHEAS and E(2). This study provides particularly evidence of the potential biological interest of pinostrobin among the flavonoids.

Comparison of estrogen concentrations, estrone sulfatase and aromatase activities in normal, and in cancerous, human breast tissues

In the present study, the concentrations of estrone (E(1)), estradiol (E(2)) and their sulfates (E(1)S and E(2)S), as well as the sulfatase and aromatase activities, were evaluated in post-menopausal patients with breast cancer. Comparative studies of the evaluation of these parameters were carried out in (a) tumor tissue, (b) areas surrounding the tumor, and (c) areas distant from the tumor (glandular tissue) which were considered as normal tissue. The levels (in pm/g; mean +/- SEM) were: for E(1) in the (a) area: 320+/-95; in (b): 232+/-86; and in (c): 203+/-71; for E(2) in the (a) area: 388+/-106; in (b): 224+/-48; and in (c): 172+/-80; for E(1)S in the (a) area: 454+/-110; in (b): 259+/-90; and in (c): 237+/-65; for E(2)S in the (a) area:318+/-67; in (b): 261+/-72; and in (c): 232+/-75, respectively. The values of E(1)S and E(2) were significantly higher in the tumor tissue than in the area considered as normal. In all the tissues studied, the sulfatase activity was much higher than aromatase (130-200). In addition, the sulfatase levels were significantly higher in the peripheral and in the tumor tissue than in the area considered as normal. The levels of aromatase were significantly higher in tumoral than in normal tissue. The present data extend the "intracrine concept" for breast cancer tumors. The physiopathology and clinical significance as promoter parameters in breast cancer is to be explored.

The SEEM: selective estrogen enzyme modulators in breast cancer

Human breast cancer tissue contains all the enzymes (estrone sulfatase, 17 beta-hydroxysteroid dehydrogenase, aromatase) involved in the last steps of estradiol biosynthesis. This tissue also contains sulfotransferase for the formation of the biologically inactive estrogen sulfates. In the past years, it has been demonstrated that various progestins (promegestone, nomegestrol acetate, medrogestone) as well as tibolone and its metabolites are potent inhibitors of sulfatase and 17 beta-hydroxysteroid dehydrogenase activities. It was also shown that medrogestone, nomegestrol acetate, promegestone or tibolone can stimulate the sulfotransferase activity for the local production of estrogen sulfates. All these data, in addition to numerous agents which can block the aromatase action, lead to the new concept of Selective Estrogen Enzyme Modulators (SEEM) which can largely apply to breast cancer tissue. The exploration of various progestins and other active agents in trials with breast cancer patients, showing an inhibitory effect on sulfatase and 17 beta-hydroxysteroid dehydrogenase, or a stimulatory effect on sulfotransferase, will provide a new option in the treatment of this disease.

Biological effects of progestins in breast cancer

Developments in the synthesis of different progestins have opened up new possibilities for the biological effects and therapeutic uses of these compounds. The actions of progestins are a function of their structure, affinity to the progesterone receptor or to other steroid receptors, the target tissue considered, the biological response, the experimental conditions, dose, and metabolic transformation. Data on the action of progestins in breast cancer patients are very limited. A positive response with the progestins medroxyprogesterone acetate and megestrol acetate has been obtained in postmenopausal patients with advanced breast cancer. However, extensive information on the effect of progestins was obtained in in vitro studies using hormone-dependent and hormone-independent human mammary cancer cell lines. It was demonstrated that in hormone-dependent breast cancer cells, various progestins (nomegestrol acetate, medrogestone, promegestone) as well as tibolone, are potent sulfatase-inhibitory agents. Progestins may also be involved in the inhibition of the mRNA of this enzyme. In another series of studies, it was also demonstrated that various progestins are very active in inhibiting the 17 beta-hydroxysteroid dehydrogenase for the conversion of estrone to estradiol. More recently, it has been observed that promegestone or medrogestone stimulates the sulfotransferase for the formation of estrogen sulfates. Clinical trials of these enzymatic effects on the formation and transformation of estradiol in breast cancer patients could be the next step to investigate new therapeutic possibilities for this disease.

Effect of Medrogestone on 17beta-hydroxysteroid dehydrogenase activity in the hormone-dependent MCF-7 and T-47D human breast cancer cell lines

Estradiol (E2) is one of the most important hormones supporting the growth and evolution of breast cancer. Consequently, to block this hormone before it enters the cancer cell, or in the cell itself, has been one of the main targets in recent years. In the present study we explored the effect of Medrogestone (Prothil) on 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activities of the hormone-dependent MCF-7 and T-47D human breast cancer cell lines. Using physiological doses of estrone ([3H]-E1: 5 x 10(-9) mol/l) this estrogen is converted in a great proportion to E2 in both cell lines. After 24 h of the cell culture, Medrogestone significantly inhibits this transformation in a dose-dependent manner by 39% and 80% at 5 x 10(-8) M and 5 x 10(-5) M, respectively in T-47D cells; the effect is less intense in MCF-7 cells: 25% and 55% respectively. The IC50 values are 0.45 micromol/l in T-47D and 17.36 micromol/l in MCF-7 cells. It is concluded that the inhibition provoked by Medrogestone on the reductive 17beta-HSD activity involved in the local biosynthesis of the biologically active estrogen estradiol, may constitute a new therapeutic approach for the treatment of breast cancer.

C19 steroids estrogenic activity in human breast cancer cell lines: importance of dehydroepiandrosterone sulfate at physiological plasma concentration

The estrogenic action of C19 steroids on breast cancer cells was measured by bioluminescence in stably transfected human breast cancer MCF-7 and T47D cell lines with a reporter gene that allows expression of the firefly luciferase enzyme under control of an estrogen regulatory element. The "estrogenic activity" of C19 steroids, such as dehydroepiandrosterone (DHEA) and its sulfate (DHEAS), androst-5-en-3 beta,17 beta-diol, androst-4-en-3,17-dione, dihydrotestosterone, testosterone, and 5 alpha-androstan-3 beta,17 beta-diol was studied. This showed that DHEAS, at concentration observed in physiological conditions (10(-6) M), had a high "estrogen-like effect" in MCF-7 and T47D cell lines. Other C19 steroids, at physiological plasma concentration, alone or together did not have any significant effect on the luciferase activity. Moreover aminoglutethimide, an inhibitor of the aromatase enzyme, in the presence of C19 steroids, partially decreased the luciferase activity. These results suggest that MCF-7 and T47D cell lines could convert DHEAS to estrogen-like compounds by different enzymatic systems.

Aromatase and 17beta-hydroxysteroid dehydrogenase inhibition by flavonoids

A method for estimating in the same assay both aromatase and 17beta-hydroxysteroid dehydrogenase activities in human placental microsomes using radiolabelled [1,2,6,7-3H]4-androstene-3,17-dione was proposed. In this assay, estrone (E1) and estradiol (E2) produced were separated by HPLC and estimated using a radioactive flow detector. Using this method, the inhibitory effect of various flavonoids, including flavone, flavanone and isoflavone, on the human placental aromatase and 17beta-hydroxysteroid dehydrogenase was studied. Flavonoids were shown to be potent inhibitors of both aromatase and 17beta-hydroxysteroid dehydrogenase activities. We found that 7-hydroxyflavone and apigenin are the most effective aromatase and 17beta-hydroxysteroid dehydrogenase inhibitors, respectively. Experiments showed that a hydroxyl group in position 7 was essential for anti-17beta-hydroxysteroid dehydrogenase activity. However, flavonoids with 7-methoxy or 8-hydroxyl groups on the A ring showed only anti-aromatase activity. Structure-activity relationships were discussed.

Estrogenic and antiproliferative activities on MCF-7 human breast cancer cells by flavonoids

The interaction between the estrogen receptor and a variety of flavonoids was studied in the presence or absence of estradiol using a stably-transfected human breast cancer cell line (MVLN). On the other hand, flavonoids were evaluated for their effects on proliferation in estrogen-dependent (MCF-7) and independent (MDA-MB231) human breast cancer cells. We established a relationship structure-activity and determined regions and/or substituents essential for estrogenic or antiestrogenic activities. In contrast, we did not find the same relationship for cell proliferation. Among all flavonoids used, only 7-methoxyflavanone and 7,8-dihydroxyflavone at high concentrations (50 microM) possess antiestrogenic and antiproliferative activities. These results suggest that two hydroxyls (in positions 7 and 8) or 7-methoxy substituents are essential for the antiestrogenic activity of flavonoids. However, it seems that flavonoids at high concentrations exert their antiproliferative activity through other estrogen receptor-independent mechanisms.

Progestins and breast cancer

In the last years there has been an extraordinary development in the synthesis of new progestins. These compounds are classified, in agreement with their structure, in various groups which include progesterone, retroprogesterones, 17alpha-hydroxyprogesterones, 19-norprogesterones, 17alpha-hydroxyprogesterone derivatives, androstane and estrane derivatives. The action of progestins is a function of many factors: its structure, affinity to the progesterone receptor or to other steroid receptors, the target tissue considered, the biological response, the experimental conditions, dose, and metabolic transformation. The information on the action of progestins in breast cancer patients is very limited. Positive response with the progestins: medroxyprogesterone acetate and megestrol acetate was obtained in post-menopausal patients with advanced breast cancer. However, extensive information on the effect of progestins was obtained in in vitro studies using hormone-dependent and hormone-independent human mammary cancer cell lines. It was demonstrated that in the hormone-dependent breast cancer cells, various progestins (nomegestrol acetate, tibolone, medrogestone, promegestone) are potent sulfatase inhibitory agents. The progestins can also involve the inhibition of mRNA of this enzyme. In another series of studies it was also demonstrated that various progestins are very active in inhibiting the 17beta-hydroxysteroid dehydrogenase for the conversion of estrone to estradiol. More recently it was observed that the progestins promegestone or medrogestone stimulate the sulfotransferase for the formation of estrogen sulfates. Consequently, the blockage in the formation of estradiol via sulfatase, or the stimulatory effect on sulfotransferase activity, by progestins can open interesting and new possibilities in clinical applications in breast cancer.

Steroid metabolism in the hormone dependent MCF-7 human breast carcinoma cell line and its two hormone resistant subpopulations MCF-7/LCC1 and MCF-7/LCC2

Androgen and estrogen metabolism was investigated in the hormone-dependent human breast cancer cell line MCF-7 and its two hormone-resistant sublines MCF-7/LCC1 and MCF-7/LCC2. Using the product isolation method, the activity of aromatase, 5alpha-reductase, 3alpha/beta-hydroxysteroid oxidoreductase and 17beta-hydroxysteroid oxidoreductase were investigated isolating the following steroids: estriol (E3), estradiol (E2), estrone (E1), 3alpha/beta-androstanediol (A-diol), testosterone (T), dihydrotestosterone (DHT), androsterone (AND), androstenedion (4-AD) and androstanedione (A-dion). For all experiments, cells were preincubated with cortisol and subsequently incubated with [14C]T or [14C]4-AD as the substrate in medium without phenol red and with serum charcoal stripped of steroids. The results showed no aromatase activity in any of the cell lines under the experimental conditions used, and preincubation with cortisol had no effect on the enzyme activity. With [14C]T as the substrate, the metabolized level of DHT was very similar in the three cell lines, though MCF-7/LCC1 and MCF-7/LCC2 utilized the substrate to a much lesser extent. The amount of DHT and 4-AD produced were comparable in the two hormone-resistant cell lines, while the amount of 4-AD was significantly higher in MCF-7 cells. No differences in enzyme activity were found in the three cell lines when [14C]4-AD was used as the substrate. This study showed an altered androgen metabolism in the MCF-7/LCC1 and MCF-7/LCC2 sublines compared to the parent MCF-7. However, since treatment with DHT and T inhibited cell growth equally well in all three tumor cell lines, it is unlikely that the found differences in steroid metabolism was involved in the acquisition of the endocrine resistance of the two MCF-7 sublines.

Concentrations of estrone, estradiol and their sulfates, and evaluation of sulfatase and aromatase activities in patients with breast fibroadenoma

In the present studies, the concentrations (mammary tissue and plasma) of estrone (E1), estradiol (E2) and their sulfates (E1S and E2S), as well as the sulfatase and aromatase activities, were evaluated in patients with breast fibroadenomas. Comparative studies of the evaluation of these parameters were carried out in: (A) tumor tissue, (B) areas surrounding the tumor and (C) areas distant from the tumor (glandular tissue) considered as normal tissue. The concentrations in the tumor tissue (in pmol/g tissue) of E1, E2 and E1S were significantly higher (2-3 times) than in the area of the breast considered as normal. Sulfatase and aromatase activities were found in the breast fibroadenoma tissue. Sulfatase activity was much higher than aromatase (30-150 times) and sulfatase levels were significantly higher in the fibroadenoma tissue than in the area considered as normal. Plasma evaluation of E1, E2, E1S and E2S concentrations showed no significant differences in relation to those of healthy control women. In conclusion, the high levels of estrogens and their sulfates, as well as the enzymes involved in estrogen formation--sulfatase and aromatase in breast fibroadenoma--contribute to the hypothesis that this disease may be hormone-dependent.

11 beta-Hydroxysteroid dehydrogenase 1 activity and gene expression in human adipose stromal cells: effect on aromatase activity

The biological activity of glucocorticoids in target tissues can be influenced by locally produced 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), the enzyme responsible for the interconversion of cortisol and its inactive metabolite cortisone. In human adipose stromal cells, glucocorticoids are potent stimulators of the conversion of androgens to estrogens (aromatase activity). The present study was designed to determine whether 11 beta-HSD activity was present in human adipose stromal cells, and if changes in the activity of this enzyme could influence aromatase activity. 11 beta-HSD activity was determined by a radiometric conversion assay in breast adipose tissue from six patients. It was found that both dehydrogenase (cortisol to cortisone) and reductase (cortisone to cortisol) activities were present in all six subjects, and the reductase activity was always predominant. Carbenoxolone (CBX), a potent inhibitor of 11 beta-HSD, added to the culture medium at 50 and 200 microM, resulted in 39 +/- 4% and 85 +/- 1% inhibition, respectively, of both reductase and dehydrogenase activity of 11 beta-HSD. To determine whether alterations in 11 beta-HSD could influence aromatase activity, the effect of CBX (200 microM) on cortisol- and cortisone-induced changes in the conversion of androstenedione to estrone was examined. CBX prevented the stimulatory effect of cortisone and minimally potentiated the stimulatory effect of cortisol on aromatase activity, reflecting an inhibition of the local activation of cortisone and the local metabolism of cortisol, respectively. In order to determine whether the product of the 11 beta-HSD 1 gene was responsible for the observed 11 beta-HSD activity, total RNA extracts from these cells were subjected to Northern blot analysis using human 11 beta-HSD 1 cDNA as the probe. A single 1.8 11 beta-HSD 1 transcript was detected, and its abundance was reduced by CBX. No 11 beta-HSD 2 mRNA was detected. The present results demonstrate that the 11 beta-HSD 1 gene is expressed and functional in human breast adipose stromal cells and that changes in 11 beta-HSD 1 activity result in alterations in aromatase activity.

Aromatase activity and CYP19 gene expression in breast cancers

The aromatase enzyme complex is responsible for the conversion of C19 androgens to oestrogens. Aromatase expression in oestrogen-responsive breast cancers may be an important mechanism of autocrine regulation in tumour growth. To evaluate whether aromatase cytochrome P450 (P450arom) transcript levels within breast tumours were correlated to the enzyme activity, a specific competitive reverse transcription-polymerase chain reaction (RT-PCR) was developed. In this reaction, a 32 base-deleted complementary RNA was used as internal standard. In vitro aromatase activity was measured by either the tritium release assay or characterization of oestrogen fractions. Results indicate that there is a positive correlation between P450arom transcript levels and enzyme activity, but the relationship does not reach statistical significance. Therefore, whereas aromatase mRNA quantification may be an option by which to monitor the potential of tumour to synthesize oestrogens, it will not accurately reflect enzyme activity in a minority of tumours. Preliminary evidence was obtained in a tumour with low enzyme activity and a high P450arom transcript level for the presence of an endogenous aromatase inhibitor. This study highlights the necessity to characterize factors involved in the regulation of aromatase activity in such tumours.

Formestane. A review of its pharmacological properties and clinical efficacy in the treatment of postmenopausal breast cancer

Formestane (4-hydroxyandrostenedione) is an aromatase inhibitor which significantly reduces plasma levels of estrogen and has shown antitumour activity in postmenopausal women with breast cancer. Objective response rates in heavily pretreated patients with advanced breast cancer generally range between 20 and 30% during treatment with intramuscular formestone 250 or 500mg once every 2 weeks, and a further 20 to 30% of patients experience disease stabilisation. The median duration of response is between 8 and 14 months. Highest response rates are observed in soft tissue metastases, in patients with estrogen-responsive tumours and in those showing a response to previous endocrine therapy. Furthermore, there is some evidence to suggest that higher response rates are achieved with formestane 500 versus 250mg once every 2 weeks. In comparative studies, the clinical efficacy of intramuscular formestane 250mg did not differ significantly from that of oral megestrol when administered as second-line endocrine therapy to patients with advanced disease in whom previous tamoxifen therapy had failed. In addition, formestane produced a response rate, duration of response and overall survival rate that was not significantly different from that of oral tamoxifen when administered as first-line endocrine therapy to patients with advanced disease, but tamoxifen was superior in some measures. Further investigation of these 2 agents, including the higher dosage of formestane (500mg), is necessary to confirm their relative efficacies. Formestane is well tolerated by the majority of patients; adverse events rarely necessitate cessation of therapy. The most common adverse events are local reactions at the injection site and systemic events usually related to the effect of the drug on the hormonal milieu. The systemic tolerability of formestane is similar to that of tamoxifen but better than that of megestrol. Thus, formestane is effective and well tolerated as first-line endocrine therapy for advanced disease. However, at present, it is unlikely to challenge tamoxifen in this indication, based on recent findings from a large comparative study and the fact that formestane requires intramuscular administration. Nonetheless, formestane, which appears to have a better tolerability profile than other currently available second-line agents (including megestrol and the aromatase inhibitor aminoglutethimide), is a valuable drug for the second-line treatment of postmenopausal women with advanced breast cancer.

An in vivo model of intratumoural aromatase using aromatase-transfected MCF7 human breast cancer cells

About two-thirds of human breast carcinomas contain detectable levels of aromatase, the enzyme which converts androgens to oestrogens. Assessment of the importance of this enzyme to breast cancer growth has been hampered by the absence of an adequate model system. We have previously reported that MCF7 human hormone-dependent breast cancer cells transfected with human aromatase cDNA (Arom1 cells) showed a growth response in vitro to exogenous androgens and this effect was blocked by aromatase inhibitors. We report here our use of these cells to develop a xenograft model in athymic nude mice. Neither MCF7 cells nor Arom1 cells formed tumours in oophorectomised (ovx) nude mice unless provided with oestradiol (E2) support. Once established, Arom1, but not MCF7, tumours could be grown in ovx females supplemented with androstenedione (delta 4A). The mean plasma level of delta 4A was 14 nmol/L in supplemented animals and < 0.5 nmol/L in unsupplemented animals. Similarly, unsupplemented male nude mice were able to support the growth of Arom1 tumours but not MCF7 tumours. The potent and highly specific aromatase inhibitor CGS20267 (letrozole) significantly decreased tumour growth at 2 mg/kg/day and completely inhibited growth at 20 mg/kg/day in delta 4A-supplemented but not E2-supplemented animals. Our results indicate that delta 4A-dependent growth of Arom1 tumours in vivo is mediated through the action of intratumoural aromatase. This model should allow an assessment of the critical levels of aromatase required for tumour growth support.

Estrone sulfate-sulfatase and 17 beta-hydroxysteroid dehydrogenase activities: a hypothesis for their role in the evolution of human breast cancer from hormone-dependence to hormone-independence

The evaluation of estrogens (estrone, estradiol, and their sulfates) in the breast tissue of post-menopausal patients with breast cancer indicates high levels, particularly of estrone sulfate (E1S) which is 15-25 times higher than in the plasma. Breast cancer tissue contains the enzymes necessary for local synthesis of estradiol and it was demonstrated that, despite the presence of the sulfatase and its messenger in hormone-dependent and hormone-independent breast cancer cells, this enzyme operates particularly in hormone-dependent cells. Different progestins: Nomegestrol acetate, Promegestone, progesterone, as well as Danazol, can block the conversion of E1S to E2 very strongly in hormone-dependent breast cancer cells. The last step in the formation of estradiol is the conversion of E1 to this estrogen by the action of 17 beta-hydroxysteroid dehydrogenase. This activity is preferentially in the reductive direction (formation of E2) in hormone-dependent cells, but oxidative (E2-->E1) in hormone-independent cells. Using intact hormone-dependent cells it was observed that Nomegestrol acetate can block the conversion of E1 to E2. It is concluded, firstly, that in addition to ER mutants other factors are involved in the transformation of hormone-dependent breast cancer to hormone-independent, this concerns the enzymatic activity in the formation of E2; it is suggested that stimulatory or repressive factor(s) involved in the enzyme activity are implicated as the cancer evolves to hormone-independence; secondly, different drugs can block the conversion of E1S to E2. Clinical trials of these "anti-enzyme" substances in breast cancer patients could be the next step to investigate new therapeutic possibilities for this disease.

Transformation of estrone and estradiol in hormone-dependent and hormone-independent human breast cancer cells. Effects of the antiestrogen ICI 164,384, danazol, and promegestone (R-5020)

Using different hormone-dependent (MCF-7, T-47D) and hormone-independent (MDA-MB-231, Hs-578S, MDA-MB-436) human breast cancer cells, the interconversion estrone (E1)<-->estradiol (E2) was explored. The data show very clearly that in the hormone-dependent cells the tendency is to form E2 after incubation with E1, whereas after incubation with E2 most of this estrogen remains unchanged. In the hormone-independent cells, in contrast most of E1 remains E1, while E2 is converted into E1. The tendency of the reductive<-->oxidative direction is supported by the analysis of estrogens in the culture medium. To explore the possible action of different drugs on the 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity, it was observed that the potent antiestrogen ICI 164,384 inhibits the conversion of E1 to E2, while a lesser effect is observed with Danazol and only weak inhibition is obtained with the progestagen Promegestone (R-5020). It is concluded that the orientation of 17 beta-HSD activity for the interconversion E1<-->E2 in hormone-dependent and -independent cells is related to the hormonal status of the cells.

Induction of aromatase gene expression in human placental choriocarcinoma (JAR) cells by phorbol esters

The expression of aromatase in JAR cells, human placental choriocarcinoma cells, was found to be induced by the treatment of phorbol 12,13-diacetate (PDA), phorbol 12,13-didecanoate (PDD), or phorbol 12-myristate 13-acetate (TPA), but not 4 alpha-phorbol, 12,13-didecanoate (4 alpha PDD). At 1 microM or higher concentrations, these phorbol esters increased the level of aromatase mRNA and aromatase activity in a dose- and time-dependent fashion. Since the rates of the decrease of aromatase mRNA in phorbol ester treated and untreated cells were not significantly different in the presence of actinomycin D, the induction was not due to an increase in the stability of aromatase mRNA, but rather due to an increase in the synthesis of aromatase mRNA. The stimulation was not inhibited by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7). It is thought that the induction either follows a protein kinase C-independent manner or results from a down-regulation of protein kinase C pathway. Studies from several laboratories have revealed that the regulation of the expression of aromatase in estrogen-producing cells involves very complex processes. The apparent induction of aromatase expression in JAR cells by phorbol esters represent a mechanism modulating estrogen production in human placental choriocarcinoma cells, that may or may not be utilized in other estrogen-producing cells.

Recent data on estrogen sulfatases and sulfotransferases activities in human breast cancer

Of the total number of breast cancers approx. 30-50% are hormone-dependent and estradiol is one of the main factors of cancerization. Consequently, the control of this hormone inside the cancer cell is of capital importance because it is well established that the inhibition of estradiol biosynthesis can have a positive effect on the evolution of the disease. The blockage of estradiol can be obtained by the action of anti-aromatases, anti-sulfatases, the control of the 17 beta-hydroxysteroid dehydrogenase activity or by the stimulation of the sulfotransferase which converted the estrogens in their sulfates. In breast cancer tissue estrone sulfate is quantitatively the most important source of estradiol. In the intact cell, estrone sulfatase activity is very intense in the hormone-dependent cell lines (e.g. MCF-7, T-47D) but very small activity is observed in the hormone-independent (e.g. MDA-MB-231, MDA-MB-436) cell lines. However, this activity became very strong after homogenization in the hormone-independent cells, suggesting the presence of repressive factor(s) for this enzyme or its sequestering in an inactive form, in the intact cells of these cell lines. In a series of previous studies it was found that in hormone-dependent cell lines different anti-estrogens: tamoxifen and derivatives, ICI 164,384, very significantly decrease the estradiol concentration originated from estrone sulfate, and recently it was observed that Decapeptyl (D-Trp6-gonadotropin-releasing hormone) in the presence of heparin can also decrease the conversion of estrone sulfate into estradiol. No significant effect was obtained in the presence of heparin or Decapeptyl alone. The estrone sulfatase activity can be inhibited by progesterone, the progestagen R-5020, and testosterone. In another series of recent studies the presence of very strong estrogen sulfotransferase activity has been shown in one breast cancer cell line, the MDA-MB-468. We can conclude that: (1) the control of estradiol concentration can be carried out in the breast cancer tissue itself; (2) estrone sulfate can play an important role in the bioavailability of estradiol in the breast cancer cell; and (3) as is the case for the aromatase, the control of: the estrogen sulfatase, estrogen sulfotransferase, and 17 beta-hydroxysteroid dehydrogenase can be new targets for therapeutic applications in breast cancer.

Multiple steroid metabolic pathways in ZR-75-1 human breast cancer cells

In order to characterize the main enzymatic systems involved in androgen and estrogen formation as well as metabolism in ZR-75-1 human breast cancer cells, incubation of intact cells was performed for 12 or 24 h at 37 degrees C with tritiated estradiol (E2), estrone (E1), androst-5-ene-3 beta, 17 beta-diol (5-ene-diol), dehydroepiandrosterone (DHEA), testosterone (T), androstenedione (4-ene-dione), dihydrotestosterone (DHT) or androsterone (ADT). The extra- and intracellular steroids were extracted, separated into free steroids, sulfates and non-polar derivatives (FAE) and identified by HPLC coupled to a Berthold radioactivity monitor. Following incubation with E2, 5-ene-diol or T, E1, DHEA and 4-ene-dione were the main products, respectively, thus indicating high levels of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD). When 4-ene-dione was used, on the other hand, a high level of transformation into 5 alpha-androstane-3,17-dione (A-dione), Epi-ADT and ADT was found, thus indicating the presence of high levels of 5 alpha-reductase as well as 3 alpha- and 3 beta-hydroxysteroid dehydrogenase. Moreover, some T was formed, due to oxidation by 17 beta-HSD. No estrogen was detected with the androgen precursors T or 4-ene-dione, thus indicating the absence of significant aromatase activity. Moreover, significant amounts of sulfates and non-polar derivatives were found with all the above-mentioned substrates. The present study shows that ZR-75-1 human breast cancer cells possess most of the enzymatic systems involved in androgen and estrogen formation and metabolism, thus offering an excellent model for studies of the control of sex steroid formation and action in breast cancer tissue.

Aromatase and other inhibitors in breast and prostatic cancer

Estrogens have an important role in the growth of breast and other hormone-sensitive cancers. We have shown that 4-hydroxyandrostenedione (4-OHA) selectively blocks estrogen synthesis by inhibiting aromatase activity in ovarian and peripheral tissues and reduces plasma estrogen levels in rat and non-human primate species. In postmenopausal men and women, estrogens are mainly of peripheral origin. When postmenopausal breast cancer patients were administered either by daily oral or parenteral weekly treatment with 4-OHA, plasma estrogen concentrations were significantly reduced. Complete or partial response to treatment occurred in 34% of 100 patients with advanced breast cancer, while the disease was stabilized in 12%. We recently studied the effects of 4-OHA and other aromatase inhibitors, 10-propargylestr-4-ene-3,17-dione (PED) and imidazo[1,5-alpha]3,4,5,6-tetrahydropyrin-6-yl-(4-benzonitrile) (CGS 16949A) as well as 5 alpha-reductase inhibitors, N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxyamide (4-MA) and 17 beta-hydroxy-4-aza-4-methyl-19norandrost-5-en-3-one (L651190) in prostatic tissue from 11 patients with prostatic cancer and six patients with benign prostatic hypertrophy (BPH), and from normal men at autopsy. We attempted to measure aromatase activity in tissue incubation by quantitating 3H2O released during aromatization of androstenedione or testosterone labeled at the C-1 position. The amount of 3H2O released from all samples was at least twice that of the heat inactivated tissue samples. The 3H2O release was significantly inhibited by 4-OHA and 4-MA, but not by the other aromatase inhibitors. However, when HPLC and TLC were used to isolate steroid products, no estrone or estradiol was detected in the incubates. Furthermore, no aromatase mRNA was detected following amplification by PCR. The 4-OHA was found to inhibit 5 alpha-reductase in both BPH and cancer tissue, although to a lesser extent than 4-MA. The other aromatase inhibitors were without effect. Although a mechanism involving intraprostatic aromatase is not likely, inhibitors may act to reduce peripherally-formed estrogens. In postmenopausal breast cancer, the results indicate that 4-OHA is of significant benefit.

Aromatase inhibitors and hormone-dependent cancers

Aromatase (estrogen synthetase) occurs in a variety of tissues. Using immunocytochemistry, we have recently located this enzyme in cellular compartments of several types of human tissue. Furthermore, we found the mRNA was located in the same structures where tested. As both gonadal and peripherally formed estrogen contribute to growth of hormone sensitive cancers, we have developed aromatase inhibitors to block synthesis of this hormone. We have determined that 4-hydroxyandrostenedione (4-OHA) selectively inhibits aromatase activity in ovarian and peripheral tissues and reduces plasma estrogen levels in rat and non-human primate species. 4-OHA was also found to inhibit gonadotropin levels and reduce estrogen and progesterone receptor levels in treated animals. The mechanism of these effects appear to be associated with the weak androgenic activity of the compound. These effects together with aromatase inhibition may result in a synergistic response reducing estrogen production and action. In postmenopausal women, estrogens are mainly of peripheral origin. When postmenopausal breast cancer patients were administered either daily oral or parenteral weekly treatment with 4-OHA at doses that did not affect their gonadotropin levels, plasma estrogen concentrations were significantly reduced. Complete or partial response to treatment occurred in 34% of 100 patients with advanced breast cancer, while the disease was stabilized in 12%. These results indicate that 4-OHA is of benefit in postmenopausal patients with advanced disease who have relapsed from prior hormonal therapies, and that steroidal inhibitors may be of value in premenopausal patients.

Comparison of the effect of cortisol on aromatase activity and androgen metabolism in two human fibroblast cell lines derived from the same individual

The effect of preincubation with cortisol on estrogen and androgen metabolism was investigated in human fibroblast monolayers grown from biopsies of genital and non-genital skin of the same person. The activity in the cells of aromatase, 5 alpha-reductase, 17 beta-hydroxysteroid oxidoreductase and 3 alpha-hydroxysteroid oxidoreductase was investigated by isolating estrone, estradiol, estriol, dihydrotestosterone, androstanedione, androsterone, 3 alpha-androstanediol, testosterone and androstenedione after incubation of the cells with [14C]testosterone or [14C]androstenedione. For experiments with 14C-labeled substrate the cells were incubated in medium, charcoal stripped of steroids without Phenol Red. Preincubation from 6 to 36 h with cortisol in concentrations of 10(-8) - 10(-6) M showed maximal stimulation of aromatase activity after 12 h preincubation with cortisol in concentrations of 0.5-1.0 x 10(-6) M in both cell lines. When preincubation with cortisol was omitted no estrogen synthesis was detected. The formation of androgen was not altered after preincubation with cortisol. Pronounced differences were found in estrogen and in androgen metabolism in the two cell lines suggesting a local regulation of the hormonal environment. The aromatase activity, which is low in many tissues could be stimulated by cortisol without altering the androgen metabolism was found to be a suitable system for investigations of the cellular interconversion of androgens and estrogens and for investigations of the in vitro regulation of the enzymes involved.

Wide spectrum of steroids serving as substrates for the formation of lipoidal derivatives in ZR-75-1 human breast cancer cells

Recently, several natural steroids have been found to be esterified to long-chain fatty acids (FAE) in various mammalian tissues. The purpose of the present study was to determine the ability of a series of 3H-labeled steroids to serve as substrates for the formation and accumulation of such non-polar derivatives in intact cells, using the hormone-responsive ZR-75-1 human breast cancer cell line as model. All 14 steroids tested were found to be converted, directly or following further metabolism, to lipoidal ester derivatives. The percentage of intracellular steroids recovered as FAE derivatives was usually substantial (14-90%), especially in the case of C-19 steroids (75-90%). The composition of the lipoidal steroid fractions recovered from the labeled cell extracts was characterized by chromatographic comparison with synthetic steroid FAEs and by saponification of the steroid FAEs and identification of the released steroidal moieties. Following metabolism, most steroid substrates were converted into multiple lipoidal esters. Furthermore, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane-3 beta, 17 beta-diol, as well as androst-5-ene-3 beta, 17 beta-diol formed lipoidal diesters in addition to the monoester form. The high level of intracellular steroid FAE accumulation reported in this study suggests that these yet poorly known steroid derivatives may play important functions in the regulation of steroid hormone metabolism and action.