Inhibition of Estrogen Signaling Reverses Established Inguinal Hernias

Background: An inguinal hernia occurs when an intestinal loop or fat pushes through a weak spot in the lower abdominal muscle (LAM), causing a painful bulge that has the potential to cause bowel obstruction. Despite a high prevalence in men (~25%), non-surgical approaches are not available to treat this disease. We recently found a critical role of estrogen and estrogen receptor alpha (ERα) in inguinal hernia formation. To examine this further, we use a humanized aromatase mouse model (Arom^hum) where all of the male mice develop scrotal hernias as a pre-clinical model to test the first pharmacological intervention for inguinal hernias. These mice are utilized because their skeletal muscle tissue contains aromatase and produces estradiol (E2), which acts via ERα in the LAM stromal fibroblasts and leads to fibrosis and muscle atrophy. Hypothesis: E2-ERα modulation can inhibit and reverse the formation of inguinal hernias in Arom^hum mice by reducing LAM fibrosis and atrophy. Results: We tested three types of treatments to inhibit E2-ERα signaling: letrozole, fulvestrant, and raloxifene. Letrozole, an aromatase inhibitor, was shown to inhibit hernia formation and reversed small (150-175 mm²) scrotal hernias (n = 10-15/group, p<0.0001). The LAM tissues also showed a reduction in fibrosis (n = 5-8/group, p = 0.0004) and a concurrent increase in myofiber cross-sectional area (n = 5-8, p=0.0356) compared to placebo-treated mice. Similarly, fulvestrant and raloxifene, E2-ERα antagonists, also inhibited hernia formation (n = 10-15/group). Most interestingly, both drugs reversed large and severe hernias (>200 mm², n = 10-15/group), accompanied by a decrease in muscle fibrosis and increase in myofiber cross-sectional area (ongoing study, n = 10-11, p<0.0001) compared to placebo mice. The drug-treated mice had lower expression of pro-fibrotic genes such as Mmp3, Emb, Spon2, Timp1, and Tgfb1 in the LAM tissues compared to placebo-treated LAM. Furthermore, we analyzed the differences in extracellular matrix producing genes and muscle regeneration markers between the placebo and drug-treated muscle tissues. Conclusion: We find that inhibition of the E2-ERα signaling pathway can reverse mild or severe inguinal hernias. Successful treatment is accompanied by decreased skeletal muscle fibrosis and reversal of myocyte atrophy. These interventions are promising non-surgical treatment options for patients suffering from severe and recurrent inguinal hernias.

Single-Cell RNA Sequencing Reveals Novel Populations of Fibroblasts and Transcriptomic Changes Within Abdominal Skeletal Muscle in a Mouse Model of Aromatase-Induced Inguinal Hernia

Introduction: Inguinal hernia is a highly prevalent condition in men, of which the only currently available treatment is invasive surgical repair. An inguinal hernia often results from a protrusion of the intra-abdominal contents through a weakened region of the lower abdominal wall, but the etiology is unknown. One potential cause is aging-related steroid hormonal changes, which coincide with an increased incidence of hernia in aged men. Our group previously developed the first mouse model of inguinal hernia (Arom^Hum) that is generated via the humanized expression of the enzyme aromatase, which converts androgens to estrogens. In the lower abdominal muscle (LAM), an aromatase-mediated increase in tissue estrogen causes fibroblast proliferation, fibrosis, and myocyte atrophy, resulting in hernias. However, the molecular mechanism of this phenotype remains unclear. In this study, we aimed to find genome-wide transcriptomic differences in Arom^Hum compared to WT mice at a single-cell resolution. We hypothesized that in relation to WT mice, Arom^Hum mice would have distinct fibroblast signatures that arise from the increased estrogen exposure to LAM tissue. Methods: LAM was harvested from 9-10-week-old male WT and Arom^Hum mice (n=3 each) and digested into a single-cell suspension. Cells were processed via the 10X Genomics Chromium platform for single-cell RNA sequencing. The 6 samples combined yielded a total of ~63,000 cells. Data was analyzed using Cell Ranger v3, Seurat v3, Slingshot, and PROGENy R packages. Results: UMAP visualization of WT and Arom^Hum LAM tissue revealed 22 cell clusters, which we grouped into 10 broad cell types through known marker gene expression. Arom^Hum LAM contained a significantly higher proportion of fibroblasts than WT (44% vs. 27% of total analyzed cells), and Arom^Hum fibroblasts expressed more pro-fibrotic genes, such as Timp1, Spon2, and Postn. In Arom^Hum and WT combined, we found 6 clusters of fibroblast-like cells. Two of these clusters (clusters 2 and 3) were heavily represented by cells derived from Arom^Hum mice (85-90% of cells in each cluster), which we termed “hernia-associated fibroblasts” (HAFs). Cluster 3 HAFs expressed high levels of Esr1 (gene encoding ERα), as well as estrogen-responsive genes such as Pgr and Greb1, and was enriched for estrogen, hypoxia, and TGFβ signaling pathways. Cluster 2 HAFs expressed genes associated with a pathological state, such as Lbp, Cthrc1, Mmp3, and Il33, and was enriched for the NF-κB and TNF-α signaling pathways. Conclusions: We found that LAM fibrosis in Arom^Hum may result from the expansion of two distinct populations of HAFs - one is estrogen-responsive, and another is pathologic. Further in vitro / in vivo experiments are required to determine the relative contributions of these sub-populations of HAFs to fibrosis and inguinal hernias, leading to developing novel intervention strategies.

SAT-736 Dissecting the Relative Role of Estrogen and Androgen in Fibrosis, Skeletal Muscle Atrophy, and Inguinal Hernia Formation

Introduction: More than one in four men develop symptomatic inguinal hernia, and hernia repair is the most commonly performed general surgical procedure in the US. Despite its prevalence, the molecular mechanisms causing inguinal hernia remain unclear. Aromatase, the key enzyme for the conversion of testosterone (T) to estradiol (E2), is present in human but not mouse skeletal muscle tissue. We recently demonstrated that robustly increased local E2 levels in lower abdominal muscle (LAM) tissue and decreased circulating T levels were associated with fibrosis and myocyte atrophy in LAM tissue, leading to severe scrotal (inguinal) hernia formation in a humanized aromatase transgenic mouse model (Arom^hum) with a high LAM human aromatase expression. To further determine the relative role of estrogen and androgen in the development of inguinal hernia, we generated a novel mild Arom^hum mouse model with lower LAM aromatase expression compared with the severe model. Methods: Mild Arom^hum mice were followed for 6 months to determine hernia incidence and measure hernia size (n=30). We treated mild Arom^hum mice with the aromatase inhibitor, letrozole (n=12) for 12 weeks. Circulating and LAM E2 levels in mice were measured using mass spectrometry. LAM tissue fibrosis and myocyte size were determined by Masson’s trichrome staining and H&E staining, respectively. Results: The mild Arom^hum mice contain a single copy of the human aromatase genomic fragment with a truncated regulatory region, giving rise to significant but mildly elevated LAM E2 levels (2.5-fold) at 15 weeks of age. Interestingly, these mice maintain normal circulating T levels. Furthermore, we show that mildly increased LAM E2 without decreased circulating T levels cause hernia formation in about 88% of mild Arom^hum mice in contrast to 100% hernia formation in mice containing the full-length human aromatase regulatory region (severe Arom^hum model), suggesting that higher LAM estrogen and low serum T levels contribute to this severe phenotype. Treatment with an aromatase inhibitor restores LAM E2 levels to normal levels and completely prevents inguinal hernia formation in the mild Arom^hum mice. In LAM fibroblasts of mild Arom^hum mice, we find very high levels of estrogen receptor-α expression, which possibly mediates estrogen-induced hernia formation. Conclusion: Taken together, our findings from the mild Arom^hum mouse model suggest that lower levels of estrogen excess in LAM are the primary driver of muscle atrophy and hernia formation because this mouse model do not exhibit circulating T deficiency. Our findings will constitute a starting point for dissecting the relative roles of estrogen and androgen action in inguinal hernia development. This has the potential to facilitate drug development to prevent and treat hernias, especially recurrent hernias after primary hernia repairs in vulnerable populations such as elderly men.

OR09-03 Brain Aromatase Is Essential for Regulation of Sexual Activity in Male Mice

Introduction: The biologically active form of estrogen, estradiol (E₂), has important organizational roles in brain development and activational roles in adult brain physiology and behavior. It has been proposed that E₂ formation in the brain might regulate sexual activity in various species. The mechanisms that link estrogen formation in the brain and sexual behavior, however, remain unclear. Aromatase is the key enzyme that catalyzes the conversion of testosterone (T) to E₂ in the testis and brain of male mice. To determine the role of brain aromatase in male sexual activity, we generated a brain-specific aromatase knockout (bArKO) mouse model. Additionally, a newly generated total aromatase knockout (tArKO) mouse model served as a positive control. Methods: We generated the floxed aromatase mice (Arom^fl/fl), which flanked the transcription and translation start sites and the common splice acceptor site for the upstream brain promoter I.f of the aromatase gene. We then crossed Nestin-Cre mice with Arom^fl/fl mice to generate bArKO mice. Using the same Arom^fl/fl mice, we bred tArKO via crossing with ZP3-Cre mice. Circulating and tissue (brain and testis) E₂ levels were measured using liquid chromatography-tandem mass spectrometry. We assessed sexual activity in 12-14 week-old bArKO, tArKO and littermate control males over two 30-minute trials. The interactions were monitored and videotaped, and the videotape was scored for the sexual activity. To investigate whether the lack of estrogen production in the brain was causative for altered sexual behavior, 20 bArKO and 20 control mice were castrated at ~nine weeks of age and supplemented with exogenous sex hormone via 60-day time release pellet implantation. Results: E₂ levels are significantly decreased in the brain but not the testis of bArKO mice as compared to control mice (P < 0.05, n=6-12). As expected, E₂ levels in the brain and testis are significantly lower in tArKO mice compared with their WT littermates (n=6-9). Furthermore, we demonstrate that local aromatase expression and estrogen production in the brain is required for male sexual behavior and sex hormone homeostasis. Male bArKO mice exhibited significantly decreased sexual activity in the presence of strikingly elevated circulating T (n=5). In castrated adult bArKO mice, administration of E₂ together with T restored maximum sexual behavior (n=5). Thus, aromatase in the brain is necessary for T-dependent male sexual activity. We also found that brain aromatase is required for negative feedback regulation of circulating T of testicular origin. Conclusion: Our findings suggest T activates male sexual behavior in part via conversion to E₂ in the brain and provide the foundation for inhibition or enhancement of brain aromatase enzyme activity and/or utilization of selective estrogen receptor modulators in modifying sexual behavior.

DCB and HZ contributed equally to this work.

SAT-749 Defining The Role Of Androgens In Hernia Associated Skeletal Muscle Fibrosis

Introduction: Inguinal hernia is a highly prevalent condition occurring in 27% of adult men in their lifetime. The recurrence rate of hernia is 5-20%, resulting in a substantial cost burden in surgical repair procedures. Until recently, the mechanisms leading to the lower abdominal muscle (LAM) weakening characteristic of hernia were unknown. Our group developed the first mouse model of inguinal hernia through expression of the human aromatase enzyme in male mice (Arom^Hum). Aromatase converts androgens to estrogens, and is expressed in the skeletal muscle in humans, but not mice. We found that locally formed estrogen from aromatase activity in LAM and decreased circulating testosterone levels are associated with muscle atrophy and fibrosis resulting in hernia. However, it is unclear how decreasing androgen levels might affect muscle fibrosis, and defining this potential mechanism could impact hernia treatment. We hypothesized that low androgen levels promote muscle fibroblast proliferation and fibrosis, and that androgen treatment would prevent hernia progression in Arom^Hum mice.

Methods: Arom^Hum mice (3 weeks old) were treated with high-dose dihydrotestosterone (DHT) via injection for 7.5 weeks with hernia volume continuously recorded (n=5/group). Primary fibroblasts were isolated from LAM from WT and Arom^Hum mice (n=5/genotype). Cells were treated for 24 hours with increasing doses (0.001, 0.01, 0.1, 1, 5, 10 and 100 nM) of R1881, a synthetic androgen, and compared to untreated cells by western blot.

Results: Hernia volume was significantly decreased in Arom^Hum mice treated with DHT compared to vehicle-treated mice, and volume remained consistently suppressed after DHT treatment (p < 0.005). In both primary fibroblast lines, R1881 treatment increased AR levels in a dose dependent manner, indicating that the treatment was effective. Preliminary data indicated that low doses of R1881 (0.001 and 0.01 nM) increased PCNA levels in LAM WT and LAM Arom^Hum fibroblasts. Densitometry normalized to GAPDH showed 80% and 60% increases for 0.001 nM and 0.01 nM respectively in LAM WT fibroblasts, and 20% and 30% increases at these doses in LAM Arom^Hum fibroblasts. Higher doses of R1881 decreased PCNA levels in LAM Arom^Hum fibroblasts by 40% (10 nM) and 30% (100 nM), whereas a 25% decrease was detected in LAM WT fibroblasts at 100 nM.

Conclusion: These data suggest that low androgen doses increase LAM fibroblast proliferation, which possibly contributes to hernia formation. Androgen treatment at higher doses can partially block the progression of hernia in vivo. However, it is unclear whether and how androgen deficiency in combination with excess estrogen affects fibroblast proliferation and hernia formation. Additional research is required to determine if androgen supplementation in sufficient doses is a potential therapeutic for inguinal hernia and other muscle weakness diseases.

Adiposity Results in Metabolic and Inflammation Differences in Premenopausal and Postmenopausal Women Consistent with the Difference in Breast Cancer Risk

Obesity is associated with increased risk of breast cancer in postmenopausal but not in premenopausal women. Many factors may be responsible for this difference. The aim of this study was to determine the mechanisms by which the genes related to the AMPK pathway, inflammation, and estrogen actions are affected by adiposity in breast tissue with the objective of identifying differences that may explain the different breast cancer risk in premenopausal and postmenopausal women. Random fine needle aspirates (rFNAs) of breast tissue were collected from 57 premenopausal and 55 postmenopausal women and were classified as normal weight, overweight, or obese. Expression levels of 21 target genes were determined using a TaqMan Low Density Array procedure. Breast tissue estradiol levels were measured by a liquid chromatography-tandem mass spectrometry procedure, and serum estradiol and follicle-stimulating hormone (FSH) were measured by a radioimmunoassay and an enzyme-linked immunosorbent assay, respectively. We found that in postmenopausal women, serum and tissue estradiol levels were increased in those who were overweight, and serum FSH levels were decreased in obese status. Interestingly, RPS6KB1, an AMPK downstream-responsive gene for protein synthesis and cell growth, and estrogen receptor α (encoded by the ESR1 gene) and its target gene GATA3 were significantly decreased in rFNA of premenopausal, obese women. In postmenopausal women, RPS6KB1, ESR1, and GATA3 expression remained unchanged in relation to adiposity. However, prostaglandin-endoperoxide synthase 2 (PTGS2), cyclin D1 (CCND1), and another ESR1 target gene, TFF1, were elevated in rFNA of obese postmenopausal women. Thus, as bodyweight increases, gene expression is indicative of increased proliferation in postmenopausal women but decreased proliferation in premenopausal women. Overall, our data reveal a novel process by which obesity promotes the risk of breast cancer in postmenopausal but not premenopausal women.

Estrogen-dependent sushi domain containing 3 regulates cytoskeleton organization and migration in breast cancer cells

Aromatase inhibitors (AIs) are the standard endocrine therapy for postmenopausal breast cancer; however, currently used biomarkers, such as, estrogen receptor-alpha/progesterone receptor (ERα/PR), predict only slightly more than half of the potential responders to AI treatment. To identify novel markers of AI responsiveness, a genome-wide microarray analysis was performed using primary breast tumor samples from 50 postmenopausal women who later developed metastatic breast cancer. Sushi domain containing 3 (SUSD3) is a significantly differentially expressed gene, with 3.38-fold higher mRNA levels in AI-responsive breast tumors vs non-responders (P<0.001). SUSD3 was highly expressed in ERα-positive breast tumors and treatment with estradiol increased SUSD3 expression in ERα-positive breast cancer cells. Treatment with an antiestrogen or ERα knockdown abolished basal and estradiol-dependent SUSD3 expression. Recruitment of ERα upstream of the transcription start site of SUSD3 was demonstrated by chromatin immunoprecipitation-PCR. Flow cytometric analysis of SUSD3-knockdown cells revealed blunted estradiol effects on progression into S and M phases. SUSD3 was localized to the plasma membrane of breast cancer cells. SUSD3 knockdown decreased the appearance of actin-rich protrusions, stress fibers and large basal focal adhesions, while increasing the presence of cortical actin concomitant with a decrease in Rho and focal adhesion kinase activity. SUSD3-deficient cells demonstrated diminished cell spreading, cell-cell adhesion and motility. In conclusion, SUSD3 is a novel promoter of estrogen-dependent cell proliferation and regulator of cell-cell and cell-substrate interactions and migration in breast cancer. It may serve as a novel predictor of response to endocrine therapy and potential therapeutic target.

ERβ- and prostaglandin E2-regulated pathways integrate cell proliferation via Ras-like and estrogen-regulated growth inhibitor in endometriosis

In endometriosis, stromal and epithelial cells from the endometrium form extrauterine lesions and persist in response to estrogen (E2) and prostaglandin E2 (PGE2). Stromal cells produce excessive quantities of estrogen and PGE2 in a feed-forward manner. However, it is unknown how estrogen stimulates cell proliferation and survival for the establishment and persistence of disease. Previous studies suggest that estrogen receptor-β (ERβ) is strikingly overexpressed in endometriotic stromal cells. Thus, we integrated genome-wide ERβ binding data from previously published studies in breast cells and gene expression profiles in human endometriosis and endometrial tissues (total sample number = 81) and identified Ras-like, estrogen-regulated, growth inhibitor (RERG) as an ERβ target. Estradiol potently induced RERG mRNA and protein levels in primary endometriotic stromal cells. Chromatin immunoprecipitation demonstrated E2-induced enrichment of ERβ at the RERG promoter region. PGE2 via protein kinase A phosphorylated RERG and enhanced the nuclear translocation of RERG. RERG induced the proliferation of primary endometriotic cells. Overall, we demonstrated that E2/ERβ and PGE2 integrate at RERG, leading to increased endometriotic cell proliferation and represents a novel candidate for therapeutic intervention.

Ligand-activated peroxisome proliferator-activated receptor β/δ modulates human endometrial cancer cell survival

Endometrial cancer is the fourth most common malignancy among women and is a major cause of morbidity contributing to approximately 8,200 annual deaths in the USA. Despite advances to the understanding of endometrial cancer, novel interventions for the disease are necessary given that many tumors become refractory to therapy. As a strategy to identify novel therapies for endometrial carcinoma, in this study, we examined the contribution of the peroxisome proliferator-activated receptor β/δ (PPARβ/δ) to endometrial cancer cell proliferation and apoptosis. We found that when activated with the highly selective PPARβ/δ agonists, GW0742 and GW501516, PPARβ/δ inhibited the proliferation and markedly induced the apoptosis of three endometrial cancer cell lines. The specificity of the PPARβ/δ-induced effects on cell proliferation and apoptosis was demonstrated using PPARβ/δ-selective antagonists and PPARβ/δ small interfering RNA in combination with PPARβ/δ-selective agonists. Furthermore, we showed that PPARβ/δ activation increased phosphatase and tensin homolog expression, which led to protein kinase B (AKT) and glycogen synthase kinase-3β (GSK3β) dephosphorylation, and increased β-catenin phosphorylation associated with its degradation. Overall, our data suggest that the antitumorigenic effect of PPARβ/δ activation in endometrial cancer is mediated through the negative regulation of the AKT/GSK3β/β-catenin pathway. These findings warrant further investigation of PPARβ/δ as a therapeutic target in endometrial cancer.

Glucocorticoid-induction of hypothalamic aromatase via its brain-specific promoter

In the brain, a 36-kb distal promoter (I.f) regulates the Cyp19a1 gene that encodes aromatase, the key enzyme for estrogen biosynthesis. Local estrogen production in the brain regulates critical functions such as gonadotropin secretion and sexual behavior. The mechanisms that control brain aromatase production are not well understood. Here we show that the glucocorticoid dexamethasone robustly increases aromatase mRNA and protein by up to 98-fold in mouse hypothalamic cell lines in a dose- and time-dependent fashion. Using deletion mutants of the brain-specific promoter I.f and chromatin immunoprecipitation-PCR, we isolated a distinct region (-500/-200 bp) which becomes enriched in bound glucocorticoid receptor upon dexamethasone stimulation. A glucocorticoid antagonist or siRNA based knockdown of glucocorticoid receptor ablated dexamethasone stimulation of aromatase expression. Our findings demonstrate how glucocorticoids alter aromatase expression in the hypothalamus and might indicate a mechanism whereby glucocorticoid action modifies gonadotropin pulses and the menstrual cycle.

Regulation of aromatase expression in breast cancer tissue

Epithelial-stromal interactions play key roles for aromatase expression and estrogen production in breast cancer tissue. Upregulated aromatase expression in breast fibroblasts increases the tissue concentration of estradiol (E2), which then activates a large number of carcinogenic genes via estrogen receptor-alpha (ERalpha) in malignant epithelial cells. This clinically pertains, since aromatase inhibitors (AIs) are the most effective hormonal treatment of ERalpha-positive breast tumors. A single gene encodes aromatase, the key enzyme in estrogen biosynthesis, the inhibition of which by an AI effectively eliminates E2 production. Since alternative promoters regulated by distinct signaling pathways control aromatase expression, it is possible to target these pathways and inhibit estrogen production in a tissue-selective fashion. We and others previously found that the majority of estrogen production in breast cancer tissue was accounted for by the aberrant activation of the proximal promoter I.3/II region. PGE(2) that is secreted in large amounts by malignant breast epithelial cells is the most potent known natural inducer of this promoter region in breast adipose fibroblasts. Signaling effectors/transcriptional regulators that mediate PGE(2) action include the activator pathways p38/CREB-ATF and JNK/jun and the inhibitory factor BRCA1 in breast adipose fibroblasts. Selective inhibition of this promoter region may treat breast cancer while permitting aromatase expression via alternative promoters in the brain and bone and thus obviate the key side effects of the current AIs. The signaling pathways that mediate the regulation of the promoter I.3/II region in undifferentiated fibroblasts in malignant breast tumors are reviewed.

Aromatase and other steroidogenic genes in endometriosis: translational aspects

Endometriosis is a common, chronic and estrogen-dependent gynaecological disorder associated with pelvic pain and infertility. In addition to, or perhaps as a consequence of, immune, environmental and genetic factors, endometriotic lesions show high estradiol (E(2)) biosynthesis and low E(2) inactivation compared with normal endometrium. Current medical therapies of pain, which aim to lower circulating E(2) concentrations, are not effective in at least half of these patients. We and others recently demonstrated the expression of a few steroidogenic genes in endometriosis. The most important genes in this group are steroidogenic acute regulatory protein (StAR) and aromatase. Both are essential for E(2) production. Prostaglandin E(2) (PGE(2)) is the most potent known stimulator of both StAR and aromatase. PGE(2) production in endometriosis is up-regulated by increased levels of the enzyme cyclo-oxygenase-2 (COX-2) in this tissue. COX-2 in turn is stimulated by E(2), interleukin-1beta (IL-1beta) and PGE(2) itself in endometrial and endometriotic cells. Thus, there is a positive feedback loop that favours continuous formation of E(2) and PGE(2) in endometriosis. These basic findings led to recent phase-II studies employing aromatase inhibitors in the treatment of endometriosis. Aromatase inhibitors treat both postmenopausal and premenopausal endometriosis at least as effectively as the existing medical treatments. In premenopausal women, we and others administered aromatase inhibitors in combination with an ovarian-suppressant treatment. In this review, we emphasize the most recent basic studies in detail and provide a short summary of recent clinical trials.

Induction of cyclooxygenase-2 in human endometrial stromal cells by malignant endometrial epithelial cells: evidence for the involvement of extracellularly regulated kinases and CCAAT/enhancer binding proteins

We previously reported that human malignant endometrial epithelial cell conditioned medium (MECM) up-regulated cyclooxygenase (COX)-2 mRNA and protein levels in human normal endometrial stromal cells (ESC). Here we showed that pretreatment with a selective inhibitor of the extracellularly regulated kinase (ERK)1/2 signaling pathway blocked the MECM-induced COX-2 expression in ESC. Transient transfection assays indicated critical roles of a cAMP response element (CRE,-59/-53 bp) and a nuclear factor for interleukin (IL)-6 expression (NF-IL6) site (-132/-124 bp) in the regulation of basal and MECM-induced activity of COX-2 gene promoter in ESC. Employing electrophoretic mobility shift assays, we demonstrated that increased functional binding of CCAAT/enhancer binding protein (C/EBP)alpha, C/EBPbeta and upstream stimulatory factor-2 to the CRE and C/EBPalpha and C/EBPbeta to the NF-IL6 site were, at least in part, responsible for MECM-induced COX-2 expression in ESC. Moreover, overexpression of C/EBPalpha and C/EBPbeta significantly induced COX-2 promoter activity in ESC. Collectively, these results suggest that the basal and MECM-induced transcription of the COX-2 gene in ESC is regulated through a combination of the CRE and the NF-IL6 site by functional interactions of C/EBPalpha and C/EBPbeta.

Stromal PRs mediate induction of 17beta-hydroxysteroid dehydrogenase type 2 expression in human endometrial epithelium: a paracrine mechanism for inactivation of E2

Progesterone stimulates the expression of 17beta-hydroxysteroid dehydrogenase (HSD) type 2, which catalyzes the conversion of the potent estrogen, E2, to an inactive form, estrone, in epithelial cells of human endometrial tissue. Various effects of progesterone on uterine epithelium have recently been shown to be mediated by stromal PRs in mice. We describe herein a critical paracrine mechanism whereby progesterone induction of 17beta-HSD type 2 enzyme activity, transcript levels, and promoter activity in human endometrial epithelial cells are mediated primarily by PR in endometrial stromal cells. Medium conditioned with progestin-pretreated human endometrial stromal cells robustly increased 17beta-HSD type 2 enzyme activity (2-fold) and mRNA levels (13.2-fold) in Ishikawa malignant endometrial epithelial cells. In contrast, direct progestin treatment of Ishikawa epithelial cells gave rise to much smaller increases in enzyme activity (1.2-fold) and mRNA levels (4-fold). These results suggest that progesterone- dependent paracrine factors arising from stromal cells are primarily responsible for the induction of epithelial 17beta-HSD type 2 expression in the endometrium. We transfected serial deletion mutants of the -1,244 bp 5'-flanking region of the 17beta-HSD type 2 gene into Ishikawa cells. No progesterone response elements could be identified upstream of the 17beta-HSD type 2 promoter. Stromal PR-dependent induction of the 17beta-HSD type 2 promoter was mediated by a critical regulatory region mapped to the -200/-100 bp sequence. Direct treatment of Ishikawa cells with progestin gave rise to a maximal increase in the activity of -200 bp/Luciferase construct only by 1.2-fold, whereas medium conditioned by progestin-pretreated endometrial stromal cells increased promoter activity up to 2.4-fold in a time- and concentration-dependent manner. The stimulatory effect of medium conditioned by progestin-pretreated stromal cells was enhanced strikingly by increasing stromal cell PR levels with the addition of estrogen. This epithelial-stromal interaction was specific for endometrial epithelial cells, since 17beta-HSD type 2 could not be induced in malignant breast epithelial cells by media conditioned with progestin-treated breast or endometrial stromal cells. In conclusion, progesterone regulates the conversion of biologically active E2 to estrone by inducing the 17beta-HSD type 2 enzyme in human endometrial epithelium primarily via PR in stromal cells, which secrete factors that induce transcription mediated primarily by the -200/-100 bp 5'-regulatory region of the 17beta-HSD type 2 promoter.

Role of aromatase in endometrial disease

Aromatase is the key enzyme for estrogen biosynthesis. It is normally expressed in the human ovary, skin, adipose tissue and brain. Aromatase activity is not detectable in normal endometrium. In contrast, aromatase is expressed aberrantly in endometriosis and is stimulated by PGE2. This results in local production of estrogen, which induces PGE2 formation and establishes a positive feedback cycle. Another abnormality in endometriosis, i.e. deficient 17beta-hydroxysteroid dehydrogenase (17beta-HSD) type 2 expression, impairs the inactivation of estradiol to estrone. These molecular aberrations collectively favor accumulation of increasing quantities of estradiol and PGE2 in endometriosis. The clinical relevance of these findings was exemplified by the successful treatment of an unusually aggressive case of post-menopausal endometriosis using an aromatase inhibitor.

Estrogen production and action

Estradiol production is most commonly thought of as an endocrine product of the ovary; however, there are many tissues that have the capacity to synthesize estrogens from androgen and to use estrogen in a paracrine or intracrine fashion. In addition, other organs such as the adipose tissue can contribute significantly to the circulating pool of estrogens. There is increasing evidence that in both men and women extraglandular production of C(18) steroids from C(19) precursors is important in normal physiology as well as in pathophysiologic states. The enzyme aromatase is found in a number of human tissues and cells, including ovarian granulosa cells, the placental syncytiotrophoblast, adipose and skin fibroblasts, bone, and the brain, and it locally catalyzes the conversion of C(19) steroids to estrogens. Aromatase expression in adipose tissue and possibly the skin primarily accounts for the extraglandular (peripheral) formation of estrogen and increases as a function of body weight and advancing age. Sufficient circulating levels of the biologically active estrogen estradiol can be produced as a result of extraglandular aromatization of androstenedione to estrone that is subsequently reduced to estradiol in peripheral tissues to cause uterine bleeding and endometrial hyperplasia and cancer in obese anovulatory or postmenopausal women. Extraglandular aromatase expression in adipose tissue and skin (via increasing circulating levels of estradiol) and bone (via increasing local estrogen concentrations) is of paramount importance in slowing the rate of postmenopausal bone loss. Moreover, excessive or inappropriate aromatase expression was demonstrated in adipose fibroblasts surrounding a breast carcinoma, endometriosis-derived stromal cells, and stromal cells in endometrial cancer, giving rise to increased local estrogen concentrations in these tissues. Whether systemically delivered or locally produced, elevated estrogen levels will promote the growth of these steroid-responsive tissues. Finally, local estrogen biosynthesis by aromatase activity in the brain may be important in the regulation of various cognitive and hypothalamic functions. The regulation of aromatase expression in human cells via alternatively used promoters, which can be activated or inhibited by various hormones, increases the complexity of estrogen biosynthesis in the human body. Aromatase expression is under the control of the classically located proximal promoter II in the ovary and a far distal promoter I.1 (40 kilobases upstream of the translation initiation site) in the placenta. In skin, the promoter is I.4. In adipose tissue, 2 other promoters (I.4 and I.3) located between I.1 and II are used in addition to the ovarian-type promoter II. In addition, promoter use in adipose fibroblasts switches between promoters II/I.3 and I.4 upon treatments of these cells with PGE(2) versus glucocorticoids plus cytokines. Moreover, the presence of a carcinoma in breast adipose tissue also causes a switch of promoter use from I.4 to II/I.3. Thus there can be complex mechanisms that regulate the extraglandular production of estrogen in a tissue-specific and state-specific fashion.

Aromatase deficiency and estrogen resistance: from molecular genetics to clinic

Our knowledge of the physiologic roles of estrogen in women and men has been advanced by recent descriptions of mutations disrupting estrogen biosynthesis and action. Aromatase deficiency results from autosomal recessive inheritance of mutations in the CYP19 gene. It gives rise to ambiguous genitalia in 46,XX individuals. At puberty, affected girls have hypergonadotropic hypogonadism, fail to develop secondary sexual characteristics, and exhibit progressive virilization. The affected 46,XY individuals have normal male sexual differentiation and pubertal maturation. These men are extremely tall and have eunuchoid proportions with continued linear growth into adulthood, lack of epiphyseal closure, and osteoporosis due to estrogen deficiency. Although estrogen was shown to be essential for normal sperm production and function in mice, its role in fertility is not clear in men. Thus far, one estrogen-resistant human, a man with a mutant estrogen receptor-alpha gene, has been described. His clinical presentation was similar to that of aromatase-deficient men.

Malignant breast epithelial cells stimulate aromatase expression via promoter II in human adipose fibroblasts: an epithelial-stromal interaction in breast tumors mediated by CCAAT/enhancer binding protein beta

Expression of aromatase P450 (P450arom), which catalyzes the formation of estrogens, is aberrantly increased in adipose fibroblasts surrounding breast carcinomas, giving rise to proliferation of malignant cells. Aromatase in human adipose tissue is primarily expressed in undifferentiated fibroblasts under the control of several distinct and alternatively used P450arom promoters. In tumor-free breast adipose tissue, P450arom is usually expressed at low levels via a distal promoter (I.4), whereas in the breast adipose tissue bearing a tumor, P450arom is increased through the activation of two proximal promoters, II and I.3. Because the in vivo activation of P450arom promoter II is a key event responsible for aberrantly high P450arom expression in breast tumors, we studied the molecular basis for the enhancement of P450arom promoter II using human adipose fibroblasts (HAFs) in primary culture treated with T47D breast cancer cell-conditioned medium (TCM) as a model system. Upon treatment with TCM, HAFs displayed a striking induction of P450arom mRNA levels via promoter II usage. This effect appeared to be specific for malignant breast epithelial cells, because conditioned media from breast cancer cell lines T47D and MCF-7 induced promoter II activity, whereas normal breast epithelial cells or liver or prostate cancer cell lines did not produce such an effect. Although treatment with a cyclic AMP analogue also caused a switch in the promoter use from I.4 to II in cultured HAFs, TCM-induced promoter II use was found to be mediated via a cyclic AMP-independent pathway. Use of serial deletion mutants of the promoter II 5'-flanking sequence revealed the presence of critical cis-acting elements in the -517/-278 bp region, which regulate the baseline activity. TCM caused a 5.7-fold induction of the -517-bp promoter II construct, whereas site-directed mutagenesis of a CCAAT/enhancer binding protein (C/EBP) binding site (-317/-304 bp) abolished both baseline and TCM-induced activities. Ectopic expressions of C/EBPalpha and C/EBPbeta, but not C/EBPdelta, significantly induced promoter II activity. Moreover, we demonstrated the presence of both C/EBPbeta and C/EBPdelta but not C/EBPalpha in a DNA-protein complex formed by the nuclear extract from TCM-treated HAFs and a probe containing this critical C/EBP binding element (-317/-304 bp). Finally, treatment of HAFs with TCM strikingly induced C/EBPbeta expression, whereas this did not affect the levels of C/EBPalpha or C/EBPdelta transcripts. In conclusion, malignant breast epithelial cells secrete factors, which induce aromatase expression in adipose fibroblasts via promoter II. This is, at least in part, mediated by a TCM-induced up-regulation and enhanced binding of C/EBPbeta to a promoter II regulatory element.

Tumor necrosis factor alpha and interleukin 11 secreted by malignant breast epithelial cells inhibit adipocyte differentiation by selectively down-regulating CCAAT/enhancer binding protein alpha and peroxisome proliferator-activated receptor gamma: mechanism of desmoplastic reaction

The dense layer of fibroblasts that accumulate around malignant breast epithelial cells (i.e., desmoplastic reaction) arises from the breast adipose tissue and provides structural and biochemical support for breast cancer. We report herein a number of epithelial-stromal interactions responsible for desmoplastic reaction in breast cancer using cultured 3T3-L1 murine fibroblasts and human adipose fibroblasts, which can be activated with a mixture of hormones to differentiate to mature adipocytes. Adipocyte differentiation was inhibited by coculturing fibroblasts with various breast cancer cell lines (T47D, MCF-7, SSC202, SSC78, and SSC30) completely or by breast cancer cell conditioned media in a dose-dependent manner; on the other hand, adipocyte differentiation was not inhibited by coculturing with normal human primary mammary epithelial cell conditioned medium. This tumor effect was eliminated using neutralizing antibodies against tumor necrosis factor (TNF)-alpha or interleukin (IL)-11. TNF-alpha and IL-11 levels were 2.5-3 times higher in T47D conditioned medium compared with control medium, and TNF-alpha transcripts were detectable in T47D but not in 3T3-L1 cells in culture, indicating that the malignant epithelial cell is the major site of cytokine production. This was confirmed in vivo in mastectomy specimens, where immunoreactive TNF-alpha and IL-11 were readily detectable in malignant epithelial cells but not in the majority of the surrounding fibroblasts. Adipocyte differentiation is mediated by the expression of a cascade of adipogenic transcription factors, including CCAAT/enhancer binding protein (C/EBP)beta, C/EBPdelta, peroxisome proliferator-activated receptor (PPAR)gamma and C/EBPalpha. C/EBPalpha and PPARgamma are essential for this process. We demonstrated by Northern analysis that exposure of activated 3T3-L1 cells to T47D cell conditioned medium strikingly decreased the levels of PPARgamma and C/EBPalpha transcripts and increased the levels of C/EBPbeta and C/EBPdelta transcripts. In these 3T3-L1 cells, inhibition of differentiation was also confirmed by markedly suppressed levels of aP2 mRNA, which is an adipocyte-specific gene. These in vitro observations were confirmed in sections of human malignant breast tumors, where immunoreactive C/EBPalpha was readily detectable in adipose flbroblasts distant to the tumor but not in intratumoral fibroblasts. Treatment of 3T3-L1 cells with T47D cell conditioned medium or TNF-alpha changed neither the numbers of cells in G0-G1, S, and G2 phases nor the rate of [3H]thymidine incorporation, thus ruling out a proliferative effect of malignant cells on the surrounding fibroblasts. In summary, desmoplastic reaction primarily occurs via the action of cytokines (TNF-alpha and IL-11) secreted by the malignant epithelial cells to inhibit differentiation of adipose fibroblasts to mature adipocytes. This tumor-induced block in adipocyte differentiation is mediated by the selective inhibition of expression of the essential adipogenic transcription factors, i.e., PPARgamma and C/EBPalpha.

Molecular basis for treating endometriosis with aromatase inhibitors

Although treatment of one unusually aggressive case of postmenopausal endometriosis with an aromatase inhibitor has been strikingly successful, large clinical trials are required to establish whether aromatase inhibitors will have a significant role in the medical management of endometriosis. Introduction of aromatase inhibitors into the treatment of endometriosis underscores the importance of basic research leading to the development of novel strategies in reproductive disorders. It was shown earlier that aromatase activity was not detectable in normal endometrium. Aromatase, however, is expressed inappropriately in endometriosis and stimulated by prostaglandin E2. Aromatase activity gives rise to local biosynthesis of oestrogen, which, in turn, stimulates prostaglandin E2 production, thus establishing a positive feedback cycle. This favours accumulation of oestrogen and prostaglandins in endometriosis, which is an inflammatory disorder dependent on oestrogen for growth.

Progesterone receptor isoform A but not B is expressed in endometriosis

We previously demonstrated that 17beta hydroxysteroid dehydrogenase type 2, the enzyme that inactivates estradiol to estrone, is expressed in luteal eutopic endometrium in response to progesterone but not in simultaneously biopsied peritoneal endometriotic tissue. This molecular evidence of progesterone resistance, together with the clinical observation of resistance of endometriosis to treatment with progestins, led us to determine the levels of progesterone receptor (PR) isoforms PR-A and PR-B in eutopic endometrial and extra-ovarian endometriotic tissues. It was proposed that progesterone action on target genes is mediated primarily by homodimers of PR-B, whereas the truncated variant PR-A acts as a repressor of PR-B function. Immunoprecipitation, followed by Western blot analysis, was performed to detect bands specific for PR-A and PR-B in paired samples of endometriotic and eutopic endometrial tissues simultaneously biopsed from 18 women undergoing laparoscopy during various phases of the menstrual cycle. PR-B was present in 17 of 18 eutopic endometrial samples, and its level increased in the preovulatory phase, as expected, whereas PR-A was detected in all samples (n = 18) with a similar, but less prominent, cyclic variation in its levels. In endometriotic samples, however, no detectable PR-B could be demonstrated, whereas PR-A was detected in all samples (n = 18), albeit in much lower levels and without any cyclic variation in contrast with the eutopic endometrium. Levels of PR-A and PR-B in endometriotic and eutopic endometrial tissues were determined and compared after normalization to total protein and estrogen receptor-alpha levels. Using RNase protection assay, we also demonstrated indirectly that only PR-A transcripts were present in endometriotic tissue samples (n = 8), whereas both PR-A and PR-B transcripts were readily detectable in all eutopic endometrial samples (n = 8). This was indicative that failure to detect PR-B protein in endometriotic tissues is due to the absence of PR-B transcripts. We conclude that progesterone resistance in endometriotic tissue from laboratory and clinical observations may be accounted for by the presence of the inhibitory PR isoform PR-A and the absence of the stimulatory isoform PR-B.

Estrogen biosynthesis in endometriosis: molecular basis and clinical relevance

Conversion of C(19) steroids to estrogens is catalyzed by aromatase in human ovary, placenta and extraglandular tissues such as adipose tissue, skin and the brain. Aromatase activity is not detectable in normal endometrium. In contrast, aromatase is expressed aberrantly in endometriosis and is stimulated by prostaglandin E(2) (PGE(2)).( )This results in local production of estrogen, which induces PGE(2) formation and establishes a positive feedback cycle. Another abnormality in endometriosis, i.e. deficient hydroxysteroid dehydrogenase (17beta-HSD) type 2 expression, impairs the inactivation of estradiol to estrone. These molecular aberrations collectively favor accumulation of increasing quantities of estradiol and PGE(2 )in endometriosis. The clinical relevance of these findings was exemplified by the successful treatment of an unusually aggressive case of postmenopausal endometriosis using an aromatase inhibitor.

Aromatase in aging women

Cessation of ovarian estrogen secretion is the key event during the climacteric. An enzyme termed aromatase in a number of human tissues and cells, including ovarian granulosa cells, the placental syncytiotrophoblast, adipose and skin fibroblasts, bone, and the brain, catalyzes the conversion of C19 steroids to estrogens. Aromatase expression in adipose tissue and possibly the skin primarily accounts for the extraglandular (peripheral) formation of estrogen and increases as a function of body weight and advancing age. Sufficient circulating levels of the biologically active estrogen, estradiol, can be produced as a result of extraglandular aromatization of androstenedione to estrone, which is subsequently reduced to estradiol in peripheral tissues, to cause uterine bleeding and endometrial hyperplasia and cancer in obese anovulatory or postmenopausal women. Extraglandular aromatase expression in adipose tissue and skin (via increasing circulating levels of estradiol) and bone (via increasing local estrogen concentrations) is of paramount importance in slowing the rate of postmenopausal bone loss. Moreover, excessive or inappropriate aromatase expression was demonstrated in adipose fibroblasts surrounding a breast carcinoma, endometriosis-derived stromal cells, and stromal cells in endometrial cancer and gave rise to increased local estrogen concentrations in these tissues. Whether systemically delivered or locally produced, elevated estrogen levels promote the growth of these steroid-responsive tissues. Finally, local estrogen biosynthesis by aromatase activity in the brain may be important in the regulation of various cognitive and hypothalamic functions. The regulation of aromatase expression in human cells via alternatively used promoters, which can be activated or inhibited by various hormones, increases the complexity of estrogen biosynthesis in the human body. Aromatase expression is under the control of the classically located proximal promoter II in the ovary and a far distal promoter I.1 (40 kb upstream of the translation initiation site) in the placenta. In adipose tissue, two other promoters (I.4 and I.3) located between I.1 and II are used in addition to the ovarian-type promoter II. To add a further twist, promoter use in adipose fibroblasts switches between promoters II/I.3 and I.4 upon treatment of these cells with prostaglandin E2 (PGE2) versus glucocorticoids plus cytokines. Moreover, the presence of a carcinoma in breast adipose tissue causes a switch of promoter use from I.4 to II/I.3. Molecular and cellular mechanisms responsible for estrogen formation and their physiologic and clinical relevance will be reviewed in this article.

Expression of dioxin-related transactivating factors and target genes in human eutopic endometrial and endometriotic tissues

OBJECTIVE

Although an association between dioxin exposure and endometriosis has been proposed, the effects of this environmental toxin on human endometriosis are not known. To understand the potential underlying molecular mechanisms we studied the expressions of cytochrome P-450 genes (CYP1A1, CYP1A2, and CYP1B1 ), which are induced by dioxin, and the expressions of cytosolic receptor for dioxin, aryl hydrocarbon receptor, and its nuclear translocator, aryl hydrocarbon receptor nuclear translocator protein, in endometriotic and eutopic endometrial tissues.

STUDY DESIGN

Levels of transcripts of CYP1A1, CYP1A2, CYP1B1, aryl hydrocarbon receptor, and aryl hydrocarbon receptor nuclear translocator protein were determined by a quantitative reverse transcriptase-polymerase chain reaction and Southern blot assay in total ribonucleic acid samples from endometriotic and eutopic endometrial tissues. Eutopic endometrial tissue samples (n = 33) and endometriotic tissue samples (n = 10) were obtained at the time of uterine curettage and laparoscopy from disease-free women and from patients with endometriosis. Portions of these eutopic endometrial and endometriotic tissues were obtained simultaneously from the same patients (n = 8 pairs of samples). Levels of transcripts of CYP1A1, CYP1A2, CYP1B1, aryl hydrocarbon receptor, and aryl hydrocarbon receptor nuclear translocator protein were determined in endometrial and endometriotic tissues during follicular and luteal phases of the cycle and in cultured endometriotic stromal cells treated with forskolin, phorbol diacetate, medroxyprogesterone acetate,and serum.

RESULTS

Transcripts of dioxin receptor, its nuclear translocator, and two dioxin-induced target genes (CYP1A2 and CYP1B1) were demonstrated during follicular and luteal phases of the cycle in both eutopic endometrial tissues and tissues affected by pelvic endometriosis, with no readily detectable differences between these tissues. On the other hand, levels of transcripts of another dioxin-induced gene, CYP1A1, were found to be strikingly higher in endometriotic tissues than in the eutopic endometrium. Mean levels in endometriotic tissues were 8.7 times those found in eutopic endometrium. Various hormonal treatments of endometriotic stromal cells did not significantly alter these levels.

CONCLUSION

We demonstrated for the first time the expression of dioxin-related transcription factors aryl hydrocarbon receptor and aryl hydrocarbon receptor nuclear translocator protein and target genes CYP1A1, CYP1A2, and CYP1B1 in endometriotic tissues and stromal cells. Strikingly elevated CYP1A1 transcripts in endometriosis may give rise to significantly increased P-4501A1 enzyme activity and thus promote the development and growth of endometriosis by either activating procarcinogens or inducing the formation of catechol estrogens or both. In fact, the proposed link between dioxin exposure and endometriosis may be explained in part by the up-regulation of the CYP1A1 gene expression in endometriotic tissues.

Aromatase as a therapeutic target in endometriosis

In contrast to normal endometrium, the expression of aromatase is aberrant in endometriosis and is stimulated by prostaglandin E2 (PGE2). This results in local production of estrogen, which induces PGE2 formation and establishes a positive feedback cycle. Another abnormality in endometriosis--deficient 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) type 2 expression--impairs the inactivation of estradiol (E2) to estrone (E1). These molecular aberrations collectively favor accumulation of increasing quantities of E2, and PGE2 in endometriosis. The clinical relevance of these findings was exemplified by the successful treatment of an unusually aggressive case of postmenopausal endometriosis with an aromatase inhibitor.

Aromatase: a key molecule in the pathophysiology of endometriosis and a therapeutic target

OBJECTIVE

To provide a clinically useful model illustrating the molecular aberrations affecting estrogen biosynthesis and metabolism in endometriosis and to discuss the therapeutic role of aromatase inhibitors.

DESIGN

Literature review.

RESULT(S)

Several molecular aberrations were found in endometriotic lesions (in contrast to eutopic endometrium) that favor increased local concentrations of E2. Endometriotic stromal cells aberrantly express aromatase, which converts C19, steroids to estrogens. Aromatase activity in these cells is stimulated by prostaglandin (PG)E2. Estrogen stimulates cyclooxygenase-2, giving rise to increased PGE2 formation. Thus, this positive feedback loop produces increasing quantities of E2 and PGE2 in endometriosis. The lack of aromatase expression in eutopic endometrium is maintained by binding of an inhibitory transcription factor, COUP-TF, to the aromatase promoter. In endometriosis, however, an aberrantly expressed factor, SF-1, displaces COUP-TF to bind to this same promoter and activates aromatase expression and thus local estrogen biosynthesis. Additionally, endometriotic glandular cells are deficient in 17beta-hydroxysteroid dehydrogenase type 2, which converts E2 to estrone in the eutopic endometrium in response to P. Deficiency of this enzyme in endometriosis impairs the inactivation of E2 and may be a consequence of insensitivity to P.

CONCLUSION(S)

Molecular aberrations that increase local E2 concentrations may be important in the etiology of endometriosis. These molecules may be targeted to develop novel therapeutic strategies. The clinical relevance of aromatase expression in endometriosis was shown recently by the successful treatment of an unusually aggressive case of postmenopausal endometriosis with use of an aromatase inhibitor.

Estrogen production in endometriosis and use of aromatase inhibitors to treat endometriosis

Estrogen is the most important known factor that stimulates the growth of endometriosis. Estrogen delivery to endometriotic implants was classically viewed to be only via the circulating blood in an endocrine fashion. We recently uncovered an autocrine positive feedback mechanism, which favored the continuous production of estrogen and prostaglandin (PG)E2 in the endometriotic stromal cells. The enzyme, aromatase, is aberrantly expressed in endometriotic stromal cells and catalyzes the conversion of C19 steroids to estrogens, which then stimulate cyclooxygenase-2 to increase the levels of PGE2. PGE2, in turn, is a potent inducer of aromatase activity in endometriotic stromal cells. Aromatase is not expressed in the eutopic endometrium. Aromatase expression in endometriosis and its inhibition in eutopic endometrium are controlled by the competitive binding of a stimulatory transcription factor, steroidogenic factor-1, and an inhibitory factor, chicken ovalbumin upstream promoter-transcription factor to a regulatory element in the aromatase P450 gene promoter. In addition, we find that endometriotic tissue is deficient in 17beta-hydroxysteroid dehydrogenase type 2, which is normally expressed in eutopic endometrial glandular cells and inactivates estradiol-17beta to estrone. This deficiency is another aberration that favors higher levels of estradiol-17beta in endometriotic tissues in comparison with the eutopic endometrium. The clinical relevance of local aromatase expression in endometriosis was exemplified by the successful treatment of an unusually aggressive form of recurrent endometriosis in a postmenopausal woman using an aromatase inhibitor.

Stimulation of aromatase P450 promoter (II) activity in endometriosis and its inhibition in endometrium are regulated by competitive binding of steroidogenic factor-1 and chicken ovalbumin upstream promoter transcription factor to the same cis-acting element

In stromal cells of endometriosis, marked levels of aromatase P450 (P450arom) mRNA and activity are present and can be vigorously stimulated by (Bu)2cAMP or PGE2 to give rise to physiologically significant estrogen biosynthesis. Since eutopic endometrial tissue or stromal cells lack P450arom expression, we studied the molecular basis for differential P450arom expression in endometriosis and eutopic endometrium. First, we demonstrated by rapid amplification of cDNA 5'-ends that P450arom expression in pelvic endometriotic lesions is regulated almost exclusively via the alternative promoter II. Then, luciferase reporter plasmids containing deletion mutations of the 5'-flanking region of promoter II were transfected into endometriotic stromal cells. We identified two critical regulatory regions for cAMP induction of promoter II activity: 1) a-214/-100 bp proximal region responsible for a 3.7-fold induction, and 2) a -517/ -214 distal region responsible for potentiation of cAMP response up to 13-fold. In the -214/-100 region, we studied eutopic endometrial and endometriotic nuclear protein binding to a nuclear receptor half-site (NRHS, AGGTCA) and an imperfect cAMP response element (TGCACGTCA). Using electrophoretic mobility shift assay, cAMP response element-binding activity in nuclear proteins from both endometriotic and eutopic endometrial cells gave rise to formation of identical DNA-protein complexes. The NRHS probe, on the other hand, formed a distinct complex with nuclear proteins from endometriotic cells, which migrated at a much faster rate compared with the complex formed with nuclear proteins from eutopic endometrial cells. Employing recombinant proteins and antibodies against steroidogenic factor-1 (SF-1) and chicken ovalbumin upstream promoter transcription factor (COUP-TF), we demonstrated that COUP-TF but not SF-1 bound to NRHS in eutopic endometrial cells, whereas SF-1 was the primary NRHS-binding protein in endometriotic cells. In fact, COUP-TF transcripts were present in both eutopic endometrial (n = 12) and endometriotic tissues (n = 8), whereas SF-1 transcripts were detected in all endometriotic tissues (n = 12), but in only 3 of 15 eutopic endometrial tissues. Moreover, we demonstrated a dose-dependent direct competition between SF-1 and COUP-TF for occupancy of the NRHS, to which SF-1 bound with a higher affinity. Finally, overexpression of SF-1 in eutopic endometrial and endometriotic cells strikingly potentiated baseline and cAMP-induced activities of -517 promoter II construct, whereas overexpression of COUP-TF almost completely abolished these activities. In conclusion, COUP-TF might be one of the factors responsible for the inhibition of P450arom expression in eutopic endometrial stromal cells, which lack SF-1 expression in the majority (80%) of the samples; in contrast, aberrant SF-1 expression in endometriotic stromal cells can override this inhibition by competing for the same DNA-binding site, which is likely to account for high levels of baseline and cAMP-induced aromatase activity.

Deficient 17beta-hydroxysteroid dehydrogenase type 2 expression in endometriosis: failure to metabolize 17beta-estradiol

Aberrant aromatase expression in stromal cells of endometriosis gives rise to conversion of circulating androstenedione to estrone in this tissue, whereas aromatase expression is absent in the eutopic endometrium. In this study, we initially demonstrated by Northern blotting transcripts of the reductive 17beta-hydroxysteroid dehydrogenase (17betaHSD) type 1, which catalyzes the conversion of estrone to 17beta-estradiol, in both eutopic endometrium and endometriosis. Thus, it follows that the product of the aromatase reaction, namely estrone, that is weakly estrogenic can be converted to the potent estrogen, 17beta-estradiol, in endometriotic tissues. It was previously demonstrated that progesterone stimulates the inactivation of 17beta-estradiol through conversion to estrone in eutopic endometrial epithelial cells. Subsequently, 17betaHSD type 2 was shown to catalyze this reaction, and its transcripts were detected in the epithelial cell component of the eutopic endometrium in secretory phase. Because 17beta-estradiol plays a critical role in the development and growth of endometriosis, we studied 17betaHSD-2 expression in endometriotic tissues and eutopic endometrium. We demonstrated, by Northern blotting, 17betaHSD-2 messenger ribonucleic acid (RNA) in all RNA samples of secretory eutopic endometrium (n=12) but not in secretory samples of endometriotic lesions (n=10), including paired samples of endometrium and endometriosis obtained simultaneously from eight patients. This messenger RNA was not detectable in any samples of proliferative eutopic endometrium or endometriosis (n=4) as expected. Next, we confirmed these findings by demonstration of immunoreactive 17betaHSD-2 in epithelial cells of secretory eutopic endometrium in 11 of 13 samples employing a monoclonal antibody against 17betaHSD-2, whereas 17betaHSD-2 was absent in paired secretory endometriotic tissues (n=4). Proliferative eutopic endometrial (n=8) and endometriotic (n=4) tissues were both negative for immunoreactive 17betaHSD-2, except for barely detectable levels in 1 eutopic endometrial sample. Finally, we sought to determine whether deficient 17betaHSD-2 expression in endometriotic tissues is due to impaired progesterone action in endometriosis. We determined by immunohistochemistry the expression of progesterone and estrogen receptors in these paired samples of secretory (n=4) and proliferative (n=4) eutopic endometrium and endometriosis, and no differences could be demonstrated. In conclusion, inactivation of 17beta-estradiol is impaired in endometriotic tissues due to deficient expression of 17betaHSD-2, which is normally expressed in eutopic endometrium in response to progesterone. The lack of 17betaHSD-2 expression in endometriosis is not due to alterations in the levels of immunoreactive progesterone or estrogen receptors in this tissue and may be related to an inhibitory aberration in the signaling pathway that regulates 17betaHSD-2 expression.

Molecular basis of severe gynecomastia associated with aromatase expression in a fibrolamellar hepatocellular carcinoma

This report represents the first study in the literature linking development of severe gynecomastia, in a 17 1/2-yr-old boy, to high levels of aromatase expression in a large fibrolamellar hepatocellular carcinoma, which gave rise to extremely elevated serum levels of estrone (1200 pg/mL) and estradiol-17 beta (312 pg/mL) that suppressed FSH and LH (1.3 and 2.8 IU/L, respectively), and consequently testosterone (1.53 ng/mL). After removal of a 1.5-kg hepatocellular carcinoma, gynecomastia partially regressed, and essentially, normal hormone levels were restored (estradiol-17 beta, < 50 pg/mL; estrone, 74 pg/mL; testosterone, 6.85 ng/mL; and FSH/LH, 6.3/3.7 mIU/mL). Conversion of C19 steroids to estrogens occurs in a number of human tissues and is catalyzed by aromatase P450 (P450arom), the product of the CYP19 gene in a number of human tissues. Tissue-specific promoters are used to regulate P450arom gene transcription in adult human tissues, e.g. promoters I.4 and I.3 in adipose fibroblasts, and promoter II in the gonads. Human fetal liver uses promoter I.4 to express markedly high levels of P450arom, whereas hepatic P450arom expression normally becomes undetectable in postnatal life. Using immunohistochemistry, diffuse intracytoplasmic aromatase expression was detected in the liver cancer cells from this severely feminized boy. Northern analysis indicated the presence of P450arom transcripts in total RNA from the hepatocellular cancer but not in the adjacent liver nor in disease-free adult liver samples. Promoter use for aromatase expression was determined by a specific RT-PCR method. Promoters I.3 and II were used for P450arom gene expression in the hepatocellular cancer tissue. Because aromatase is not expressed in the disease-free adult liver, the presence of extremely high levels of aromatase expression in this fibrolamellar hepatocellular carcinoma tissue is intriguing, particularly because there is preferential use of the proximally located P450arom promoters I.3 and II by the tumor, instead of the much more distally located fetal liver-type promoter I.4.

Multiple splicing events involved in regulation of human aromatase expression by a novel promoter, I.6

The expression of aromatase is regulated in a tissue-specific fashion through alternative use of multiple promoter-specific first exons. To date, eight different first exons have been reported in human aromatase, namely I.1., I.2, I.3. I.4, I.5, PII, 2a, and 1f. Recently, we have found a new putative exon I in a RACE-generated library of THP-1 cells and have conducted studies to characterize this new exon I. We confirmed that the constructs containing -1552/+17 or less flanking sequence of this exon function as a promoter in THP-1 cells, JEG-3 cells and osteoblast-like cells obtained from a human fetus. Results of transfection assays using a series of deletion constructs and mutation constructs indicate that a 1-bp mismatch of the consensus TATA-like box (TTTAAT) and the consensus sequence of the initiator site, which is located 45 bp downstream of the putative TATA box, were functioning cooperatively as a core promoter. The putative transcription site was confirmed by the results of RT-PCR southern blot analysis. We examined the regulation and the expression of this exon, I.6, in several human cells and tissues by RT-PCR Southern blot analysis. THP-1 cells (mononuclear leukemic origin) and JEG-3 cells (choriocarcinoma origin) expressed exon I.6 in serum-free media. The level of expression was increased by serum and phorbol myristyl acetate (PMA) in both cell lines. Adipose stromal cells also expressed exon I.6 in the presence of PMA. In fetal osteoblasts, the expression of exon I.6 was increased most effectively by serum and less so by dexamethasone (DEX) + IL-1beta and DEX + IL-11, whereas induction by serum was suppressed by the addition of DEX. The level of expression was low in granulosa cells in culture and did not change with forskolin. On the other hand, dibutyryl cAMP suppressed PMA-stimulated expression of exon I.6 in THP-1 cells and adipose stromal cells. This result supports the hypothesis that the expression of exon I.6 is regulated mainly via an AP-1 binding site that is found upstream of the initiator site of the promoter region. Expression of exon I.6-specific transcripts was examined in several human tissues. Testis and bone obtained from normal adults expressed exon I.6. Testicular tumor and hepatic carcinoma expressed high levels of exon I.6, whereas granulosa cell tumor did not. Fetal liver and bone also showed a significant level of exon I.6 expression, but not so much as testicular tumor and hepatic tumor. Several splicing variants of exon I.6 were detected especially in THP-1 and JEG-3 cells, and to a lesser extent in primary cultures and tissue samples. These variants were identified as an unspliced form, a form spliced at the end of exon I.4, a form spliced at the end of exon I.3 (truncated) and a form spliced 220 bp downstream of the 3' end of exon I.6. The last variant revealed a new splicing site. Because most of the splicing variants contain the sequence specific for exon I.3, RT-PCR specific for exon I.3 can coamplify these splicing variants of exon I.6 transcripts. These results suggests that it is necessary to examine the expression of I.6 in tissues that are known to express exon I.3 such as breast adipose tissue, in which promoter usage of exon I of the aromatase gene switches from exon I.4 to I.3 in the course of malignant transformation.

Treatment of severe postmenopausal endometriosis with an aromatase inhibitor

OBJECTIVE

To treat an unusually aggressive case of recurrent postmenopausal endometriosis.

DESIGN

Case report.

SETTING

University of Texas Southwestern Medical Center (Dallas, Texas).

PATIENT(S)

A 57-year-old woman who presented with recurrent severe endometriosis after hysterectomy and bilateral salpingo-oophorectomy.

INTERVENTION(S)

Oral administration of anastrozole (an aromatase inhibitor) (1 mg/d) and elemental calcium (1.5 g/d) for 9 months. Alendronate (a nonestrogenic inhibitor of bone resorption), 10 mg/d, was added to this regimen.

MAIN OUTCOME MEASURE(S)

Reduction in size of endometriotic lesion, pain relief, tissue levels of aromatase P450 messenger RNA, bone density.

RESULT(S)

Circulating levels of estradiol-17beta were reduced to approximately 50% of the baseline value after the onset of treatment with anastrozole. Pain rapidly decreased and completely disappeared after the 2nd month of treatment. The 30 x 30 x 20-mm bright red polypoid vaginal lesion was reduced to a 3-mm gray tissue by the end of 9 months of treatment. Markedly high pretreatment levels of aromatase P450 messenger RNA in the endometriotic tissue became undetectable in a specimen obtained from a repeated biopsy after 6 months of treatment. Bone density of lumbar spine decreased by 6.2% after 9 months of treatment.

CONCLUSION(S)

This is the first description of the use of an aromatase inhibitor in the treatment of endometriosis. The short-term results were extraordinarily successful in elimination of pain and near-complete eradication of implants associated with severe endometriosis not responsive to other therapy. We conclude that the recently developed potent aromatase inhibitors are candidate drugs in the treatment of endometriosis that is resistant to standard regimens.

Endocrine disorders associated with inappropriately high aromatase expression

Aromatase P450 (P450arom) is responsible for conversion of C19 steroids to estrogens in a number of human tissues, such as the placenta, gonads, adipose tissue, skin and the brain. Aromatase expression in human tissues is regulated by use of alternative promoters in the placenta (promoter I.1), adipose tissue (promoters I.4, I.3 and II) and gonads (promoter II). Aromatase expression is absent in the disease-free adult liver, adrenal and uterine tissues. Excessive or inappropriate aromatase expression in adipose fibroblasts and endometriosis-derived stromal cells, as well as in testicular, hepatic, adrenal and uterine tumors, is associated with abnormally high circulating estrogen levels and/or with increased local estrogen concentrations in these tissues. Whether systemically delivered or locally produced, elevated estrogen levels will in turn promote the growth of hormone-responsive tissues. We recently studied aromatase expression in testicular tumor and adipose tissue samples from prepubertal boys with gynecomastia, in hepatocellular cancer and adrenocortical tumor samples from adult men with gynecomastia, in breast adipose tissue samples proximal to breast tumors, and in endometrial cancer, leiomyoma and endometriosis tissues. Excessive aromatase activity and P450arom transcript levels were found in these tissue samples or in cultured cells derived from these tissues. In these neoplastic or non-neoplastic tissues or cells, the regulation of aromatase expression was studied in terms of alternative promoter use, both in vivo and in response to various hormonal stimuli. Our results were suggestive of a common metabolic abnormality associated with activation of a cyclic AMP-dependent signalling pathway that gives rise to transcriptional transactivation of aromatase expression via promoters I.3 and II in all of the above tissues. This article describes the common pathophysiological and molecular features of excessive aromatase expression in these disease states.

Prostaglandin E2 stimulates aromatase expression in endometriosis-derived stromal cells

C19 steroids are converted to estrogens by aromatase P450 (P450arom). Aromatase expression in humans is regulated by use of tissue-specific promoters in the placenta (promoter I.1), adipose tissue (promoters I.4, I.3, and II), and gonads (promoter II). The use of each promoter gives rise to a population of P450arom messenger ribonucleic acid (mRNA) species with a unique untranslated 5'-terminus. Aromatase is not expressed in the endometrium of disease-free women. We demonstrated, however, the presence of P450arom mRNA in pelvic endometriotic implants and eutopic endometrial curettings of women with endometriosis. In the current report, aromatase activity and P450arom gene expression were investigated in cultured stromal cells derived from eutopic endometrium and ovarian endometriomas of women with pelvic endometriosis. We also investigated the hormonal regulation of aromatase expression and alternative promoter use in these cells. The effects of interleukin-1 beta (IL-1 beta), IL-2, IL-6, IL-11, oncostatin M, IL-15, tumor necrosis factor-alpha, PGE2, estradiol, R5020, dexamethasone, and dibutyryl cAMP (Bt2cAMP) on aromatase activity in endometriosis-derived stromal cells were assessed. We chose treatments with PGs and ILs because of the inflammatory nature of endometriosis. PGE2 stimulated aromatase activity in endometriosis-derived stromal cells by 19- to 44-fold (37-221 pmol/mg protein-4 h), whereas Bt2cAMP induction was 26- to 60-fold the baseline level. No stimulation was observed by estradiol or R5020 or by IL-1 beta, IL-2, IL-6, IL-11, IL-15, or TNF alpha in the presence or absence of glucocorticoids. A modest induction of aromatase activity (2-fold) was observed in dexamethasone- plus oncostatin M-treated cells. These changes in aromatase activity were accompanied by comparable changes in the levels of P450arom mRNA levels, determined by a quantitative reverse transcription-PCR method. Promoter-specific 5'-ends of P450arom transcripts in total RNA from endometriosis-derived stromal cells treated with PGE2 and Bt2cAMP were amplified employing a novel modified rapid amplification of cDNA5'-ends/Southern hybridization method using exon-specific oligonucleotide probes. The majority of P450arom transcripts in these cells contained the gonadal-type promoter II-specific sequences, whereas very few transcripts contained adipose-type promoter I.3- and I.4-specific sequences. PGE2 appears to be the most potent known stimulator of aromatase in endometriosis. Aromatase expression in PGE2-stimulated stromal cells of endometriosis is regulated primarily by the classically located promoter II, which, in turn, is regulated by cAMP. As PGE2 is known to increase intracellular cAMP levels, estrogen biosynthesis in endometriosis may be primarily regulated by PGE2 that is locally produced. Consequent local estrogen production may promote the growth of endometriotic implants.

Cytochromes P450 11: expression of the CYP19 (aromatase) gene: an unusual case of alternative promoter usage

Family 19 of the P450 super family is responsible for the conversion of C19 androgenic steroids to the corresponding estrogens, a reaction known as aromatization because it involves conversion of the delta4-3-one A-ring of the androgens to the corresponding phenolic A-ring characteristic of estrogens. The gene encoding human aromatase has been cloned and characterized and shown to be unusual compared to genes encoding other P450 enzymes, because there are numerous untranslated first exons that occur in aromatase transcripts in a tissue-specific fashion due to differential splicing as a consequence of the use of tissue-specific promoters. Thus, expression in the ovary uses a proximal promoter that is regulated primarily by cAMP. On the other hand, expression in the placenta uses a distal promoter located at least 40 kb upstream of the start of transcription that is regulated by retinoids. Other promoters are used in brain and adipose tissue. In the latter case, class I cytokines such as IL-6 and IL-11, as well as TNF-alpha, are important regulatory factors. A common 3'-splice junction located upstream of the start of translation is used in all of the splicing events involved in the use of these various promoters. Thus, the coding region of the transcripts, and hence the protein, are identical regardless of the tissue site of expression; what differs in a tissue-specific fashion is the 5'-end of the transcripts. This pattern of expression has great significance both from a phylogenetic and ontogenetic standpoint, as well as for the physiology and pathophysiology of estrogen formation, as will be discussed in this review.

Alternatively spliced transcripts of the aromatase cytochrome P450 (CYP19) gene in adipose tissue of women

Estrogen biosynthesis in adipose tissue has assumed great significance in terms of a number of estrogen-related diseases. The biosynthesis of estrogens from C19 steroids is catalyzed by a specific form of cytochrome P450, namely aromatase cytochrome P450 (P450arom; the product of the CYP19 gene). The human CYP19 gene comprises nine coding exons, II-X, and its transcripts are expressed in the ovary, placenta, testes, adipose tissue, and brain. Tissue-specific expression of the CYP19 gene is determined at least in part by the use of tissue-specific promoters, which give rise to transcripts with unique 5'-noncoding termini. Thus, the distal promoter I.1 is responsible for expression uniquely in placenta. On the other hand, the proximal promoter II, which regulates expression via a cAMP-dependent signaling pathway, is responsible for expression in the gonads. Transcripts in breast adipose tissue contain 5'-termini corresponding to expression derived from promoters I.4, II, and I.3, with I.4-specific termini predominating. The latter are derived from promoter I.4, which contains a glucocorticoid response element and an interferon-gamma activation site element and is responsible for expression in the presence of glucocorticoids and members of the class I cytokine family. The object of the present study was to determine the distribution of these various transcripts in adipose tissue from abdomen, buttocks, and thighs of women, as this would provide important clues to the factors regulating aromatase expression in these sites. To achieve this, we employed competitive reverse transcription-PCR to amplify unique 5'-ends of each of the transcripts of the CYP19 gene that are expressed in adipose tissue as well as for the coding region to evaluate total CYP19 gene (P450arom) transcript levels. We observed that exon I.4-specific transcripts were predominantly present in adipose tissue samples obtained from women regardless of the tissue site or the age of the individual. In these tissues, promoter II- and exon I.3-specific transcripts were present in lower copy numbers. We also demonstrated that in these sites total or exon-specific P450arom transcripts levels increased in direct proportion to advancing age and that transcript levels were the highest in buttocks, followed by thighs, and lowest in the abdomen. These results suggest that in normal human adipose tissue, aromatase expression is mainly under local control by a number of cytokines via paracrine and autocrine mechanisms in the presence of systemic glucocorticoids.

Aromatase expression in health and disease

Family 19 of the P450 superfamily is responsible for the conversion of C19 androgenic steroids to the corresponding estrogens, a reaction known as aromatization, since it involves conversion of the delta 4-3-one A-ring of the androgens to the corresponding phenolic A-ring characteristic of estrogens. Its members occur throughout the entire vertebrate phylum. The reaction mechanism of aromatase is very interesting from a chemical point of view and has been studied extensively; however, a detailed examination of structure-function relationships has not been possible due to lack of a crystal structure. Recent attempts to model the three-dimensional structure of aromatase have permitted a model that accounts for the reaction mechanism and predicts the location of aromatase inhibitors. The gene encoding human aromatase has been cloned and characterized and shown to be unusual compared to genes encoding other P450 enzymes, since there are a number of untranslated first exons that occur in aromatase transcripts in a tissue-specific fashion, due to differential splicing as a consequence of the use of tissue-specific promoters. Thus, expression in ovary utilizes a proximal promoter that is regulated primarily by cAMP. On the other hand, expression in placenta utilizes a distal promoter that is located at least 40 kb upstream of the start of transcription and that is regulated by retinoids. Other promoters are employed in brain and adipose tissue. In the latter case, class I cytokines such as IL-6 and IL-11 as well as TNF alpha are important regulatory factors. PGE2 is also an important regulator of aromatase expression in adipose mesenchymal cells via cAMP and PGE2 appears to be a major factor produced by breast tumors that stimulates estrogen biosynthesis in local mesenchymal sites. In all of the splicing events involved in the use of these various promoters, a common 3'-splice junction is employed that is located upstream of the start of translation; thus, the coding regions of the transcripts- and hence the protein-are identical regardless of the tissue site of expression; what differ in a tissue-specific fashion are the 5'-ends of the transcripts. This pattern of expression has great significance both from a phylogenetic and ontogenetic standpoint as well as for the physiology and pathophysiology of estrogen formation. Recently, a number of mutations of the aromatase gene have been described, which give rise to complete estrogen deficiency. In females this results in virilization in utero and primary amenorrhea with hypergonadotropic hypogonadism at the time of puberty. In men the most striking feature is continued linear bone growth beyond the time of puberty, delayed bone age, and failure of epiphyseal closure, thus indicating an important role of estrogens in bone metabolism in men. In both sexes the symptoms can be alleviated by estrogen administration.

Aromatase and 17 beta-hydroxysteroid dehydrogenase type 1 in human breast carcinoma

The in situ formation of estradiol plays an important role in the development and biological behavior of human breast cancer Aromatase and 17 beta-hydroxysteroid dehydrogenase type 1 (17 beta-HSD type 1) are two principal enzymes involved in in situ estradiol production. We evaluated the expression of aromatase and 17 beta-HSD type 1 by immunohistochemistry in 41 cases of invasive breast carcinoma (19 lobular and 22 ductal). We then examined the correlation among the expression of these enzymes, estrogen (ER) and progesterone (PR) receptor status, Ki67 labeling index of carcinoma cells, age, and the clinical stage of the patients. Marked aromatase immunoreactivity was observed in stromal cells around carcinomatous glands in 32 of 41 cases (78%), and 17 beta-HSD type 1 immunoreactivity was detected in carcinoma cells in 23 of 41 cases (56%). There was a significant correlation observed between expression of 17 beta-HSD type 1 and aromatase in invasive lobular carcinoma (P = 0.0119), but not in invasive ductal carcinoma. There was an inverse correlation between aromatase and ER status in invasive ductal carcinoma (P = 0.0213), but not in invasive lobular carcinoma. No other correlations were observed among 17 beta-HSD type 1, aromatase, PR, ER, clinical stage, age, and Ki67 labeling indexes. Aromatase and 17 beta-HSD are not always expressed simultaneously in human breast carcinoma, but their simultaneous expression is more frequent in invasive lobular carcinoma than invasive ductal carcinoma. Consequently, different mechanisms may be involved in the regulation of expression of these two enzymes in human breast carcinoma.

Use of alternative promoters to express the aromatase cytochrome P450 (CYP19) gene in breast adipose tissues of cancer-free and breast cancer patients

Estrogen biosynthesis in adipose tissue has assumed great significance in terms of a number of estrogen-related diseases. Recent evidence suggests that estrogen synthesized locally in the breast is of singular significance in the development of breast cancer in elderly women. The biosynthesis of estrogen from C19 steroids is catalyzed by a specific form of cytochrome P450, namely aromatase cytochrome P450 (P450arom; the product of the CYP19 gene). The human CYP19 gene comprises nine coding exons, II-X, and its transcripts are expressed in the ovary, placenta, testes, adipose tissue, and brain. Tissue-specific expression of the CYP19 gene is determined, at least in part, by the use of tissue-specific promoters, which give rise to transcripts with unique 5'-noncoding termini. Transcripts in adipose tissue contain 5'-termini derived from specific untranslated exons, corresponding to expression derived from the proximal promoter II and its splice variant I.3, as well as a distal promoter, I.4. The object of the present study was to determine the distribution of these various exon-specific transcripts in breast adipose tissues from cancer-free women undergoing reduction mammoplasty and from patients with breast cancer, because this would provide important clues as to the nature of the factors regulating aromatase expression in these sites. To achieve this, we employed competitive RT-PCR, utilizing an internal standard for each exon-specific transcript of the CYP19 gene, as well as for the coding region, to evaluate total CYP19 gene transcripts. In cancer patients (n = 18), total CYP19 gene transcript levels were significantly higher in adipose tissue proximal to a tumor in comparison with adipose tissue distal to a tumor, in agreement with previous findings. Moreover, total transcript levels were higher in breast adipose tissue of cancer patients in comparison with those of cancer-free individuals (n = 9), even when the adipose tissue from the cancer patient was taken from a quadrant with no detectable tumor. We observed that exon I.4-specific transcripts were predominant in breast adipose obtained from cancer-free women. In this tissue, promoter-II-specific and exon I.3-specific transcripts were present in low copy number. On the other hand, in breast cancer patients, CYP19 gene transcripts from breast adipose tissue had primarily promoter-II-specific and exon I.3-specific sequence, whereas comparatively few transcripts had exon I.4-specific sequence at the 5'-terminus. We conclude that CYP19 gene transcription in breast adipose tissue of cancer-free individuals uses preferably promoter I.4, implicating a role of glucocorticoids and members of the IL-6 cytokine family in the regulation of this expression. On the other hand, the increased expression in breast adipose tissue bearing a carcinoma results from expression from promoters II and I.3, which are regulated by unknown factors acting via increased cAMP formation, which are presumably secreted by the tumor or associated cells.

Cellular characterization of adipose tissue from various body sites of women

Adipose tissue is the primary site of estrogen biosynthesis in postmenopausal women. The two main histologic components of adipose tissue are mature adipocytes and fibroblasts. Aromatase P450 expressed in the fibroblast component of adipose tissue is responsible for catalyzing conversion of C19 steroids to estrogens. We previously have demonstrated that in women, aromatase expression in adipose tissue of various body sites increases with age and that aromatase expression in the hip is markedly higher than in the abdomen. To determine whether this age- and regional-dependent variation in aromatase expression is caused by an alteration in the ratio of fibroblasts to mature adipocytes, we collected sc adipose tissue samples from 19 women (age range: 21-93 yr) at the time of autopsy. Using a computerized image analysis system, we determined by morphometry the proportions of adipocytes, fibroblasts, and vascular endothelial cells within histologic sections of adipose tissue from midabdomen, both breasts, and both hips. The percentage of each cell component at each body site was expressed as the mean of triplicate replicates. Statistical analysis of our results did not indicate any correlation between advancing age and fibroblast to adipocyte ratios in the breast, abdomen, or hip. Fibroblast to adipocyte ratios were found to be significantly higher in the breast and abdomen compared with the hip ( P < 0.05). No statistical differences were found between the breast and abdomen. These findings suggest that the increase in aromatase expression with advancing age and the higher aromatase expression in the hip compared with the abdomen in women may be caused by alterations in specific signal transduction mechanisms rather than a simple increase in local adipose fibroblast numbers.

Expression of transcripts of interleukin-6 and related cytokines by human breast tumors, breast cancer cells, and adipose stromal cells

The expression of transcripts of cytokines of the interleukin-6 (IL-6) family has been examined in human breast tumors, breast cancer cell lines, and adipose stromal cells, by means of reverse transcription polymerase chain reaction amplification. Of the six breast tumor samples examined, all expressed transcripts encoding IL-6 and Leukemia Inhibitory Factor (LIF). Four of the samples also expressed transcripts for oncostatin M (OSM) and IL-11, and three expressed the IL-6 receptor. Adipose stromal cells expressed IL-6, IL-11 and LIF, but not the IL-6 receptor, consistent with previous conclusions that IL-6 activity in these cells required addition of IL-6 soluble receptor. In the case of T47D cells, expression of IL-11 protein was confirmed by immunotitration. Moreover, in these cells, expression of IL-11 transcripts was induced 3-fold by addition of estradiol to the culture medium. These results add credence to our previous proposal that breast cancer development is regulated in part by local autocrine and paracrine mechanisms via epithelial/mesenchymal interactions, in which estrogen produced by stromal cells surrounding the tumor acts to stimulate the production of growth factors and cytokines by the tumor cells. Some of these may act to stimulate further the growth and development of the tumor, while these or other factors may act on the surrounding mesenchymal cells in a paracrine fashion to stimulate aromatase expression in the presence of glucocorticoids. Thus, a positive feedback loop is established which leads to the development and growth of the tumor.

Distribution of aromatase P450 transcripts and adipose fibroblasts in the human breast

The fibroblast component of adipose tissue is the primary extraglandular site of aromatase P450 (P450arom) expression, which is responsible for the conversion of C19 steroids to estrogens. Previously, we have shown positive correlations between the level of P450arom transcripts and the ratio of fibroblasts to mature adipocytes in adipose tissue samples proximal to breast tumors. The present study was conducted to determine the distribution of P450arom messenger ribonucleic acid (RNA) levels and fibroblast to adipocyte ratios in disease-free breasts of premenopausal women. Adipose tissue samples were collected from 3 regions (outer, upper, and inner) of both breasts of 13 women undergoing reduction mammoplasty. The histological composition of adipose tissue (n = 12) was determined by morphometry using a computerized image analysis program. We used a competitive RT-PCR method employing rat P450arom complementary RNA as an internal standard to quantify adipose P450arom transcripts in tissue total RNA samples (n = 11). Overall, 67% of the highest fibroblast to adipocyte ratios and 64% of the highest P450arom transcript levels were detected in an outer breast region, whereas in only 1 patient were the highest values detected in an inner region. Parametric ANOVA showed significant differences between the fibroblast content of the regions [p(F) = 0.037]. This distribution pattern directly correlates with the most common or the least common sites of carcinoma in the breast, the outer and inner regions, respectively. Moreover, a direct relationship was demonstrated between adipose fibroblasts and P450arom transcripts within the breast, in that regions with the highest fibroblast to adipocyte ratios contained the highest P450arom transcript levels (by ANOVA of contrast variables, P = 0.0009). These results suggest that, similar to our previous findings in the breast bearing a tumor, adipose tissue aromatase expression in the disease-free breast is determined by the local ratio of fibroblasts to adipocytes.

Aromatase expression in endometriosis

The conversion of C19 steroids to estrogens occurs in a number of tissues, such as the ovary and placenta, and is catalyzed by aromatase P450 (P450arom; the product of the CYP19 gene). P450arom expression has also been detected in a number of uterine tumors, such as leiomyomas and endometrial cancer. On the other hand, P450arom expression was undetectable in normal endometrial and myometrial tissues. The present study was conducted to determine the presence or absence of aromatase expression in peritoneal endometriotic implants and in the eutopic endometrium of women with endometriosis. Endometriotic implants in pelvic peritoneum (n = 17; e.g. posterior culdesac, bladder, and anterior culdesac) and eutopic endometrial curettings (n = 11) of 14 patients with histologically documented pelvic endometriosis were obtained at the time of laparoscopy or laparotomy. Pelvic peritoneal biopsies distal to endometriotic implants as well as normal endometrial tissues (n = 7) from disease-free women were used as negative controls. We used competitive RT-PCR technology employing an internal standard to amplify P450arom transcripts in total ribonucleic acid (RNA) isolated from these tissues. P450arom transcripts were detected in all endometriotic implants and in all eutopic endometrial tissues from patients with endometriosis. P450arom messenger RNA species were not detectable in endometrial tissues from disease-free women or in endometriosis-free peritoneal tissues. The highest levels of transcripts were detected in an endometriotic implant that involved the full thickness of the anterior abdominal wall. The P450arom transcript level within the core of this endometriotic mass was 4-fold higher than that in the surrounding adipose tissue. It has been shown recently that aromatase expression in various human tissues is regulated by the use of tissue-specific promoters via alternative splicing. To analyze promoter usage, we amplified by RT-PCR the most likely promoter-specific untranslated 5'-termini of P450arom transcripts in 2 endometriotic implants. It appears that these endometriotic implants use both the adipose-type promoter I.4 and gonadal-type promoter II for aromatase expression. The use of promoter I.4 for aromatase expression in adipose tissue has been recently observed to be regulated by members of the interleukin-6 (IL-6) cytokine family. Based on these findings, we examined by RT-PCR, IL-6 and IL-11 messenger RNA expression in 5 endometriotic tissues and 1 eutopic endometrial sample from a patient with endometriosis. We detected IL-6 and IL-11 transcripts in all endometriotic tissues and in the eutopic endometrial tissue sample studied. Our findings indicate that both eutopic endometrial tissues and endometriotic implants from patients with endometriosis are biochemically different from normal endometrial tissues of disease-free women. The presence of aromatase expression in eutopic endometrial tissues from patients with endometriosis may be related to the capability of implantation of these tissues on peritoneal surfaces. Furthermore, the possibility of estrogen production in these implants may serve to promote their growth. Increased IL-6 and IL-11 expression in these tissues suggests that P450arom expression in endometriosis may be regulated in part by these cytokines.

Quantitative detection of alternatively spliced transcripts of the aromatase cytochrome P450 (CYP19) gene in aromatase-expressing human cells by competitive RT-PCR

C19 steroids are converted to oestrogens in a number of tissues by a specific form of cytochrome P450, namely aromatase P450 (P450arom; the product of the CYP19 gene). The human CYP19 gene comprises nine coding exons, II-X. The tissue-specific expression is determined by the use of tissue-specific promoters, which give rise to P450arom transcripts with unique 5'-untranslated sequences. The majority of the transcripts present in the ovary contain promoter-II-specific sequences, while transcripts in the placenta contain exon I.1. Transcripts in adipose tissue possess exon I.3 and exon I.4. Also, the distribution of alternative transcripts in adipose stromal cells depends on the culture conditions. Therefore, a competitive RT-PCR method was designed to quantitatively detect alternatively spliced transcripts present in various tissues and cells maintained in different culture conditions. Specific synthetic transcripts with different 5' termini (exon I.3, exon I.4 and promoter-II-specific sequences) and the coding region were used as internal standards. This competitive RT-PCR method was used to quantitatively detect three 5' termini, i.e. promoter-II-specific sequence, exon I.3 and exon I.4, in transcripts in human adipose stromal cells and ovarian granulosa cells in primary culture. The quantity of total P450arom transcripts was judged by amplifying the coding region. We were also able to quantify rare transcripts which could not be detected previously by Northern analysis.

Aromatase P450 gene expression in human adipose tissue. Role of a Jak/STAT pathway in regulation of the adipose-specific promoter

In the present report we describe a heretofore unrecognized role for a Jak/STAT signaling pathway, namely the stimulation of expression of the aromatase P450 (CYP19) gene, and hence of estrogen biosynthesis, in human adipose tissue. Expression of this gene in adipose tissue as well as in adipose stromal cells maintained in the presence of serum and glucocorticoids is regulated by a distal TATA-less promoter, I.4, which contains a glucocorticoid response element, an Sp1 binding site, and an interferon-gamma activation site (GAS) element. The stimulatory action of serum (in the presence of dexamethasone) can be replaced by interleukin (IL)-11, leukemia inhibitory factor, and oncostatin-M, as well as by IL-6, providing the IL-6 soluble receptor is also present. Stimulation of the cells by these factors led to rapid phosphorylation of Jak1, but not Jak2 or Jak3, on tyrosine residues. STAT3 but not STAT1 was also phosphorylated and bound to the GAS element in the I.4 promoter region. When regions of this promoter were fused upstream of the chloramphenicol acetyltransferase reporter gene and transfected into the cells, mutagenesis or deletion of the GAS element led to complete loss of reporter gene expression. Since adipose tissue is the major site of estrogen biosynthesis in men and in postmenopausal women, this pathway involving a Jak/STAT signaling mechanism acting together with glucocorticoids and Sp1 appears to be the principal means whereby estrogen biosynthesis is regulated in the elderly.