Immunocytochemical determination of estrogen and progesterone receptors in human endometrial adenocarcinoma cells (Ishikawa cells)

An Assessment of the Mechanophysical and Hormonal Impact on Human Endometrial Epithelium Mechanics and Receptivity

The endometrial epithelium and underlying stroma undergo profound changes to support and limit embryo adhesion and invasion, which occur in the secretory phase of the menstrual cycle during the window of implantation. This coincides with a peak in progesterone and estradiol production. We hypothesized that the interplay between hormone-induced changes in the mechanical properties of the endometrial epithelium and stroma supports this process. To study it, we used hormone-responsive endometrial adenocarcinoma-derived Ishikawa cells growing on substrates of different stiffness. We showed that Ishikawa monolayers on soft substrates are more tightly clustered and uniform than on stiff substrates. Probing for mechanical alterations, we found accelerated stress-relaxation after apical nanoindentation in hormone-stimulated monolayers on stiff substrates. Traction force microscopy furthermore revealed an increased number of foci with high traction in the presence of estradiol and progesterone on soft substrates. The detection of single cells and small cell clusters positive for the intermediate filament protein vimentin and the progesterone receptor further underscored monolayer heterogeneity. Finally, adhesion assays with trophoblast-derived AC-1M-88 spheroids were used to examine the effects of substrate stiffness and steroid hormones on endometrial receptivity. We conclude that the extracellular matrix and hormones act together to determine mechanical properties and, ultimately, embryo implantation.

An integrated approach of network pharmacology, molecular docking, and experimental verification uncovers kaempferol as the effective modulator of HSD17B1 for treatment of endometrial cancer

BACKGROUND

Endometrial cancer (EC) is one of the most common gynecological malignancies globally, and the development of innovative, effective drugs against EC remains a key issue. Phytoestrogen kaempferol exhibits anti-cancer effects, but the action mechanisms are still unclear.

METHOD

MTT assays, colony-forming assays, flow cytometry, scratch healing, and transwell assays were used to evaluate the proliferation, apoptosis, cell cycle, migration, and invasion of both ER-subtype EC cells. Xenograft experiments were used to assess the effects of kaempferol inhibition on tumor growth. Next-generation RNA sequencing was used to compare the gene expression levels in vehicle-treated versus kaempferol-treated Ishikawa and HEC-1-A cells. A network pharmacology and molecular docking technique were applied to identify the anti-cancer mechanism of kaempferol, including the building of target-pathway network. GO analysis and KEGG pathway enrichment analysis were used to identify cancer-related targets. Finally, the study validated the mRNA and protein expression using real-time quantitative PCR, western blotting, and immunohistochemical analysis.

RESULTS

Kaempferol was found to suppress the proliferation, promote apoptosis, and limit the tumor-forming, scratch healing, invasion, and migration capacities of EC cells. Kaempferol inhibited tumor growth and promotes apoptosis in a human endometrial cancer xenograft mouse model. No significant toxicity of kaempferol was found in human monocytes and normal cell lines at non-cytotoxic concentrations. No adverse effects or significant changes in body weight or organ coefficients were observed in 3-7 weeks' kaempferol-treated animals. The RNA sequencing, network pharmacology, and molecular docking approaches identified the overall survival-related differentially expressed gene HSD17B1. Interestingly, kaempferol upregulated HSD17B1 expression and sensitivity in ER-negative EC cells. Kaempferol differentially regulated PPARG expression in EC cells of different ER subtypes, independent of its effect on ESR1. HSD17B1 and HSD17B1-associated genes, such as ESR1, ESRRA, PPARG, AKT1, and AKR1C1\2\3, were involved in several estrogen metabolism pathways, such as steroid binding, 17-beta-hydroxysteroid dehydrogenase (NADP+) activity, steroid hormone biosynthesis, and regulation of hormone levels. The molecular basis of the effects of kaempferol treatment was evaluated.

CONCLUSIONS

Kaempferol is a novel therapeutic candidate for EC via HSD17B1-related estrogen metabolism pathways. These results provide new insights into the efficiency of the medical translation of phytoestrogens.

Identification of LncRNAs/mRNAs related to endometrium function regulated by Homeobox A10 in Ishikawa cells

As a well-known transcription factor, Homeobox A10 (HOXA10) regulates a large number of downstream target genes, leading to the proper function development of endometrium for embryo implantation. The change of HOXA10 gene expression level can alter the expressions of many other genes, including coding and noncoding transcripts. In our study, mRNA and LncRNA expression profiles screening was performed by microarray when the HOXA10 gene expression level increased in Ishikawa cells. A total of 907 mRNAs and 1,026 LncRNAs were identified as differentially expressed transcripts (Fold Change ≥2, P-value <0.05, and Q-value <0.05) between HOXA10 overexpressed and control Ishikawa cells. Further analysis identified that these mRNAs participated in various biological processes, such as blood vessel development, cell adhesion, cell cycle, etc. Also, 14 enhancer-like LncRNAs and 108 LincRNAs with their nearby mRNAs were identified as coregulated transcripts. Our results showed that the mRNA and LncRNA expression profiles differed significantly between the two groups and provided useful information for further studying the molecular mechanisms of HOXA10 in endometrium.

A novel role for the AAA ATPase spastin as a HOXA10 transcriptional corepressor in Ishikawa endometrial cells

Homeobox A10 (HOXA10), a transcription factor required for uterine development and embryo receptivity, functions downstream of estrogen and progesterone in uterine endometrium. HOXA10 represses endometrial expression of empty spiracles homeobox 2 (EMX2), the human ortholog of Drosophila empty spiracles. The ATPases associated with various cellular activities (AAA) ATPase spastin has a well-characterized role in neurotransmitter trafficking. In this study, we characterize a novel role of spastin in transcriptional regulation. We identified spastin as a novel component of the HOXA10 transcriptional complex in Ishikawa nuclear extracts by immunoprecipitation and mass spectrophotometry. Using EMX2 as a model endometrial HOXA10 target gene, we show that the HOXA10-spastin corepressor complex bound the EMX2 promoter in chromatin immunoprecipitation assays. HOXA10 has been previously shown to repress endometrial EMX2 expression. We further observed that, although cotransfection of HOXA10 and spastin continued to repress endometrial EMX2-luciferase expression, the repression was reversed when spastin small interfering RNA was cotransfected with HOXA10. Mutations in the nuclear localization signal sequences of spastin abrogated not only its nuclear translocation but also its colocalization with HOXA10 as well as reversed EMX2-luciferase repression. Here, we describe a novel role for the AAA ATPase spastin in Ishikawa cells as a HOXA10 corepressor of EMX2. Uterine EMX2 levels are inversely related to embryo implantation rates. HOXA10 acts downstream of progesterone and has been shown to facilitate embryo implantation through regulation of endometrial EMX2 expression. Endometrial spastin, therefore, likely has a novel function downstream of estrogen and progesterone in implantation biology as a cofactor of HOXA10.

The mechanism of action of the histone deacetylase inhibitor vorinostat involves interaction with the insulin-like growth factor signaling pathway

A correlation between components of the insulin-like growth factor (IGF) system and endometrial cancer risk has been shown in recent studies. The antitumor action of vorinostat, a histone deacetylase inhibitor, involves changes in the expression of specific genes via acetylation of histones and transcription factors. The aim of this study was to establish whether vorinostat can modify the expression of specific genes related to the IGF-I receptor (IGF-IR) signaling pathway and revert the transformed phenotype. Human endometrioid (Type I, Ishikawa) and uterine serous papillary (Type II, USPC-2) endometrial cancer cell lines were treated with vorinostat in the presence or absence of IGF-I. Vorinostat increased IGF-IR phosphorylation, produced acetylation of histone H3, up-regulated pTEN and p21 expression, and reduced p53 and cyclin D1 levels in Ishikawa cells. Vorinostat up-regulated IGF-IR and p21 expression, produced acetylation of histone H3, and down-regulated the expression of total AKT, pTEN and cyclin D1 in USPC-2 cells. Of interest, IGF-IR activation was associated with a major elevation in IGF-IR promoter activity. In addition, vorinostat treatment induced apoptosis in both cell lines and abolished the anti-apoptotic activity of IGF-I both in the absence or presence of a humanized monoclonal IGF-IR antibody, MK-0646. Finally, vorinostat treatment led to a significant decrease in proliferation and colony forming capability in both cell lines. In summary, our studies demonstrate that vorinostat exhibits a potent apoptotic and anti-proliferative effect in both Type I and II endometrial cancer cells, thus suggesting that endometrial cancer may be therapeutically targeted by vorinostat.

Early stages of implantation as revealed by an in vitro model

Our limited understanding of the processes underlying steroid hormonal control of human endometrial receptivity is largely due to the lack of a relevant model system. To overcome scarcity of material, we have developed a model in which mouse embryos attach to human Ishikawa cells, which express functional steroid hormone receptors. Blastocysts flushed from day 4 pregnant superovulated mice were transferred to confluent Ishikawa cell monolayers. After 48 h of co-culture, 85% of the blastocysts had attached loosely, but only 40% attached stably to the epithelial cell surface. In contrast, 95% of the embryos attached stably to tissue culture plastic. Thus, weak attachment of a majority of the embryos was followed by stronger adhesion of a smaller proportion. Seventeen percent of the transferred blastocysts modified the epithelial cell surface with loss of MUC1 at the attachment site, extending variably to adjacent epithelial cells. Initially, stable attachment occurred without disruption to the integrity of the epithelial monolayer, but at later stages after the embryo had spread laterally, displacement of subjacent cells was observed. A modest increase in stable attachment, but no changes to MUC1 clearance, was observed after assisted hatching. After 24 h priming of Ishikawa cells by 17β-oestradiol (OE2) followed by 72-h incubation with medroxyprogesterone acetate and OE2, stable attachment increased from 40 to 70%. Initial attachment is efficient either in the presence or in the absence of hormone; steroid treatment increased the incidence of stable attachment. Implantation failure is predicted to occur in this model when embryos fail to progress from initial to stable attachment.

HOXA10 regulates endometrial GABAA {pi} receptor expression and membrane translocation

Expression of the GABA(A) pi receptor has been described previously in the human endometrium in both luminal epithelium and stroma. Its expression is increased during decidualization in rodents and in the implantation window of human endometrium. Here we localized GABA pi subunit receptor protein in human endometrium and identified regulators of gene expression and activation. GABA(A) pi was localized to the cell surface, and expression increased during the window of embryo implantation in human endometrium. The well-differentiated human endometrial adenocarcinoma cell line Ishikawa was treated with progesterone and transfected with pcDNA-HOXA10, HOXA10 siRNA, or respective controls. GABA(A) pi receptor mRNA expression was evaluated by real-time RT-PCR. Protein expression and localization were evaluated using immunofluorescence. GABA(A) pi receptor mRNA expression was increased significantly after either progesterone treatment or HOXA10 transfection. Coadministration of progesterone along with HOXA10 transfection had no additional effect on the expression of GABA(A) pi receptor mRNA over either agent alone. Blocking HOXA10 expression with siRNA prevented progesterone-induced GABA(A) pi receptor mRNA expression. Additionally, either HOXA10 or progesterone independently caused increased translocation of the GABA receptor from the cytoplasm to the cell membrane. Translocation in response to progesterone was blocked with HOXA10 siRNA. Progesterone-induced GABA(A) pi subunit receptor expression is likely mediated indirectly through progesterone's regulation of HOXA10 expression. Modification of subtype composition and translocation of the GABA receptor ion channel likely modulate endometrial receptivity. Whereas HOXA10 typically enhances the expression of progesterone-responsive genes, here HOXA10 expression leads to production of a less progestin-responsive GABA receptor subtype, likely buffering the effects of luteal phase progesterone on GABA receptor activity.

Enhanced estrogen-induced proliferation in obese rat endometrium

OBJECTIVE

We tested the hypothesis that the proliferative estrogen effect on the endometrium is enhanced in obese vs lean animals.

STUDY DESIGN

Using Zucker fa/fa obese rats and lean control, we examined endometrial cell proliferation and the expression patterns of certain estrogen-regulated proproliferative and antiproliferative genes after short-term treatment with estradiol.

RESULTS

No significant morphologic/histologic difference was seen between the obese rats and the lean rats. Estrogen-induced proproliferative genes cyclin A and c-Myc messenger RNA expression were significantly higher in the endometrium of obese rats compared with those of the lean control. Expression of the antiproliferative gene p27Kip1 was suppressed by estrogen treatment in both obese and lean rats; however, the decrease was more pronounced in obese rats. Estrogen more strongly induced the antiproliferative genes retinaldehyde dehydrogenases 2 and secreted frizzled-related protein 4 in lean rats but had little or no effect in obese rats.

CONCLUSION

Enhancement of estrogen-induced endometrial proproliferative gene expression and suppression of antiproliferative gene expression was seen in the endometrium of obese vs lean animals.

Stable inhibition of interleukin 1 receptor type II in Ishikawa cells augments secretion of matrix metalloproteinases: possible role in endometriosis pathophysiology

Our previous studies showed a marked deficiency in interleukin 1 receptor type II (IL1R2) in the endometrial tissue of women with endometriosis, particularly in epithelial cells. We believe that such a deficiency in IL1R2, a potent and specific IL1 inhibitor, makes endometrial cells more sensitive to IL1 and less capable of buffering the cytokine's effects, which may lead to functional changes that favor endometriosis development. The main objective of our study was to stably inhibit IL1R2 expression in endometrial cells in order to evaluate the role of IL1R2 deficiency in endometriosis pathophysiology. Stable clones of Ishikawa adenocarcinoma endometrial cells transfected with IL1R2 antisense and showing downregulation of IL1R2 protein expression, or with the empty expression vector alone and showing no noticeable difference in IL1R2 expression, were selected. The downregulation of IL1R2 expression in IL1R2 antisense transfectants when compared with control cells was confirmed by ELISA, Western blot and immunofluorescence. In these cells, IL1R2 expression was markedly reduced, compared with non-transfected cells or cells transfected with the empty vector, and there was a significant increase in the basal and the IL1-beta (IL1B)-induced levels of matrix metalloproteinase (MMP)-2 and MMP-9 secretion. Furthermore, a significant decrease in IL1B-induced secretion of tissue inhibitor of MMPs-1, a known MMP-9 inhibitor, was observed. These in vitro data make plausible a role for IL1R2 deficiency in the capability of endometrial cells to invade the host tissue and develop in ectopic locations.

Stimulatory effect of estrogen on the growth of endometrial cancer cells is regulated by cell-cycle regulators

Estrogen is known as a major risk factor in tumorigenesis of the endometrium. The aim of this study is to establish stable estrogen-responsive endometrial cancer cell lines and to investigate the mechanism of estrogen action, focusing on cell-cycle regulation. Human wild-type estrogen receptor cDNA was transfected into endometrial cancer cells (Ishikawa) and estrogen-responsive cell lines were cloned. Their estrogen responsiveness was evaluated by the effect of estrogen on cellular growth and progesterone receptor expression. It was quantitatively estimated by immunocytochemistry or immunoblotting how the expression of cell-cycle regulators such as cyclin D1, cyclin E, Cyclin A, p53, p21 and p27 was regulated by estrogen. A cell line stably responsive to estrogen was established, and cells proliferated and the glandular structure was formed by estrogen stimulation. Cyclin D1 expression increased at 6-24h and cyclin A gradually increased until 48h of estrogen treatment compared with untreated cells. On the other hand, p53 and p21 expressions decreased at 6-24h, and p27 gradually decreased until 24h by estrogen. Our results show that the stimulatory effect of estrogen on cell proliferation may be regulated by the up-regulation of cyclin D1 and cyclin A, and down-regulation of p53, p21 and p27. This cell line is useful to clarify the molecular mechanism of estrogen action on endometrial cancer.

Macrophage migration inhibitory factor up-regulates alpha(v)beta(3) integrin and vascular endothelial growth factor expression in endometrial adenocarcinoma cell line Ishikawa

Human endometrium undergoes a series of dynamic physiological changes during the menstrual cycle of reproductive age women. Many factors, including hormones, cytokines, growth factors, matrix metalloproteinases and integrins, are essential for the success of embryonic implantation into endometrial tissue. Herein, we used a well-differentiated endometrial adenocarcinoma cell line, Ishikawa, to investigate in vitro the role played by macrophage migration inhibitory factor (MIF) in the regulation of endometrial receptivity markers. Quantitative real-time polymerase chain reaction (qRT-PCR) showed that MIF induced a slight increase in alpha(v) (alphav) mRNA integrin subunit expression during the first 12h, but reached a significant difference after 24h MIF treatment compared to control, whereas beta(3) (beta3) integrin subunit displayed significant increase in mRNA 2h following treatment. Immunocytofluorescence showed strong alphav and beta3 immunostaining at 25 ng/ml MIF, and Western blotting clearly indicated increased alphav and beta3 protein expression. MIF treatment significantly stimulated vascular endothelial growth factor (VEGF) mRNA expression in a dose- and time-dependent manner after 24 h treatment. Moreover, immunocytofluorescence revealed positive VEGF immunostaining compared to control, and analysis by ELISA of VEGF release in culture supernatants demonstrated that MIF (25 ng/ml) significantly induced VEGF secretion at 12 and 24 h. In conclusion, this study provides evidence that MIF directly up-regulates alphavbeta3 integrin and VEGF expression in human endometrial Ishikawa cells and may advance our understanding of factors involved in the establishment of endometrial receptivity and successful implantation.

ECC-1 Cells: A Well-Differentiated Steroid-Responsive Endometrial Cell Line with Characteristics of Luminal Epithelium1

Endometrial cancer cell lines have provided a valuable model to study endometrial epithelial cells in vitro. Since the first development of HEC1B over 35 yr ago, many different cell lines have been isolated and described. One valuable cell line that maintains hormone responsiveness and unique stability over time is the ECC-1 cell line, developed originally by the late P.G. Satyaswaroop. In this study, we investigated some of the properties of these cells and present their salient characteristics. Like Ishikawa cells, ECC-1 cells maintain both estrogen receptors (ESR1 [ER alpha] and ESR2 [ER beta]), progesterone receptors (PR A and B; PGRs), and androgen receptors (ARs), along with the p160 steroid receptor coactivators NCOA1 (formerly SRC1), NCOA2 (formerly TIF2), and NCOA3 (formerly AIB1). The karyotype of these cells is abnormal, with multiple structural rearrangements in all cells analyzed. Unlike Ishikawa cells that express glandular epithelial antigens, ECC-1 cells maintain a luminal phenotype, with expression of KRT13 (cytokeratin 13) and KRT18 (cytokeratin 18). Apparent differences in the regulation of ESR2 also were evident in ECC-1 cells compared to Ishikawa cells. Like other endometrial cell lines, ECC-1 cells express the steroid receptor coactivators and exhibit epidermal growth factor-stimulated expression of known luminal proteins thought to be involved in implantation, including the hyaluronate receptor CD44 and SPP1 (formerly osteopontin) and CD55 (decay-accelerating factor). These characteristics appear to be stable and persistent over multiple cell passages, making this well-differentiated cell line an excellent choice to study endocrine and paracrine regulation of endometrial epithelium in vitro.

Endocrine regulation of HOX genes

Hox genes have a well-characterized role in embryonic development, where they determine identity along the anteroposterior body axis. Hox genes are expressed not only during embryogenesis but also in the adult, where they are necessary for functional differentiation. Despite the known function of these genes as transcription factors, few regulatory mechanisms that drive Hox expression are known. Recently, several hormones and their cognate receptors have been shown to regulate Hox gene expression and thereby mediate development in the embryo as well as functional differentiation in the adult organism. Estradiol, progesterone, testosterone, retinoic acid, and vitamin D have been shown to regulate Hox gene expression. In the embryo, the endocrine system directs axial Hox gene expression; aberrant Hox gene expression due to exposure to endocrine disruptors contributes to the teratogenicity of these compounds. In the adult, endocrine regulation of Hox genes is necessary to enable such diverse functions as hematopoiesis and reproduction; endocrinopathies can result in dysregulated HOX gene expression affecting physiology. By regulating HOX genes, hormonal signals utilize a conserved mechanism that allows generation of structural and functional diversity in both developing and adult tissues. This review discusses endocrine Hox regulation and its impact on physiology and human pathology.

Regulatory expression of lipoxin A4 receptor in physiologically estrus cycle and pathologically endometriosis

Expression of receptors for prostaglandin (PG) and leukotriene (LT) has been reported to detect in endometrium and smooth muscle of uterus, suggesting involvement of these arachidonic metabolites in endometrial pathology and reproductive biology. Lipoxin (LX), which is produced by lipoxygenases from arachidonic acid, has been characterized as an anti-inflammatory lipid mediator. Biological actions of Lipoxin A4 (LXA4) are mediated through the specific receptor. In order to know roles of LXA4 in female genitalia, expression of LXA4 receptor mRNA was quantified by real-time polymerase chain reaction. Significantly higher expression of the receptor was detected in endometrium and myometrium than ovary in normal rats. Expression of the receptor in endometrium was increased at stage of proestrus cycle under physiological condition. Exogenous administration of progesterone into female rats significantly reduced the expression, while administration of estradiol or pregnant mare serum gonadotropin (PMSG) did not. Both, endometrium in experimental endometriosis induced in rats and the tissues from patients with ectopic endometriosis showed a higher expression of LXA4 receptor compared to the normal tissues. In contrast, expressions of BLT1 and BLT2, receptors for leukotriene B4, did not change in the endometriosis. These observations suggest a possible role of LXA4 and the receptor under physiological estrus cycle and pathological condition as endometriosis.

In vivo and in vitro estrogenic and progestagenic actions of Tibolone

Estrogen and progestin combination in hormone replacement therapy (HRT) increases the incidence of breast cancer, but decreases the endometrial cancer risk of unopposed estrogen. Therefore, a SERM such as Tibolone, that delivers the beneficial, but not the adverse side effects, of steroid hormones would be clinically advantageous. However, data from the Million Women Study suggests that Tibolone increases the risk of both breast and endometrial cancer. Herein, we assessed the estrogenic and progestagenic actions of Tibolone using transvaginal sonography studies and an in vitro model of breast (ZR-75, MCF7) and endometrial cancer (Ishikawa). The known cancer associated proteins (ER, EGFR, STATS, tissue factor and Bcl-xL) were selected for study. Transvaginal sonography demonstrated that postmenopausal women treated with Tibolone displayed a thinner endometrium than in the late proliferative phase, but had a phenotype characteristic of the secretory phase, thus demonstrating the estrogenic and progestagenic actions of this SERM. In vitro, Tibolone acted as an estrogen in downregulating ER and upregulating Bcl-xL, yet as progesterone, increasing STAT5 and tissue factor in breast cancer cells. The increase in tissue factor by Tibolone correlated with its coagulative potential. Interestingly, EGFR was up-regulated by progesterone in the breast and by estrogen in endometrial cells, while Tibolone increased protein levels in both cell types. In conclusion, this study further demonstrates the estrogenic and progestagenic nature of Tibolone. The pattern of regulation of known oncogenes in cells of breast and endometrial origin dictates caution and vigilance in the prescription of Tibolone and subsequent patient monitoring.

Estrogen receptor-alpha (ER-alpha) and defects in uterine receptivity in women

Endometriosis is a disorder that affects 5% of the normal population but is present in up to 40% of women with pelvic pain and/or infertility. Recent evidence suggests that the endometrium of women with endometriosis exhibits progesterone insensitivity. One endometrial protein that fluctuates in response to progesterone is the estrogen receptor-alpha (ER alpha), being down-regulated at the time of peak progesterone secretion during the window of implantation. Here we demonstrate that the biomarker of uterine receptivity, beta 3 integrin subunit, is reduced or absent in some women with endometriosis and that such defects are accompanied by inappropriate over-expression of ER alpha during the mid-secretory phase. Using a well-differentiated endometrial cell line we showed that the beta 3 integrin protein is negatively regulated by estrogen and positively regulated by epidermal growth factor (EGF). By competing against estrogen with various selective estrogen receptor modulators (SERMs) and estrogen receptor agonists and antagonists, inhibition of expression of the beta 3 integrin by estrogen can be mitigated. In conclusion, we hypothesize that certain types of uterine receptivity defects may be caused by the loss of appropriate ER alpha down-regulation in the mid-secretory phase, leading to defects in uterine receptivity. Such changes might be effectively treated by timely administration of the appropriate anti-estrogens to artificially block ER alpha and restore normal patterns of gene expression. Such treatments will require further clinical studies.

A soluble molecule secreted by human blastocysts modulates regulation of HOXA10 expression in an epithelial endometrial cell line

OBJECTIVE

To determine the existence of a soluble signal, secreted from the human blastocyst embryo, that induces HOXA10 gene expression before cell-cell contact.

DESIGN

To analyze, by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR), cell-free media that had contained human embryos cultured to the blastocyst stage for a soluble molecule that induces HOXA10 expression in an endometrial epithelial cell line (Ishikawa).

SETTING

Assisted reproduction technology program of Yale University, New Haven, Connecticut.

PATIENT(S)

Patients undergoing intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF) cycles. Treatment of Ishikawa cells with blastocyst-conditioned media.

MAIN OUTCOME MEASURE(S)

Determination of HOXA10 gene expression.

RESULT(S)

We demonstrate that cell-free media that had contained human embryos cultured to the blastocyst stage contain a soluble molecule that induces HOXA10 expression in an endometrial epithelial cell line (Ishikawa). We found that hCG does not induce HOXA10 in Ishikawa cells.

CONCLUSION(S)

Soluble molecules induce a well-characterized marker of endometrial receptivity in endometrial cells without blastocyst apposition. Additionally, HOXA10 induction can serve as a means of evaluating human embryos cultured for IVF and ET. High quality embryos may induce local endometrial receptivity before trophectoderm-endometrial contact.

Regulation of vascular endothelial growth factor by tamoxifen in vitro and in vivo

OBJECTIVE

To evaluate the effects of tamoxifen on human endometrial vascular endothelial growth factor (VEGF) gene expression in vitro and in vivo.

STUDY DESIGN

Ishikawa cells were transiently co-transfected with plasmids expressing human estrogen receptor (ER)-alpha or -beta and a 2.3-kb human VEGF promoter-luciferase construct. Transfected cells were treated with tamoxifen and the increase in luciferase activity was compared to controls. In addition, immunohistochemical analysis of VEGF expression in endometrial biopsies from 11 postmenopausal women receiving tamoxifen was compared to 24 postmenopausal women on no hormone replacement.

RESULTS

In transfected cells expressing ERalpha, tamoxifen induced a significant VEGF promoter activation (3.2-fold, p < 0.01), whereas cells expressing ERbeta showed a 1.6-fold stimulation (p = NS). No significant differences in VEGF immunostaining were observed in tamoxifen-exposed women.

CONCLUSIONS

Although tamoxifen exposure increases VEGF expression in vitro, a significant increase in VEGF expression is not apparent in endometrial biopsies of postmenopausal women treated with this drug.

Endometrial HOXA10 expression after controlled ovarian hyperstimulation with recombinant follicle-stimulating hormone

OBJECTIVE

To determine the effects of controlled ovarian hyperstimulation and resultant high levels of E(2) on endometrial HOXA10 expression (a marker of endometrial receptivity).

DESIGN

Prospective study.

SETTING

University academic medical center.

PATIENT(S)

Twenty-five women undergoing controlled ovarian hyperstimulation with recombinant FSH and 30 fertile controls.

INTERVENTION(S)

Endometrium was obtained by Pipelle endometrial biopsy on cycle days 21-25. In addition, Ishikawa cells (a well-differentiated endometrial adenocarcinoma cell line) were treated with either E(2), recombinant FSH, GnRH agonist, or GnRH antagonist. RNA was extracted and analyzed by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR).

MAIN OUTCOME MEASURE(S)

HOXA10 expression.

RESULT(S)

Endometrial HOXA10 expression in women undergoing controlled ovarian hyperstimulation (COH) with recombinant FSH was not different from that in fertile controls. Estradiol increased HOXA10 expression in Ishikawa cells in a dose-dependent manner from 10(-9) to 10(-7) M. Neither recombinant FSH, GnRH agonist, nor GnRH antagonist altered HOXA10 expression in these cells.

CONCLUSION(S)

Controlled ovarian hyperstimulation did not inhibit endometrial HOXA10 expression in vivo. In addition, in vitro endometrial cell HOXA10 expression was not altered by either recombinant FSH, GnRH agonist, or GnRH antagonist. COH is unlikely to adversely impact endometrial receptivity.

Target specificity of selective estrogen receptor modulators within human endometrial cancer cells

Selective estrogen receptor modulators (SERMs) are estrogen receptor (ER) ligands that function as antagonists in some tissues, but have either partial or full agonist activity in others. SERMs often display variable partial agonist activity in uterine tissues and this activity can be displayed in uterine cell lines such as the human Ishikawa endometrial adenocarcinoma cell line. In this study, we compared the effects of several ER ligands including some SERMs on alkaline phosphatase (AP) activity and the expression of an ER target gene, the progesterone receptor (PR), in Ishikawa cells. As expected, estradiol (E2) was a potent and efficacious activator of both AP activity and PR mRNA expression. 4-Hydroxytamoxifen (4OHT) stimulated AP activity to a level 47% of that of E2 (100nM), while CP 336156 (lasofoxifene) increased AP activity 18%. A benzothiophene, such as LY 117018, a raloxifene analog, stimulated AP even less with values approximately 11% of E2-stimulated levels. A pure antiestrogen, ICI 182,780 did not stimulate AP activity. Interestingly, when we examined the ability of these compounds to increase the expression of the ER target gene, PR, a different rank order of efficacy was detected. After E2, CP 336156 was the most efficacious in increasing PR mRNA with a maximal stimulation of 20% of E2 levels, while 4OHT stimulated only 17%. LY 117018 increased PR mRNA expression 8% while ICI 182,780 did not increase PR mRNA expression at all. These data illustrate the target specificity that a SERM is able to display within a single cell type independent of "tissue specificity" and differential levels of expression of various cofactors. While 4OHT is 160% more active than CP 336156 in terms of inducing AP activity in the Ishikawa cells, CP 336156 has equivalent activity as 4OHT when one examines the ability of these SERMs to induce PR mRNA expression. Since the stimulation of Ishikawa cells by ER ligands is often used to assess the potential in vivo uterotrophic activity, these data indicate that examination of several endpoints in these cells may be necessary in order to fully characterize the activity of SERMs.

Activation of estrogen receptor alpha and ERbeta by 4-methylbenzylidene-camphor in human and rat cells: comparison with phyto- and xenoestrogens

4-Methylbenzylidene-camphor (4-MBC) is an organic sunscreen that protects against UV radiation and may therefore help in the prevention of skin cancer. Recent results on the estrogenicity of 4-MBC have raised concerns about a potential of 4-MBC to act as an endocrine disruptor. Here, we investigated the direct interaction of 4-MBC with estrogen receptor (ER) alpha and ERbeta in a series of studies including receptor binding, ER transactivation and functional tests in human and rat cells. 4-MBC induced alkaline phosphatase activity, a surrogate marker for estrogenic activity, in human endometrial Ishikawa cells. Interestingly, 4-MBC induced weakly ERalpha and with a higher potency ERbeta mediated transactivation in Ishikawa cells at doses more than 1 microM, but showed no distinct binding affinity to ERalpha or ERbeta. In addition, 4-MBC was an effective antagonist for ERalpha and ERbeta. In an attempt to put 4-MBC's estrogenic activity into perspective we compared binding affinity and potency to activate ER with phyto- and xenoestrogens. 4-MBC showed lower estrogenic potency than genistein, coumestrol, resveratrol, bisphenol A and also camphor. Analysis of a potential metabolic activation of 4-MBC that could account for 4-MBC's more distinct estrogenic effects observed in vivo revealed that no estrogenic metabolites of 4-MBC are formed in primary rat or human hepatocytes. In conclusion, we were able to show that 4-MBC is able to induce ERalpha and ERbeta activity. However, for a hazard assessment of 4-MBC's estrogenic effects, the very high doses of 4-MBC required to elicit the reported effects, its anti-estrogenic properties as well as its low estrogenic potency compared to phytoestrogens and camphor has to be taken into account.

The effects of estradiol and selective estrogen receptor modulators on gene expression and messenger RNA stability in immortalized sheep endometrial stromal cells and human endometrial adenocarcinoma cells

The purpose of this study was to identify an endometrial cell line that maintained the E2 up-regulation of estrogen receptor (ER) mRNA by enhanced message stability and to assess its dependence on ER protein. Estradiol (E2) effects on gene expression were measured in three cell lines: one immortalized from sheep endometrial stroma (ST) and two from human endometrial adenocarcinomas (Ishikawa and ECC-1). E2 up-regulated ER mRNA levels in ST and Ishikawa cells, but down-regulated ER mRNA levels in ECC-1 cells. E2 up-regulated progesterone receptor (PR), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and transforming growth factor-alpha (TGF-alpha) in both Ishikawa and ECC-1 cells. The selective estrogen receptor modulator ICI 182,780 antagonized the E2-induced up-regulation of ER and/or PR mRNA levels in all three cells, while another, GW 5638, antagonized the up-regulation of PR mRNA in Ishikawa and ECC-1 cells. In mechanistic studies, E2 had no effect on ER mRNA stability in ST cells and it destabilized ER mRNA in ECC-1 cells. Thus, Ishikawa cells appear to be the most physiologically relevant cell line in which to study the up-regulation of ER mRNA levels by enhanced mRNA stability. Its antagonism by ICI 182,780 reveals that ER protein is involved in this E2 response.

HEC-1 cells

HEC-1 cell line was the first in vitro cell line of a human endometrial adenocarcinoma which enabled us to perform research work on the endometrium and endometrial carcinoma at a simplified cellular system, contributing cell and molecular biological studies on endometrial carcinoma. Once a cell line is established, it provides a stable experimental system that facilitates and progresses in the study of the tissues and/or neoplasias from which they are derived. In this article we report how HEC-1 cells have been established and cleared the proposed requirements to characterize the established cell line. Also to show the usefulness of the cell line for research work, once it was established, we illustrate these concepts by recalling results obtained with HEC-1 cells and reviewing the literature on what has been achieved by using these cells.

Direct regulation of beta3-integrin subunit gene expression by HOXA10 in endometrial cells

Estrogen and progesterone regulate HOXA10 expression in the endometrium, where HOXA10 is necessary for implantation. The integrins are also involved in early embryo-endometrial interactions. Here we show that HOXA10 directly regulates beta3-integrin subunit expression in the endometrium, likely mediating the effect of sex steroids on beta3-integrin expression. beta3-Integrin expression was decreased in endometrium shown to have low HOXA10 expression. beta3-Integrin mRNA levels were increased in endometrial adenocarcinoma cells (Ishikawa) transfected with pcDNA3.1/HOXA10, and decreased in cells treated with HOXA10 antisense. Seven consensus HOXA10 binding sites were identified 5' of the beta3-integrin gene. Direct binding of HOXA10 protein to four sites was demonstrated by EMSA. Reporter gene expression increased in BT-20 cells cotransfected with pcDNA3.1/ HOXA10 and pGL3-promoter vector containing region F (encompassing all seven HOXA10 consensus sites). A 41-bp segment (Region A) showed highest affinity binding to HOXA10 protein. Increased reporter expression, equal in magnitude to that obtained with Region F, was obtained with Region A. HOXA10 protein binding within Region A was localized by deoxyribonuclease I footprinting. beta3-Integrin expression was directly up-regulated by HOXA10 through a 41-bp 5'-regulatory element. Sex steroids regulate the expression of endometrial beta3-integrin through a pathway involving HOXA10.

Elevated endometrial androgen receptor expression in women with polycystic ovarian syndrome

Androgen receptors (AR) have been identified in human endometrium; however, their role in endometrial cyclic development and function remains poorly understood. The objective of the present study was to investigate the profile of endometrial AR in normal menstrual cycles and in the endometrium of women with polycystic ovarian syndrome (PCOS). This syndrome is characterized by chronic hyperandrogenism and oligo-ovulation, and it is often associated with poor reproductive performance. Using immunohistochemistry and reverse transcription-polymerase chain reaction, we found that women with PCOS exhibited elevated endometrial AR expression compared to normal, fertile controls. This increase was most apparent in glandular and luminal epithelium. Furthermore, when compared to endometrium from fertile women, PCOS endometrium showed other abnormalities in endometrial development, including delay or absence of the alpha(v)beta3 integrin, a well-characterized biomarker of uterine receptivity described previously (Lessey et al., JCI 1992; 90:188-195). To better understand and to gain insights regarding these findings, we used in vitro cell-culture models to study the regulation of AR in primary endometrial stromal and the well-differentiated epithelial cell line (Ishikawa). Based on Western blot analysis, epithelial AR is up-regulated by estrogens and androgens and is inhibited by progestins and epidermal growth factor (EGF). On the other hand, EGF significantly induced the expression of alpha(v)beta3, whereas estrogen and androgen treatment inhibited its expression. Collectively, these results suggest that the poor reproductive performance observed in women with PCOS may be due, in part, to the concomitant increase in both serum androgens and elevations in endometrial AR. This combination may reduce endometrial receptivity as judged by the down-regulation of alpha(v)beta3 integrin.

Divergent effects of retinoic acids on the expression of ERalpha and 17beta-hydroxysteroid dehydrogenase type 2 in endometrial carcinoma cells (RL 95-2)

The effects of E2 are dependent on ERs and local E2 concentration in target cells. Modulation of intracellular E2 concentration involves the action of 17beta-hydroxysteroid dehydrogenase (17HSD) type 2, the enzyme converting E2 to estrone. In the present study, the influence of RAs on the growth of endometrial cancer cell line RL 95-2 as well as the expression of ERs and 17HSD type 2 have been investigated. It was found that RAs repress the growth of RL 95-2 cells, which express all subtypes of RXR and RAR, as examined by RT-PCR. Also, quantitative RT-PCR analysis showed that both ERalpha and ERbeta are present in RL 95-2 cells, and Western blot assay further revealed that ERalpha expression was decreased by all trans-RA treatment. In contrast, RAs induced 17HSD type 2 mRNA expression in a dose- and time-dependent fashion. This stimulatory effect was also detected at the level of in vivo oxidative 17HSD activity in cultured cells. On the other hand, the abundance of 17HSD type 2 mRNA was not altered by RAs in cultured normal epithelial cells isolated from human early- and late-secretory endometrium. The data indicate that RAs have an inhibitory effect on the growth of RL 95-2 cells and a cross-talk with the estrogen pathway in estrogen-responsive endometrial cancer cells.

Natural modulators of estrogen biosynthesis and function as chemopreventive agents

There is clearly a need for novel breast cancer chemopreventive agents with enhanced potency and specificity with little or no side effects. To this end, several new chemical moieties have been synthesized or isolated from natural sources. In this review, we have described some agents currently in use or under development for treatment or prevention of breast cancer, as well as our own strategies for the discovery of natural product modulators of estrogen biosynthesis and function. In particular, bioassay-guided fractionation of active plant extracts is a unique method for identifying agents with novel mechanisms of action, some of which should be useful for prevention of human cancer. Further, with the advent of combinatorial chemistry and high throughput screening, even greater progress may now be expected with natural product leads.

Direct effects of GnRH agonists in human hormone-sensitive endometrial cells

The antiproliferative effect of two GnRH agonists (leuprorelin acetate and triptorelin), alone or combined with tamoxifen (TAM) or medroxyprogesterone acetate (MPA), on human estrogen-sensitive endometrial cancer cells (Ishikawa) was investigated. Although ineffective when tested alone in all the culture conditions used, both analogues counteracted or even suppressed the estrogen-stimulated growth of Ishikawa cells. The antiestrogenic effect of TAM or MPA was not modified by their association with high doses of the GnRH analogues, but low concentrations of triptorelin combined with MPA 10(-7) M determined a reduction in cell numbers which was greater than that obtained with the progestin or the analogue alone. In addition, analogue treatment prevented the estrogen-induced decrease in the level of estrogen receptors. Our data provide evidence that GnRH agonists can directly inhibit estrogen-stimulated endometrial cancer cell growth and suggest that they may interfere with steroid-receptor machinery.

Characterization of androgen receptors in a well-differentiated endometrial adenocarcinoma cell line (Ishikawa)

Androgen receptors (AR) have been identified in the human endometrium, but their role in endometrial function and development towards endometrial receptivity remains poorly understood. In an effort to study the regulation and possible function in endometrial epithelium, we utilized the well-differentiated endometrial adenocarcinoma cell line, Ishikawa, as a model system. This cell line has proven to be stable, hormonally responsive, contains both estrogen and progesterone receptors, and has been shown to express endometrial proteins in a hormone responsive manner. In the present study, we demonstrate that Ishikawa cells also express AR, based on immunohistochemical staining, radioactive binding studies, RT-PCR and Northern blot analysis. The expression of AR is induced in Ishikawa cells by estrogens, similar to that reported for normal endometrium. Further, using an estrogen-responsive gene that has been characterized in this cell line, alkaline phosphatase, we show that androgens act as antiestrogens in diethylstilbestrol (DES) treated cells, inhibiting enzymatic activity in a dose-dependent manner. These data support a physiologic role for AR in the endometrium. Elevations in endometrial AR in certain clinical situations such as polycystic ovarian syndrome (PCOS) may amplify the effects of androgens on the endometrium leading to suspected defects in uterine receptivity, higher than expected infertility and high miscarriage rates observed in patients with this disorder.

Regulation of vascular endothelial growth factor (VEGF) gene transcription by estrogen receptors alpha and beta

Vascular endothelial growth factor (VEGF) mediates angiogenic activity in a variety of estrogen target tissues. To determine whether estrogen has a direct transcriptional effect on VEGF gene expression, we developed a model system by transiently transfecting human VEGF promoter-luciferase reporter constructs into primary human endometrial cells and into Ishikawa cells, derived from a well-differentiated human endometrial adenocarcinoma. In primary endometrial epithelial cells, treatment with 17beta-estradiol (E(2)) resulted in a 3.8-fold increase in luciferase activity, whereas a 3. 2-fold induction was demonstrated for stromal cells. Our Ishikawa cells had less than 100 functional estrogen receptors (ER)/cell and were therefore cotransfected with expression vectors encoding either the alpha- or the beta-form of the human ER. In cells cotransfected with ERalpha, E(2) induced 3.2-fold induction in VEGF-promoter luciferase activity. A 2.3-fold increase was observed in cells cotransfected with ERbeta. Through specific deletions, the E(2) response was restricted to a single 385-bp PvuII-SstI fragment in the 5' flanking DNA. Cotransfection of this upstream region with a DNA binding domain ER mutant, or site-directed mutagenesis of a variant ERE within this fragment, resulted in the loss of the E(2) response. Electromobility shift assays demonstrated that this same ERE sequence specifically binds estradiol-ER complexes. These studies demonstrate that E(2)-regulated VEGF gene transcription requires a variant ERE located 1.5 kb upstream from the transcriptional start site. Site-directed mutagenesis of this ERE abrogated E(2)-induced VEGF gene expression.

Alteration of maternal Hoxa10 expression by in vivo gene transfection affects implantation

Mice with a targeted mutation of the Hoxa10 gene demonstrate uterine factor infertility. It is unclear if the defect in the uterine environment arises due to the absence of Hoxa10 expression during embryonic development or in the adult. We have recently demonstrated that HOXA10 expression in human endometrium rises dramatically at the time of implantation, suggesting maternal expression of Hoxa10/HOXA10 may be essential to the process. To assess the importance of maternal Hoxa 10 expression, the uteri of day 2 pregnant mice were injected with a DNA/liposome complex containing constructs designed to alter maternal Hoxa10 expression before implantation. Transfection with a Hoxa10 antisense oligodeoxyribonucleotide significantly decreased the number of implantation sites. Transfection with a plasmid which constitutively expresses Hoxa10 optimized survival of implanted embryos resulting in increased litter size. These results demonstrate that maternal Hoxa10 expression is essential for implantation and is the first report of the maternal alteration of a gene known to affect implantation specifically. We also demonstrate that DNA/liposome complexes containing the same Hoxa10 constructs that alter fertility in mice, can affect Hoxa10 expression in a human endometrial cell line. Alteration of human endometrial HOXA10 via liposome-mediated gene transfection is a potential contraceptive agent or fertility treatment.

Estrogen and aryl hydrocarbon receptor expression and crosstalk in human Ishikawa endometrial cancer cells

Ishikawa endometrial cancer cells express the estrogen receptor (ER), and this study investigates aryl hydrocarbon receptor (AhR) expression and inhibitory AhR-ER crosstalk in this cell line. Treatment of Ishikawa cells with the AhR agonist [3H]2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) gave a radiolabeled nuclear complex that sedimented at 6.0 S in sucrose density gradients, and Western blot analysis confirmed that Ishikawa cells expressed human AhR and AhR nuclear translocator (Arnt) proteins. Treatment of Ishikawa cells with 10 nM TCDD induced a 9.7-fold increase in CYP1A1-dependent ethoxyresorufin O-deethylase (EROD) activity and a 10.5-fold increase in chloramphenicol acetyltransferase (CAT) activity in cells transfected with pRNH11c containing an Ah-responsive human CYP1A1 gene promoter insert (-1142 to +2434). Inhibitory AhR-ER crosstalk was investigated in Ishikawa cells using E2-induced cell proliferation and transcriptional activation assays in cells transfected with E2-responsive constructs containing promoter inserts from the progesterone receptor and vitellogenin A2 genes. AhR agonists including TCDD, benzo[a]pyrene (BaP) and 6-methyl-1,3,8-trichlorodibenzofuran, inhibited 32-47% of the E2-induced responses. In contrast, neither estrogen nor progesterone inhibited EROD activity induced by TCDD in Ishikawa cells, whereas inhibitory ER-AhR crosstalk was observed in ECC-1 endometrial cells suggesting that these interactions were cell context-dependent.

Functional oxytocin receptors in a human endometrial cell line

OBJECTIVE

Our goal was to demonstrate expression and functionality of oxytocin receptors in a human endometrial cell line. This cell line could then be used for further investigation of the role of oxytocin in reproductive function at the cellular level.

STUDY DESIGN

Oxytocin receptor messenger ribonucleic acid expression was determined by reverse transcriptase-polymerase chain reaction deoxyribonucleic acid amplification with ribonucleic acid from confluent Ishikawa cells. Ligand binding to whole cells was evaluated by nonlinear regression analysis with an iodinated oxytocin antagonist. The coupling of the oxytocin receptor to signaling pathways was evaluated by measuring oxytocin-stimulated increases in intracellular calcium concentration, phosphorylation of ERK2 (extracellular-regulated protein kinase 2) mitogen-activated protein kinase, and prostaglandin E(2) release.

RESULTS

Polyacrylamide gel electrophoresis of the reverse transcriptase-polymerase chain reaction products demonstrated the presence of oxytocin receptor messenger ribonucleic acid in Ishikawa cells. Ligand-binding analysis of these cells demonstrated a single class of noninteracting sites, with a B(max) (maximal number of binding sites) of 77.7 fmol/mg deoxyribonucleic acid and an apparent dissociation constant of 8.3 x 10(-11) mol/L. Stimulation with 100-nmol/L oxytocin caused a rapid transient increase in intracellular free calcium concentration, which was blocked by 1-micromol/L oxytocin antagonist. Treatment of cells with oxytocin for 10 minutes resulted in a marked increase in the phosphorylation of ERK2, as determined by Western blot analysis, and a 5-fold increase in prostaglandin E(2) release.

CONCLUSION

This study is the first to demonstrate functional oxytocin receptors in an established human endometrial cell line. This cell line will be useful in elucidating the mechanisms of action of oxytocin in the reproductive tract at the molecular level.

Role of estrogen and estrogen-related growth factor in the mechanism of hormone dependency of endometrial carcinoma cells

The role of estrogen and estrogen-related growth factors in the mechanism of hormone dependency of endometrial adenocarcinoma cells was investigated. The proliferation of hormone-responsive human endometrial adenocarcinoma cells (Ishikawa cells), which possess both estrogen and progesterone receptors, was optimally stimulated by 10 nM estradiol. Both transforming growth factor (TGF)-alpha and epidermal growth factor (EGF), added to the culture media, stimulated the proliferation of Ishikawa cells in a dose-dependent manner. Anti-TGF-alpha antibody completely eliminated the stimulatory effects of TGF-alpha. Anti-EGF receptor antibody inhibited the proliferation of these cells. The production of TGF-alpha into culture media was 5-40 pg/10 cells/24 h in 9 human endometrial adenocarcinoma cells. Ten nanomoles of estradiol increased the TGF-alpha production of Ishikawa cells by approximately 2.5-fold of the control level. In contrast, the production of TGF-alpha in hormone-unresponsive HEC-50 cels was not influenced by estradiol. C-erbB-2 oncoprotein expression of human endometrial adenocarcinoma cells, detected by both immunocytochemical staining and Western blot analysis, was associated with the tumor grade of the original tumor tissues. Ten nanomoles of estradiol clearly increased the c-erbB-2 oncoprotein levels at an optimal incubation period of 72 h, whereas estradiol did not affect the expression in HEC-50 cells.

Characterization of the functional progesterone receptor in an endometrial adenocarcinoma cell line (Ishikawa): progesterone-induced expression of the alpha1 integrin

Endometrial progesterone receptors (PR) are regulated by both estrogen (E2) and progesterone (P) and mediate the expression of specific endometrial proteins. Ishikawa cells are a well-differentiated human endometrial adenocarcinoma cell line, with both estrogen receptors (ER) and PR, regulated in a manner similar to that of normal endometrium. Immunohistochemical and biochemical analyses demonstrate that the concentration of PR is increased by E2 priming and decreased by subsequent treatment with P. Scatchard plot analysis showed a K(d) of 1 nM. On the basis of biochemical analysis, PR concentrations reached approximately 1400 fmol/mg cytosol protein in cells after treatment with E2 (10(-8) M) for 4 days. Immunoprecipitation and Western blot studies revealed the presence of both the 116 kDa and 81 kDa proteins with multiple isoforms of the high molecular weight (MW) protein. Northern blot analysis demonstrated transcriptional control of PR by steroid treatment. These studies demonstrate the coordinate regulation of all PR mRNA species. The functionality of Ishikawa PR was demonstrated by the expression of alpha1beta1 integrin in response to E2 plus P, at the level of transcription and translation. This effect was blocked by the addition of the anti-progestin, RU-486. These studies reconfirm that the Ishikawa cell line is an excellent model for the study of hormonally regulated events in the human endometrial epithelium.