Functions of estrogens and anti-estrogens in the rat endometrial adenocarcinoma cell lines RUCA-I and RUCA-II

Development of adverse outcome pathways relevant for the identification of substances having endocrine disruption properties Uterine adenocarcinoma as adverse outcome

Development of adverse outcome pathways (AOPs) for uterine adenocarcinoma can provide a practical tool to implement the EFSA-ECHA Guidance (2018) for the identification of endocrine disruptors in the context of Regulations (EU) No 528/2012 and (EC) No 1107/2009. AOPs can give indications about the strength of the relationship between an adverse outcome (intended as a human health outcome) and chemicals (pesticides but not only) affecting the pathways. In this scientific opinion, the PPR Panel explored the development of AOPs for uterine adenocarcinoma. An evidence-based approach methodology was applied, and literature reviews were produced using a structured framework assuring transparency, objectivity, and comprehensiveness. Several AOPs were developed; these converged to a common critical node, that is increased estradiol availability in the uterus followed by estrogen receptor activation in the endometrium; therefore, a putative AOP network was considered. An uncertainty analysis and a probabilistic quantification of the weight of evidence have been carried out via expert knowledge elicitation for each set of MIEs/KEs/KERs included in individual AOPs. The collected data on the AOP network were evaluated qualitatively, whereas a quantitative uncertainty analysis for weight of the AOP network certainty has not been performed. Recommendations are provided, including exploring further the uncertainties identified in the AOPs and putative AOP network; further methodological developments for quantifying the certainty of the KERs and of the overall AOPs and AOP network; and investigating of NAMs applications in the context of some of the MIEs/KEs currently part of the putative AOP network developed.

Role of miR-203 in estrogen receptor-mediated signaling in the rat uterus and endometrial carcinoma

The role of microRNAs (miRNA) in estrogen receptor (ER) signaling in the uterus and in endometrial cancer is not well understood. We therefore analyzed miRNA expression in uterine samples from a standard 3-day uterotrophic assay using young female adult rats to identify E2-regulated miRNAs. Microarray analysis identified 47 E2 down-regulated miRNAs including miR-30a, and 25 E2up-regulated miRNAs including miR-672, miR-203, and miR-146b. The strongly E2-upregulated miR-203 was selected for further analysis. miR-203 was deleted in the rat endometrial adenocarcinoma cell line, RUCA-I, using CRISPR/CAS9. Five clones devoid of miR-203 expression were generated. Proliferation was reduced and G2-arrest was observed in all miR-203 deficient RUCA-I clones. Transfection with a miR-203-3p mimic partially rescues this effect. Comparison of mRNA expression in three miR-203 knockout clones to wild type RUCA-I cells reveals 566 miR-203-upregulated and 592 miR-203-downregulated genes. 43 of the genes that are upregulated by miR-203 knockout in vitro are downregulated in the uterus by E2. Of these Acer2, Zbtb20, Ptn, Rcbtb2, Mum1l1, Hmgn3, and Nfat5 possess one or more seed sequence matches in their 3'-UTR that are predicted to be targets of miR-203. These data demonstrate the importance of E2 regulated miRNAs in general, and miR-203 in particular, for E2 regulated gene expression and physiological processes including proliferation and cell migration, in the uterus as well as in the etiology of endometrial carcinomas.

Estrogenic and antiestrogenic regulation of MMP-2 and MMP-13 mRNA in RUCA-I endometrial tumor cells in vitro and in vivo

We investigated the influence of estrogenic and antiestrogenic treatment on proteolytic activity--especially on MMP-2 and MMP-13--in the RUCA-I transplantable endometrial tumor model. Morphological studies demonstrate that RUCA-I cells are forming highly differentiated gland-like structures by remodelling and invading the underlying ECM. Estrogens upregulate the mRNA levels of MMP-2 and MMP-13 in the rat uterus. Treatment with the pure antiestrogen ICI 182,780 results in the downregulation of MMP-2 and MMP-13 mRNA. The same regulation for MMP-13 mRNA is found in vitro in RUCA-I cells. In contrast, in the transplantation tumor, the mRNA level of MMP-13 is repressed by estrogens and induced by ICI 182,780. MMP-2 mRNA is not regulated by hormones in the transplantation tumor and in RUCA-I cells. The divergent regulation suggests a varying influence of cell-cell-, cell-extracellular matrix interactions and soluble factors.

Phytoestrogens and carcinogenesis-differential effects of genistein in experimental models of normal and malignant rat endometrium

The phytoestrogen genistein was studied in normal and malignant experimental uterine models in vivo. The action of genistein on the uterus and vagina of ovariectomized DA/Han rats after 3 day oral administration (25, 50 or 100 mg/kg/BW/d) was compared to ethinyl oestradiol (0.1 mg/kg/BW/d). Effects on uterine and vaginal morphology, uterine growth and uterine gene expression were studied. A dose dependent increase of the uterine wet weight and the uterine and vaginal epithelial height, a dose dependent up-regulation of complement C3, down-regulation of clusterin mRNA expression and a stimulation of the vaginal cornification was observed after administration of genistein. Uterine gene expression and vaginal epithelium respond to genistein at doses where no significant effects on uterine wet weight were detectable. In general the vagina was more sensitive to genistein than the uterus. To analyse the action of genistein in malignant uterine tissue, the impact of a 28 d treatment with 50 mg/kg/d of genistein on the in-vivo tumour growth of RUCA I endometrial adenocarcinoma cells, following subcutaneous inoculation into syngeneic DA/Han rats, was assessed. In contrast to ethinyl oestradiol (0.1 mg/kg/BW/d), a dose of 50 mg/kg/BW/d of genistein did not affect tumour growth. Nevertheless C3 and TRPM2 mRNA expression in the tumour were both significantly stimulated by ethinyl oestradiol and genistein. In comparison to ovariectomized animals genistein up-regulated uterine wet weight and uterine dependent gene expression in tumour bearing animals. In conclusion, four independent uterine and vaginal parameters indicate genistein is a weak oestrogen receptor agonist in the uterus and vagina of female DA/Han rats, and evidence is provided for a selective oestrogen receptor modulator (SERM)-like action of genistein in normal and malignant uterine tissue.

Basement membrane induced differentiation of HEC-1B(L) endometrial adenocarcinoma cells affects both morphology and gene expression

In vitro studies of endometrial carcinogenesis have been hampered by dedifferentiation of the cells in culture. Using the endometrial carcinoma cell line HEC-1B(L), we aimed to establish and characterize culture conditions that preserve a more differentiated state of the tumor cells. HEC-1B(L) cells grown in a serum-free defined medium on plastic (PL/SFDM) on top of a reconstituted basement membrane (Matrigel, MG/SFDM) or in a thick layer of Matrigel showed pronounced morphological differentiation as compared with HEC-1B(L) cells cultured on plastic in a medium containing serum (PL/10% FCS). Features of differentiation included cuboidal to columnar cell shape and an increase of rough endoplastic reticulum in Matrigel cultures. Gene expression of HEC-1B(L) cells was studied by metabolic [35S]methionine labeling and SDS-gel electrophoresis. HEC-1B(L) cells cultured in the presence of Matrigel showed two additional secretory proteins approximately 31 kD and 77 kD in size. rt-PCR was used to screen cell cultures for the presence of estrogen receptor, progesterone receptor, and lactoferrin-mRNA, genes typically expressed by normal endometrial epithelium. We found no expression of the estrogen receptor or progesterone receptor. Lactoferrin-mRNA was present under all culture conditions tested. Our results suggest a regulatory role of the extracellular matrix for the differentiation of the HEC-1B(L) cell line.

Modulation of the intracellular calcium level in mammalian cells caused by 17beta-estradiol, different phytoestrogens and the anti-estrogen ICI 182780

In previous investigations it was shown that the synthetic estrogen diethylstilbestrol (DES) induces a rise of the intracellular calcium level ([Ca2+]i) in C6 rat glioma cells [P. Tas, H. Stopper, K. Koschel, D. Schiffmann, Influence of the carcinogenic oestrogen diethylstilboestrol on the intracellular calcium level in C6 rat glioma cells. Toxic. In vitro 5 (1991) 463-465] which is accompanied by changes of the arrangement of the cytoskeleton. In the present study, we compared the induction of these effects in COS (monkey kidney cells) lacking estrogen receptors (ER) with those in RUCA-I (rat endometrial carcinoma) cells containing ER. The [Ca2+]i in RUCA-I and COS cells following 17beta-estradiol (ES), genistein (GEN), daidzein (DZ) and coumestrol (CES) treatment was analyzed. A significant increase of [Ca2+]i induced by all compounds was observed in RUCA-I cells. No effects were detected in COS cells after ES and GEN treatment. The anti-estrogen ICI 182780 completely blocked the ES-and GEN-induced rise of [Ca2+]i. Dose and time dependencies of changes of calcium levels were analyzed and a biphasic response could be observed. The actin staining showed disintegrated stress fibers in RUCA-I cells. The degree of the observed effects correlates with the known estrogenicity of the applied compounds (DES > ES > GEN). It remains to be elucidated whether or not the effects observed are mediated by the "classic" genomic estrogen receptor pathway or by alternate nongenomic or receptor-independent pathways.

Estrogenic regulation of clusterin mRNA in normal and malignant endometrial tissue

Clusterin is a heterodimeric, 80kDa, glycoprotein that is synthesized in a wide variety of tissues in response to a number of diverse stimuli, including hormone ablation. We have investigated the regulation of clusterin expression by estradiol and anti-estrogens in RUCA-I rat endometrial adenocarcinoma cells in vitro and in vivo. We have also compared clusterin expression in endometrial tumors and in normal uterine tissue. Estradiol treatment significantly increases the steady state mRNA levels of clusterin in RUCA-I cells cultured on a reconstituted basement membrane, with a maximal induction 24 hr after estradiol treatment. The inductive effects of estrogen on clusterin mRNA steady state levels in vitro are significantly more pronounced than the effects on fibronectin mRNA levels, an estrogen-repressed gene in RUCA-I. In vivo, induction of clusterin expression in primary and metastatic endometrial adenocarcinoma is also dependent on the presence of estradiol, in marked contrast to expression of clusterin in the normal endometrium of the same animals. These data suggest that clusterin mRNA expression in rat endometrial adenocarcinoma cells is tightly regulated by estrogens and anti-estrogens in vitro and in vivo, and that there is a complex mechanism of regulation of clusterin expression in the normal and cancerous endometrium.

Estrogen-dependent and cell-specific regulation of gene expression in RUCA-I endometrial adenocarcinoma cells

Estrogens are believed to play a crucial role in growth regulation and differentiation of the normal endometrial tissue as well as in the carcinogenesis of the endometrium. Therefore, the influence of estrogens and antiestrogens on gene expression in the estrogen receptor-positive rat endometrial adenocarcinoma cell line RUCA-I was investigated. Differentially expressed genes were detected by differential display PCR of RNA of untreated, estradiol-treated and antiestrogen-treated RUCA-I cells. By means of the PCR technique, 14 differentially expressed fragments could be detected. Three of these 14 differentially expressed fragments were confirmed by Northern blotting. The steady state mRNA levels of the three gene fragments named AH41, AH42 and AH44 were downregulated by the antiestrogen ICI 164384. Further characterization revealed that the fragment AH41 is not expressed in stromal cells but in the human and rodent epithelial cell lines, BG-1 and RUCA-II. A comparison of the cDNA sequence of fragment AH41 with the EMBL database showed no high homology to known genes. Therefore, fragment AH41 has to be regarded as a fragment of a novel, estradiol-sensitive gene.

The rat endometrial adenocarcinoma cell line RUCA-I: a novel hormone-responsive in vivo/in vitro tumor model

The recently established, estrogen receptor positive rat endometrial adenocarcinoma cell line RUCA-I was tested for estrogen responsiveness in vivo and in vitro. In vivo, 10(6) RUCA-I cells were injected subcutaneously into intact, ovariectomized, or ovariectomized, estradiol-substituted syngenic DA/Han rats. All animals developed well differentiated endometrial adenocarcinoma, that had metastasized to peripheral lymph nodes and into the lung. Ovariectomy reduced tumor and lymph node weight, as well as number of lung metastases significantly compared to controls. In another series of experiments, treatment with the pure anti-estrogen ZK 119010 basically gave the same results as seen in ovariectomized animals, whereas tamoxifen treatment had no effect on metastasis of RUCA-I cells. These findings clearly demonstrate the estrogen dependency of growth and metastasis of RUCA-I cells in vivo. In vitro, we assessed the estrogenic and anti-estrogenic potency of various anti-estrogens, thereby investigating their effects on the expression of components of the complement C3 complex as an estradiol-induced protein and on the expression of fibronectin as an estrogen-repressed protein. Evaluating the relative anti-estrogenic potency of these anti-estrogens we found that ICI 164384 and ICI 182780 behaved as complete antagonists in vitro. Tamoxifen, like estradiol, stimulated complement C3 production and repressed fibronectin expression and has to be regarded as an agonist in this particular in vitro system. ZK 119010 if given alone had no significant influence on the biosynthesis of complement C3 and of fibronectin if compared to the unstimulated control. In addition, another estrogen dependent parameter was identified. Estrogen and anti-estrogen treatment affected glycosylation of complement C3 components. After estradiol treatment predominantly the higher glycosylated epitope of complement C3 became detectable, which could be transformed into the low molecular weight epitope by treatment with hyaluronidase. Finally, we compared the anti-proliferative effects of ICI 164384 and of tamoxifen in vitro. Both anti-estrogens slightly inhibited the growth of RUCA-I rat endometrial adenocarcinoma cells. In conclusion, RUCA-I cells represent a powerful, endometrial derived experimental model to test the agonistic and antagonistic properties of anti-estrogens on growth and metastasis in vivo and on gene expression in vitro. The effects of the tested anti-estrogens on gene expression of RUCA-I cells were found to be useful in predicting their effectiveness on tumor growth in vivo.

Fibronectin is an estrogen-repressed protein in RUCA-I rat endometrial adenocarcinoma cells

We recently established and characterized two rat endometrial adenocarcinoma cell lines which we called RUCA-I and RUCA-II. Despite high estrogen receptor levels neither cell line responded to estradiol in conventional cell culture conditions on plastic and in the presence of charcoal stripped fetal calf serum. We further demonstrated that culturing of these cells on a reconstituted basement membrane induced the estrogen responsiveness for both proliferation and gene expression. Particularly, the expression of components of the complement C3 system, which represent major estradiol inducible proteins in the rat uterus in vivo, were found to be under the control of estrogens and antiestrogens. In this paper the search for estrogen repressed proteins is reported. For this purpose secretory proteins of RUCA-I cells were metabolically labelled with 35S-methionine and tested for the presence of estrogen-repressed, antiestrogen-inducible protein species. Analyzing cell culture supernatants of RUCA-I cells by polyacrylamide gel electrophoresis under reducing conditions a protein with an apparent size of approx. 250-270 kDa became conspicuous. The formation and secretion of this protein was suppressed by estradiol and induced by the antiestrogen ICI 164384. Gel electrophoresis performed under non-reducing conditions and hyaluronidase digestion showed that this estrogen-repressed protein represents a dimeric glycoprotein. By immunoprecipitation this glycoprotein was identified as fibronectin. Investigations of steady state mRNA levels of fibronectin by rtPCR suggested a post-transcriptional regulation of this molecule by estradiol. This is the first report on repression of components of the extracellular matrix by estradiol and induction by the complete antiestrogen ICI 164384. The consequences of this finding in regard to growth and invasion of endometrial tumors are discussed.

Extracellular matrix induces hormone responsiveness and differentiation in RUCA-I rat endometrial adenocarcinoma cells

We recently described the establishment and the characterization of two rat endometrial adenocarcinoma cell lines which we called RUCA-I and RUCA-II. Despite fairly high estrogen receptor levels neither cell line responded to estradiol in conventional cell culture conditions on plastic and in the presence of serum. A limited hormonal response to the antiestrogen tamoxifen was detectable in RUCA-I but not in RUCA-II cells. To advance our cell culture conditions we plated RUCA-I cells on a layer of reconstituted basement membrane (Harbor Matrix) in the presence of a serum-free defined medium. These cell culture conditions induced hormone responsiveness of RUCA-I cells and permitted a stimulation of proliferation by estradiol. Further, two estradiol-induced secretory proteins with an apparent molecular weight of 115 kD and 60 kD could be identified by SDS-gelelectrophoresis if analyzed under reducing conditions. These proteins migrated as a single band in a non-reducing electrophoresis gel and were identified as components of the complement C3 system. Additionally, our results suggest that the effects of extracellular matrix and hormones on the expression of these proteins are additive. We conclude that processes of functional differentiation are most likely to occur in this in vitro model, particularly since the expression of components of the complement C3 system was under estrogenic control. Complement C3 proteins represent major estradiol-inducible secretory protein of the immature rat uterus in vivo. Culturing RUCA-I cells on top of a layer of reconstituted basement membrane provides a novel tool to study the importance of the extracellular environment on the hormone-induced gene expression in endometrial carcinogenesis in vitro.

Stromal expression of tenascin is inversely correlated to epithelial differentiation of hormone dependent tissues

We were previously investigating the expression of the extracellular matrix glycoprotein tenascin in normal and malignant endometrial tissues of humans and rodents. These studies suggested that the expression of tenascin was induced by proliferating epithelia (normal and particularly malignant) and was downregulated with their differentiation. The aim of this study was to investigate the hormone dependency of tenascin expression in (a) the transplantable EnDA endometrial tumor model with or without estrogen deprivation (ovariectomy) of the animals, (b) DMBA-induced rat mammary tumors with or without a hormonal treatment of the animals [ovariectomy, antiestrogen (tamoxifen) or antiprogestin (ZK 98299) treatment] and (c) in the rat prostate of untreated or androgen deprived animals (orchiectomy, flutamide-, casodex- or cyproterone acetate (CPA)-treatment). 1. Estrogen withdrawal by ovariectomy did not affect tenascin expression in transplantable EnDA endometrial adenocarcinoma, meaning the entire extracellular space of the stromal mesenchyme was decorated by tenascin immunoreactivity. 2. In untreated DMBA-induced rat mammary tumors almost the entire extracellular space of the stroma was stained by tenascin immunoreactivity. Ovariectomy and antiestrogen treatment did not affect tenascin expression. In contrast, antiprogestin treatment induced terminal differentiation of mammary tumor cells and in parallel downregulated tenascin expression. 3. In the normal rat prostate no tenascin was detectable by immunocytochemistry. However, following androgen deprivation we found tenascin expression in the stroma of the prostate. The most prominent expression was observable after CPA-treatment, possibly due to its progestagenic potency. In conclusion, the hormones and antihormones tested show no direct effect on the stromal expression of tenascin. However, proliferative activity and a low degree of differentiation of the epithelium induces tenascin expression, whereas epithelial differentiation apparently shuts down tenascin expression. Preliminary in vitro studies suggest that paracrine acting growth factors trigger the hormonal regulation of tenascin expression.