Endometrial tumorigenesis in Pten(+/-) mice is independent of coexistence of estrogen and estrogen receptor α

Roles of estrogen receptor α in endometrial carcinoma (Review)

Endometrial carcinoma (EC) is a group of endometrial epithelial malignancies, most of which are adenocarcinomas and occur in perimenopausal and postmenopausal women. It is one of the most common carcinomas of the female reproductive system. It has been shown that the occurrence and development of EC is closely associated with the interaction between estrogen (estradiol, E2) and estrogen receptors (ERs), particularly ERα. As a key nuclear transcription factor, ERα is a carcinogenic factor in EC. Its interactions with upstream and downstream effectors and co-regulators have important implications for the proliferation, metastasis, invasion and inhibition of apoptosis of EC. In the present review, the structure of ERα and the regulation of ERα in multiple dimensions are described. In addition, the classical E2/ERα signaling pathway and the crosstalk between ERα and other EC regulators are elucidated, as well as the therapeutic targeting of ERα, which may provide a new direction for clinical applications of ERα in the future.

Endometrial hyperplasia and progesterone resistance: a complex relationship

The endometrium is one of the most dynamic tissues that constantly undergoes changes during the menstrual cycle in women of the reproductive period. All these processes take place mainly under the influence of steroid hormones that are produced in the woman’s body. However, it is important to remember that throughout life the endometrial tissue undergoes changes under the influence of various factors that lead to imbalances in hormonal regulation. All these changes can lead to the development of endometrial hyperplasia, which has a high risk of both recurrence and malignization. Over the past few decades, the incidence of endometrial cancer has increased in many countries. This trend is thought to be related to the increasing prevalence of obesity, as well as to changing female reproductive patterns. Although there are currently no well-established screening programmers for endometrial cancer, endometrial hyperplasia is a recognized precursor, and its detection provides an opportunity for prevention. Studying the pathogenesis and risk factors will give a great advantage in the future to prevent possible complications. At this point, the activity and inhibition of the different hormone isoforms can lead to different hyperplastic processes. The management of patients depends on many factors: age, species, reproductive potential and other factors. Therefore, a comprehensive approach to treatment is always necessary. In recent years, interest in the study of endometrial hyperplasia has increased dramatically due to the increase in endometrial cancer. Therefore, the issue of early diagnosis and prevention is most urgent in modern gynecology and requires further study. This review reflects the current understanding of the disruption of progesterone signaling mechanisms in endometrial hyperplasia according to domestic and foreign literature.

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.

ENDOMETRIAL CARCINOMA: THE INTERPLAY OF GENETICS AND HORMONES

Endometrial carcinoma is the most common malignancy of the genital tract in females in the United States, and it is one of the few human cancers increasing in incidence and mortality. Numerous studies have found an association of endometrial carcinoma with obesity, diabetes, and unopposed estrogen stimulation. Molecular studies, in our lab and others, have shown that endometrial carcinoma has a high frequency of alterations in the Phosphoinositide 3-kinase (PIK3) pathway, and notably, coexisting abnormalities in more than one member of the pathway are common. We have combined studies on primary human tumors and genetic mouse models to explore the role of the PIK3 pathway and estrogen, and their interactions, in the development and progression of endometrial carcinoma. Abnormalities in the PIK3 pathway do not simply play redundant roles in endometrial carcinoma and, although not required, the presence of estrogen can alter the course of the disease.

Progesterone Actions and Resistance in Gynecological Disorders

Estrogen and progesterone and their signaling mechanisms are tightly regulated to maintain a normal menstrual cycle and to support a successful pregnancy. The imbalance of estrogen and progesterone disrupts their complex regulatory mechanisms, leading to estrogen dominance and progesterone resistance. Gynecological diseases are heavily associated with dysregulated steroid hormones and can induce chronic pelvic pain, dysmenorrhea, dyspareunia, heavy bleeding, and infertility, which substantially impact the quality of women's lives. Because the menstrual cycle repeatably occurs during reproductive ages with dynamic changes and remodeling of reproductive-related tissues, these alterations can accumulate and induce chronic and recurrent conditions. This review focuses on faulty progesterone signaling mechanisms and cellular responses to progesterone in endometriosis, adenomyosis, leiomyoma (uterine fibroids), polycystic ovary syndrome (PCOS), and endometrial hyperplasia. We also summarize the association with gene mutations and steroid hormone regulation in disease progression as well as current hormonal therapies and the clinical consequences of progesterone resistance.

Two-Way Development of the Genetic Model for Endometrial Tumorigenesis in Mice: Current and Future Perspectives

Endometrial cancer (EC) is the most common malignancy of the female reproductive tract worldwide. Although comprehensive genomic analyses of EC have already uncovered many recurrent genetic alterations and deregulated signaling pathways, its disease model has been limited in quantity and quality. Here, we review the current status of genetic models for EC in mice, which have been developed in two distinct ways at the level of organisms and cells. Accordingly, we first describe the in vivo model using genetic engineering. This approach has been applied to only a subset of genes, with a primary focus on Pten inactivation, given that PTEN is the most frequently altered gene in human EC. In these models, the tissue specificity in genetic engineering determined by the Cre transgenic line has been insufficient. Consequently, the molecular mechanisms underlying EC development remain poorly understood, and preclinical models are still limited in number. Recently, refined Cre transgenic mice have been created to address this issue. With highly specific gene recombination in the endometrial cell lineage, acceptable in vivo modeling of EC development is warranted using these Cre lines. Second, we illustrate an emerging cell-based model. This hybrid approach comprises ex vivo genetic engineering of organoids and in vivo tumor development in immunocompromised mice. Although only a few successful cases have been reported as proof of concept, this approach allows quick and comprehensive analysis, ensuring a high potential for reconstituting carcinogenesis. Hence, ex vivo/in vivo hybrid modeling of EC development and its comparison with corresponding in vivo models may dramatically accelerate EC research. Finally, we provide perspectives on future directions of EC modeling.

[Abnormal gut microbiota-induced hypoestrogenemia as a possible risk factor for malignancy in endometrioid heterotopia]

This paper reveals the pathogenetic impact of the abnormal gut microbiota on the development of female reproductive system diseases. A dynamic imbalance between the altered microbiota and the macroorganism has many manifestations as hormonal homeostatic disorders, one of which is dysbiosis-induced hypoestrogenemia. Using endometrioid heterotopia as an example, the authors trace the possibility of its progression and malignancy due to the occurrence of primary breakdown of the PTEN tumor-suppressor gene with subsequent genetic abnormalities in the ARID1A and TP53 genes. PTEN mutation in both endometriosis itself and its malignancy indicates that dysbiosis-induced hypoestrogenemia may be implicated in the pathogenesis of endometriosis. Thus, the relationship between female reproductive system diseases and gut microbiome disorders may be more significant; and the possibility of correcting the gut microbiota with prebiotics and probiotics opens new horizons not only in the prevention, but also in the treatment of many gynecological diseases associated with hormone disorders.

Two-sided role of estrogen on endometrial carcinogenesis: stimulator or suppressor?

Endometrial carcinoma (EC) often expresses estrogen receptors (ER), and the growth of EC is stimulated by estrogen. Therefore, EC is considered to be an estrogen-dependent tumor. However, the role of estrogen in endometrial carcinogenesis is somewhat unclear because the majority of EC occurs at peri- or post menopause when serum estrogen levels are generally decreased. In this article, we describe the double-edged role of estrogen in the genesis of EC, especially in terms of mismatch repair functions in vitro and in vivo, i.e. when serum estradiol (E2) levels are relatively low (approximately less than 90 pg/ml), and E2 enhance the carcinogenesis, whereas high E2 levels may suppress the carcinogenesis. This will deepen mechanistic insight into unopposed estrogen.

Preventive Effects by Black Raspberries of Endometrial Carcinoma Initiation and Promotion Induced by a High-Fat Diet

SCOPE

The chemopreventive effects of black raspberries (BRBs) have not been studied in endometrial tumorigenesis. Here, they are examined in a mouse model of endometrial cancer.

METHODS AND RESULTS

Wild-type and Pten heterozygous (+/-) female mice are weaned at 3 weeks and fed with four AIN-93G diets: 93G; 93G+5% BRBs powder; high-fat (HF); and HF+5% BRBs. Body weight and diet consumption are recorded weekly until the mice are euthanized at 28 weeks of age. Mice fed with HF diets are found to significantly gain body weight over time. BRBs are not found to affect the development of obesity. Mice in the HF+BRBs group consume less food than the HF-only mice. HF+BRBs diets suppress uterine tumor initiation and promotion more than the HF-only diet by inhibiting cell proliferation. It also reduces HF-induced levels of plasma leptin and 17β-estradiol (E2). Urolithin A, a metabolite of BRBs, suppresses cell proliferation induced by leptin and E2.

CONCLUSION

BRBs are preventive in HF-mediated uterine tumorigenesis because they suppress cell growth and plasma leptin and E2 levels.

Estrogen affects the negative feedback loop of PTENP1-miR200c to inhibit PTEN expression in the development of endometrioid endometrial carcinoma

Endometrial carcinoma is one of the most common malignancies in the female reproductive system. It is well-known that estrogen plays an important role in the pathogenesis of endometrioid endometrial carcinoma (EEC), and induces the cancer suppressor gene PTEN deletion. However, how estrogen affects PTEN expression remains unknown. In the present study, we found in 40 EEC specimens, miR-200c level was higher in most cancer areas than that in the adjacent normal endometrium, while PTEN and PTENP1 were lower. Moreover, the expression of PTEN/PTENP1 and miR-200c also showed a converse relationship in EEC cell lines. In addition, we demonstrated that miR-200c bound directly to PTEN and PTENP1, and PTENP1 could reverse miR-200c inhibition function to PTEN using a dual-luciferase reporter and RNA binding protein immunoprecipitation (RIP) assays. Next, 17β-estradiol (E2) treatment could improve miR-200c and drop the PTEN level, which caused a consequential increase of the phospho-PI3K-AKT pathway genes. When we stably knocked down estrogen receptor α (ERα) expression in the EEC cell line, the effects of E2 on miR-200c and PTEN declined. In addition, it was demonstrated that E2 might modulate cell proliferation, migration and invasion relying on the expression of miR-200c. Taken together, it can be concluded that estrogen improves the miR-200c level by combining with ER, PTENP1 and PTEN could be inhibited by miR-200c, and then activate the PI3K-AKT pathway. This work provided a new mechanism of EEC development and a new potential therapeutic target.

Modeling Endometrial Cancer: Past, Present, and Future

Endometrial cancer is the most common type of cancer of the female reproductive tract. Although prognosis is generally good for patients with low-grade and early-stage diseases, the outcomes for high-grade and metastatic/recurrent cases remain poor, since traditional chemotherapy regimens based on platinum and taxanes have limited effects. No targeted agents have been approved so far, although several new drugs have been tested without striking results in clinical trials. Over the last decades, many efforts have been made towards the establishment and development of preclinical models, aiming at recapitulating the structural and molecular determinants of the disease. Here, we present an overview of the most commonly used in vitro and in vivo models and discuss their peculiar features, describing their main applications and the value in the advancement of both fundamental and translational endometrial cancer research.

Pir2/Rnf144b is a potential endometrial cancer biomarker that promotes cell proliferation

Endometrial cancer is one of the most common gynaecological cancers in developed countries. Its incidence has increased 20% over the last decade and the death rate has increased >100% over the past two decades. Current models for prediction of prognosis and treatment response are suboptimal, and as such biomarkers to support clinical decision-making and contribute to individualised treatment are needed. In this study, we show that the E3-ubiquitin ligase PIR2/RNF144B is a potential targetable biomarker in endometrial cancer. At transcript level, it is expressed both in normal endometrium and tumour samples, but at protein level, it is expressed in tumours only. By using endometrial cancer cell lines, we demonstrated that PIR2/RNF144B is stabilised via phosphorylation downstream of GSK3β and this is necessary for the proliferation of endometrial cancer cells, in the absence of oestrogenic growth stimuli. Here, inactivation of GSK3β activity is associated with loss of PIR2/RNF144B protein and consequent inhibition of cell proliferation. Our results, therefore, substantiate PIR2/RNF144B as a novel candidate for targeted therapy in endometrial cancer.

Epidemiology of Endometrial Carcinoma: Etiologic Importance of Hormonal and Metabolic Influences

Endometrial carcinoma is the most common gynecologic cancer in developed nations, and the annual incidence is projected to increase, secondary to the high prevalence of obesity, a strong endometrial carcinoma risk factor. Although endometrial carcinomas are etiologically, biologically, and clinically diverse, hormonal and metabolic mechanisms are particularly strongly implicated in the pathogenesis of endometrioid carcinoma, the numerically predominant subtype. The centrality of hormonal and metabolic disturbances in the pathogenesis of endometrial carcinoma, combined with its slow development from well-characterized precursors in most cases, offers a substantial opportunity to reduce endometrial carcinoma mortality through early detection, lifestyle modification, and chemoprevention. In this chapter, we review the epidemiology of endometrial carcinoma, emphasizing theories that link risk factors for these tumors to hormonal and metabolic mechanisms. Future translational research opportunities related to prevention are discussed.

Lean Body Weight and Metformin Are Insufficient to Prevent Endometrial Hyperplasia in Mice Harboring Inactivating Mutations in PTEN

OBJECTIVES

Obesity is a major risk factor for endometrial cancer. We evaluated whether obesity exacerbates progression of endometrial hyperplasia (EH) using the PRCre/+ PTENflox/+ mouse model and examined if the type 2 diabetes drug, metformin, could prevent EH.

METHODS

Twenty obese (PRCre/+ PTENflox/+) mice were maintained on a high-fat diet, while 20 lean mice ate a matching low-fat diet. Ten mice from each group received metformin (1,000 mg/day) in drinking water. Mice were euthanized at 26 weeks. Uterine tissue was scored for degree of EH. Immunohistochemical staining for Ki67 was used to evaluate cellular proliferation. Markers of PI3K/AKT/mTOR activity were evaluated by immunohistochemistry using activation-specific antibodies. Serum adiponectin was quantified by ELISA.

RESULTS

Obesity had no effect on the extent of EH in (PRCre/+ PTENflox/+) mice. While metformin significantly altered circulating adiponectin levels in obese and lean animals, it had no effect on EH. There were no differences in endometrial proliferation as measured by Ki67 staining. Neither obesity nor metformin altered PI3K/AKT/mTOR activity in these animals.

CONCLUSIONS

Weight and metformin did not affect the severity of EH resulting from PTEN inactivation. Alternative mouse models of early endometrial cancer are required for preclinical cancer prevention studies.

Urolithin A suppresses the proliferation of endometrial cancer cells by mediating estrogen receptor-α-dependent gene expression

SCOPE

Obese and overweight women are at high risk of developing endometrial cancer; indeed, many of endometrial cancer patients are obese. The increased number and size of adipocytes due to obesity elevate levels of circulating estrogens that stimulate cell proliferation in the endometrium. However, black raspberries are a promising approach to preventing endometrial cancer.

METHODS AND RESULTS

We examined 17 black raspberry constituents and metabolites (10 μM or 10 μg/mL, 48 h) for their ability to prevent endometrial cancer cells from proliferating. Urolithin A (UA) was most able to suppress proliferation in a time- and dose-dependent manner (p < 0.05). It arrested the G2/M phase of the cell cycle by upregulating cyclin-B1, cyclin-E2, p21, phospho-cdc2, and CDC25B. UA also acted as an estrogen agonist by modulating estrogen receptor-α (ERα) dependent gene expression in ER-positive endometrial cancer cells. UA enhanced the expression of ERβ, PGR, pS2, GREB1 while inhibiting the expression of ERα and GRIP1. Coincubating UA-treated cells with the estrogen antagonist ICI182,780 abolished UA's estrogenic effects. Knocking down ERα suppressed PGR, pS2, and GREB gene expression but increased GRIP1 expression. Thus, UA's actions appear to be mediated through ERα.

CONCLUSION

This study suggests that UA modulates ERα-dependent gene expression, thereby inhibiting endometrial cancer proliferation.

Tumor progression, metastasis, and modulators of epithelial-mesenchymal transition in endometrioid endometrial carcinoma: an update

Endometrioid endometrial carcinoma (EEC), also known as type 1 endometrial cancer (EC), accounts for over 70-80% of all cases that are usually associated with estrogen stimulation and often develops in a background of atypical endometrial hyperplasia. The increased incidence of EC is mainly confined to this type of cancer. Most EEC patients present at an early stage and generally have a favorable prognosis; however, up to 30% of EEC present as high risk tumors, which have invaded deep into the myometrium at diagnosis and progressively lead to local or extra pelvic metastasis. The poor survival of advanced EC is related to the lack of effective therapies, which can be attributed to poor understanding of the molecular mechanisms underlying the progression of disease toward invasion and metastasis. Multiple lines of evidence illustrate that epithelial-mesenchymal transition (EMT)-like events are central to tumor progression and malignant transformation, endowing the incipient cancer cell with invasive and metastatic properties. The aim of this review is to summarize the current knowledge on molecular events associated with EMT in progression, invasion, and metastasis of EEC. Further, the role of epigenetic modifications and microRNA regulation, tumor microenvironment, and microcystic elongated and fragmented glands like invasion pattern have been discussed. We believe this article may perhaps stimulate further research in this field that may aid in identifying high risk patients within this clinically challenging patient group and also lead to the recognition of novel targets for the prevention of metastasis - the most fatal consequence of endometrial carcinogenesis.

Activated mutant p110α causes endometrial carcinoma in the setting of biallelic Pten deletion

PTEN and PIK3CA mutations occur with high frequency in uterine endometrioid carcinoma (UEC). Although PTEN mutations are present in complex atypical hyperplasia and carcinoma, PIK3CA mutations are restricted to carcinoma. We generated mouse models harboring Pten loss and/or activated Pik3ca in the endometrial epithelium to investigate their respective roles in the pathogenesis of UEC. Presence of an activated mutant Pik3ca on the background of Pten loss led to aggressive disease, with 100% of mice exhibiting carcinoma. Expression of Pik3ca with E545K mutation alone was unable to cause hyperplasia or cancer in the uterus and did not activate Akt as effectively as Pten deletion in short-term cultures of mouse endometrial epithelium, likely explaining the lack of phenotype in vivo. We also report that nuclear localization of FOXO1 correlated with PTEN mutational status irrespective of the PIK3CA status in endometrial cancer cell lines. Furthermore, gene expression profiles resulting from Pten loss or activation of Pik3ca in primary mouse endometrial epithelial cells exhibit minimal overlap. Thus, Pten and Pik3ca have distinct consequences on the activation of the phosphatidylinositol 3-kinase pathway in endometrial epithelium and are likely to affect other nonoverlapping cellular mechanisms involved in the development and progression of the most common type of uterine cancer.

4-hydroxy estrogen induces DNA damage on codon 130/131 of PTEN in endometrial carcinoma cells

Catechol estrogens, such as 4-hydroxyestradiol (4-OHE2), are estrogen metabolites that form DNA adducts and may induce mutations and subsequent cell transformation in mammary cells; however, little is known about their roles in endometrial carcinogenesis. Furthermore, it remains unclear whether 4-OHE2 is able to induce DNA damage on specific genes involved in carcinogenesis or a 'pro'-mutation status such as microsatellite instability (MSI). Therefore, we modified terminal transferase-dependent PCR by the application of a capillary sequencer to detect DNA damage at the single base level. Using this method, we demonstrated that 4-OHE2 directly induced DNA damage on codon 130/131 in exon 5 of PTEN, which is a mutation hot spot for PTEN in endometrial carcinoma. Whereas, both estradiol and 4-OHE2 treatment did not affect MSI status in immortalized endometrial glandular cells. 4-OHE2 might contribute to endometrial carcinogenesis by inducing PTEN mutation on codon 130/131.

Steroid hormone intervenes in the endometrial tumorigenesis of pten ablation

Background:

Endometrial cancer, the most common gynecological cancer, is closely associated with endometrial hyperplasia, unopposed estrogen exposure, and genetic alterations. Phosphatase and tensin homologue (PTEN) is a tumor suppressor genes completely lost or mutated in >50% of primary endometrioid endometrial cancers. Estrogen-dependent endometrioid carcinoma is the most common type of endometrial cancer. Progesterone is a hormone that antagonizes the growth-promoting properties of estrogen in the uterus. Progestin is used as a conservative endocrine treatment of early endometrial cancer in order to preserve fertility as well as a palliative measure for advanced-stage patients. Progesterone therapy has been shown to be effective in preventing endometrial cancer as well as controlling growth of the endometrium. However, the effectiveness of progestin for women with endometrial cancer is less clear.

Methods:

In order to understand the effect of steroid hormone on endometrial cancer progression, we used a mouse endometrial cancer model with conditional loss of Pten in the mouse uterus (PR^cre/+Pten^f/f, Pten^d/d). To assess the effect of steroid hormones, ovariectomized Pten^f/f and Pten^d/d mice were treated with estrogen or progesterone over a period of three month.

Results:

Uterine weight gain was significantly decreased in ovariectomized PR^cre/+Pten^f/f mice compared to intact PR^cre/+Pten^f/f mice. Ovariectomized PR^cre/+Pten^f/f mice treated with P4 or vehicle also exhibited decreased uterine cancer size compared with intact PR^cre/+Pten^f/f mice. Proliferation of ovariectomized PR^cre/+Pten^f/f mice treated with P4 is highly decreased compared to other groups. The levels of stromal progesterone receptor were highly increased in ovariectomized PR^cre/+Pten^f/f mice treated with P4 which resulted in decreased epithelial proliferation.

Conclusions:

These results suggest that P4 treatment significantly reduces tumor mass but does not affect cancer progression in PR^cre/+Pten^f/f mice.

High frequency strand slippage mutations in CTCF in MSI-positive endometrial cancers

Tumors with defective mismatch repair acquire large numbers of strand slippage mutations including frameshifts in coding sequence repeats. We identified a mutational hotspot, p.T204fs, in the insulator-binding protein (CTCF) in MSI-positive endometrial cancers. Although CTCF was described as a significantly mutated gene by the endometrial cancer TCGA, the A₇ track variants leading to T204 frameshifts were not reported. Reanalysis of TCGA data using Pindel revealed frequent T204fs mutations, confirming CTCF is an MSI target gene and revealed the same frameshifts in tumors with intact mismatch repair. We show that T204fs transcripts are subject to nonsense-mediated decay and as such, T204fs mutations are unlikely to act as dominant negatives. The spectrum and pattern of mutations observed is consistent with CTCF acting as a haploinsufficient tumor suppressor.