Rapid estrogen signaling negatively regulates PTEN activity through phosphorylation in endometrial cancer cells

Uterine histopathology and steroid metabolism in a polycystic ovary syndrome rat model

The aim of this study was to investigate uterine lesions, uterine endocrine status and expression of genes involved in uterine differentiation in a rat model of polycystic ovary syndrome (PCOS). The possible involvement of the androgen receptor (AR) was also investigated. PCOS rats showed an increased incidence of uterine epithelial and glandular lesions and elevated serum testosterone level, which was not detected in uterine tissue. Uterine 17β-estradiol, estrone and progesterone were detected in 100%, 75% and 50% of the animals, respectively. This was associated with a decrease in Star and an increase in Hsd17b2, Srd5a1 and Cyp19a1, suggesting that uterine steroids are not synthesized de novo in PCOS and that alterations in these enzymes may explain the absence of testosterone and low progesterone. In addition, ESR2 decreased and AR increased, suggesting possible steroid receptor crosstalk. Genes associated with uterine differentiation, PTEN and WNT5a, also showed reduced expression. PCOS rats treated with flutamide, an AR antagonist, were similar to PCOS rats in terms of uterine lesions, serum steroid levels, ESR2, PTEN and WNT5a expression. However, testosterone, AR and aromatase levels were similar to control rats, with decreased expression of ESR1 and HOXA10, suggesting that these expressions are AR dependent. Our results suggest that the primary cause of the observed uterine lesions in the PCOS rat model is the altered endocrine status and consequently changes in genes related to uterine differentiation.

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.

Role of Tumor Suppressor PTEN and Its Regulation in Malignant Transformation of Endometrium

Tumor-suppressive effects of PTEN are well-known, but modern evidence suggest that they are not limited to its ability to inhibit pro-oncogenic PI3K/AKT signaling pathway. Features of PTEN structure facilitate its interaction with substrates of different nature and display its activity in various ways both in the cytoplasm and in cell nuclei, which makes it possible to take a broader look at its ability to suppress tumor growth. The possible mechanisms of the loss of PTEN effects are also diverse - PTEN can be regulated at many levels, leading to change in the protein activity or its amount in the cell, while their significance for the development of malignant tumors has yet to be studied. Here we summarize the current data on the PTEN structure, its functions and changes in its regulatory mechanisms during malignant transformation of the cells, focusing on one of the most sensitive to the loss of PTEN types of malignant tumors - endometrial cancer.

Estrogen Protects Cardiac Function and Energy Metabolism in Dilated Cardiomyopathy Induced by Loss of Cardiac IRS1 and IRS2

BACKGROUND

Type 2 diabetes (T2D) is a high-risk factor for incident of cardiovascular diseases. Women at young ages show a reduced incidence of both T2D and cardiovascular diseases compared with men, but these disparities disappear in postmenopausal women versus age-matched men. Thus, ovaries and ovarian hormones, such as estrogen, are expected to protect from T2D and cardiovascular diseases. In this study, we aimed to investigate the role of ovaries and ovarian hormone estrogen in cardiac function and energy metabolism using the cardiac IRS (insulin receptor substrate) 1 and IRS2 double genes knockout mice that mimic cardiac insulin resistance.

METHODS

Control and heart-specific IRS1/2 double genes knockout mice were treated with placebo or 17β-estradiol (E2) pellets, respectively, through subcutaneous implantation. Female mice were subjected to a bilateral ovariectomy surgery to remove endogenous E2. The cardiac function and energy metabolism were determined using echocardiography and indirect calorimeter, respectively.

RESULTS

All male heart-specific IRS1/2 double genes knockout mice died of heart failure at 6 to 8 weeks as we previously described (Qi et al), but all female heart-specific IRS1/2 double genes knockout mice survived >1 year. Removal of ovaries in heart-specific IRS1/2 double genes knockout female mice resulted in cardiac dysfunction, and ultimately animal death. However, E2 supplementation prevented the dilated cardiomyopathy, improved cardiac function and energy metabolism, and enhanced lifespan in both male and ovariectomy female mice deficient for cardiac IRS1 and IRS2 genes, largely owing to the activation of Akt (protein kinase B)-Foxo1 (O1 class of forkhead/winged helix transcription factor) signaling cascades.

CONCLUSIONS

These results show that estrogen protects mice from cardiac insulin resistance-induced diabetic cardiomyopathy. This may provide a fundamental mechanism for the gender difference for the incidence of both T2D and cardiovascular diseases. This study highlights that estrogen signaling could be a potential target for improving cardiac function and energy metabolism in humans with T2D.

Extracellular Vesicles Derived from Acidified Metastatic Melanoma Cells Stimulate Growth, Migration, and Stemness of Normal Keratinocytes

Metastatic melanoma is a highly malignant tumor. Melanoma cells release extracellular vesicles (EVs), which contribute to the growth, metastasis, and malignancy of neighboring cells by transfer of tumor-promoting miRNAs, mRNA, and proteins. Melanoma microenvironment acidification promotes tumor progression and determines EVs’ properties. We studied the influence of EVs derived from metastatic melanoma cells cultivated at acidic (6.5) and normal (7.4) pH on the morphology and homeostasis of normal keratinocytes. Acidification of metastatic melanoma environment made EVs more prooncogenic with increased expression of prooncogenic mi221 RNA, stemless factor CD133, and pro-migration factor SNAI1, as well as with downregulated antitumor mir7 RNA. Incubation with EVs stimulated growth and migration both of metastatic melanoma cells and keratinocytes and changed the morphology of keratinocytes to stem-like phenotype, which was confirmed by increased expression of the stemness factors KLF and CD133. Activation of the AKT/mTOR and ERK signaling pathways and increased expression of epidermal growth factor receptor EGFR and SNAI1 were detected in keratinocytes upon incubation with EVs. Moreover, EVs reduced the production of different cytokines (IL6, IL10, and IL12) and adhesion factors (sICAM-1, sICAM-3, sPecam-1, and sCD40L) usually secreted by keratinocytes to control melanoma progression. Bioinformatic analysis revealed the correlation between decreased expression of these secreted factors and worse survival prognosis for patients with metastatic melanoma. Altogether, our data mean that metastatic melanoma EVs are important players in the transformation of normal keratinocytes.

SLURP-1 Controls Growth and Migration of Lung Adenocarcinoma Cells, Forming a Complex With α7-nAChR and PDGFR/EGFR Heterodimer

Secreted Ly6/uPAR-related protein 1 (SLURP-1) is a secreted Ly6/uPAR protein that negatively modulates the nicotinic acetylcholine receptor of α7 type (α7-nAChR), participating in control of cancer cell growth. Previously we showed, that a recombinant analogue of human SLURP-1 (rSLURP-1) diminishes the lung adenocarcinoma A549 cell proliferation and abolishes the nicotine-induced growth stimulation. Here, using multiplex immunoassay, we demonstrated a decrease in PTEN and mammalian target of rapamycin (mTOR) kinase phosphorylation in A549 cells upon the rSLURP-1 treatment pointing on down-regulation of the PI3K/AKT/mTOR signaling pathway. Decreased phosphorylation of the platelet-derived growth factor receptor type β (PDGFRβ) and arrest of the A549 cell cycle in the S and G2/M phases without apoptosis induction was also observed. Using a scratch migration assay, inhibition of A549 cell migration under the rSLURP-1 treatment was found. Affinity extraction demonstrated that rSLURP-1 in A549 cells forms a complex not only with α7-nAChR, but also with PDGFRα and epidermal growth factor receptor (EGFR), which are known to be involved in regulation of cancer cell growth and migration and are able to form a heterodimer. Knock-down of the genes encoding α7-nAChR, PDGFRα, and EGFR confirmed the involvement of these receptors in the anti-migration effect of SLURP-1. Thus, SLURP-1 can target the α7-nAChR complexes with PDGFRα and EGFR in the membrane of epithelial cells. Using chimeric proteins with grafted SLURP-1 loops we demonstrated that loop I is the principal active site responsible for the SLURP-1 interaction with α7-nAChR and its antiproliferative effect. Synthetic peptide mimicking the loop I cyclized by a disulfide bond inhibited ACh-evoked current at α7-nAChR, as well as A549 cell proliferation and migration. This synthetic peptide represents a promising prototype of new antitumor drug with the properties close to that of the native SLURP-1 protein.

PTEN Expression in Human Granulosa Cells Is Associated with Ovarian Responses and Clinical Outcomes in IVF

The ovarian reserve determines the success of in vitro fertilization (IVF) and embryo transfer treatment. It predicts the ovarian response in controlled ovarian hyperstimulation cycles. Apoptosis in granulosa cells surrounding oocytes is important for ovarian function and has been closely associated with follicular atresia. PTEN (encoding phosphatase and tensin homolog) is a well-known tumor suppressor gene that functions as a mediator of apoptosis and is crucial for mammal reproduction. In the present study, we analyzed the expression level of PTEN in human granulosa cells and aimed to investigate its association with the ovarian response and clinical outcomes in IVF. Apoptosis in granulosa cells were analyzed using Annexin V-Allophycocyanin staining after PTEN short hairpin RNA lentivirus transfection. Real-time fluorescent quantitative PCR analysis showed that the PTEN transcript level was significantly higher in poor responders and significantly lower in high responders, compared with that in normal responders. However, PTEN expression in the pregnancy group decreased slightly, but not significantly, compared with that in the non-pregnancy group. The apoptosis rate of granulosa cells declined significantly after 24-h transfection of the PTEN-shRNA lentivirus. These results suggest a fundamental role of PTEN in the regulation of follicular development, and that it might be involved in the pathogenesis of follicular dysplasia and ovarian dysfunction.

Putative adverse outcome pathways for female reproductive disorders to improve testing and regulation of chemicals

Modern living challenges female reproductive health. We are witnessing a rise in reproductive disorders and drop in birth rates across the world. The reasons for these manifestations are multifaceted and most likely include continuous exposure to an ever-increasing number of chemicals. The cause–effect relationships between chemical exposure and female reproductive disorders, however, have proven problematic to determine. This has made it difficult to assess the risks chemical exposures pose to a woman’s reproductive development and function. To address this challenge, this review uses the adverse outcome pathway (AOP) concept to summarize current knowledge about how chemical exposure can affect female reproductive health. We have a special focus on effects on the ovaries, since they are essential for lifelong reproductive health in women, being the source of both oocytes and several reproductive hormones, including sex steroids. The AOP framework is widely accepted as a new tool for toxicological safety assessment that enables better use of mechanistic knowledge for regulatory purposes. AOPs equip assessors and regulators with a pragmatic network of linear cause–effect relationships, enabling the use of a wider range of test method data in chemical risk assessment and regulation. Based on current knowledge, we propose ten putative AOPs relevant for female reproductive disorders that can be further elaborated and potentially be included in the AOPwiki. This effort is an important step towards better safeguarding the reproductive health of all girls and women.

[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.

Metformin Promotes Anti-tumor Biomarkers in Human Endometrial Cancer Cells

Metformin (MET) is increasingly implicated in reducing the incidence of multiple cancer types in patients with diabetes. However, similar effects of MET in non-diabetic women with endometrial cancer (EC) remain unknown. In a pilot study, obese non-diabetic women diagnosed with type 1, grade 1/2 EC, and consenting to participate were randomly assigned to receive MET or no MET (control (CON)) during the pre-surgical window between diagnosis and hysterectomy. Endometrial tumors obtained at surgery (MET, n = 4; CON, n = 4) were analyzed for proliferation (Ki67), apoptosis (TUNEL), and nuclear expression of ERα, PGR, PTEN, and KLF9 proteins in tumor glandular epithelial (GE) and stromal (ST) cells. The percentages of immunopositive cells for PGR and for KLF9 in GE and for PTEN in ST were higher while those for ERα in GE but not ST were lower, in tumors of MET vs. CON patients. The numbers of Ki67- and TUNEL-positive cells in tumor GE and ST did not differ between groups. In human Ishikawa endometrial cancer cells, MET treatment (60 μM) decreased cell numbers and elicited distinct temporal changes in ESR1, KLF9, PGR, PGR-B, KLF4, DKK1, and other tumor biomarker mRNA levels. In the context of reduced KLF9 expression (by siRNA targeting), MET rapidly amplified PGR, PGR-B, and KLF4 transcript levels. Our findings suggest that MET acts directly in EC cells to modify steroid receptor expression and signaling network and may constitute a preventative strategy against EC in high-risk non-diabetic women.

Everolimus inhibits the proliferation and migration of epidermal growth factor receptor-resistant lung cancer cells A549 via regulating the microRNA-4328/phosphatase and tensin homolog signaling pathway

Lung cancer is the most common cancer type worldwide, and investigating novel therapeutics methods for the treatment of chemoresistant lung cancer are of notable clinical significance. Reverse transcription-quantitative polymerase chain reaction and western blotting assays were performed to analyze the expression levels of phosphatase and tensin homolog (PTEN) and microRNA-4328 (miR-4328), and Cell Counting Kit-8 (CCK-8) and Transwell migration assays were conducted to evaluate the proliferation and migration of A549 cells, respectively. Everolimus was observed to upregulate the expression of PTEN and inhibit the proliferation and migration of A549 cells in a dose-dependent manner. The knockdown of PTEN abolished the effects of everolimus on the proliferation and migration of A549 cells, and everolimus was demonstrated to upregulate PTEN, and inhibit the proliferation and migration of A549 cells via downregulating miR-4328. Collectively, the results of the present study indicate that everolimus inhibited the proliferation and migration of EGFR-resistant A549 lung cancer cells via regulating the miR-4328/PTEN signaling pathway.

The PTEN Tumor Suppressor Gene in Soft Tissue Sarcoma

Soft tissue sarcoma (STS) is a rare malignancy of mesenchymal origin classified into more than 50 different subtypes with distinct clinical and pathologic features. Despite the poor prognosis in the majority of patients, only modest improvements in treatment strategies have been achieved, largely due to the rarity and heterogeneity of these tumors. Therefore, the discovery of new prognostic and predictive biomarkers, together with new therapeutic targets, is of enormous interest. Phosphatase and tensin homolog (PTEN) is a well-known tumor suppressor that commonly loses its function via mutation, deletion, transcriptional silencing, or protein instability, and is frequently downregulated in distinct sarcoma subtypes. The loss of PTEN function has consequent alterations in important pathways implicated in cell proliferation, survival, migration, and genomic stability. PTEN can also interact with other tumor suppressors and oncogenic signaling pathways that have important implications for the pathogenesis in certain STSs. The aim of the present review is to summarize the biological significance of PTEN in STS and its potential role in the development of new therapeutic strategies.

Expression of p53 and PTEN in human primary endometrial carcinomas: Clinicopathological and immunohistochemical analysis and study of their concomitant expression

Endometrial carcinoma is a common malignancy of the female genital tract. Alterations in the expression levels of various oncogenes and tumor suppressor genes serve important roles in the carcinogenesis and biological behavior of endometrial carcinoma. The aim of the present study was to evaluate the combination and individual expression of p53 and phosphatase and tensin homolog (PTEN) protein in human endometrial carcinoma. In addition, the correlation of these proteins with clinicopathological parameters was also assessed. Retrospective immunohistochemical analysis of the expression of p53 and PTEN tumor suppressor proteins was conducted in 99 women with endometrial carcinoma. The overall rate of p53 and PTEN positivity was 89 and 77%, respectively, according to the sum of stain intensity and scores of immunopositive cells. The sum of p53 positivity correlated strongly with PTEN expression (ρ=0.256; P=0.044). The concomitant sum of p53 and PTEN expression was identified in 45% of patients with endometrial adenocarcinoma. Notably, the sum of the immunohistochemical expression of p53 was significantly correlated with patient age (P=0.037), histologic type (P=0.008), histologic grade (P=0.002) and fallopian and/or ovarian invasion (P=0.014). Furthermore, PTEN expression was associated with myometrial invasion (ρ=−0.377; P=0.002) and clinical stage (P=0.019). In addition, concomitant p53 and PTEN expression was correlated with patient age (P=0.008) and histologic differentiation (P=0.028). The findings indicated a correlation between the expression of p53 and PTEN in endometrial adenocarcinoma, which suggested an intrinsic association between expression levels of these tumor suppressor genes. The study also suggested that concomitant p53 and PTEN expression contributed in characterizing the tumor behavior of endometrial carcinoma. Taken together, the present study suggested the combined expression of p53 and PTEN in the development of high-grade endometrial carcinoma in older patients. In addition, the findings indicated activation of different molecular pathways in the tumor progression between low-grade and high-grade endometrial carcinomas.

Kaempferol, a natural dietary flavonoid, suppresses 17β-estradiol-induced survivin expression and causes apoptotic cell death in endometrial cancer

Endometrioid endometrial carcinoma, commonly known as type 1 endometrial cancer, accounts for >80% of endometrial carcinomas and is dependent on estrogen. We recently reported on the prognostic significance of the BIRC5 survivin gene in endometrial cancer. Estradiol induces survivin expression in estrogen receptor-positive, but not in estrogen receptor-negative, cancer cells. Kaempferol, a bioflavonoid, reportedly inhibits estrogen receptor-α (ERα) in hormone receptor-positive breast cancer cells. However, whether kaempferol-mediated inhibition of ERα suppresses survivin and induces cell death in endometrial cancer remains unclarified. The present study evaluated the antitumor effects of kaempferol on endometrial cancer cells. Cell viability assays, flow cytometry analysis, western blotting and annexin V analyses were used to analyze the antitumor effects of kaempferol. The results demonstrated that kaempferol successfully suppressed the viability of two ER-positive endometrial cancer cell lines, with IC₅₀ values of 83 and 65 µM. In addition, kaempferol induced sub-G1 cell accumulation and apoptotic cell death (P<0.01) in a dose-dependent manner. Treatment of cells with estradiol significantly induced co-expression of nuclear ERα and survivin proteins (P<0.001). Further evaluation revealed that kaempferol causes apoptotic cell death largely by suppressing ERα, survivin and Bcl-2 protein. Therefore, the results of the present study suggested that targeting ERα and survivin with kaempferol may be a novel therapeutic option against endometrial carcinoma.

Up-regulation of genes involved in the insulin signalling pathway (IGF1, PTEN and IGFBP1) in the endometrium may link polycystic ovarian syndrome and endometrial cancer

BACKGROUND

Endometrial cancer (EC) is the most common gynaecological cancer amongst women in the UK. Although previous studies have found that women with polycystic ovary syndrome (PCOS) have at least a three-fold increase in endometrial cancer (EC) risk compared to women without PCOS, the precise molecular mechanisms which link between PCOS and EC remain unclear. It has been suggested that insulin resistance may contribute to the increased risk of EC in PCOS. The specific expression of genes related to the insulin-signalling pathway including the IGF system in the endometrium of women with PCOS has however never been measured and compared to that in women with EC without PCOS and control women without EC or PCOS. .

OBJECTIVES

To test the hypothesis that insulin signalling plays a key role in the development of EC in women with PCOS by measuring and comparing the expression of three key genes involved in the insulin signalling pathway (IGF1, PTEN and IGFBP1) in endometrial tissue obtained from three groups of women; PCOS without EC, women with EC without PCOS and non-PCOS women without EC (controls). We also aimed to determine the correlation between the gene expressions to various clinical variables among participants.

METHODS

This was a cross-sectional study of 102 women in 3 groups (PCOS, EC and controls) at a University teaching hospital in the United Kingdom. Clinical assessment (blood pressure, body mass index (BMI) and waist-hip-circumference ratio), venepuntures (fasting blood sugar, insulin, lipid profile, hormones) and endometrial tissue biopsies were taken in all participants. Endometrial tissue RNA extraction was performed before real time polymerase-chain-reaction for the genes of interest (IGF1, IGFBP1 and PTEN) was carried out. To compare the baseline characteristics of the study population, One-Way-ANOVA test or the Independent t-test was used. For variables that were not normally distributed, the Spearman correlation test was used to calculate the r value. A "p" value of <0.05 was considered statistically significant.

RESULTS

IGF1, IGFBP1 and PTEN gene expression were significantly up-regulated in the endometrium of PCOS and EC women compared to controls. However there was no significant difference in the expression of these genes in PCOS compared to EC endometrium. The BMI of women with PCOS and controls, were not significantly different (29.28 (± 2.91) vs 28.58 (± 2.62) kg/m(2)) respectively, women with EC however had a higher mean BMI (32.22 (± 5.70) kg/m(2)). PCOS women were younger (31.8 (± 5.97) years) than women with EC (63.44 (± 10.07) years) and controls (43.68 (± 13.12) years). The changes in gene expression were independent of BMI, waist hip ratio, estradiol and androgen levels. Protein validation test in the serum samples in the three groups were consistent with the gene findings.

CONCLUSION

Women with PCOS and EC have an increased endometrial expression of genes (IGF1, IGFBP1 and PTEN) involved in the insulin signalling pathway compared with control women. This may explain the increased risk of EC in PCOS women. This study provides a strong basis for clinical trials aiming to prevent EC in women with PCOS by investigating drugs targeting the insulin signalling pathway. This panel of genes may also serve as clinically useful early biomarkers which predict which women with PCOS will go on to develop EC.