Endometrial Cancer and Hypermethylation: Regulation of DNA and MicroRNA by Epigenetics

Surface-Enhanced Raman Spectroscopy-Based Detection of EMT-Related Targets in Endometrial Cancer: Potential for Diagnosis and Prognostic Prediction

Epithelial-mesenchymal transformation (EMT) is one of the important mechanisms of malignancy in endometrial cancer, and detection of EMT targets is a key challenge to explore the mechanism of endometrial carcinoma (EC) malignancy and discover novel therapeutic targets. This study attempts to use surface-enhanced Raman spectroscopy (SERS), a highly sensitive, ultrafast, and highly specific analytical technology, to rapidly detect microRNA-200a-3p and ZEB1 in endometrial cancer cell lines. The silver nanoparticles were decorated with iodine and calcium ions, can capture the SERS fingerprints of microRNA-200a-3p and ZEB1 protein, and effectively avoid the interference of impurity signals. At the same time, the method has high sensitivity for the detection of the above EMT targets, and the lowest detection limits for microRNA-200a-3p and ZEB1 are 4.5 pmol/mL and 10 ng/mL, respectively. At the lowest detection concentration, the method still has high stability. In addition, principal component analysis can not only identify microRNA-200a-3p and ZEB1 protein from a variety of EMT-associated microRNA and proteins but also identify them in the total RNA and total protein of endometrial cancer cell lines and normal endometrial epithelial cell lines. This study modified silver nanoparticles with iodine and calcium ions and for the first time captured the fingerprints of EMT-related targets microRNA-200a-3p and ZEB1 at the same time without label, and the method has high sensitivity and stability. This SERS-based method has immense potential for elucidating the molecular mechanisms of EMT-related EC, as well as identifying biomarkers for malignant degree and prognosis prediction.

Promoter methylation status of RASSF1A and RASSF2A tumor suppressor genes in endometrial endometrioid carcinomas

We aimed to investigate the promoter methylation status of RASSF1A and RASSF2A tumor suppressor genes in endometrial endometrioid carcinomas with p53 wild type and mismatch repair proficient. Genomic DNAs were isolated from 50 specimens (15 formalin-fixed paraffin embedded tumor tissues, 15 paired blood samples and 20 normal endometrial tissues). Bisulfide modification and methylation-specific polymerase chain reaction were performed. As a result of the study, while no significance was found for RASSF1A gene (p = 0.08), a statistically significance was found for RASSF2A gene (p < 0.001), RASSF2A gene methylation status was also found higher in high grade tumors, advanced age (≥50) and nonsmokers groups. Our results indicate that RASSF2A gene may play a role in the carcinogenesis of endometrioid and it could be potential biomarker for early detection for endometrioid carcinoma. Further and larger investigations are needed to confirm our results.

MicroRNA as Epigenetic Modifiers in Endometrial Cancer: A Systematic Review

Simple Summary

Endometrial cancer (EC) is the 2nd most common gynecologic cancer worldwide. MicroRNAs (miRNAs) are small noncoding RNAs that contribute to epigenetic regulation. The objective of this systematic review is to summarize our current knowledge on the role of miRNAs in the epigenetic deregulation of tumor-related genes in EC. It includes all miRNAs reported to be involved in EC including their roles in DNA methylation and RNA-associated silencing. This systematic review should be useful for development of novel strategies to improve diagnosis and risk assessment as well as for new treatments aimed at miRNAs, their target genes or DNA methylation.

Abstract

The objective of this systematic review is to summarize our current knowledge on the influence of miRNAs in the epigenetic deregulation of tumor-related genes in endometrial cancer (EC). We conducted a literature search on the role of miRNAs in the epigenetic regulation of EC applying the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The following terms were used: microRNA, miRNA, miR, endometrial cancer, endometrium, epigenetic, epimutation, hypermethylation, lynch, deacetylase, DICER, novel biomarker, histone, chromatin. The miRNAs were classified and are presented according to their function (tumor suppressor or onco-miRNA), their targets (when known), their expression levels in EC tissue vs the normal surrounding tissue, and the degree of DNA methylation in miRNA loci and CpG sites. Data were collected from 201 articles, including 190 original articles, published between November 1, 2008 and September 30, 2020 identifying 313 different miRNAs implicated in epigenetic regulation of EC. Overall, we identified a total of 148 miRNAs with decreased expression in EC, 140 miRNAs with increased expression in EC, and 22 miRNAs with discordant expression levels. The literature implicated different epigenetic phenomena including altered miRNA expression levels (miR-182, -230), changes in the methylation of miRNA loci (miR-34b, -129-2, -130a/b, -152, -200b, -625) and increased/decreased methylation of target genes (miR-30d,-191). This work provides an overview of all miRNAs reported to be involved in epigenetic regulation in EC including DNA methylation and RNA-associated silencing. These findings may contribute to novel strategies in diagnosis, risk assessment, and treatments aimed at miRNAs, their target genes or DNA methylation.

Insulin Resistance and Endometrial Cancer: Emerging Role for microRNA

Endometrial cancer (EC) remains one of the most common cancers of the female reproductive system. Epidemiological and clinical data implicate insulin resistance (IR) and its accompanying hyperinsulinemia as key factors in the development of EC. MicroRNAs (miRNAs) are short molecules of non-coding endogenous RNA that function as post-transcriptional regulators. Accumulating evidence has shown that the miRNA expression pattern is also likely to be associated with EC risk factors. The aim of this work was the verification of the relationships between IR, EC, and miRNA, and, as based on the literature data, elucidation of miRNA's potential utility for EC prevention in IR patients. The pathways affected in IR relate to the insulin receptors, insulin-like growth factors and their receptors, insulin-like growth factor binding proteins, sex hormone-binding globulin, and estrogens. Herein, we present and discuss arguments for miRNAs as a plausible molecular link between IR and EC development. Specifically, our careful literature search indicated that dysregulation of at least 13 miRNAs has been ascribed to both conditions. We conclude that there is a reasonable possibility for miRNAs to become a predictive factor of future EC in IR patients.

Molecular Modifiers of Hormone Receptor Action: Decreased Androgen Receptor Expression in Mismatch Repair Deficient Endometrial Endometrioid Adenocarcinoma

Endometrial endometrioid carcinoma is related to estrogen excess and expression of estrogen and progesterone receptors. Epidemiological evidence suggests that exposure to elevated androgens, as in polycystic ovarian syndrome, increases the risk of endometrial cancer. Factors impacting androgen receptor (AR) expression are not well studied. Mismatch repair (MMR) deficiency due to MLH1 gene methylation is one of the most common molecular alterations in endometrial cancer, occurring in 15% to 20% of cases. MLH1 methylation can be associated with decreased expression of other genes, so we examined the effect of MMR status on AR expression. As NF-κB is known to induce AR, this transcription factor was also examined. Three hundred forty-four unselected endometrial carcinomas were evaluated for DNA MMR. Loss of expression of MLH1 with MLH1 methylation was defined as MMR deficient, and positive expression of MMR proteins was defined as MMR intact. A case-control cohort of 96 grade 2 endometrioid carcinomas was studied from this set (47 MMR deficient, 49 MMR intact). Cases were matched for histotype, grade, and age. AR and NF-κB immunohistochemical expression were evaluated by 2 different scoring systems (CAP/ASCO and Allred) used for estrogen receptor. Despite higher levels of NF-κB, MMR deficiency was associated with a significantly lower mean percentage of AR expression. The MMR deficient group had more variable AR expression, with more cases scoring on the lower end of the spectrum. These findings have implications for clinical trials of AR antagonists in gynecologic cancers.

Potential of RASSF1A promoter methylation as biomarker for endometrial cancer: A systematic review and meta-analysis

BACKGROUND

An epigenetic approach to explaining endometrial carcinogenesis necessitates good understanding of Ras association domain family 1 isoform A (RASSF1A) promoter methylation data from primary studies.

AIMS

Differential magnitude of reported associations between RASSF1A promoter methylation and endometrial cancer (EC) prompted a meta-analysis to obtain more precise estimates.

METHODS

Literature search yielded eight included articles. We calculated pooled odds ratios (OR) and 95% confidence intervals and subgrouped the data by race. Sources of heterogeneity were investigated with outlier analysis.

RESULTS

The pooled ORs indicated increased risk, mostly significant. The overall effect (OR 11.46) was reflected in the European outcome (OR 15.07). However, both findings were heterogeneous (I²=57-70%) which when subjected to outlier treatment, erased heterogeneity (I²=0%) and retained significance (OR 9.85-12.66). Significance of these pre- and post-outlier outcomes were pegged at P≤0.0001. Only the Asian pre-outlier (OR 6.85) and heterogeneous (I²=82%) outcome was not significant (P=0.12) but when subjected to outlier treatment, erased heterogeneity (I²=0%) and generated significance (OR 23.74, P≤0.0001).

CONCLUSIONS

Consistent increased risk associations underpinned by significance and robustness render RASSF1A with good biomarker potential for EC.

Genome-wide DNA methylation sequencing reveals miR-663a is a novel epimutation candidate in CIMP-high endometrial cancer

Aberrant DNA methylation is widely observed in many cancers. Concurrent DNA methylation of multiple genes occurs in endometrial cancer and is referred to as the CpG island methylator phenotype (CIMP). However, the features and causes of CIMP-positive endometrial cancer are not well understood. To investigate DNA methylation features characteristic to CIMP-positive endometrial cancer, we first classified samples from 25 patients with endometrial cancer based on the methylation status of three genes, i.e. MLH1, CDH1 (E-cadherin) and APC: CIMP-high (CIMP-H, 2/25, 8.0%), CIMP-low (CIMP-L, 7/25, 28.0%) and CIMP-negative (CIMP(-), 16/25, 64.0%). We then selected two samples each from CIMP-H and CIMP(-) classes, and analyzed DNA methylation status of both normal (peripheral blood cells: PBCs) and cancer tissues by genome-wide, targeted bisulfite sequencing. Genomes of the CIMP-H cancer tissues were significantly hypermethylated compared to those of the CIMP(-). Surprisingly, in normal tissues of the CIMP-H patients, promoter region of the miR-663a locus is hypermethylated relative to CIMP(-) samples. Consistent with this finding, miR-663a expression was lower in the CIMP-H PBCs than in the CIMP(-) PBCs. The same region of the miR663a locus is found to be highly methylated in cancer tissues of both CIMP-H and CIMP(-) cases. This is the first report showing that aberrant DNA methylation of the miR-663a promoter can occur in normal tissue of the cancer patients, suggesting a possible link between this epigenetic abnormality and endometrial cancer. This raises the possibility that the hypermethylation of the miR-663a promoter represents an epimutation associated with the CIMP-H endometrial cancers. Based on these findings, relationship of the aberrant DNA methylation and CIMP-H phenotype is discussed.

An integrative transcriptomic analysis reveals bisphenol A exposure-induced dysregulation of microRNA expression in human endometrial cells

Bisphenol A (BPA) are commonly used in the manufacture of polycarbonate plastics. Higher BPA exposure levels have been found in patients with endometrial hyperplasia that is one of risk factors of endometrial cancer (EC). Aberrant microRNAs (miRNAs) regulation has been observed in the development of cancer. Thus, this study investigated whether BPA exposure can disrupt miRNA regulation and its gene expression regarding to EC carcinogenic progress. Microarray experiments of miRNA and mRNA were performed in human endometrial cancer RL95-2 cells with treatment of low-to-moderate (10, 10³ and 10⁵nM) BPA to explore the aberrant genes corresponding to human EC progression. According to the analysis of KEGG pathway and Cytoscape gene network, this study identified that BPA exposure reduced miR-149 expression to down-regulate DNA repair gene ARF6 (ADP-ribosylation factor 6) and tumor protein p53 (TP53), and up-regulate CCNE2 (cyclin E2) potentially to interrupt cell cycle. BPA also increased miR-107 to suppress hedgehog signaling factors, suppressor of fused homolog (SUFU) and GLI family zinc finger 3 (GLI3) to activate hedgehog signaling for cell proliferation underlying carcinogenesis. Furthermore, the BPA-induced cell proliferation was attenuated by transfection with miR-149 mimic and miR-107 inhibitor. These findings provided an insight into potential epigenetic mechanism of BPA exposure on the risk of endometrial carcinogenesis.

Methylation Analysis of DNA Mismatch Repair Genes Using DNA Derived from the Peripheral Blood of Patients with Endometrial Cancer: Epimutation in Endometrial Carcinogenesis

Germline mutation of DNA mismatch repair (MMR) genes is a cause of Lynch syndrome. Methylation of MutL homolog 1 (MLH1) and MutS homolog 2 (MSH2) has been detected in peripheral blood cells of patients with colorectal cancer. This methylation is referred to as epimutation. Methylation of these genes has not been studied in an unselected series of endometrial cancer cases. Therefore, we examined methylation of MLH1, MSH2, and MSH6 promoter regions of peripheral blood cells in 206 patients with endometrial cancer using a methylation-specific polymerase chain reaction (MSP). Germline mutation of MMR genes, microsatellite instability (MSI), and immunohistochemistry (IHC) were also analyzed in each case with epimutation. MLH1 epimutation was detected in a single patient out of a total of 206 (0.49%)-1 out of 58 (1.72%) with an onset age of less than 50 years. The patient with MLH1 epimutation showed high level MSI (MSI-H), loss of MLH1 expression and had developed endometrial cancer at 46 years old, complicated with colorectal cancer. No case had epimutation of MSH2 or MSH6. The MLH1 epimutation detected in a patient with endometrial cancer may be a cause of endometrial carcinogenesis. This result indicates that it is important to check epimutation in patients with endometrial cancer without a germline mutation of MMR genes.

The future therapy of endometrial cancer: microRNA's functionality, capability, and putative clinical application

PURPOSE

Endometrial cancer (EC) therapy is characterized by the heterogeneity of EC subtypes resulting in unclear clinical behavior as well as in unsatisfactory treatment options. The available biomarkers, such as cellular tumor antigen p53 (TP53), phosphatidylinositol 3,4,5-trisphosphate 3-phosphatase and dual-specificity protein phosphatase (PTEN), and phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) genes alone might not be sufficient, and thus, new predictive and prognostic biomarkers are urgently required. The biomolecule class of microRNA represents a group of endogenously expressed regulatory factors primarily involved in control of pivotal cancer-related mechanisms including cell cycle, proliferation, apoptosis, and metastasis. Here, we review the current state of science regarding microRNA functionality in EC progression.

The important application of thioridazine in the endometrial cancer

BACKGROUND

Endometrial cancer (ECa) is one of the serious healthy burden for female worldwide. The treatments of ECa focus on the application of endocrine therapy and aberrant signaling proteins expression recently years. Medroxyprogesterone acrtate (MPA) plays crucial role in the endocrine therapy for ECa patients. However, the outcomes are still not ideal in the advanced stage tumor, especially in the progesterone-resistant ECa. Thioridazine (THIO) is an anti-psychotic agent, which has been reported to suppress the development of several human cancers. In this study, we aimed at to explore the clinical significant of THIO in the treatment of ECa.

METHODS

Two ECa cell lines (ISK and KLE) were enrolled in this study, and were grouped into fore groups based on the treatment with different agents. Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay was used to analyze the viability of ECa cell lines. The apoptosis of ECa cells was examined by using the flow cytometer. To investigate the expression of important proteins, we applied the quantitative real-time RT-PCR (qRT-PCR) method and western blot analysis.

RESULTS

The viability of ECa cells was downregulated, and the apoptosis of ECa cells was upregulated after treating with the THIO plus MPA. The expression of progesterone receptor B (PRB) and dopamine receptor D2 (DRD2) were increased, and epidermal growth factor receptor (EGFR) and p-AKT were decreased in the THIO+MPA group. All these results suggested that the THIO could promote MPA to inhibit the growth of cells in ECa, especially in the progesterone-resistant ECa.

CONCLUSION

Taken together, all the data in the present study suggested that the THIO plus MPA might act as the suppressor of tumor growth in ECa by inhibiting the PI3K/AKT signal transduction pathway, which was mediated by PRB, DRD2 and EGFR.

Utility of Serum miR-125b as a Diagnostic and Prognostic Indicator and Its Alliance with a Panel of Tumor Suppressor Genes in Epithelial Ovarian Cancer

MicroRNAs (miRNAs) have been found to be dysregulated in epithelial ovarian cancer (EOC) and may function as either tumor suppressor genes (TSGs) or as oncogenes. Hypermethylation of miRNA silences the tumour suppressive function of a miRNA or hypermethylation of a TSG regulating that miRNA (or vice versa) leads to its loss of function. The present study aims to evaluate the impact of aberrant microRNA-125b (miR-125b) expression on various clinicopathological features in epithelial ovarian cancer and its association with anomalous methylation of several TSGs. We enrolled 70 newly diagnosed cases of epithelial ovarian cancer, recorded their clinical history and 70 healthy female volunteers. Serum miR-125b levels were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and the methylation status of various TSGs was investigated by methylation specific PCR. ROC curves were constructed to estimate the diagnostic and prognostic usefulness of miR-125b. The Kaplan-Meier method was applied to compare survival curves. Expression of miR-125b was found to be significantly upregulated (p<0.0001) in comparison with healthy controls. The expression level of miR-125b was found to be significantly associated with FIGO stage, lymph node and distant metastasis. ROC curve for diagnostic potential yielded significant AUC with an equitable sensitivity and specificity. ROC curves for prognosis yielded significant AUCs for histological grade, distal metastasis, lymph node status and survival. The expression of miR-125b also correlated significantly with the hypermethylation of TSGs. Our results indicate that DNA hypermethylation may be involved in the inactivation of miR-125b and miR-125b may function as a potential independent biomarker for clinical outcome in EOC.

The Role of Epigenomics in the Study of Cancer Biomarkers and in the Development of Diagnostic Tools

Epigenetics plays a key role in cancer development. Genetics alone cannot explain sporadic cancer and cancer development in individuals with no family history or a weak family history of cancer. Epigenetics provides a mechanism to explain the development of cancer in such situations. Alterations in epigenetic profiling may provide important insights into the etiology and natural history of cancer. Because several epigenetic changes occur before histopathological changes, they can serve as biomarkers for cancer diagnosis and risk assessment. Many cancers may remain asymptomatic until relatively late stages; in managing the disease, efforts should be focused on early detection, accurate prediction of disease progression, and frequent monitoring. This chapter describes epigenetic biomarkers as they are expressed during cancer development and their potential use in cancer diagnosis and prognosis. Based on epigenomic information, biomarkers have been identified that may serve as diagnostic tools; some such biomarkers also may be useful in identifying individuals who will respond to therapy and survive longer. The importance of analytical and clinical validation of biomarkers is discussed, along with challenges and opportunities in this field.

The Significance of miR-34a Expression in Endometrial Carcinogenesis: Correlation With Expression of p16 and Ki-67 Proteins in Endometrial Cancers

Background:

A microRNA, miR-34a, plays a key role in inhibiting cellular transformation and carcinogenesis by controlling cell cycle regulation and cell proliferation in various human tumors. However, miR-34a has rarely been reported in endometrial cancer research in Korea. This study was undertaken to analyze miR-34a expression in simple endometrial hyperplasia and endometrial cancer, and to evaluate the relationship between expression of miR-34a and p16 and Ki-67 proteins in endometrial cancers.

Methods:

A retrospective study was carried out on 66 formalin-fixed, paraffin-embedded tissues with simple endometrial hyperplasia (31 cases) and endometrial cancer (35 cases) patients. These were analyzed for miR-34a expression by quantitative real-time PCR, and the expression of p16 and Ki-67 proteins in endometrial cancers was evaluated by immunohistochemistry.

Results:

The miR-34a expression level was lower in endometrial cancer tissues (−0.71 ± 3.90) than in simple endometrial hyperplasia tissues (2.68 ± 8.62). The endometrial hyperplasia tissues showed underexpression of miR-34a in 13 of the 31 cases (41.9%) while the endometrial cancer tissues showed underexpression of miR-34a in 24 of 35 cases (68.6%). Thus, miR-34a was significantly underexpressed in endometrial cancer tissues when compared endometrial hyperplasia tissues (P = 0.046). Overexpression of p16 was detected in 25 (71.4%) and Ki-67 immunoreactivity was detected in 27 (77.1%) of the 35 endometrial cancers. Although not statistically significant, the frequency of p16 and Ki-67 overexpression tended to be lower in the cases with miR-34a underexpression than in cases with miR-34a overexpression.

Conclusions:

These findings suggest that underexpression of miR-34a might be involved in endometrial carcinogenesis. Further studies are needed to define the relationship between miR-34a expression and tissue specific protein expression.

MicroRNA and signal transduction pathways in tumor radiation response

Tumor radiation response is an essential issue in radiotherapy and a core determining factor of tumor radioresistance or radiosensitivity. Multiple factors can influence tumor radiation response, and among them tumor genetic and epigenetic background, tumor microenvironment and tumor blood flow status may take a leading role. During the whole process of tumor radiation response, tumor radiosensitivity can be regulated in an orderly manner through some classical signal transduction pathways. Although these pathways have already owned multiple biological functions and involved in the process of carcinogenesis, their regulatory roles in tumor radiation response can not be ignored. MicroRNA (miRNA) is a class of non-coding RNA of about 22 nucleotides in length, which binds to the 3'-untranslated region (3'-UTR) of target gene and controls the expression of it at the post-transcriptional level. MiRNA participates in numerous physiology and pathology processes and acts as oncogene or tumor suppressor to affect cancer progression. Through interplaying with the key components in radiation related signal transduction pathways, miRNA could effectively activate the expression of DNA damage response genes and cell cycle related genes in the nucleus, and play a critical role in the modulation of radiation response and radiosensitivity in tumor cells. In this review, we mainly elucidate the regulatory mechanisms and functions of miRNA in these radiation related signal transduction pathways from three different aspects which include the upstream receptors, midstream transducer pathways, and downstream effector genes.