Current data and future perspectives on DNA methylation in ovarian cancer (Review)

Ovarian cancer (OC) represents the most prevalent malignancy of the female reproductive system. Its distinguishing features include a high aggressiveness, substantial morbidity and mortality, and a lack of apparent symptoms, which collectively pose significant challenges for early detection. Given that aberrant DNA methylation events leading to altered gene expression are characteristic of numerous tumor types, there has been extensive research into epigenetic mechanisms, particularly DNA methylation, in human cancers. In the context of OC, DNA methylation is often associated with the regulation of critical genes, such as BRCA1/2 and Ras‑association domain family 1A. Methylation modifications within the promoter regions of these genes not only contribute to the pathogenesis of OC, but also induce medication resistance and influence the prognosis of patients with OC. As such, a more in‑depth understanding of DNA methylation underpinning carcinogenesis could potentially facilitate the development of more effective therapeutic approaches for this intricate disease. The present review focuses on classical tumor suppressor genes, oncogenes, signaling pathways and associated microRNAs in an aim to elucidate the influence of DNA methylation on the development and progression of OC. The advantages and limitations of employing DNA methylation in the diagnosis, treatment and prevention of OC are also discussed. On the whole, the present literature review indicates that the DNA methylation of specific genes could potentially serve as a prognostic biomarker for OC and a therapeutic target for personalized treatment strategies. Further investigations in this field may yield more efficacious diagnostic and therapeutic alternatives for patients with OC.

Ras association domain family protein 1a hypermethylation and PD-L1 expression in ovarian cancer: A retrospective study of 112 cases

OBJECTIVE

This study assessed the interrelationships between Ras association domain family protein 1a (RASSF1A) gene hypermethylation, PD-L1 protein expression, and the clinicopathological characteristics of 112 ovarian cancer (OC) samples.

METHODS

Formalin-fixed paraffin-embedded OC tissue samples from surgical resection were assessed. Bisulfite pyrosequencing and immunohistochemistry were applied to detect RASSF1A gene methylation and PD-L1 protein expression in tumor cells, respectively. RASSF1A gene methylation and PD-L1 protein expression levels were analyzed against clinicopathological features and prognosis through standard statistical methods.

RESULTS

Of the 112 OC samples, 49.1% (55/112) exhibited RASSF1A gene hypermethylation. The frequency of RASSF1A hypermethylation was significantly higher in nonserous subtype (73.0%), early stage (66.7%), and nonrecurrent OC (62.9%, p < 0.05). Among all samples, 61.6% (69/112) were positive for PD-L1 protein expression in tumor cells. No significant differences in PD-L1 expression were identified for age, menstrual status, histological type, tumor location, grade, stage, lymph node metastasis, or prognosis (p > 0.05). RASSF1A methylation and PD-L1 expression were not correlated (p > 0.05).

CONCLUSIONS

This was the first study linking RASSF1A hypermethylation variability to PD-L1 expression and clinicopathological characteristics of OC. Epigenetic alteration of RASSF1A was closely associated with nonserous subtype, early stage, and nonrecurrent OC, indicating that RASSF1A hypermethylation may play a role in early detection of OC. Expression of PD-L1 had no relationship with the studied clinicopathological characteristics or RASSF1A hypermethylation in the 112 OC samples.

FOXD3 may be a new cellular target biomarker as a hypermethylation gene in human ovarian cancer

Background

FOXD3 is aberrantly regulated in several tumors, but its underlying mechanisms in ovarian cancer (OC) remains largely unknown. The present study aimed to explore the role and associated mechanisms of FOXD3 in OC.

Methods

Microarray data from GEO was used to analyze differential CpG sites and differentially methylated regions (DMR) in tumor tissues and Illumina 450 genome-wide methylation data was employed. The FOXD3 expression level was determined through qRT-PCR and western blot analysis. Wound healing test, colony formation and flow cytometry assay were utilized to analyze cell migration, proliferation abilities, cell cycle and cell apoptosis, respectively. Finally, the effect of FOXD3 on tumor growth was investigated through in vivo xenograft experiments.

Results

GEO data analysis showed that FOXD3 was hypermethylated in OC tissues. Also, qRT-PCR revealed that FOXD3 was low expressed and methylation-specific PCR (MSP) confirmed that the methylation level of FOXD3 was hypermethylated. Combined treatment of 5-aza-2′-deoxycytidine (5-Aza-dC) could synergistically restored FOXD3 expression. Finally, in vitro and in vivo experiments showed that demethylated FOXD3 decreased cell proliferation and migration abilities, and increased the cell apoptosis. In vivo experiment detected that demethylated FOXD3 restrained tumor growth.

Conclusions

FOXD3 could act as a tumor suppressor to inhibit cell proliferation, migration and promote cell apoptosis in OC cells.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0755-8) contains supplementary material, which is available to authorized users.

Methylation Profiles of BRCA1, RASSF1A and GSTP1 in Vietnamese Women with Breast Cancer

Objective: This study investigated the DNA promoter methylation profiles of BRCA1, RASSF1A and GSTP1 genes, both individually and in an integrative manner in order to clarify their correlation with clinicopathological parameters of breast cancer from Vietnamese patients, and establish new potential integrative methylation biomarkers for breast cancer detection. Material and methods: The methylation frequencies of BRCA1, RASSF1A and GSTP1 were analyzed by methylation specific polymerase chain reaction (MSP) in 70 specimens of breast carcinomas and 79 pairs of tumor and matched adjacent normal tissues from breast cancer patients. Results: All the three analyzed genes showed a concordance concerning their promoter methylation in tumor and adjacent normal tissue. The methylation of BRCA1, RASSF1A and GSTP1 was found in 58.23 %, 74.68 % and 59.49 % of tumor tissues and 51.90 %, 63.29 % and 35.44 % of corresponding adjacent tissues, respectively. When each gene was assessed individually, only the methylation of GSTP1 was significantly associated with tumor tissues (p=0.003). However, the methylation frequency of at least one of the three genes and the methylation frequency of all the three genes both showed significant association with tumor (p=0.008 and p=0.04, respectively). The methylation of BRCA1 was found to be significantly associated with tumor grade (p=0.01). Conclusion: This study emphasized that the panel of the three genes BRCA1, RASSF1A and GSTP1 can be further developed as potential biomarkers in diagnosis and classification of breast cancer in Vietnamese women.

ESR1 methylation in primary tumors and paired circulating tumor DNA of patients with high-grade serous ovarian cancer

OBJECTIVE

Estrogen receptor, coded by the ESR1 gene, is highly expressed in epithelial ovarian cancer. ESR1 gene is frequently methylated in many types of gynecological malignancies. However, only a few studies attempted to investigate the role of ESR1 methylation and its clinical significance in ovarian cancer so far. The aim of our study was to examine ESR1 methylation status in primary tumors and corresponding circulating tumor DNA of patients with high-grade serous ovarian cancer (HGSC).

METHODS

ESR1 methylation was detected by a highly specific and sensitive real-time methylation-specific PCR assay. Two groups of HGSC samples were analyzed: group A (n = 66 primary tumors) and group B (n = 53 primary tumors and 50 corresponding plasma samples).

RESULTS

ESR1 was found methylated in both groups of primary tumors: in 32/66 (48.5%) of group A and in 15/53 (28.3%) of group B. 19/50 (38.0%) corresponding plasma samples of group B were also methylated for ESR1. A significant agreement for ESR1 methylation was observed between primary tumors and paired plasma ctDNA samples (P = 0.004). Interestingly, the presence of ESR1 methylation in primary tumor samples of group B was significantly correlated with a better overall survival (P = 0.027) and progression-free survival (P = 0.041).

CONCLUSIONS

We report for the first time the presence of ESR1 methylation in plasma ctDNA of patients with HGSC. The agreement between ESR1 methylation in primary tumors and paired ctDNA is statistically significant. Our results indicate a correlation between the presence of ESR1 methylation and a better clinical outcome in HGSC patients.

Association between Ras association domain family 1A promoter methylation and esophageal squamous cell carcinoma: a meta-analysis

RASSF1A has been reported to be a candidate tumor suppressor in esophageal squamous cell carcinoma (ESCC). However, the association between RASSF1A promoter methylation and ESCC remains unclear. Eligible studies were identified through searching PubMed, Medline, Web of Science, and the China National Knowledge Infrastucture database. Studies were pooled and odds ratios (ORs) with corresponding confidence intervals (CIs) were calculated. Funnel plots were also performed to evaluate publication bias. Twelve studies involving 859 cases and 675 controls were included in this meta-analysis. A significant association was observed between RASSF1A methylation and ESCC overall (OR = 11.7, 95% CI: 6.59-20.9, z=8.36, P<0.00001). Subgroup analysis showed that the OR for heterogeneous tissues was 5.35 (95% CI = 2.95-9.71) while for autologous tissues it was 16.0 (8.31-30.96). For patient sample size, the OR for the <50 subgroup was 9.92 (95% CI = 2.88-34.2) and for the 50 case group was 13.1 (95% CI = 6.59-25.91). The OR for a relationship between RASSF1A methylation and TNM stages was 0.27 (95% CI=0.10-0.77), whereas there were no significant differences in RASSF1A methylation in relation to gender and differentiation among ESCC cases. This meta-analysis suggests a significant association between RASSF1A methylation and ESCC.

Methylation status and immunohistochemistry of BRCA1 in epithelial ovarian cancer

BACKGROUND

Cancer initiation and progression are controlled by genetic and epigenetic events. One epigenetic process which is widely known is DNA methylation, a cause of gene silencing. If a gene is silenced the protein which it encodes will not expressed.

OBJECTIVES

1. Identify the methylation status of BRCA1 in patients with epithelial ovarian cancer (EOC)and assess BRCA1 protein expression in tumor tissue. 2. Examine whether BRCA1 gene methylation and BRCA1 protein are associated with survival of epithelial ovarian cancer patients.

METHODS

The study design was a prospective-cohort study, conducted at Sardjito hospital, Yogyakarta, Indonesia.

RESULTS

A total of 69 cases were analyzed in this study. The data showed that the methylation status of BRCA1 in EOC was positive in 89.9%, with clear protein expression of BRCA1 in 31.9%. Methylation status and expression of BRCA1 were not prognosticators of EOC patients. Menarche, CA125 level, clinical stage and residual tumor were independent factors for prognosis.

Association between cigarette smoking and RASSF1A gene promoter hypermethylation in lung cancer patients: a meta- analysis

OBJECTIVES

Epidemiological studies have shown that molecular mechanisms underlying the development of lung cancers differ between smokers and unsmokers. Aberrant promoter methylation in some tumor suppressor genes is frequent in lung tumors from smokers but rare in those from non-smokers. Recently, many studies have investigated the association between cigarette smoking and RASSF1A gene promoter hypermethylation in lung cancer patients, but a unanimous conclusion could not be reached. We therefore performed this meta-analysis to derive a more precise estimation of any association.

STUDY DESIGN

An electronic search of PubMed and Chinese Biomedicine databases was conducted to select studies. A total of 19 case-control studies were chosen, and odds ratios (ORs) with confidence intervals (CIs) were used to assess the strength of associations.

RESULTS

The case-control studies covered 2, 287 lung cancer patients: 63.4%(1449) of the patients were smokers, 36.6% (838) were unsmokers. The overall results suggested that smokers with lung cancer had a 1.297-fold (95% CI: 1.066~1.580, p=0.010, p=0.087) higher risk for RASSF1A gene hypermethylation than the non-smokers. In the stratified analysis, an increased risk of RASSF1A gene hypermethylation in smokers than in non-smokers was found in Asian (OR=1.481, 95%CI: 1.179~1.861, p=0.001, p=0.186).

CONCLUSIONS

This meta-analysis supports the idea that RASSF1A gene hypermethylation is associated with cigarette smoking-induced lung cancer.

Methylation of RASSF1A gene promoter and the correlation with DNMT1 expression that may contribute to esophageal squamous cell carcinoma

Background

Esophageal squamous cell carcinoma is one of the most common malignancies in the world. Studies have confirmed that there are many genes abnormally hypermethylated in esophageal squamous cell carcinoma. The objective is to detect methylation of the RASSF1A gene promoter and the expression of the DNA methyltransferase 1 (DNMT1) protein in esophageal cancer tissue and discuss their relationship with esophageal squamous cell carcinoma.

Methods

The CpG island methylation status of RASSF1A genes were analyzed in 100 cases of tumor specimens as well as their adjacent tissues which was used for methylation-specific polymerase chain reaction (MSP). The expression of DNMT1 protein was determined by immunohistochemistry. Difference between measurement data and categorical data was compared through analysis of t test and chi-square test. All the statistics were taken with a bilateral test. The difference was statistically significant (P < 0.05).

Results

The promoter methylation of the RASSF1A gene promoter has been detected in 45 out of 100 (45%) esophageal squamous carcinoma cases, while methylation of RASSF1A gene has been detected in 2 out of 100 adjacent normal tissues (2%). The RASSF1A gene promoter was highly methylated in cancer tissues, and there were significant differences between normal esophagus tissues and esophageal squamous carcinoma (P < 0.05). The expression of DNMT1 protein has been detected in 61 out of 100 (61%) esophageal squamous carcinoma cases, including 41 cases in the above 45 methylated samples of RASSF1A gene promoter, and none in adjacent tissues. DNMT1 proteins are highly expressed in cancer tissues, and there were significant differences (P < 0.05). In positive cases for methylation of RASSF1A, the DNMT1 protein had been detected in 41 out of 45 (91%), while in non-methylated cancer cases, 20 out of 55(36.3%), and the difference is significant (P < 0.05).

Conclusions

Esophageal squamous carcinoma tumorigenesis may be related with hypermethylation of DNMT1 and RASSF1A promoter CpG island due to their high expression and also their hypermethylation.

Combined effects methylation of FHIT, RASSF1A and RARβ genes on non-small cell lung cancer in the Chinese population

Epigenetic modifications of tumour suppressor genes are involved in all kinds of human cancer. Aberrant promoter methylation is also considered to play an essential role in development of lung cancer, but the pathogenesis remains unclear.We collected the data of 112 subjects, including 56 diagnosed patients with lung cancer and 56 controls without cancer. Methylation of the FHIT, RASSF1A and RAR-β genes in DNA from all samples and the corresponding gene methylation status were assessed using the methylation-specific polymerase chain reaction (PCR, MSP). The results showed that the total frequency of separate gene methylation was significantly higher in lung cancer compared with controls (33.9-85.7 vs 0 %) (p<0.01).Similar outcomes were obtained from the aberrant methylation of combinations of any two or three genes (p<0.01). There was a tendency that the frequency of combinations of any two or three genes was higher in stage I+II than that in stage III+IV with lung cancer. However, no significant difference was found across various clinical stages and clinic pathological gradings of lung cancer (p>0.05).These observations suggest that there is a significant association of promoter methylation of individual genes with lung cancer risk, and that aberrant methylation of combination of any two or three genes may be associated with clinical stage in lung cancer patients and involved in the initiation of lung cancer tumorigenesis. Methylation of FHIT, RASSF1A and RARβ genes may be related to progression of lung oncogenesis.

Methylation of RASSF1A and CDH13 genes in individualized chemotherapy for patients with non-small cell lung cancer

BACKGROUND

This study aimed to evaluate the methylation of RASSF1A and CDH13 gene promoter regions as a marker for monitoring chemotherapeutic efficacy with personalized medicine for patients with NSCLC, in the hope of providing a new direction for NSCLC individualized chemotherapy.

MATERIALS AND METHODS

42 NSCLC patients and 40 healthy controls were included. Patient blood samples were collected in the whole process of chemotherapy. Methylation of RASSF1A and CDH13 gene promoter regions was detected by the methylation specific polymerase chain reaction (MSP).

RESULTS

The rate of RASSF1A and CDH13 gene methylation in 42 cases of NSCLC patients was significantly higher than in 40 healthy controls (52.4% to 0.0%, 54.8% to 0.0%, p<0.05). After the chemotherapy, the hyper-methylation of RASSF1A and CDH13 genes in PR group and SD group decreased significantly (p<0.05), and was significantly different from that in PD group (p<0.05), but not as compared with healthy controls (P>0.05). With chemotherapy, RASSF1A and CDH13 promoter region methylation rate in 42 cases of patients showed a declining trend.

CONCLUSIONS

The methylation level of RASSF1A and CDH13 gene promoter region can reflect drug sensitivity of tumors to individualized treatment.

Association between RASSF1A Ala133Ser polymorphism and cancer susceptibility: a meta-analysis involving 8,892 subjects

BACKGROUND

Published studies on the association between the Ras Association Domain Family 1 isoform A (RASSF1A) Ala133Ser polymorphism and cancer susceptibility have yielded conflicting results. Thus, a meta- analysis was here performed to assess the possible association.

MATERIALS AND METHODS

All eligible case-control studies published up to November 2013 on the association between RASSF1A Ala133Ser polymorphism and cancer susceptibility were identified by searching PubMed, Web of Science, Science Direct and hand search. Bothfixed- effect and random-effect models were used to calculate pooled odds ratios (ORs) with 95% confidence intervals (CIs) by using the Comprehensive Meta-Analysis software version 2.2.

RESULTS

A total of 10 studies including 4,572 cancer cases and 4,320 controls were included in the meta-analysis. Overall, significantly increased cancer risk was associated with the variant Ser133 when all studies were pooled (Ser vs Ala: OR=1.51, 95% CI=1.08- 2.12, Pheterogeneity≤0.001; Ser/Ser+Ala/Ser vs Ala/Ala: OR=1.55, 95% CI=1.08-2.22, Pheterogeneity ≤ 0.001). Moreover, in subgroup analyses by cancer types, a significant association between RASSF1A Ala133Ser polymorphism and lung cancer risk was found (Ser vs Ala: OR=2.27, 95% CI=1.29-4.02, Pheterogeneity=0.61; Ser/Ser+Ala/ Ser vs Ala/Ala: OR=2.42, 95% CI=1.33-4.42, Pheterogeneity=0.75). In addition, in subgroup analyses by ethnicity, it was found that the RASSF1A Ala133Ser polymorphism was associated with overall cancer risk in Asians (Ser vs Ala: OR=1.37, 95% CI=1.06-1.77, Pheterogeneity=0.06) and Caucasians (Ser/Ser+Ala/Ser vs Ala/Ala: OR=2.21, 95% CI=1.01-4.82, Pheterogeneity≤0.001).

CONCLUSIONS

This meta-analysis suggests, for the first time, that RASSF1A Ala133Ser polymorphism may contribute to cancer susceptibility, especially for lung cancer. Besides, additional well-designed studies with larger sample size focusing on different ethnicities and cancer types are needed to confirm these findings.