Aberrant gene methylation in the lymph nodes provides a possible marker for diagnosing micrometastasis in gastric cancer

CHFR Promoter Hypermethylation Is Associated with Gastric Cancer and Plays a Protective Role in Gastric Cancer Process

Background: Chromosomally unstable tumors account for 50% of gastric cancer. CHFR plays a role in controlling chromosomal instability and its inactivation will eventually lead to tumorigenesis. In addition to genetic deletion, DNA methylation could silence the expression of many cancer-related genes including CHFR. Its methylation was found to be associated with the initiation and progression of gastric cancer.

Methods: We performed a meta-analysis involving methylation analyses of CHFR promoter in gastric cancer. Nineteen studies with 1,249 tumor tissues and 745 normal tissues had been included in current study.

Results: We found that CHFR methylation was significantly higher in gastric cancer (studies numbers = 15, cases/controls = 862/745, odds ratio (OR) = 7.46, 95% confidence index (95% CI) = 4.99-11.14). Methylation array data was also obtained from Gene Expression Omnibus (GEO) and The Cancer Genome Atlas network (TCGA). There were 7 out of 13 CHFR methylation probes target to the same CpG island region (hg19, 131973620-131975130) showed the CHFR methylation was higher in gastric cancers than normal controls. Eight probes showed CHFR promoter hypermethylation was associated with longer overall survival of gastric cancer patients (Hazard Ratio < 1).

Conclusions: The CHFR promoter hypermethylation was associated with gastric cancer and played a protective role in gastric cancer process. Its methylation could be a potential biomarker for the diagnosis and prognosis of gastric cancer.

Role of probe-based confocal laser endomicroscopy-targeted biopsy in the molecular and histopathological study of gastric cancer

BACKGROUND AND AIM

A high yield of biopsy is mandatory to perform molecular genetic research with endoscopically obtained gastric cancer tissues. We evaluated whether probe-based confocal laser endomicroscopy (pCLE) can increase the yield of endoscopic biopsy for gastric cancer compared with white light endoscopy (WLE).

METHODS

All lesions in the pCLE and WLE groups were initially evaluated through WLE. In the pCLE group, lesions were further examined through pCLE. In the pilot study, five and three biopsy specimens were obtained for histopathological examination and tumor marker analysis, respectively. In the confirmatory study, six biopsy specimens for histopathological evaluation were obtained.

RESULTS

A total of 30 gastric cancers and 61 undifferentiated-type gastric cancers were analyzed in the pilot and confirmatory studies, respectively. The proportion of cancer cells in biopsy samples of poorly differentiated adenocarcinoma or signet ring cell carcinoma was higher in the pCLE group than in the WLE group in both the pilot and confirmatory studies (pilot: median proportion, 65% vs 30%, P = 0.010; confirmatory: mean ± standard deviation, 49.5 ± 29.3 vs 29.3 ± 13.7, P = 0.002). The expression ratio of tumor markers including carcinoembryonic antigen, GW112, HOX transcript antisense RNA, and H19 tended to be higher in the pCLE group than in the WLE group.

CONCLUSION

Probe-based confocal laser endomicroscopy-targeted biopsy provided superior results in terms of the proportion of cancer cells in biopsy samples compared with WLE-targeted biopsy in gastric cancer with undifferentiated histology.

Epigenetic biomarkers of promoter DNA methylation in the new era of cancer treatment

Promoter DNA methylation, which occurs on cytosine nucleotides across CpG islands, results in gene silencing and represents a major epigenetic alteration in human cancer. Methylation-specific PCR can amplify these modifications as markers in cancer cells. In the present work, we rigorously review the published literatures describing DNA methylation in the promoters of critical tumor suppressor genes; detection of promoter DNA methylation in various body fluids permits early detection of cancer cells during perioperative courses of clinical treatment. The latest whole-genome comprehensive explorations identified excellent epigenetic biomarkers that could be detected at high frequency with high specificity; these biomarkers, which are designated highly relevant methylation genes (HRMG), permit the discrimination of tumor tissues from the corresponding normal tissues; these markers are also associated with unique cancer phenotypes, including dismal prognosis. In humans, HRMG include the CDO1, GSHR, RASSF1 and SFRP1 genes, with these markers permitting discrimination depending on the organs tested. The combination of several HRMG increased the early detection of cancer and exhibited reliable surveillance potential in human body fluids. Cancer clinics using such epigenetic biomarkers are entering a new era of enhanced decision-making with the potential for improved cancer prognosis.

MLH1 Promoter Methylation and Prediction/Prognosis of Gastric Cancer: A Systematic Review and Meta and Bioinformatic Analysis

Background: The promoter methylation of MLH1 gene and gastric cancer (GC)has been investigated previously. To get a more credible conclusion, we performed a systematic review and meta and bioinformatic analysis to clarify the role of MLH1 methylation in the prediction and prognosis of GC.

Methods: Eligible studies were targeted after searching the PubMed, Web of Science, Embase, BIOSIS, CNKI and Wanfang Data to collect the information of MLH1 methylation and GC. The link strength between the two was estimated by odds ratio with its 95% confidence interval. The Newcastle-Ottawa scale was used for quantity assessment. Subgroup and sensitivity analysis were conducted to explore sources of heterogeneity. The Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) were employed for bioinformatics analysis on the correlation between MLH1 methylation and GC risk, clinicopathological behavior as well as prognosis.

Results: 2365 GC and 1563 controls were included in the meta-analysis. The pooled OR of MLH1 methylation in GC was 4.895 (95% CI: 3.149-7.611, P<0.001), which considerably associated with increased GC risk. No significant difference was found in relation to Lauren classification, tumor invasion, lymph node/distant metastasis and tumor stage in GC. Analysis based on GEO and TCGA showed that high MLH1 methylation enhanced GC risk but might not related with GC clinicopathological features and prognosis.

Conclusion:MLH1 methylation is an alive biomarker for the prediction of GC and it might not affect GC behavior. Further study could be conducted to verify the impact of MLH1 methylation on GC prognosis.

Association Between hMLH1 Promoter Methylation and Risk of Gastric Cancer: A Meta-Analysis

Background: Human mutL homolog 1 (hMLH1) is located on chromosome 3q21-23. As a classic tumor suppressor gene, many researchers have studied the association between hMLH1 promoter methylation and gastric cancer, but their conclusions were not always consistent. Therefore, we performed a meta-analysis to make a more integrated and precise estimate of the associations.

Method: PubMed, EMBASE, and Cochrane Library were retrieved without language restrictions. Data were analyzed by Review Manager 5.2 and Stata 12.0 software. Odds ratio (OR) with 95% confidence interval (95%CI) was used to assess the statistical associations.

Result: A total of 39 studies published before January 20, 2018 were included in this study. The results indicated that the frequency of hMLH1 promoter methylation in gastric cancers was substantially higher than that in non-cancer controls (OR = 7.94, 95%CI = 4.32–14.58, P < 0.001). Furthermore, hMLH1 promoter methylation had considerable associations with lymph node metastasis, microsatellite instability (MSI), and low expression of hMLH1 protein (OR = 1.53, 95%CI = 1.04–2.26, P = 0.03; OR = 15.33, 95%CI = 9.26–25.36, P < 0.001; OR = 37.86, 95%CI = 18.03–79.50, P < 0.001, respectively). No association was found between hMLH1 promoter methylation and Lauren classification or Helicobacter pylori (HP) infection status.

Conclusion: The present study provides evidence that promoter methylation of hMLH1 is a major causative event in the occurrence and development of human gastric cancer.

Epigenetic Modifications as Biomarkers of Tumor Development, Therapy Response, and Recurrence across the Cancer Care Continuum

Aberrant epigenetic modifications are an early event in carcinogenesis, with the epigenetic landscape continuing to change during tumor progression and metastasis—these observations suggest that specific epigenetic modifications could be used as diagnostic and prognostic biomarkers for many cancer types. DNA methylation, post-translational histone modifications, and non-coding RNAs are all dysregulated in cancer and are detectable to various degrees in liquid biopsies such as sputum, urine, stool, and blood. Here, we will focus on the application of liquid biopsies, as opposed to tissue biopsies, because of their potential as non-invasive diagnostic tools and possible use in monitoring therapy response and progression to metastatic disease. This includes a discussion of septin-9 (SEPT9) DNA hypermethylation for detecting colorectal cancer, which is by far the most developed epigenetic biomarker assay. Despite their potential as prognostic and diagnostic biomarkers, technical issues such as inconsistent methodology between studies, overall low yield of epigenetic material in samples, and the need for improved histone and non-coding RNA purification methods are limiting the use of epigenetic biomarkers. Once these technical limitations are overcome, epigenetic biomarkers could be used to monitor cancer development, disease progression, therapeutic response, and recurrence across the entire cancer care continuum.

Runt-related Transcription Factor 3 Promoter Hypermethylation and Gastric Cancer Risk: A Meta-analysis

OBJECTIVE

The aim of this study was to investigate the correlation between runt-related transcription factor 3 (RUNX3) gene promoter hypermethylation and gastric cancer risk by meta-analysis.

METHODS

By searching Medline, PubMed, Embase, Cochrane, Ovid and CNKI electronic databases, the open published studies about the association between RUNX3 gene promoter hypermethylation and gastric cancer risk were screened. The hypermethylation rate in cancer tissue and autologous control tissue (normal gastric tissue of gastric cancer patients) were extracted from each included study. The odds ratio (OR) and corresponding 95% confidence interval (95% CI) of RUNX3 gene promoter hypermethylation in cancer tissue versus autologous control tissue of gastric cancer patients were pooled with random or fixed effect models. The publication bias was evaluated by Begg's funnel plot and Egger's line regression test.

RESULTS

Finally, twenty three relevant studies were included in this meta-analysis. The hypermethylation rate in cancer tissue and autologous control tissue of gastric cancer patients were 0.56±0.16 and 0.18±0.22 respectively, which demonstrated a hypermethylation rate in cancer tissue significantly higher than that of autologous controls (P<0.05). A significant positive correlation of hypermethylation rate between cancer tissue and autologous control existed for the included 23 studies(r_pearson =0.62, P<0.05). For significant heterogeneity across the studies, the OR was pooled by random effects model. The combined OR was 8.06 with the 95% CI of 5.73~11.32, which indicated the hypermethylation frequency in cancer tissue was higher than that of autologous controls.

CONCLUSION

The RUNX3 gene promoter hypermethylation rate was much higher in cancer tissue than that of normal gastric tissue in patients with gastric cancer, which indicates a close association between gastric cancer and RUNX3 gene promoter hypermethylation. Furthermore, RUNX3 gene promoter hypermethylation may be a potential biomarker for gastric cancer diagnosis.

Clinicopathological significance of CHFR promoter methylation in gastric cancer: a meta-analysis

The mitotic checkpoint gene (CHFR) (Checkpoint with Forkhead-associated and Ring finger domains is a G2 phase/mitosis checkpoint and tumor-suppressor gene. Recent studies have reported the relationship of CHFR promoter methylation with clinicopathological significance of gastric cancer. However, the results remain unclear due to small size of sample. We pooled 15 studies including 827 gastric cancer patients and conducted a meta-analysis to investigate the clinicopathological significance of CHFR promoter methylation in gastric cancer. Our data revealed that the frequency of CHFR promoter methylation was higher in gastric cancer than in normal gastric tissue, Odd Ratio (OR) was 10.12 with 95% CI 5.17–19.79, p < 0.00001. Additionally, the rate of CHFR promoter methylation was significantly increased in high grade of gastric cancer compared to low grade, OR was 1.64 with 95% CI 1.00–2.68, p = 0.05. CHFR methylation was significantly associated with the positive lymph node metastasis, OR was 1.56 with 95% CI 1.05–2.32, p = 0.03. We concluded that CHFR could serve as a biomarker for diagnosis of gastric cancer, and a drug target for development of gene therapy in gastric cancer. CHFR promoter methylation is associated with tumor poor differentiation and lymph node metastasis.

Promoter hypermethylation of MGMT gene may contribute to the pathogenesis of gastric cancer: A PRISMA-compliant meta-analysis

BECKGROUND

The association of MGMT (O-methyguanine deoxyribonucleic acid methyltransferase) promoter hypermethylation with gastric cancer (GC) risk has been studied extensively, but the results remained unclear. Here, we performed a meta-analysis to evaluate whether promoter hypermethylation of the MGMT gene contributed to gastric pathogenesis.

METHODS

Relevant studies were identified by retrieving the PubMed, Web of Science, Embase, and China National Knowledge Infrastructure (CNKI) databases. The Newcastle-Ottawa Scale was applied to assess methodological quality of the included studies. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to evaluate the association of MGMT promoter hypermethylation with gastric pathogenesis. Moreover, STATA 12.0 software was used to summarize the extracted data in this meta-analysis.

RESULTS

Seventeen studies, comprising 1736 cases and 1291 controls, were included in this meta-analysis. The frequency of MGMT promoter hypermethylation in the GC group (32.97%) was significantly higher than those in the control group (18.00%) (OR = 2.83, CI = 1.93-4.15, P < .05). When stratified by cancer subtype, the results indicated that the frequency of MGMT promoter hypermethylation was significantly higher in gastric adenocarcinoma than in control group (OR = 3.47, CI = 1.06-11.35, P < .05). In addition, MGMT promoter hypermethylation significantly promoted distant metastasis and lymph node (LN) metastasis of gastric tumor (for distant metastasis, OR = 4.22, CI = 2.42-7.37, P < .05; for LN metastasis, OR = 1.56, CI = 1.14-2.13, P < .05). A significant association between MGMT promoter hypermethylation and TNM-stage was also found in the present meta-analysis (OR = 2.70, CI = 1.79-4.08, P < .05).

CONCLUSION

The results of this meta-analysis suggested that MGMT gene-promoter hypermethylation was significantly associated with an increased risk of GC, especially in Asians. Furthermore, MGMT gene-promoter hypermethylation might be correlated with the distant metastasis and LN metastasis of GC.

Association between CHFR gene hypermethylation and gastric cancer risk: a meta-analysis

BACKGROUND

The association between the hypermethylation of CHFR gene and gastric cancer risk has been investigated by a number of studies. However, the sample size of the majority of these studies was very small. To get a more a convincing conclusion, here we performed a meta-analysis of the previously published studies to assess the association between CHFR methylation and the risk of gastric cancer.

METHODS

Eligible studies were identified by searching the MEDLINE/PubMed, Embase, and Web of Science databases before May 2016 without any language restriction. The strength of the association was estimated by odds ratio with its 95% confidence interval (CI).

RESULTS

Totally 1,399 samples, including 758 gastric cancer cases and 641 controls, from 13 studies were included in the present meta-analysis. Compared with non-cancer controls, the pooled OR of CHFR methylation in gastric cancer patients was 9.08 (95% CI: 6.40-12.88, P<0.001), suggesting that the methylation of CHFR was significantly associated with increased risk of gastric cancer. Similar results were observed when subgroup analyses were performed stratified by country, ethnicity, and methylation testing methods.

CONCLUSION

Our meta-analysis showed a strong positive correlation between CHFR methylation and risk of gastric cancer, suggesting that CHFR methylation might be a promising biomarker for the diagnosis of gastric cancer.

The Correlation of MGMT Promoter Methylation and Clinicopathological Features in Gastric Cancer: A Systematic Review and Meta-Analysis

The silencing of the tumor suppressor gene O-6-methylguanine-DNA methyltransferase (MGMT) by promoter methylation commonly occurs in human cancers. The relationship between MGMT promoter methylation and gastric cancer (GC) remains inconsistent. This study aimed to evaluate the potential value of MGMT promoter methylation in GC patients. Electronic databases were searched to identify eligible studies. The pooled odds ratio (OR) and the corresponding 95% confidence interval (95% CI) were used to evaluate the effects of MGMT methylation on GC risk and clinicopathological characteristics. In total, 31 eligible studies including 2988 GC patients and 2189 nonmalignant controls were involved in meta-analysis. In the pooled analysis, MGMT promoter methylation was significantly associated with GC risk (OR = 3.34, P < 0.001) and substantial heterogeneity (P < 0.001). Meta-regression and subgroup analyses based on the testing method, sample material and ethnicity failed to explain the sources of heterogeneity. Interestingly, MGMT methylation showed a trend associated with gender, and methylation is lower in males compared with females (OR = 0.76, 95% CI = 0.56–1.03). We did not find a significant association in relation to tumor types, clinical stage, age status or H. pylori status in cancer (all P > 0.1). MGMT promoter methylation may be correlated with the prognosis of GCs in disease free survival (DFS) or overall survival (OS) for univariate analysis. MGMT promoter methylation may play a crucial role in the carcinogenesis and prognosis of GC. MGMT methylation was not correlated with tumor types, clinical stage, age status, H. pylori status. However, the result of the association of MGMT methylation and gender should be considered with caution.

Relationships between MGMT promoter methylation and gastric cancer: a meta-analysis

A DNA repair enzyme, O6-methylguanine-DNA methyltransferase (MGMT), plays an important role in the development of gastric cancers. However, the role of MGMT promoter methylation in the occurrence of gastric cancer and its relationships with clinicopathologic characteristics has not been fully clarified. Thus, we performed a meta-analysis to evaluate the associations between MGMT promoter methylation and gastric cancer. Electronic databases, including PubMed and Web of Science, were used to systematically search related clinical studies published in English until April 1, 2016. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to evaluate the associations between MGMT promoter methylation and gastric cancer risk or clinicopathologic characteristics. A total of 16 studies including 1,935 patients and 1,948 control persons were included in the analysis. Our study suggested that MGMT promoter methylation frequency was associated with gastric cancer (OR=3.46, 95% CI: 2.13–5.61, P<0.001). Moreover, the frequency of MGMT promoter methylation in the no lymph node metastasis group was lower than that in lymph node metastasis group, with marginal significance (OR=0.65, 95% CI: 0.42–1.01, P=0.05). Additionally, the methylation rate of the MGMT promoter was much lower in patients without distant metastases than in those with metastases (OR=0.27, 95% CI: 0.18–0.40, P<0.001). No significant association of MGMT promoter methylation with Lauren classification, tumor location, tumor invasion, or Helicobacter pylori infection was found. In conclusion, the methylation status of the MGMT promoter was related to gastric cancer risk, distant metastasis, and lymph node metastasis, which indicates that MGMT promoter methylation may play an important role in gastric cancer development.

Chidamide alleviates TGF-β-induced epithelial-mesenchymal transition in lung cancer cell lines

Transforming growth factor-β (TGF-β)-induced epithelial-mesenchymal transition is a critical process in the initiation of metastasis of various types of cancer. Chidamide is a class I histone deacetylase inhibitor with anti-tumor activity. This study investigated the effects of chidamide on TGF-β-mediated suppression of E-cadherin expression in adenocarcinomic lung epithelial cells and the molecular mechanisms involved in these effects. Western blot analysis, confocal microscopy, Quantitative methyl-specific PCR and bisulfite sequencing were used to evaluate the effects of different treatments on chidamide ameliorating TGF-β induced-E-cadherin loss. H3 acetylation binding to the promoter of E-cadherin was detected by chromatin immunoprecipitations (CHIP). We found that chidamide reduced the level of lung cancer cell migration observed using a Boyden chamber assay (as an indicator of metastatic potential). Chidamide inhibited TGF-β-induced SMAD2 phosphorylation and attenuated TGF-β-induced loss of E-cadherin expression in lung cancer cells by Western blotting and confocal microscopy, respectively. Quantitative methyl-specific PCR and bisulfite sequencing revealed that TGF-β-enhanced E-cadherin promoter methylation was ameliorated in cells treated with chidamide. We demonstrated that histone H3 deacetylation within the E-cadherin promoter was required for TGF-β-induced E-cadherin loss; cell treatment with chidamide increased the H3 acetylation detected by CHIP. Taken together, our results demonstrate that TGF-β suppressed E-cadherin expression by regulating promoter methylation and histone H3 acetylation. Chidamide significantly enhanced E-cadherin expression in TGF-β-treated cells and inhibited lung cancer cell migration. These findings indicate that chidamide has a potential therapeutic use due to its capacity to prevent cancer cell metastasis.

Gene methylation profile of gastric cancerous tissue according to tumor site in the stomach

Background

There is considerable information on the methylation of the promoter regions of different genes involved in gastric carcinogenesis. However, there is a lack of information on how this epigenetic process differs in tumors originating at different sites in the stomach.

The aim of this study is to assess the methylation profiles of the MLH1, MGMT, and DAPK-1 genes in cancerous tissues from different stomach sites.

Methods

Samples were acquired from 81 patients suffering stomach adenocarcinoma who underwent surgery for gastric cancer in the Lithuanian University of Health Sciences Hospital Kaunas Clinics in 2009–2012. Gene methylation was investigated with methylation-specific PCR. The study was approved by the Lithuanian Biomedical Research Ethics Committee.

Results

The frequencies of methylation in cancerous tissues from the upper, middle, and lower thirds of the stomach were 11.1, 23.1, and 45.4 %, respectively, for MLH1; 22.2, 30.8, and 57.6 %, respectively, for MGMT; and 44.4, 48.7, and 51.5 %, respectively, for DAPK-1. MLH1 and MGMT methylation was observed more often in the lower third of the stomach than in the upper third (p < 0.05). In the middle third, DAPK-1 promoter methylation was related to more-advanced disease in the lymph nodes (N2–3 compared with N0–1 [p = 0.02]) and advanced tumor stage (stage III rather than stages I–II [p = 0.05]). MLH1 and MGMT methylation correlated inversely when the tumor was located in the lower third of the stomach (coefficient, –0.48; p = 0.01). DAPK-1 and MLH1 methylation correlated inversely in tumors in the middle-third of the stomach (coefficient, –0.41; p = 0.01).

Conclusion

Gene promoter methylation depends on the gastric tumor location.

Cancer type-specific epigenetic changes: gastric cancer

Gastric cancer (GC) remains a major cause of mortality despite declining rate in the world. Epigenetic alterations contribute significantly to the development and progression of gastric tumors. Epigenetic refers to the number of modifications of the chromatin structure that affect gene expression without altering the primary sequence of DNA, and these changes lead to transcriptional activation or silencing of the gene. Over the years, the study of epigenetic processes has increased, and novel therapeutic approaches have emerged. This chapter summarizes the main epigenomic mechanisms described recently involved in gastric carcinogenesis, focusing on the roles that aberrant DNA methylation, histone modifications (histone acetylation and methylation), and miRNAs (oncogenic and tumor suppressor function of miRNA) play in the onset and progression of gastric tumors. Clinical implications of these epigenetic alterations in GC are also discussed.

Methylation-mediated gene silencing as biomarkers of gastric cancer: A review

Despite a decline in the overall incidence of gastric cancer (GC), the disease remains the second most common cause of cancer-related death worldwide and is thus a significant global health problem. The best means of improving the survival of GC patients is to screen for and treat early lesions. However, GC is often diagnosed at an advanced stage and is associated with a poor prognosis. Current diagnostic and therapeutic strategies have not been successful in decreasing the global burden of the disease; therefore, the identification of reliable biomarkers for an early diagnosis, predictive markers of recurrence and survival and markers of drug sensitivity and/or resistance is urgently needed. The initiation and progression of GC depends not only on genetic alterations but also epigenetic changes, such as DNA methylation and histone modification. Aberrant DNA methylation is the most well-defined epigenetic change in human cancers and is associated with inappropriate gene silencing. Therefore, an increasing number of genes methylated at the promoter region have been targeted as possible biomarkers for different purposes, including early detection, classification, the assessment of the tumor prognosis, the development of therapeutic strategies and patient follow-up. This review article summarizes the current understanding and recent evidence regarding DNA methylation markers in GC with a focus on the clinical potential of these markers.

Perspectives on new biomarkers in gastric cancer: Diagnostic and prognostic applications

Gastric cancer is considered one of the most deadly tumors worldwide. Even with the decline in its incidence, the mortality rate of this disease has remained high, mainly due to its late diagnosis and to the lack of precise prognostic markers. The main purpose of this review is to present genetic, epigenetic and proteomic molecular markers that may be used in a diagnostic and prognostic manner and to discuss the pros and cons of each type of marker for improving clinical practice. In this sense, we observed that the use of genetic markers, especially mutations and polymorphisms, should be carefully considered, as they are strongly affected by ethnicity. Proteomic-based markers show promise, but the higher costs of the associated techniques continue to make this approach expensive for routine use. Alternatively, epigenetic markers appear to be very promising, as they can be detected in bodily fluids as well as tissues. However, such markers must be used carefully because epigenetic changes may occur due to environmental factors and aging. Despite the advances in technology and its access, to date, there are few defined biomarkers of prognostic and diagnostic use for gastric tumors. Therefore, the use of a panel of several approaches (genetic, epigenetic and proteomic) should be considered the best alternative for clinical practice.

p16 Methylation is associated with chemosensitivity to fluorouracil in patients with advanced gastric cancer

No effective biomarkers have been confirmed to predict chemosensitivity for patients with gastric cancer. The purpose of this study was to investigate whether DNA methylation is associated with chemosensitivity in patients with gastric cancer. Tumors and matched non-tumor biopsy tissues collected from 134 advanced gastric cancer (AGC) patients prior to fluorouracil-based chemotherapy were retrospectively analyzed. The methylation status of p16, E-cadherin (CDH1), MGMT (O-6-methylguanine-DNA methyltransferase), and human mutL homolog 1 (hMLH1) was evaluated using a Methylight assay, and the association between p16 methylation and the sensitivity of 5-fluorouracil in cell lines was determined by in vitro assay. The methylation of p16 (17.9 vs. 0 %, P = 0.002), CDH1 (20.9 vs. 2.2 %, P < 0.001), MGMT (17.9 vs. 0 %, P = 0.052), and hMLH1 (14.9 vs. 2.2 %, P = 0.024) was more common in gastric cancer tissues (n = 134) than in non-tumor tissues (n = 46). For all patients, a reverse correlation was only found between p16 methylation and clinical response (P = 0.017), which suggested that p16 methylation might be associated with chemosensitivity of fluorouracil in gastric cancer patients. Results from in vitro experiments demonstrated that p16 methylation was closely correlated with the sensitivity of 5-fluorouracil in gastric cancer cells. The present results indicated that the methylation of p16, CDH1, MGMT, and hMLH1 was both frequent and specific in gastric cancer tissues. p16 Methylation might be used to predict chemosensitivity of fluorouracil for patients with AGC when validated in large samples in the future.

DNA and histone methylation in gastric carcinogenesis

Epigenetic alterations contribute significantly to the development and progression of gastric cancer, one of the leading causes of cancer death worldwide. Epigenetics refers to the number of modifications of the chromatin structure that affect gene expression without altering the primary sequence of DNA, and these changes lead to transcriptional activation or silencing of the gene. Over the years, the study of epigenetic processes has increased, and novel therapeutic approaches that target DNA methylation and histone modifications have emerged. A greater understanding of epigenetics and the therapeutic potential of manipulating these processes is necessary for gastric cancer treatment. Here, we review recent research on the effects of aberrant DNA and histone methylation on the onset and progression of gastric tumors and the development of compounds that target enzymes that regulate the epigenome.

Nickel-induced epithelial-mesenchymal transition by reactive oxygen species generation and E-cadherin promoter hypermethylation

Epithelial-mesenchymal transition (EMT) is considered a critical event in the pathogenesis of lung fibrosis and tumor metastasis. During EMT, the expression of differentiation markers switches from cell-cell junction proteins such as E-cadherin to mesenchymal markers such as fibronectin. Although nickel-containing compounds have been shown to be associated with lung carcinogenesis, the role of nickel in the EMT process in bronchial epithelial cells is not clear. The aim of this study was to examine whether nickel contributes to EMT in human bronchial epithelial cells. We also attempted to clarify the mechanisms involved in NiCl(2)-induced EMT. Our results showed that NiCl(2) induced EMT phenotype marker alterations such as up-regulation of fibronectin and down-regulation of E-cadherin. In addition, the potent antioxidant N-acetylcysteine blocked EMT and expression of HIF-1α induced by NiCl(2), whereas the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine restored the down-regulation of E-cadherin induced by NiCl(2). Promoter hypermethylation of E-cadherin, determined by quantitative real time methyl-specific PCR and bisulfate sequencing, was also induced by NiCl(2). These results shed new light on the contribution of NiCl(2) to carcinogenesis. Specifically, NiCl(2) induces down-regulation of E-cadherin by reactive oxygen species generation and promoter hypermethylation. This study demonstrates for the first time that nickel induces EMT in bronchial epithelial cells.

CHFR: a key checkpoint component implicated in a wide range of cancers

CHFR (Checkpoint with Forkhead-associated and RING finger domains) has been implicated in a checkpoint regulating entry into mitosis. However, the details underlying its roles and regulation are unclear due to conflicting lines of evidence supporting different notions of its functions. We provide here an overview of how CHFR is thought to contribute towards regulating mitotic entry and present possible explanations for contradictory observations published on the functions and regulation of CHFR. Furthermore, we survey key data showing correlations between promoter hypermethylation or down-regulation of CHFR and cancers, with a view on the likely reasons why different extents of correlations have been reported. Lastly, we explore the possibilities of exploiting CHFR promoter hypermethylation status in diagnostics and therapeutics for cancer patients. With keen interest currently focused on the association between hypermethylation of CHFR and cancers, details of how CHFR functions require further study to reveal how its absence might possibly contribute to tumorigenesis.

CHFR suppression by hypermethylation sensitizes endometrial cancer cells to paclitaxel

OBJECTIVE

Impairment of a cell cycle checkpoint is often associated with sensitivity to chemotherapeutic drugs. Here, we studied the correlations between the checkpoint with forkhead-associated and ring finger (CHFR) gene expression and responses to paclitaxel in endometrial cancer cells.

METHODS

We cultured 6 endometrial cancer cell lines exposed to paclitaxel, studied the cell cytotoxicity, cell cycle distribution, CHFR expression, and methylation status before and after a demethylation agent (5-aza) treatment. CHFR was silenced by small interfering RNA (siRNA). Then we examined tumor growth and CHFR expression with paclitaxel alone or combined with 5-aza pretreatment in vivo.

RESULTS

We found that HEC-1B, RL-952, and AN3CA cells were sensitive to paclitaxel. Moreover, CHFR was weakly expressed in these cells, whereas paclitaxel-resistant cells (ISH, HEC-1A, and KLE) had high CHFR expression. Then we found that restored expression of CHFR by demethylation decreased the sensitivity to paclitaxel in AN3CA cells. In addition, cells with CHFR demethylation resulted in G2/M phase arrest that induced to paclitaxel resistance. These results were confirmed again in small interfering RNA-transfected HEC-1A cells. Furthermore, in nude mice model, restored expression of CHFR by demethylation inhibited tumor growth and decreased sensitivity to paclitaxel.

CONCLUSION

Our data suggest that CHFR suppression regulated by hypermethylation may sensitize endometrial cancer cells to paclitaxel, and CHFR may be a promising marker to predict the response of endometrial cancer to paclitaxel.

Identification of inguinofemoral lymph node metastases by methylation markers in vulvar cancer

OBJECTIVE

Lymph node status in early-stage vulvar cancer can be accurately assessed by the sentinel-node (SN) procedure. Molecular techniques, such as DNA-methylation assay, might improve SN assessment. In this study, we selected methylation markers for vulvar cancer and determined if these methylation markers were suitable for lymph node assessment.

METHODS

We performed methylation specific PCR on DNA isolated from primary tumors, metastatic lymph nodes, and negative lymph nodes from twenty vulvar cancer patients using the following genes: P16INK4a, MGMT, TWIST1, CADM1, TERT, and TFPI2. For P16INK4a and MGMT immunohistochemistry was performed on primary tumors and metastatic lymph nodes in order to explore intratumor heterogeneity in gene expression patterns.

RESULTS

TERT was methylated in all vulvar cancers, P16INK4a in 13/20, TFPI2 in 12/20, CADM1 in 11/20, MGMT in 9/20, and TWIST1 in 7/20. A panel of three methylation markers (P16INK4a, TERT and TFPI2) reached a sensitivity of 67% and specificity of 100% for detection of metastatic lymph nodes. Immunohistochemistry showed intratumor heterogeneity for expression of P16INK4a and MGMT in respectively 55% and 45% of primary tumors.

CONCLUSIONS

Our study shows methylation for one or more methylation markers in all vulvar cancers. Despite a specificity of 100% our panel of three methylation markers had only moderate sensitivity for metastatic lymph node detection, thereby limiting its applicability for lymph node assessment. Intratumor heterogeneity for expression of P16INK4a and MGMT may reflect intratumor heterogeneity for methylation patterns and thereby in general explain the moderate sensitivity of our marker panel for detection of metastases.

Association between RUNX3 promoter methylation and gastric cancer: a meta-analysis

Background

Runt-related transcription factor 3 (RUNX3) is a member of the runt-domain family of transcription factors and has been reported to be a candidate tumor suppressor in gastric cancer. However, the association between RUNX3 promoter methylation and gastric cancer remains unclear.

Methods

We systematically reviewed studies of RUNX3 promoter methylation and gastric cancer published in English or Chinese from January 2000 to January 2011, and quantified the association between RUNX3 promoter methylation and gastric cancer using meta-analysis methods.

Results

A total of 1740 samples in 974 participants from seventeen studies were included in the meta-analysis. A significant association was observed between RUNX3 promoter methylation and gastric cancer, with an aggregated odds ratio (OR) of 5.63 (95%CI 3.15, 10.07). There was obvious heterogeneity among studies. Subgroup analyses (including by tissue origin, country and age), meta-regression were performed to determine the source of the heterogeneity. Meta-regression showed that the trend in ORs was inversely correlated with age. No publication bias was detected. The ORs for RUNX3 methylation in well-differentiated vs undifferentiated gastric cancers, and in intestinal-type vs diffuse-type carcinomas were 0.59 (95%CI: 0.30, 1.16) and 2.62 (95%CI: 1.33, 5.14), respectively. There were no significant differences in RUNX3 methylation in cancer tissues in relation to age, gender, TNM stage, invasion of tumors into blood vessel or lymphatic ducts, or tumor stage.

Conclusions

This meta-analysis identified a strong association between methylation of the RUNX3 promoter and gastric cancer, confirming the role of RUNX3 as a tumor suppressor gene.

Aberrant gene methylation is a biomarker for the detection of cancer cells in peritoneal wash samples from advanced gastric cancer patients

PURPOSE

To assess whether gene methylation in peritoneal fluid (PF) is clinically feasible for determining micrometastasis to the peritoneum in gastric cancer.

METHODS

The gene methylation of BNIP3, CHFR, CYP1B1, MINT25, SFRP2, and RASSF2 were analyzed in 107 specimens of PF by quantitative methylation-specific polymerase chain reaction. All patients were placed into one of 3 groups: group A (n = 42), patients with depth of cancer invasion at muscularis propria (MP) or less than MP; group B (n = 45), depth of cancer invasion beyond the MP; and group C (n = 20), histologically diagnosed peritoneal metastasis or cancer cells cytologically defined in the peritoneal cavity. Patients in both groups A and B were diagnosed as having no cancer cells by peritoneal cytology and histology.

RESULTS

The methylation status of the 6 genes was found to be significantly different among the 3 groups (group A, 0-5%; group B, 0-15%; group C, 15-45%; P < 0.01). Furthermore, the rate of positive methylation in any of the 6 genes was significantly different in each group (group A, 7%; group B, 20%; group C, 75%; P < 0.001). Three of 9 patients in group B with positive methylation in any of 6 genes experienced peritoneal recurrence. On the other hand, only 1 of 36 patients without gene methylation experienced peritoneal recurrence (P < 0.05).

CONCLUSIONS

DNA methylation in PFs is a possible marker detecting occult neoplastic cells on the peritoneum. Methylation analysis along with a cytological examination might therefore improve the positive detection of cancer cells in PF of gastric cancer.