DNA hypermethylation of tumor-related genes in gastric carcinoma

IL10 hypomethylation is associated with the risk of gastric cancer

Interleukin-10 (IL10), a pleiotropic cytokine secreted by type-2 helper (Th2) T cells, contributes to the oncogenic activation or inactivation of tumor-suppressor genes. The present study investigated whether hypomethylation of IL10 CpG island (CGI) was associated with the risk of developing gastric cancer (GC) and the prognosis of patients with GC. A fragment (hg18, chr1: 206945638-206945774) at the CGI of IL10 was selected for the present methylation assay. Quantitative methylation-specific PCR was used to evaluate the methylation of IL10 CGI in 117 tumor samples from patients with GC. The results demonstrated that IL10 CGI methylation was significantly lower in the tumor tissues compared with that in the paired adjacent non-tumor tissues (median percentage of methylated reference, 29.16 vs. 42.82%, respectively; P=4×10⁻⁸). Furthermore, results from receiver operating characteristic curve analysis identified a significant area under the curve of 0.706, with a sensitivity and a specificity of 77.8 and 58.1%, respectively, between cancer tissues and paired adjacent non-tumor tissues. Furthermore, the methylation of IL10 CGI was significantly associated with patients' age at diagnosis (r=−0.201; P=0.03). Subgroup analyses demonstrated that the association between IL10 CGI hypomethylation and the risk of GC was specific for patients with low differentiation (P=1×10⁻⁷) and Borrmann types III+IV (P=1×10⁻⁷). In addition, IL10 CGI hypomethylation was significantly associated with the risk of GC for patients without smoking history (P=3×10⁻⁷) or a family history of cancer (P=2×10⁻⁷). The results from Kaplan-Meier survival analysis demonstrated that IL10 CGI hypomethylation was associated with a significantly shorter overall survival of patients with GC (P=0.041). Similar results were identified for patients with GC who did not have smoking history (P=0.037) or a family history of cancer (P=0.049). The results from this study demonstrated that IL10 CGI hypomethylation may be considered as a potential biomarker for the diagnosis and prognosis of patients with GC in the Chinese population.

GSTP1 methylation in cancer: a liquid biopsy biomarker?

The coding region of GSTP1 gene is preceded by a large CpG-rich region that is frequently affected by methylation. In many cancer types, GSTP1 is affected by hypermethylation and, as a consequence, it has a low expression. The aim of this review is to give an overview on GSTP1 methylation studies with a special focus on liquid biopsy, thus to summarize methods, results, sample types, different diseases, to have a complete information regarding this promising epigenetic biomarker. We used all the most valuable scientific search engines (PubMed, Medline, Scopus and Web of Science) searching the following keywords: GSTP1, methylation, cancer, urine, serum, plasma and blood. GSTP1 is a largely investigated tissue biomarker in several malignancies such as prostate, breast, lung and hepatocellular carcinoma with good performances especially for diagnostic purposes. As a liquid biopsy biomarker, it has been mainly investigated in prostate cancer (PCa) where it showed a high specificity but a low sensitivity; thus, it is recommended in combination with other biomarkers. Despite the large number of published papers and the promising results, GSTP1 has not yet entered the clinical practice even for PCa diagnosis. For this reason, further large and prospective studies are needed to validate this assay.

The Relevance of Gender in Tumor-Influencing Epigenetic Traits

Tumorigenesis as well as the molecular orchestration of cancer progression are very complex mechanisms that comprise numerous elements of influence and regulation. Today, many of the major concepts are well described and a basic understanding of a tumor's fine-tuning is given. Throughout the last decade epigenetics has been featured in cancer research and it is now clear that the underlying mechanisms, especially DNA and histone modifications, are important regulators of carcinogenesis and tumor progression. Another key regulator, which is well known but has been neglected in scientific approaches as well as molecular diagnostics and, consequently, treatment conceptualization for a long time, is the subtle influence patient gender has on molecular processes. Naturally, this is greatly based on hormonal differences, but from an epigenetic point of view, the diverse susceptibility to stress and environmental influences is of prime interest. In this review we present the current view on which and how epigenetic modifications, emphasizing DNA methylation, regulate various tumor diseases. It is our aim to elucidate gender and epigenetics and their interconnectedness, which will contribute to understanding of the prospect molecular orchestration of cancer in individual tumors.

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.

CYP1A1 and GSTP1 gene variations in breast cancer: a systematic review and case-control study

In first part of this study, a systematic review was designed to explore the involvement of CYP1A1 and GSTP1 genes in breast cancerogenesis. Based on systematic review, we designed a study to screen CYP1A1 and GSTP1 genes for mutation and their possible association with breast carcinogenesis. A total of 400 individuals were collected and analyzed by PCR-SSCP. After sequence analysis of coding region of CYP1A1 we identified eleven mutations in different exons of respective gene. Among these eleven mutations, ~3 folds increased breast cancer risk was found associated with Asp82Glu mutation (OR 2.99; 95% CI 1.26-7.09), with Ser83Thr mutation (OR 2.99; 95% CI 1.26-7.09) and with Glu86Ala mutation (OR 3.18; 95% CI 1.27-7.93) in cancer patients compared to controls. Furthermore, ~4 folds increase in breast cancer risk was found associated with Asp347Glu, Phe398Tyr and 5178delT mutations (OR 3.92; 95% CI 1.35-11.3) in patients compared to controls. The sequence analysis of GSTP1 resulted in identification of total five mutations. Among these five mutations, ~3 folds increase in breast cancer risk was observed associated with 1860G>A mutation, with 1861-1876delCAGCCCTCTGGAGTGG mutation (OR 2.70; 95% CI 1.10-6.62) and with 1861C>A mutation (OR 2.97; 95% CI 1.01-8.45) in cancer patients compared to controls. Furthermore, ~5 folds increase in breast cancer risk was associated with 1883G>T mutation (OR 4.75; 95% CI 1.46-15.3) and ~6 folds increase in breast cancer risk was found associated with Iso105Val mutation (OR 6.43; 95% CI 1.41-29.3) in cancer patients compared to controls. Our finding, based on systematic review and experimental data suggest that the polymorphic CYP1A1 and GSTP1 genes may contribute to risk of developing breast 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.

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.

AID, p53 and MLH1 expression in early gastric neoplasms and the correlation with the background mucosa

A number of tumor-associated genes have been associated with gastric cancer development. The present study evaluated differences in tumor-associated protein expression and phenotype among early gastric neoplasms, and correlated these data with those of the background mucosa. The expression of activation-induced cytidine deaminase (AID), p53 and MLH1 in 151 early gastric neoplasms [22 gastric adenomas, 92 intramucosal carcinomas (MCs), and 37 submucosal carcinomas (SMCs)] was examined immunohistochemically and compared with that of the corresponding background mucosal condition. The cellular phenotypes of the neoplasms and the corresponding background intestinal metaplasia were also determined. Aberrant AID, p53 and MLH1 expression was detected in 36.4, 0 and 0% of the adenomas, in 35.9, 32.6 and 16.3% of the MCs, and in 56.8, 62.2 and 21.6% of the SMCs, respectively. The frequency of aberrant AID and p53 expression in the SMCs was significantly increased compared with that in the MCs (AID, P<0.05; p53, P<0.01). Aberrant AID expression was significantly associated with p53 overexpression in the SMCs (P<0.01), but not in the adenomas or MCs. In addition, AID expression was associated with the severity of mononuclear cell activity in the non-cancerous mucosa adjacent to the tumor (P<0.05), particularly in the SMC cases. The percentage of MCs (34.8%) and SMCs (24.3%) that were of the gastric phenotype was higher compared with the percentage of adenomas (18.2%). These results indicated that p53 and MLH1 expression and a gastric phenotype may be important for carcinogenesis, and that chronic inflammation and AID and p53 expression are associated with submucosal progression.

DNA promoter methylation as a diagnostic and therapeutic biomarker in gallbladder cancer

Gallbladder cancer is an infrequent neoplasia with noticeable geographical variations in its incidence around the world. In Chile, it is the main cause of death owing to cancer in women over 40 years old, with mortality rates up to 16.5 per 100,000 cases. The prognosis is poor with few therapeutic options; in advanced cases there is only a 10% survival at 5 years.

Several studies mention the possible role of DNA methylation in gallbladder carcinogenesis. This epigenetic modification affects tumor suppressor genes involved in regulation pathways, cell cycle control, cell adhesion and extracellular matrix degradation, in a sequential and cumulative way. Determining DNA methylation patterns would allow them to be used as biomarkers for the early detection, diagnosis, prognosis and/or therapeutic selection in gallbladder cancer.

Expression of AID, P53, and Mlh1 proteins in endoscopically resected differentiated-type early gastric cancer

AIM

To analyze the expression of the tumor-related proteins in differentiated-type early gastric carcinoma (DEGC) samples.

METHODS

Tumor specimens were obtained from 102 patients (75 males and 27 females) who had received an endoscopic tumor resection at Tottori University Hospital between 2007 and 2009. Ninety-one cancer samples corresponded to noninvasive or intramucosal carcinoma according to the Vienna classification system, and 11 samples were submucosal invasive carcinomas. All of the EGCs were histologically differentiated carcinomas. All patients were classified as having Helicobacter pylori (H. pylori) infections by endoscopic atrophic changes or by testing seropositive for H. pylori IgG. All of the samples were histopathologically classified as either tubular or papillary adenocarcinoma according to their structure. The immunohistochemical staining was performed in a blinded manner with respect to the clinical information. Two independent observers evaluated protein expression. All data were statistically analyzed then.

RESULTS

The rates of aberrant activation-induced cytidine deaminase (AID) expression and P53 overexpression were both 34.3% in DEGCs. The expression of Mlh1 was lost in 18.6% of DEGCs. Aberrant AID expression was not significantly associated with P53 overexpression in DEGCs. However, AID expression was associated with the severity of mononuclear cell activity in the non-cancerous mucosa adjacent to the tumor (P = 0.064). The rate of P53 expression was significantly greater in flat or depressed tumors than in elevated tumors. The frequency of Mlh1 loss was significantly increased in distal tumors, elevated gross-type tumors, papillary histological-type tumors, and tumors with a severe degree of endoscopic atrophic gastritis (P < 0.05).

CONCLUSION

Aberrant AID expression, P53 overexpression, and the loss of Mlh1 were all associated with clinicopathological features and gastric mucosal alterations in DEGCs. The aberrant expression of AID protein may partly contribute to the induction of nuclear P53 expression.

Clinicopathological and patient characteristics of early gastric neoplasia endoscopically resected with loss of Mlh1 expression

Hypermethylation of the promoter region of the MLH1 gene leads to loss of Mlh1 protein expression and plays a key role in the development of gastric cancer. Little is known about the association between Mlh1 expression and the clinicopathological and patient characteristics in early gastric neoplasia, particularly in endoscopically resected tumors. Immunohistochemistry was used to examine Mlh1 expression in 140 early gastric neoplasias obtained by endoscopic resection and comprising 31 gastric adenomas (GAs) and 109 early gastric cancers (EGCs), and compared them to corresponding clinicopathological and patient data. P53 expression and phenotypic profiles were also analyzed. The rate of reduced Mlh1 expression and P53 overexpression was 9.6 and 6.5% in GAs, and 27.5 and 27.5% in EGCs, respectively. In elderly patients (≥65 years of age), the aberrant expression of Mlh1 in EGCs was more significant in female than in male patients (59.9 vs. 29.8%; P=0.016). In addition, the frequency of aberrant Mlh1 expression in EGCs increased significantly in patients with oncological family histories and elevated gross type (P=0.033 and P=0.04, respectively). Moreover, a significant correlation was observed among aberrant Mlh1, P53-negative and HGM expression. The present findings suggest that loss of Mlh1 expression is associated with age, gender, oncological family history and tumor growth pattern in EGC. Patient and tumor characteristics are key factors in the screening, surveillance and diagnosis of early gastric neoplasia, particularly in elderly individuals.

CpG methylation and reduced expression of O6-methylguanine DNA methyltransferase is associated with Helicobacter pylori infection

BACKGROUND & AIMS

The gastric epithelium genome undergoes extensive epigenetic alterations during Helicobacter pylori-induced gastritis. Expression of the gene encoding the DNA repair protein O6-methylguanine DNA methyltransferase (MGMT) might be reduced via hypermethylation of its promoter in patients with H pylori gastritis. We characterized expression of MGMT and its epigenetic regulation via CpG methylation in gastric tissue from patients with H pylori gastritis and investigated the effects of H pylori infection eradication on MGMT expression.

METHODS

Gastric biopsy samples were collected from patients with H pylori gastritis before and after eradication and from H pylori-negative control subjects. AGS cells were cocultured with H pylori to study the effects of H pylori infection on MGMT RNA, protein expression, and CpG methylation.

RESULTS

CpG methylation of MGMT was more frequent in the gastric mucosa of patients with H pylori gastritis (69.7%) than in those without (28.6%, P = .022). MGMT methylation was significantly reduced after H pylori eradication (from 70% to 48% of cases, P = .039), and mean levels of CpG methylation decreased from 12.6% to 5.7% (P = .025), increasing MGMT expression. MGMT methylation was significantly associated with CagA-positive H pylori (P = .035). H pylori reduced MGMT protein and RNA levels and induced MGMT CpG methylation in gastric AGS cells.

CONCLUSIONS

H pylori gastritis, particularly in patients infected with H pylori CagA-positive strains, is associated with hypermethylation of MGMT and reduced levels of MGMT in the gastric epithelium. MGMT promoter methylation is partially reversible after eradication of H pylori infection. These data indicate that DNA repair is disrupted during H pylori gastritis, increasing mutagenesis in H pylori-infected gastric mucosa.

Relationship between mismatch repair gene hMSH2 promoter methylation and gastric carcinoma

AIM: To detect the role of methylation of the 5'CpG island located in the promoter region of the human mutS homolog-2 (hMSH2) gene in the pathogenesis of gastric carcinoma.

METHODS: The methylation of the hMSH2 promoter was examined by methylation-specific polymerase chain reaction (MSP) in 40 gastric carcinoma specimens, 40 matched cancer-adjacent mucosa specimens, 14 chronic atrophic gastritis (CAG) specimens, and 6 chronic superficial gastritis (CSG) specimens.

RESULTS: The methylation of the hMSH2 promoter was detected in 24 out of the 40 (60%) gastric cancer specimens, 15 out of the 40 (37.5%) cancer-adjacent mucosa specimens, and 5 out of the 14 (35.7%) CAG specimens. No methylation was detected in 6 CSG specimens. The rate of hMSH2 promoter methylation was significantly higher in gastric cancer tissue than in non-carcinoma tissue (P < 0.05). No significant differences were detected in the rates of hMSH2 promoter methylation among cancer-adjacent mucosa specimens, CAG specimens and CSG specimens. The rate of hMSH2 promoter methylation is not correlated with the clinicopathological parameters of gastric cancer.

CONCLUSION: The hMSH2 promoter methylation may be a main mechanism responsible for mismatch repair (MMR) dysfunction that is involved in the development, but not the progression, of gastric cancer.

Analysis of DNA methylation status of the promoter of human telomerase reverse transcriptase in gastric carcinogenesis

BACKGROUND AND AIMS

Telomerase is expressed in normal somatic cells and reactivated in majority of tumor cells. Human telomerase reverse transcriptase (hTERT), a catalytic subunit of telomerase, is a rate-limiting factor of telomerase activity. Evidence has shown that gastric cancer is the result of genetics and epignomics. DNA methylation is one of the most important research fields in epigenomics. It is one of the mechanisms resulting in gene silencing in carcinogenesis.

METHODS

Genomic DNAs were extracted from normal gastric mucosa, precancerous lesions and gastric cancer samples and were modified by sodium bisulfite. The modified genomic DNAs were amplified by PCR with primers that did not contain CpG sites. Each PCR product was sequenced. By matching the sequencing results and the original sequence, the status of each sample was obtained. PCR was carried out to identify hTERT expression.

RESULTS

The promoter of hTERT in gastric cancer was more methylated than in the precancerous lesions and normal gastric mucosa (p<0.05). hTERT was absent in normal gastric mucosa and its positive rate was higher in gastric cancer than in precancerous lesions (p<0.05).

CONCLUSIONS

hTERT promoter in gastric cancer was more methylated than in the precancerous lesions and normal gastric mucosa. This may suggest that the degree of methylation of the hTERT promoter was increased during gastric carcinogenesis and may be a potential biological maker in early diagnosis of gastric cancer. During gastric carcinogenesis, expression of hTERT was increased. This may suggest that methylation of hTERT may influence expression of hTERT.

Aberrant methylation of DNA mismatch repair genes in elderly patients with sporadic gastric carcinoma: A comparison with younger patients

BACKGROUND

Hypermethylation of promoters that regulate the expression of DNA repair genes is associated with gastric carcinoma (GC). Little is known regarding the association between age of disease onset and differences in molecular profiles.

METHODS

The two study groups consisted of 100 elderly patients and 100 younger patients. The aberrant DNA methylation patterns of four mismatch repair genes, hMLH1, hMSH2, hMSH3, and MGMT, were compared by bisulfite modification and methylation-specific PCR (MSP).

RESULTS

The methylation frequencies for hMLH1 and hMSH3 were significantly higher for the elderly than for the younger GC patients (P < 0.001 and P = 0.031, respectively). A significant correlation was observed between aberrant hMLH1, hMSH3, and MGMT methylation and the loss of hMLH1, hMSH3, and MGMT protein expression (P < 0.001, P = 0.002, and P = 0.001, respectively). The prevalence of aberrant hMLH1 and hMSH3 methylation increased significantly with age.

CONCLUSION

These results suggest that the methylation of hMLH1 and hMSH3 is age related and thus may play an important role in gastric carcinogenesis in the elderly. Screening for hMLH1 and hMSH3 methylation may have clinical significance for the evaluation of elderly patients with GC.

Promoter hypermethylation of mismatch repair genes, hMLH1 and hMSH2 in oral squamous cell carcinoma

OBJECTIVES

Major risk factors of oral squamous cell carcinoma (OSCC) are environmental and can lead to DNA mutagenesis. Mismatch repair (MMR) system functions to repair small DNA lesions, which can be targeted for promoter hypermethylation. We therefore wanted to test whether hypermethylation of MMR genes (hMLH1, hMSH2) could contribute to oral carcinogenesis by correlating the information to patient clinical data.

METHODS

Genomic DNA was extracted from 28 OSCC and six normal oral epithelium samples. The methylation status of the two MMR genes was assessed using Methylation Specific PCR after DNA modification with sodium bisulfite. Serial sections of the same tissues were immunostained with antibodies against hMLH1 and hMSH2 protein.

RESULTS

Promoter hypermethylation was observed in 14/28 OSCC cases. Remarkably, 100% of patients with multiple oral malignancies showed hypermethylation in hMLH1 or hMSH2 compared with 31.5% of single tumor patients. In 10 cancer cases, expression of the hMLH1 and hMSH2 genes by immunostaining showed reduced or absence of expression of one of the genes, although some did not reflect the methylation status.

CONCLUSIONS

Hypermethylation of hMLH1 and hMSH2 might play a role in oral carcinogenesis and may be correlated with a tendency to develop multiple oral malignancies.

Methylation status of Runx3 gene in human gastric cancer

AIM: To investigate the relationship between the methylation status of Runx3 gene and human primary gastric cancer.

METHODS: The methylation status of Runx3 gene in 38 gastric carcinoma specimens, the corresponding normal gastric mucosa and lymph nodes was detected by methylation-specific polymerase chain reaction (MS-PCR).

RESULTS: Aberrant methylation of Runx3 gene was detected in 73.7% of gastric cancer specimens, 65.8% of lymph nodes and 21.1% of the corresponding normal mucosa, and there were significant differences between the former two and the latter. Runx3 methylation was significantly correlated with the tumor size (P = 0.021), but not with the general types, differentiation degree, invasion depth and growth style of gastric cancer.

CONCLUSION: Aberrant methylation of Runx3 gene is a common event in the occurrence and progression of gastric cancer, which may provide useful information for the early diagnosis and assessment of lymph node metastasis.

Epigenetics, disease, and therapeutic interventions

Heritable changes in gene expression that do not involve coding sequence modifications are referred to as "epigenetic". Epigenetic mechanisms principally include DNA methylation and a variety of histone modifications, of which the best characterized is acetylation. DNA hypermethylation and histone hypoacetylation are hallmarks of gene silencing, while DNA hypomethylation and acetylated histones promote active transcription. Aberrant DNA methylation and histone acetylation have been linked to a number of age related disorders including cancer, autoimmune disorders and others. Since epigenetic alterations are reversible, modifying epigenetic marks contributing to disease development may provide an approach to designing new therapies. Herein we review the role of epigenetic changes in disease development, and recent advances in the therapeutic modification of epigenetic marks.

The role of sex in cardiac function and disease

In the past decade, increasing attention has been paid to the importance of sex in the etiology of cardiac dysfunction. While focus has been primarily on how sex modulates atherogenesis, it is becoming clear that sex is both a predictor of outcome and an independent risk factor for a number of other cardiac diseases. Animal models and human studies have begun to shed light on the mechanisms by which sex influences the function of cardiomyocytes in health and disease. This review will survey the current literature on cardiac diseases that are influenced by sex and discuss the intracellular mechanisms by which steroid sex hormones affect heart function. A theory on how sex may regulate myocardial energy metabolism to affect disease susceptibility and progression will be presented, as well as a discussion of how sex may influence outcomes of experiments on isolated cardiomyocytes by epigenetic marking.

Microsatellite instability and methylation of the DNA mismatch repair genes in head and neck cancer

BACKGROUND

Methylation in the promoter region of the DNA mismatch repair genes hMLH1 and hMSH2 and microsatellite instability at three loci were analyzed in the tumor tissue from patients with head and neck cancer.

METHODS

Microsatellite instability and promoter methylation were investigated by PCR, denaturing-polyacrylamide gel electrophoresis and digestion with methylation-specific restriction enzymes.

RESULTS

Microsatellite instability was observed in 41% of the patients. hMLH1 and hMSH2 genes were methylated in 47% and 30% of the patients, respectively. BAT25 and BAT26 instability were associated with age and histopathology, respectively. Methylation frequency of the hMLH1 gene promoter was significantly higher in patients displaying a high level of microsatellite instability. Instability at the BAT 26 and D2S123 loci were associated with the MSI-high status.

CONCLUSIONS

Our results indicate that microsatellite instability and modifications in the hMLH1 and hMSH2 genes are implicated in a significant proportion of the patients with head and neck cancer.

Pathology and molecular biology of gastric cancer

Several attempts to classify gastric cancer (GCA) have been made over the past decades. Most successful, and widely used, is the classification by Laurén, which distinguishes, by microscopical morphology alone, two main cancer pathogeneses, diffuse (DGCA) and intestinal (IGCA) subtypes, which appear clearly as dissimilar clinical and epidemiological entities. Here we review the main differences in epidemiology, histopathology, and molecular pathology of the two main subtypes of gastric carcinomas based on Laurén classification. In clinical practice, however, clinical staging, particularly in predicting the survival, still remains superior to all classifications of gastric cancer independent of cancer type. The existence of local precursor lesions or conditions of IGCA tumours, i.e. Helicobacter pylori gastritis, atrophic gastritis (AG), intestinal metaplasia (IM), adenoma, dysplasia, and intramucosal neoplasia, is firmly established. The links of DGCA with intestinal-type epithelium, AG or IM are poor, or do not exist. So far, H. pylori gastritis is the only universal precursor condition for DGCA. It implies that AG and achlorhydria are of minor significance and infrequent in the development of DGCA but are important steps in that of IGCA. Despite an increasing body of data, the overall view on molecular pathology of GCA remains fragmentary. No consistent differences in the molecular pathology of GCA subtypes to meet the Laurén classification have been established. With the exception of TP53, no gene mutation occurring regularly in both histological types of GCA has been reported. Chromosomal aberrations and loss of heterozygosity seem to be non-specific and do not follow any consistent route in the progression of GCA. Microsatellite instability is more commonly found in IGCA than in DGCA. The present epigenetic data suggest that most of the decrease (or loss) of gene expression may be explained by promoter hypermethylation which is more often found in IGCA. In DGCA specific genes such as CDH1 are more often hypermethylated. Compared with GCA, in premalignant condition lesions gene mutations and chromosomal aberrations are infrequent. Epigenetic dysregulation might also represent a major mechanism for altered gene expression in premalignant stages in gastric carcinogenesis.