Role of methylation of the hMLH1 gene promoter in the development of gastric and colorectal carcinoma in the elderly

Helicobacter pylori-positive chronic atrophic gastritis and cellular senescence

BACKGROUND

Chronic atrophic gastritis (CAG) is a pathological stage in the Correa's cascade, whereby Helicobacter pylori (H. pylori) infection is the primary cause. Cellular senescence is an inducing factor for cancer occurrence and cellular senescence is an obvious phenomenon in gastric mucosal tissues of H. pylori-positive CAG patients.

METHODS

In this review, we collated the information on cellular senescence and H. pylori-positive CAG.

RESULTS

At present, only a few studies have observed the effect of cellular senescence on precancerous lesions. In combination with the latest research, this review has collated the information on cellular senescence and H. pylori-positive CAG from four aspects- telomere shortening, DNA methylation, increased reacive oxygen species (ROS) production, and failure of autophagy.

CONCLUSION

This is expected to be helpful for exploring the relevant mechanisms underlying inflammatory cancerous transformation and formulating appropriate treatment strategies.

The multifaceted roles of DNA repair and replication proteins in aging and obesity

Efficient mechanisms for genomic maintenance (i.e., DNA repair and DNA replication) are crucial for cell survival. Aging and obesity can lead to the dysregulation of genomic maintenance proteins/pathways and are significant risk factors for the development of cancer, metabolic disorders, and other genetic diseases. Mutations in genes that code for proteins involved in DNA repair and DNA replication can also exacerbate aging- and obesity-related disorders and lead to the development of progeroid diseases. In this review, we will discuss the roles of various DNA repair and replication proteins in aging and obesity as well as investigate the possible mechanisms by which aging and obesity can lead to the dysregulation of these proteins and pathways.

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.

The Ageing Brain: Effects on DNA Repair and DNA Methylation in Mice

Base excision repair (BER) may become less effective with ageing resulting in accumulation of DNA lesions, genome instability and altered gene expression that contribute to age-related degenerative diseases. The brain is particularly vulnerable to the accumulation of DNA lesions; hence, proper functioning of DNA repair mechanisms is important for neuronal survival. Although the mechanism of age-related decline in DNA repair capacity is unknown, growing evidence suggests that epigenetic events (e.g., DNA methylation) contribute to the ageing process and may be functionally important through the regulation of the expression of DNA repair genes. We hypothesize that epigenetic mechanisms are involved in mediating the age-related decline in BER in the brain. Brains from male mice were isolated at 3-32 months of age. Pyrosequencing analyses revealed significantly increased Ogg1 methylation with ageing, which correlated inversely with Ogg1 expression. The reduced Ogg1 expression correlated with enhanced expression of methyl-CpG binding protein 2 and ten-eleven translocation enzyme 2. A significant inverse correlation between Neil1 methylation at CpG-site2 and expression was also observed. BER activity was significantly reduced and associated with increased 8-oxo-7,8-dihydro-2'-deoxyguanosine levels. These data indicate that Ogg1 and Neil1 expression can be epigenetically regulated, which may mediate the effects of ageing on DNA repair in the brain.

Microsatellite Instability of Gastric and Colorectal Cancers as a Predictor of Synchronous Gastric or Colorectal Neoplasms

BACKGROUND/AIMS

Microsatellite instability (MSI) plays a crucial role in gastrointestinal carcinogenesis. The aim of this study was to clarify whether MSI is a useful marker for predicting synchronous gastric and colorectal neoplasms.

METHODS

Consecutive patients who underwent both esophagogastroduodenoscopy and colonoscopy before the resection of gastric or colorectal cancers were included. MSI was analyzed using two mononucleotide and three dinucleotide markers.

RESULTS

In total, 434 gastric cancers (372 microsatellite stability [MSS], 21 low incidence of MSI [MSI-L], and 41 high incidence of MSI [MSI-H]) and 162 colorectal cancers (138 MSS, 9 MSI-L, and 15 MSI-H) were included. Patients with MSI gastric cancer had a higher prevalence of synchronous colorectal cancer, colorectal adenoma, and gastric adenoma than those with MSS gastric cancers (4.8% vs 0.5%, p=0.023; 11.3% vs 3.2%, p=0.011; 3.2% vs 1.2%, p=0.00, respectively). The prevalence of synchronous colorectal adenomas was highest in MSI-L gastric cancers (19.0%), compared with MSI-H (7.3%) or MSS (3.2%) gastric cancers (p=0.002). In addition, there were no significant differences in the prevalence rates of synchronous colorectal adenoma among the MSI-H (13.3%), MSI-L (11.1%), and MSS (12.3%) colorectal cancers (p=0.987).

CONCLUSIONS

The presence of MSI in gastric cancer may be a predictor of synchronous gastric and colorectal neoplasms, whereas MSI in colorectal cancer is not a predictor of synchronous colorectal adenoma.

The clinicopathological significance of hMLH1 hypermethylation in non-small-cell lung cancer: a meta-analysis and literature review

The hMLH1 gene plays an essential role in DNA repair. Methylation of the hMLH1 gene is common in many types of cancer and can lead to the loss of hMLH1 expression. However, the association and clinicopathological significance between hMLH1 promoter hypermethylation and non-small-cell lung cancer (NSCLC) is elusive. Here, we investigated the correlation of hMLH1 promoter hypermethylation and NSCLC using 13 studies by comprising 1,056 lung cancer patients via a meta-analysis. We observed that 1) loss of hMLH1 protein expression was significantly associated with its promoter hypermethylation, 2) hMLH1 gene inactivation through hypermethylation contributed to the tumorigenesis of NSCLC, which could be a decisive factor for the pathogenesis of NSCLC due to its high occurrence in NSCLC tissues compared to normal lung tissues, 3) a correlation exists between histologic subtypes/disease stages (TNM I+II vs III+IV) and hypermethylation status of hMLH1 gene, and 4) NSCLC patients with hMLH1 hypermethylation and subsequent low expression levels of hMLH1 have a short overall survival period than those patients with normal expression of hMLH1 gene. hMLH1 mRNA predicts patient survival in lung cancer, and this was confirmed by using a public database. We then discussed the tumor suppressor function of hMLH1 and the clinicopathological significance of hMLH1 in NSCLC. We concluded that hMLH1 hypermethylation should be an early diagnostic marker for NSCLC and also a prognostic index for NSCLC. hMLH1 is an interesting therapeutic target in human lung cancers.

Estrogen and cancers of the colorectum, breast, and lung in postmenopausal women

As estrogens play an important role in maintaining physiological function in various organs, the estrogen decrease after menopause is thought to cause various diseases frequently observed in postmenopausal or elderly women. With the aging of society and a decrease in infectious or vascular diseases, neoplasms have now become the most frequent cause of death in Japan. Cancers of the colorectum, breast, and lung have been rapidly increasing both in incidence and death, especially among postmenopausal women. Interestingly, all three of these cancers are associated with estrogens. In premenopausal women, ovarian estrogens plays major roles in the female reproductive organs through the classic estrogen receptor, ER-α. In postmenopausal women, however, estrogens produced/activated by peripherally localized estrogen-metabolizing enzymes such as aromatase, which converts androgen into estrogens, are thought to play physiologically and pathobiologically important roles in various organs through second ER, namely ER-β, distributing systemically. In this article, the association of estrogens with these cancers in postmenopausal or elderly women are reviewed, especially focusing on the role of ER-β and peripheral estrogen metabolism. The possibility of prevention or treatment of these diseases through estrogenic control is also discussed.

Colorectal cancer morbidity in Poland and Japan in the years 1999-2006 - a comparison

INTRODUCTION

The frequency of colorectal cancer (CRC) is dependent on sex and age. The illness more often affects men than women, and a considerable increase in morbidity is noted after 65 years of age. The aim of the study was to assess the influence of various risk factors on CRC morbidity, statistical data from countries varied in cultural, socioeconomic and biological terms need to be studied. Poland and Japan can serve as examples of such contrasts.

MATERIAL AND METHODS

The basis for the analysis of CRC morbidity was statistical data from Poland and Japan gathered in the period 1999-2006. They were expressed in absolute numbers and were related to the total morbidity, as well as morbidity according to sex and age.

RESULTS

In the years 1999-2006, the total morbidity in Japan was on average 2.3 times higher than in Poland. The value was 2.5 times higher among men and 2.1 times among women when compared to Poland. In both countries morbidity is closely related to age and it reaches a peak between 65 and 74 years of age. Although the change in morbidity over the period was the same for Poland and Japan, there are considerable differences concerning the sex of the patients.

CONCLUSIONS

There is a substantial increase in CRC morbidity in both countries, especially among elderly people, which may point to the predominant influence of environmental factors and population aging in both countries. The much higher increase in morbidity among Polish men when compared to Polish women, not observed in the Japanese population, requires further study.

Gene promoter methylation in colorectal cancer and healthy adjacent mucosa specimens: correlation with physiological and pathological characteristics, and with biomarkers of one-carbon metabolism

We evaluated the promoter methylation levels of the APC, MGMT, hMLH1, RASSF1A and CDKN2A genes in 107 colorectal cancer (CRC) samples and 80 healthy adjacent tissues. We searched for correlation with both physical and pathological features, polymorphisms of folate metabolism pathway genes (MTHFR, MTRR, MTR, RFC1, TYMS, and DNMT3B), and data on circulating folate, vitamin B12 and homocysteine, which were available in a subgroup of the CRC patients. An increased number of methylated samples were found in CRC respect to adjacent healthy tissues, with the exception of APC, which was also frequently methylated in healthy colonic mucosa. Statistically significant associations were found between RASSF1A promoter methylation and tumor stage, and between hMLH1 promoter methylation and tumor location. Increasing age positively correlated with both hMLH1 and MGMT methylation levels in CRC tissues, and with APC methylation levels in the adjacent healthy mucosa. Concerning gender, females showed higher hMLH1 promoter methylation levels with respect to males. In CRC samples, the MTR 2756AG genotype correlated with higher methylation levels of RASSF1A, and the TYMS 1494 6bp ins/del polymorphism correlated with the methylation levels of both APC and hMLH1. In adjacent healthy tissues, MTR 2756AG and TYMS 1494 6bp del/del genotypes correlated with APC and MGMT promoter methylation, respectively. Low folate levels were associated with hMLH1 hypermethylation. Present results support the hypothesis that DNA methylation in CRC depends from both physiological and environmental factors, with one-carbon metabolism largely involved in this process.

Relationship between hMLH1 methylation, microsatellite instability and gastric cancer

Gastric cancer is one of the most common malignant tumors, and its development is a very complicated process. Although great progress has been made in the understanding of gastric cancer, its exact mechanism is still unclear. The human mutL homolog 1 (hMLH1), a main member of the mismatch repair system, participates in mismatch repair during DNA replication, and plays an important role in maintaining genome stability. The reduction or loss of hMLH1 expression, which often shows as microsatellite instability (MSI), is closely related to the development, treatment and prognosis of gastric cancer, and the main reason is hMLH1 promoter methylation. In this paper, we will review the recent progress in understanding the relationship between hMLH1 methylation, MSI and development, treatment and prognosis of gastric cancer.

Interleukin polymorphisms and differential methylation status in gastric cancer: an association with Helicobacter pylori infection

AIM

Interleukin polymorphisms and Helicobacter pylori infection are believed to play critical roles in DNA methylation, a process frequently associated with carcinogenesis. The aim of this study was to determine the associations between interleukin polymorphisms and methylation status of three genes related to gastric cancer. Furthermore, the influence of the H. pylori strains was evaluated.

MATERIALS & METHODS

75 gastric tumor samples had the DNA extracted for interleukin polymorphisms genotyping by PCR-RFLP, promoter methylation by MS-PCR and detection and subtyping of H. pylori by PCR.

RESULTS

In the cardia tumors, methylation in the COX-2 promoter was associated with IL1RN*2 (p = 0.015), and the associated genotypes IL1B511T + IL1RN*2 seem to be important in the methylation of COX-2 (p = 0.013), especially in the presence of cagA(+) (p = 0.026) and vacAs1 (p = 0.025) H. pylori strains. The associated genotypes IL6 CC+TNF GG seem to be involved in the unmethylation of CDKN2A (p = 0.046), along with H. pylori cagA(+) infection.

CONCLUSION

DNA methylation in gastric cancer seems to be influenced by the presence of interleukin polymorphisms and by the H. pylori cagA/vacAs1m1 strains.

Gene methylation in gastric cancer

Gastric cancer is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. Over 70% of new cases and deaths occur in developing countries. In the early years of the molecular biology revolution, cancer research mainly focuses on genetic alterations, including gastric cancer. Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression patterns in mammals. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Recent advancements in the rapidly evolving field of cancer epigenetics have shown extensive reprogramming of every component of the epigenetic machinery in cancer, including DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs, and microRNAs. Aberrant DNA methylation in the promoter regions of gene, which leads to inactivation of tumor suppressor and other cancer-related genes in cancer cells, is the most well-defined epigenetic hallmark in gastric cancer. The advantages of gene methylation as a target for detection and diagnosis of cancer in biopsy specimens and non-invasive body fluids such as serum and gastric washes have led to many studies of application in gastric cancer. This review focuses on the most common and important phenomenon of epigenetics, DNA methylation, in gastric cancer and illustrates the impact epigenetics has had on this field.

Epidemiological, genetic and epigenetic aspects of the research on healthy ageing and longevity

Healthy ageing and longevity in humans result from a number of factors, including genetic background, favorable environmental and social factors and chance.

In this article we aimed to overview the research on the biological basis of human healthy ageing and longevity, discussing the role of epidemiological, genetic and epigenetic factors in the variation of quality of ageing and lifespan, including the most promising candidate genes investigated so far. Moreover, we reported the methodologies applied for their identification, discussing advantages and disadvantages of the different approaches and possible solutions that can be taken to overcome them. Finally, we illustrated the recent approaches to define healthy ageing and underlined the role that the emerging field of epigenetics is gaining in the search for the determinants of healthy ageing and longevity.

Global DNA methylation in old subjects is correlated with frailty

Epigenetic variations have been widely described to occur during the aging process. To verify if these modifications are correlated with the inter-individual phenotypic variability of elderly people, we searched for a correlation between global DNA methylation levels and frailty. We found that the global DNA methylation levels were correlated to the frailty status in middle/advanced-aged subjects but not with age. A 7-year follow-up study also revealed that a worsening in the frailty status was associated to a significant decrease in the global DNA methylation levels. These results suggest that the relaxation of the epigenetic control in aging is specifically associated with the functional decline rather than with the chronological age of individuals. Thus, the modifications of DNA methylation, representing a drawbridge between the genetic and the environmental factors affecting the age-related decay of the organism, may play an important role in determining physiological changes over old age.

DNA methylation and gastric cancer

Methylation of cytosine bases in DNA provides a layer of epigenetic control in many eukaryotes that has important implications for normal biology and disease. DNA methylation is a crucial epigenetic modification of the genome that is involved in regulating many cellular processes. A growing number of human diseases including cancer have been found to be associated with aberrant DNA methylation. Recent advancements in the rapidly evolving field of cancer epigenetics have described extensive reprogramming of every component of the epigenetic machinery in cancer, such as DNA demethylation. In this review, we discuss the current understanding of alterations in DNA methylation composing the epigenetic landscape that occurs in gastric cancer compared with normal cells, the roles of these changes in gastric cancer initiation and progression, and the potential use of this knowledge in designing more effective treatment strategies.

Aberrant methylation of different DNA repair genes demonstrates distinct prognostic value for esophageal cancer

BACKGROUND

DNA mismatch repair (MMR) deficiency results in a strong mutator phenotype and high-frequency microsatellite instability (MSI-H), which are the hallmarks of many tumors.

AIM

The objective of this study is to investigate the promoter CpG island methylation status of mismatch repair genes human mutL homolog 1 (hMLH1), human mutS homolog 2 (hMSH2), and O(6)-methylguanine-DNA methyltransferase (MGMT) in esophageal squamous cell carcinoma (ESCC) and its roles in alkylating agents chemotherapy.

METHODS

Real-time methylation-specific polymerase chain reaction (PCR) (real-time MSP) was employed to detect promoter CpG island methylation of the hMLH1, hMSH2, as well as MGMT genes in 235 surgical tumor tissue samples from ESCC patients and their corresponding normal tissue samples.

RESULTS

Promoter CpG island methylation of hMLH1, hMSH2, and MGMT were detectable in 43.4, 28.9, and 40.4% of ESCC tumor DNA, respectively, and the loss rates of hMLH1, hMSH2, and MGMT protein expression were 48.6, 34.5, and 40.9% in tumor tissues, respectively. For the entire population of 235 ESCC patients who were enrolled in operating treatment combined with radiotherapy and chemotherapy with alkylating agents, there was a significant difference in the overall survival between patients with methylated MGMT promoter and those with an unmethylated MGMT promoter (P < 0.05).

CONCLUSION

Promoter CpG island methylation may be a frequent event in ESCC carcinogenesis. Detection of the methylated sequences of hMLH1, hMSH2, and MGMT appears to be promising as a predictive factor in primary ESCC.

CDH13 and FLBN3 gene methylation are associated with poor prognosis in colorectal cancer

The aim of this study was to identify potential epigenetic prognostic biomarkers for colorectal cancer (CRC) in the Chinese population. The methylation status of five tumor suppressor genes (CDH13, DLEC1, FBLN3, hMHL1 and RUNX3) was determined using manual microdissection followed by methylation-specific PCR in 85 paired CRC specimens and adjacent normal tissue. The results showed that methylation frequencies in cancerous tissues were 31.8% for CDH13, 37.6% for DLEC1, 38.8% for FBLN3, 22.4% for hMHL1 and 27.1% for RUNX3, all of which were significantly higher than in corresponding normal tissue. Furthermore, CDH13 methylation was associated with poor differentiation (P = 0.019) and tended to be predominant in advanced stages (P = 0.084); FBLN3 methylation was associated with advanced stages (P = 0.027) and lymph node metastasis (P = 0.029). Accordingly, the methylation status of CDH13 (P = 0.022), FBLN3 (P = 0.008), CDH13 and/or FBLN3 (P = 0.001) predicted adverse overall survival in CRC, while hMHL1 methylation showed a protective role in survival (P = 0.046). Cox proportional hazard models further indicated that CDH13 and/or FBLN3 methylation, but not that of hMHL1, was an independent prognostic factor for CRC. In conclusion, we found CDH13 and FBLN3 gene methylation are potential biomarkers for poor prognosis in CRC.