• Asian Pacific Journal of Cancer Prevention
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• v.16 no.18
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• pp.8059-8065
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• 2016

Nasopharyngeal carcinoma (NPC) is a common tumor in southern China and south-eastern Asia. Effective strategies for the prevention or screening of NPC are limited. Exploring effective biomarkers for the early diagnosis and prognosis of NPC continues to be a rigorous challenge. Evidence is accumulating that DNA methylation alterations are involved in the initiation and progression of NPC. Over the past few decades, aberrant DNA methylation in single or multiple tumor suppressor genes (TSGs) in various biologic samples have been described in NPC, which potentially represents useful biomarkers. Recently, large-scale DNA methylation analysis by genome-wide methylation platform provides a new way to identify candidate DNA methylated markers of NPC. This review summarizes the published research on the diagnostic and prognostic potential biomarkers of DNA methylation for NPC and discusses the current knowledge on DNA methylation as a biomarker for the early detection and monitoring of progression of NPC.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.6
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• pp.2209-2213
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• 2015

DNA methylation of tumor suppressor gene promoters is the most frequent phenomenon leading to inactivation of function, consequently driving malignant cell transformation. Cyclin D2 is implicated in tumor suppression. In our study, we carried out the MSP assay to evaluation the methylation status at CpG islands in the cyclin D2 promoter in breast cancer cases from the Vietnamese population. The results showed that the frequency of methylation reached 62.1% (59 of 95 breast cancer tumors), but was low in non-cancer specimens at 10% (2 of 20 non-cancer specimens). Additionally, with an RR (relative risk) and OR (odd ratios) of 6.21 and 14.8, DNA hypermethylation of cyclin D2 increased the possibility of malignant transformation. Our results confirmed the cyclin D2 hypermethylation could be used as the potential biomarker which could be applied in prognosis and early diagnosis of Vietnamese breast cancer patients.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.11
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• pp.5563-5568
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• 2012

Based on our previous report on gastric cancer which documented ATP4A and ATP4B mRNA down-regulation in gastric tumors relative to normal gastric tissues, we hypothesized that epigenetic mechanisms could be responsible. ATP4A and ATP4B mRNA expression in gastric cancer cell lines AGS, SNU638 and NUGC-3 was examined using reverse transcriptase PCR (RT-PCR). AGS cells were treated with TSA or 5'-AzaDC and methylation specific PCR (MSP) and bisulfite sequencing PCR (BSP) analysis were performed. MSP analysis was on DNA from paraffin embedded tissues sections and plasma. Expression analysis revealed downregulation of ATP4A and ATP4B genes in gastric cancer cell lines relative to normal gastric tissue, while treatment with 5'-AzaDC re-activated expression of both. Search for CpG islands in their putative promoter regions did not indicate CpG islands (CGI) but only further downstream in the bodies of the genes. Methylation specific PCR (MSP) in the exon1 of the ATP4B gene and exon7 in ATP4A indicated methylation in all the gastric cancer cell lines tested. MSP analysis in tumor tissue samples revealed methylation in the majority of tumor samples, 15/19, for ATP4B and 8/8 for ATP4A. There was concordance between ATP4B and ATP4A down-regulation and methylation status in the tumour samples tested. ATP4B methylation was detectable in cell free DNA from gastric cancer patient's plasma samples. Thus ATP4A and ATP4B down-regulation involves DNA methylation and methylated ATP4B DNA in plasma is a potential biomarker for gastric cancer.

• Korean Journal of Head & Neck Oncology
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• v.33 no.1
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• pp.21-29
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• 2017

Methylation of CpG islands in the promoter region of genes acts as a significant mechanism of epigenetic gene silencing in head and neck squamous cell carcinoma (HNSCC). DNA methylation markers are particularly advantageous because DNA methylation is an early event in tumorigenesis, and the epigenetic modification, 5-methylcytosine, is a stable mark. In the present study, we assessed the genome-wide preliminary screening and were to identify novel methylation biomarker candidate in HNSCC. Genome-wide methylation analysis was performed on 10 HNSCC tumors using the Methylated DNA Isolation Assay (MeDIA) CpG island microarray. Validation was done using immunohistochemistry using tissue microarray of 135 independent HNSCC tumors. In addition, in vitro proliferation, migration/invasion assays, RT-PCR and immunoblotting were performed to elucidate molecular regulating mechanisms. Our preliminary validation using CpG microarray data set, immunohisto-chemistry for HNSCC tumor tissues and in vitro functional assays revealed that methylation of the Homeobox B5 (HOXB5) and H6 Family Homeobox 2 (HMX2) could be possible novel methylation biomarkers in HNSCC.

• Genomics & Informatics
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• v.17 no.4
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• pp.38.1-38.6
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• 2019

DNA methylation is a relatively stable epigenetic modification that can regulate and stabilize gene expression patterns and hence establish cell identity. Because metabolic intermediates are key factors of DNA methylation and demethylation, perturbations in metabolic homeostasis can trigger alterations in cell-specific patterns of DNA methylation and contribute to disease development, including type 2 diabetes (T2D). During the past decade, genome-wide DNA methylation studies of T2D have expanded our knowledge of the molecular mechanisms underlying T2D. This review summarizes case-control studies of the DNA methylome of T2D and discusses DNA methylation as both a cause and consequence of T2D. Therefore, DNA methylation has potential as a promising T2D biomarker that can be applied to the development of therapeutic strategies for T2D.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.22
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• pp.9955-9960
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• 2014

Background: Promoter hypermethylation is a common event in human cancer. O6-methylguanine-DNA methyltransferase (MGMT) is a gene involved in DNA repair, which is methylated in a variety of cancers. We aimed to explore the methylation status of MGMT gene among the North Eastern population where esophageal cancer incidence and exposure to carcinogens like nitrosamines is high. Materials and Methods: A total of 100 newly diagnosed esophageal cancer cases along with equal number of age, sex and ethnicity matched controls were included in this study. Methylation specific PCR was used to determine the MGMT methylation status in serum samples. Results: Aberrant promoter methylation of the MGMT gene was detected in 70% of esophageal cancer cases. Hypermethylation of MGMT gene was found to be influenced by environmental factors like betel quid and tobacco which contain potent carcinogens like nitrosamines. Tobacco chewing and tobacco smoking habit synergistically with MGMT methylation elevated the risk for esophageal cancer development [adjusted OR=5.02, 95% CI=1.35-18.74; p=0.010 for tobacco chewing and Adjusted OR=3.00, 95% CI=1.22-7.36; p=0.014 for tobacco smoking]. Conclusions: Results suggest that the DNA hypermethylation of MGMT is an important mechanism for MGMT gene silencing resulting in esophageal cancer development and is influenced by the environmental factors. Thus MGMT hypermethylation can be used as a biomarker for esophageal cancer in high incidence region of North East India.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.1
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• pp.219-223
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• 2016

Background: Promoter hypermethylation is a frequent epigenetic mechanism for gene transcription repression in cancer and is one of the hallmarks of the disease. Cadherin EGF LAG seven-pass G-type receptor 3 (CELSR3) contributes to cell contact-mediated communication. Dysregulation of promoter methylation has been reported in various cancers. Objectives: The objectives of this study were to investigate the CELSR3 hypermethylation level in oral squamous cell carcinomas (OSCCs) using methylation-sensitive high-resolution melting analysis (MS-HRM) and to correlate CELSR3 methylation with patient demographic and clinicopathological parameters. Materials and Methods: Frozen tissue samples of healthy subjects' normal mucosa and OSCCs were examined with regard to their methylation levels of the CELSR3 gene using MS-HRM. Results: MS-HRM analysis revealed a high methylation level of CELSR3 in 86% of OSCC cases. Significant correlations were found between CELSR3 quantitative methylation levels with patient ethnicity (P=0.005), age (P=0.024) and pathological stages (P=0.004). A moderate positive correlation between CELSR3 and patient age was also evident (R=0.444, P=0.001). Conclusions: CELSR3 promoter hypermethylation may be an important mechanism involved in oral carcinogenesis. It may thus be used as a biomarker in OSCC prognostication.

• BMB Reports
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• v.56 no.6
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• pp.347-352
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• 2023

The protein family of poly (ADP-ribose) polymerases (PARPs) is comprised of multifunctional nuclear enzymes. Several PARP inhibitors have been developed as new anticancer drugs to combat resistance to chemotherapy. Herein, we characterized PARP4 mRNA expression profiles in cisplatin-sensitive and cisplatin-resistant ovarian cancer cell lines. PARP4 mRNA expression was significantly upregulated in cisplatin-resistant ovarian cancer cell lines, and this upregulation was associated with the hypomethylation of specific cytosine-phosphate-guanine (CpG) sites (cg18582260 and cg17117459) on its promoter. Reduced PARP4 expression was restored by treating cisplatin-sensitive cell lines with a demethylation agent, implicating the epigenetic regulation of PARP4 expression by promoter methylation. Depletion of PARP4 expression in cisplatin-resistant cell lines reduced cisplatin chemoresistance and promoted cisplatin-induced DNA fragmentation. The differential mRNA expression and DNA methylation status at specific PARP4 promoter CpG sites (cg18582260 and cg17117459) according to cisplatin responses, was further validated in primary ovarian tumor tissues. The results showed significantly increased PARP4 mRNA expressions and decreased DNA methylation levels at specific PARP4 promoter CpG sites (cg18582260 and cg17117459) in cisplatin-resistant patients. Additionally, the DNA methylation status at cg18582260 CpG sites in ovarian tumor tissues showed fairly clear discrimination between cisplatin-resistant patients and cisplatin-sensitive patients, with high accuracy (area under the curve = 0.86, P = 0.003845). Our findings suggest that the DNA methylation status of PARP4 at the specific promoter site (cg18582260) may be a useful diagnostic biomarker for predicting the response to cisplatin in ovarian cancer patients.

• Genomics & Informatics
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• v.12 no.4
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• pp.171-180
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• 2014

Aberrant DNA methylation, as an epigenetic marker of cancer, influences tumor development and progression. We downloaded publicly available DNA methylation and gene expression datasets of matched cancer and normal pairs from the Cancer Genome Atlas Data Portal and performed a systematic computational analysis. This study has three aims to screen genes that show hypermethylation and downregulated patterns in colorectal cancers, to identify differentially methylated regions in one of these genes, SFRP1, and to test whether the SFRP genes affect survival or not. Our results show that 31 hypermethylated genes had a negative correlation with gene expression. Among them, SFRP1 had a differentially methylated pattern at each methylation site. We also show that SFRP1 may be a potential biomarker for colorectal cancer survival.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.8
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• pp.4149-4154
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• 2016

Background: Cervical carcinoma is one of the main causes of mortality in women worldwide as well as in India. It occurs as a result of various molecular events that develop from the combined influences of an individual's genetic predisposition and external agents such as smoking and menstrual hygiene, for example. However, infection with human papillomavirus (HPV) is the established major risk factor. The aim of the current study was to investigate p16 CpG island methylation and establish any correlation with mRNA expression in north Indian population. Materials and Methods: We analyzed 196 woman volunteer out of which 98 were cases and 98 healthy controls. For the analysis of methylation pattern, DNA extracted from blood samples was modified with a bisulfate kit and used as template for methylation specific PCR (MSP). Quantitative real-time PCR (QRT-PCR) was performed to check mRNA expression. Results: Correlation between methylation status of p16 gene and poor menstrual hygiene was significant (p=0.006), high parity cases showed methylation of p16 gene (p=0.031) with increased risk up to 1.86 times for cervical cancer and smoking was a strong risk factor associated with cervical cancer. We analyzed methylation pattern and found 60.3% methylation in cases with low mRNA expression level (0.014) as compare to controls (1.24). It was also observed that promoter methylation of p16 gene was significantly greater in FIGO stage III. Conclusions: We conclude that p16 methylation plays an important role in cervical cancer in the north Indian population and its methylation decreases mRNA expression. It can be used as an important and consistent blood biomarker in cervical cancer patients.