MGMT-B gene promoter hypermethylation in patients with inflammatory bowel disease - a novel finding

DNA Methylation Profiles of PSMA6, PSMB5, KEAP1, and HIF1A Genes in Patients with Type 1 Diabetes and Diabetic Retinopathy

We explored differences in the DNA methylation statuses of PSMA6, PSMB5, HIF1A, and KEAP1 gene promoter regions in patients with type 1 diabetes and different diabetic retinopathy (DR) stages. Study subjects included individuals with no DR (NDR, n = 41), those with non-proliferative DR (NPDR, n = 27), and individuals with proliferative DR or those who underwent laser photocoagulation (PDR/LPC, n = 46). DNA methylation was determined by Zymo OneStep qMethyl technique. The methylation of PSMA6 (NDR 5.9 (3.9-8.7) %, NPDR 4.5 (3.8-5.7) %, PDR/LPC 6.6 (4.7-10.7) %, p = 0.003) and PSMB5 (NDR 2.2 (1.9-3.7) %, NPDR 2.2 (1.9-3.0) %, PDR/LPC 3.2 (2.5-7.1) %, p < 0.01) differed across the groups. Consistent correlations were observed between the methylation levels of HIF1A and PSMA6 in all study groups. DNA methylation levels of PSMA6, PSMB5, and HIF1A genes were positively correlated with the duration of diabetes, HbA1c, and albuminuria in certain study groups. Univariate regression models revealed a significant association between the methylation level z-scores of PSMA6, PSMB5, and HIF1A and severe DR (PSMA6: OR = 1.96 (1.15; 3.33), p = 0.013; PSMB5: OR = 1.90 (1.14; 3.16), p = 0.013; HIF1A: OR = 3.19 (1.26; 8.06), p = 0.014). PSMB5 remained significantly associated with DR in multivariate analysis. Our findings suggest significant associations between the severity of DR and the DNA methylation levels of the genes PSMA6, PSMB5, and HIF1A, but not KEAP1 gene.

O6-methylguanine DNA methyltransferase regulates β-glucan-induced trained immunity of macrophages via farnesoid X receptor and AMPK

Trained immunity is the heightened state of innate immune memory that enhances immune response resulting in nonspecific protection. Epigenetic changes and metabolic reprogramming are critical steps that regulate trained immunity. In this study, we reported the involvement of O6-methylguanine DNA methyltransferase (MGMT), a DNA repair enzyme of lesion induced by alkylating agents, in regulation the trained immunity induced by β-glucan (BG). Pharmacological inhibition or silencing of MGMT expression altered LPS stimulated pro-inflammatory cytokine productions in BG-trained bone marrow derived macrophages (BMMs). Targeted deletion of Mgmt in BMMs resulted in reduction of the trained responses both in vitro and in vivo models. The transcriptomic analysis revealed that the dampening trained immunity in MGMT KO BMMs is partially mediated by ATM/FXR/AMPK axis affecting the MAPK/mTOR/HIF1α pathways and the reduction in glycolysis function. Taken together, a failure to resolve a DNA damage may have consequences for innate immune memory.

Epigenetic Alteration in Colorectal Cancer: A Biomarker for Diagnostic and Therapeutic Application

Colorectal cancer (CRC) is the leading cause of cancer death worldwide. A crucial process that initiates and progresses CRC is various epigenetic and genetic changes occurring in colon epithelial cells. Recently, huge progress has been made to understand cancer epigenetics, especially regarding DNA methylation changes, histone modifications, dysregulation of miRNAs and noncoding RNAs. In the "epigenome" of colon cancer, abnormal methylation of genes that cause gene alterations or expression of miRNA has been reported in nearly all CRC; these findings can be encountered in the average CRC methylome. Epigenetic changes, known as driving events, are assumed to play a dominant part in CRC. Furthermore, as epigenetic changes in CRC become properly understood, these changes are being established as clinical biomarkers for therapeutic and diagnostic purposes. Progression in this area indicates that epigenetic changes will often be utilized in the future to prevent and treat CRC.

MGMT-Methylation in Non-Neoplastic Diseases of the Central Nervous System

Quantifying O⁶-methylguanine-DNA methyltransferase (MGMT) promoter methylation plays an essential role in assessing the potential efficacy of alkylating agents in the chemotherapy of malignant gliomas. MGMT promoter methylation is considered to be a characteristic of subgroups of certain malignancies but has also been described in various peripheral inflammatory diseases. However, MGMT promoter methylation levels have not yet been investigated in non-neoplastic brain diseases. This study demonstrates for the first time that one can indeed detect slightly enhanced MGMT promoter methylation in individual cases of inflammatory demyelinating CNS diseases such as multiple sclerosis and progressive multifocal leucencephalopathy (PML), as well as in other demyelinating diseases such as central pontine and exptrapontine myelinolysis, and diseases with myelin damage such as Wallerian degeneration. In this context, we identified a reduction in the expression of the demethylase TET1 as a possible cause for the enhanced MGMT promoter methylation. Hence, we show for the first time that MGMT hypermethylation occurs in chronic diseases that are not strictly associated to distinct pathogens, oncogenic viruses or neoplasms but that lead to damage of the myelin sheath in various ways. While this gives new insights into epigenetic and pathophysiological processes involved in de- and remyelination, which might offer new therapeutic opportunities for demyelinating diseases in the future, it also reduces the specificity of MGMT hypermethylation as a tumor biomarker.

Molecular determinants of response to 5-fluorouracil-based chemotherapy in colorectal cancer: The undisputable role of micro-ribonucleic acids

5-flurouracil (5-FU)-based chemotherapy is the main pharmacological therapy for advanced colorectal cancer (CRC). Despite significant progress in the treatment of CRC during the last decades, 5-FU drug resistance remains the most important cause of failure in CRC therapy. Resistance to 5-FU is a complex and multistep process. Different mechanisms including microsatellite instability, increased expression level of key enzyme thymidylate synthase and its polymorphism, increased level of 5-FU-activating enzymes and mutation of TP53 are proposed as the main determinants of resistance to 5-FU in CRC cells. Recently, micro-ribonucleic acids (miRNA) and their alterations were found to have a crucial role in 5-FU resistance. In this regard, the miRNA-mediated mechanisms of 5-FU drug resistance reside among the new fields of pharmacogenetics of CRC drug response that has not been completely discovered. Identification of the biological markers that are related to response to 5-FU-based chemotherapy is an emerging field of precision medicine. This approach will have an important role in defining those patients who are most likely to benefit from 5-FU-based chemotherapy in the future. Thereby, the identification of 5-FU drug resistance mechanisms is an essential step to predict and eventually overcome resistance. In the present comprehensive review, we will summarize the latest knowledge regarding the molecular determinants of response to 5-FU-based chemotherapy in CRC by emphasizing the role of miRNAs.

Polyunsaturated fatty acids and DNA methylation in colorectal cancer

Colorectal cancer (CRC) has been designated a major global problem, especially due to its high prevalence in developed countries. CRC mostly occurs sporadically (75%-80%), and only 20%-25% of patients have a family history. Several processes are involved in the development of CRC such as a combination of genetic and epigenetic alterations. Epigenetic changes, including DNA methylation play a vital role in the progression of CRC. Complex interactions between susceptibility genes and environmental factors, such as a diet and sedentary lifestyle, lead to the development of CRC. Clinical and experimental studies have confirmed the beneficial effects of dietary polyunsaturated fatty acids (PUFAs) in preventing CRC. From a mechanistic viewpoint, it has been suggested that PUFAs are pleiotropic agents that alter chromatin remodeling, membrane structure and downstream cell signaling. Moreover, PUFAs can alter the epigenome via modulation of DNA methylation. In this review, we summarize recent investigations linking PUFAs and DNA methylation-associated CRC risk.

Best practices in DNA methylation: lessons from inflammatory bowel disease, psoriasis and ankylosing spondylitis

Advances in genomic technology have enabled a greater understanding of the genetics of common immune-mediated diseases such as ankylosing spondylitis (AS), inflammatory bowel disease (IBD) and psoriasis. The substantial overlap in genetically identified pathogenic pathways has been demonstrated between these diseases. However, to date, gene discovery approaches have only mapped a minority of the heritability of these common diseases, and most disease-associated variants have been found to be non-coding, suggesting mechanisms of disease-association through transcriptional regulatory effects.

Epigenetics is a major interface between genetic and environmental modifiers of disease and strongly influence transcription. DNA methylation is a well-characterised epigenetic mechanism, and a highly stable epigenetic marker, that is implicated in disease pathogenesis. DNA methylation is an under-investigated area in immune-mediated diseases, and many studies in the field are affected by experimental design limitations, related to study design, technical limitations of the methylation typing methods employed, and statistical issues. This has resulted in both sparsity of investigations into disease-related changes in DNA methylation, a paucity of robust findings, and difficulties comparing studies in the same disease.

In this review, we cover the basics of DNA methylation establishment and control, and the methods used to examine it. We examine the current state of DNA methylation studies in AS, IBD and psoriasis; the limitations of previous studies; and the best practices for DNA methylation studies. The purpose of this review is to assist with proper experimental design and consistency of approach in future studies to enable a better understanding of the functional role of DNA methylation in immune-mediated disease.

O6-Methyguanine-DNA Methyl Transferase (MGMT) Promoter Methylation in Serum DNA of Iranian Patients with Colorectal Cancer

Introduction:

Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide but current molecular targeted therapy is not providing major success in CRC treatment, so early detection by non-invasive methods continues to be vital. Aberrant methylation of CpG islands in promoter regions is associated with inactivation of various tumor suppressor genes. O6-methyguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that removes mutagenic and cytotoxic adducts from O6-guanine in DNA. Aberrant hypermethylation of the MGMT promoter has been associated with lack of mRNA expression, with concomitant loss of protein content and enzyme activity.

AIM:

Our aim was to determine whether MGMT promoter methylation might be detectable in circulating free DNA in the serum of CRC patients and normal individuals using a methylation specific (MSP) polymerase chain reaction (PCR) method.

Methods:

A total of 70 subjects were enrolled in the study. Of these, 30 patients who were diagnosed previously as untreated colon adenocarcinoma by a gastroenterologist and the other 40 were nearly age-matched individuals who had a normal colonoscopic evaluation (except for hemorrhoids or fissures) and normal pathologic reports. After bisulphite modification of DNA, serum samples were examined for MGMT promoter methylation using MSP.

Results:

Ninety percent of CRC patients had MGMT promoter hypermethylation as compared to no methylation in normal subjects’ serum. Most of the cancers were stage П and moderately differentiated adenocarcinomas; nearly 60% were found in the left colon. No statistically significant correlation was found between the promoter methylation status and gender and age.

Discussion and Conclusions:

MGMT hypermethylation can be detected in free circulating DNA in serum of CRC patients and can be used “as a clinical biomarker” for early diagnosis and prognostic assessment of the disease. Our data confirm previous studies indicating utility for free circulating DNA as a serum biomarker for early detection, diagnosis and monitoring of CRC patients.

Colorectal Cancer and Precancerous Lesions Associated with Ulcerative Colitis in Thailand

Background:

Ulcerative colitis(UC) is important risk factor of colorectal cancer. Many evidences from western countries confirmed this relationship but limited studies were reported in ASEAN. This study was aimed to investigate prevalence, clinical presentations, endoscopic findings, histopathology, disease progression and risk for colorectal cancer(CRC) of UC patients in Thailand.

Methods:

We conducted a retrospective cohort study using computer data base from Thammasat University Hospital, Pathumthani, Thailand between September 2011 and December 2015, follow-up through May 2016. Diagnosis of UC was confirmed by histopathology and whole clinical course.

Results:

We identified 6,082 patients who diagnosed with colitis during the study period. Of whom, only 22 patients(<1%) was confirmed of UC. Male to female ratio was 13:9 (mean age of 47.2 years). Clinical presentations were bloody diarrhea in 86.4%, watery diarrhea in 31.8% and abdominal pain in 59.1%. According to Montreal classification, disease extensions were ulcerative proctitis in 22.7%, distal UC in 50%, and pancolitis in 27.3%. Disease grading was mild in 31.8%, moderate in 9.1%, and severe in 59.1%. The prevalence of precancerous lesions were 2/22 patients(9.1%). There was no definite invasive colorectal cancer patient during study period. However, history of malnutrition was significantly higher in patients with dysplasia than those without dysplastic lesions(50%vs.0%, P-value=0.045). There was no difference in duration and disease extension between 2 groups. Interestingly, subgroup analysis demonstrated that pancolitis was significantly more common in female than male (55.6%vs.7.7%, P-value=0.02, OR=15.0, 95%CI=1.3-169.9). Furthermore, patients’ age> 35 years had significantly more severe colitis than younger group (81.25%vs.0%, P-value=0.0006)

Conclusions:

Although UC is rare disease in ASEAN, precancerous lesions for CRC were not uncommon. UC with pancolitis was common in female whereas severe colitis was common in elderly patients. Proper screening program and careful surveillance for precancerous lesions in patients at risk might be appropriate approach for early detection and improvement the treatment outcome.

Sensitive and Noninvasive Detection of Aberrant SFRP2 and MGMT-B Methylation in Iranian Patients with Colon Polyps

BACKGROUND

The pathogenesis of sporadic colorectal cancer (CRC) is influenced by the patient genetic background and environmental factors. Based on prior understanding, these are classified in two major pathways of genetic instability. Microsatellite instability (MSI) and CPG island methylator phenotype (CIMP) are categorized as features of the hypermethylated prototype, and chromosomal instability (CIN) is known to be indicative of the non-hypermethylated category. Secreted frizzled related protein 2 (SFRP2), APC1A in WNT signaling pathway and the DNA repair gene, O6-methylguanine-DNA methyltransferase (MGMT), are frequently hypermethylated in colorectal cancer. Detection of methylated DNA as a biomarker by easy and inexpensive methods might improve the quality of life of patients with CRC via early detection of cancer or a precancerous condition.

AIM

To evaluate the rate of SFRP2 and MGMT hypermethylation in both polyp tissue and serum of patients in south Iran as compared with matched control normal population corresponding samples.

MATERIALS AND METHODS

Methylation-specific PCR was used to detect hypermethylation in DNA extracted from 48 polypoid tissue samples and 25 healthy individuals.

RESULTS

Of total polyp samples, 89.5% had at least one promoter gene hypermethylation. The most frequent methylated locus was SFRP2 followed by MGMT-B (81.2 and 66.6 percent respectively). Serologic detection of hypermethylation was 95% sensitive as compared with polyp tissue. No hypermethylation was detected in normal tissue and serum and its detection in patients with polyps, especially of serrated type, was specific.

CONCLUSIONS

Serologic investigation for detection of MGMT-B, SFRP2 hypermethylation could facilitate prioritization of high risk patients for colonoscopic polyp detection and excision.

Epigenetic biomarkers in colorectal cancer: premises and prospects

CONTEXT

Colorectal cancer is one of the most common cancers worldwide. Epigenetic alterations play an important role in the pathogenesis of the colorectal cancer.

OBJECTIVE

This review has focused on the most recent investigations, which has suggested potential epigenetic biomarkers in colorectal cancer.

METHODS

Evidences were achieved by searching online medical databases including Google scholar, Pubmed, Scopus and Science Direct.

RESULTS

Extensive studies have indicated that aberrant epigenetic modifications could serve as potential biomarkers for diagnosis, prognosis and prediction of colorectal cancer.

CONCLUSION

Advances in aberrant epigenetic modifications can open new avenues for exploration of reliable and robust biomarkers to improve the management of CRC patients.