Graded methylation in the promoter and body of the O6-methylguanine DNA methyltransferase (MGMT) gene correlates with MGMT expression in human glioma cells.

Costello, J; Futscher, Bernard W.; Tano, Keizo; Graunke, Dawn M.; Pieper, Russell O.

doi:10.1016/s0021-9258(17)32544-9

Cited by 173 publications

(22 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…If a CpG island becomes aberrantly methylated in cancer, heterogeneous methylation is frequently observed. The evidence for heterogeneous DNA methylation has largely come from bisulfite sequencing of single clones, for example for the DNA repair gene MGMT [16], the RB1 tumor suppressor gene [17], the cell cycle progression inhibitor CDKN2B (p15) [18][19][20] and the proapoptotic gene DAPK1 [21]. The spectrum of heterogeneous methylation usually varies between different samples.…”

Section: Review Mikeska Candiloro and Dobrovicmentioning

confidence: 99%

“…However, commonly used methodologies such as methylation-specific PCR (MSP) (reviewed later) are unreliable in the assessment of MGMT promoter methylation [30]. This derives from the heterogeneous methylation that this locus often shows [16], the low level of DNA methylation in the normal tissues of some individuals [31] and technical issues in the reliable performance of MSP. The region of a CpG island that is tested for DNA methylation may also play a crucial role [32][33][34], highlighting the importance of preliminary work to determine the likelihood of the methylation of particular regions or positions being more important or informative than others [34,35].…”

Section: Review Mikeska Candiloro and Dobrovicmentioning

confidence: 99%

See 1 more Smart Citation

The Implications of Heterogeneous DNA Methylation for The Accurate Quantification of Methylation

Mikeska¹,

2010

View full text Add to dashboard Cite

DNA methylation based biomarkers have considerable potential for molecular diagnostics, both as tumor specific biomarkers for the early detection or post-therapeutic monitoring of cancer as well as prognostic and predictive biomarkers for therapeutic stratification. Particularly in the former, the accurate estimation of DNA methylation is of compelling importance. However, quantification of DNA methylation has many traps for the unwary, especially when heterogeneous methylation comprising multiple alleles with varied DNA methylation patterns (epialleles) is present. The frequent occurrence of heterogeneous methylation as distinct from a simple mixture of fully methylated and unmethylated alleles is generally not taken into account when DNA methylation is considered as a cancer biomarker. When heterogeneous DNA methylation is present, the proportion of methylated molecules is difficult to quantify without a method that allows the measurement of individual epialleles. In this article, we critically assess the methodologies frequently used to investigate DNA methylation, with an emphasis on the detection and measurement of heterogeneous DNA methylation. The adoption of digital approaches will enable the effective use of heterogeneous DNA methylation as a cancer biomarker.

show abstract

Section: Review Mikeska Candiloro and Dobrovicmentioning

confidence: 99%

Section: Review Mikeska Candiloro and Dobrovicmentioning

confidence: 99%

The Implications of Heterogeneous DNA Methylation for The Accurate Quantification of Methylation

Mikeska¹,

2010

View full text Add to dashboard Cite

show abstract

“…The activity of MGMT is regulated by its promoter and its hypermethylation leads to gene silencing in cancer [ 153 , 154 ]. Epimutations in MGMT have been linked to various types of cancer, such as colorectal cancer, lung cancer, and brain gliomas [ 125 , 153 , 154 , 155 , 156 , 157 ]. An epimutation in the promoter region of the MGMT gene is one of the most important prognostic factors for patients with glioblastoma and it can predict the response to treatment with alkylating agents such as temozolomide [ 155 ].…”

Section: Cis -Acting Factors Causing Secondary Epimutations: Historical Evidencementioning

confidence: 99%

Cis-Acting Factors Causing Secondary Epimutations: Impact on the Risk for Cancer and Other Diseases

Cruz

Cruz-Montoya

Jiménez

et al. 2021

Cancers

View full text Add to dashboard Cite

Epigenetics affects gene expression and contributes to disease development by alterations known as epimutations. Hypermethylation that results in transcriptional silencing of tumor suppressor genes has been described in patients with hereditary cancers and without pathogenic variants in the coding region of cancer susceptibility genes. Although somatic promoter hypermethylation of these genes can occur in later stages of the carcinogenic process, constitutional methylation can be a crucial event during the first steps of tumorigenesis, accelerating tumor development. Primary epimutations originate independently of changes in the DNA sequence, while secondary epimutations are a consequence of a mutation in a cis or trans-acting factor. Secondary epimutations have a genetic basis in cis of the promoter regions of genes involved in familial cancers. This highlights epimutations as a novel carcinogenic mechanism whose contribution to human diseases is underestimated by the scarcity of the variants described. In this review, we provide an overview of secondary epimutations and present evidence of their impact on cancer. We propose the necessity for genetic screening of loci associated with secondary epimutations in familial cancer as part of prevention programs to improve molecular diagnosis, secondary prevention, and reduce the mortality of these diseases.

show abstract

“…It is now well established MGMT expression is epigenetically silenced through promoter methylation in a large subset of brain tumors [11], and MGMT has emerged as one of the best-studied candidates for its susceptibility to cytosine-phosphate-guanine (CpG) island (CGI) for DNA methylation in glioma and other cancers [12,13]. Many studies have shown a correlation between MGMT protein expression in gliomas and the methylation level of the promoter region, which is usually about 30 to 60% [14,15]. To be more specific, the MGMT promoter methylation levels are 20-30% for grade I gliomas, 60-80% for grade II, 40-50% for grade III, and 20-45% for grade IV tumors [16].…”

Section: Introductionmentioning

confidence: 99%

Transcriptional Pausing and Activation at Exons-1 and -2, Respectively, Mediate the MGMT Gene Expression in Human Glioblastoma Cells

Al‐Obaide

Srivenugopal

2021

Genes

View full text Add to dashboard Cite

Background: The therapeutically important DNA repair gene O6-methylguanine DNA methyltransferase (MGMT) is silenced by promoter methylation in human brain cancers. The co-players/regulators associated with this process and the subsequent progression of MGMT gene transcription beyond the non-coding exon 1 are unknown. As a follow-up to our recent finding of a predicted second promoter mapped proximal to the exon 2 [Int. J. Mol. Sci.2021, 22(5), 2492], we addressed its significance in MGMT transcription. Methods: RT-PCR, RT q-PCR, and nuclear run-on transcription assays were performed to compare and contrast the transcription rates of exon 1 and exon 2 of the MGMT gene in glioblastoma cells. Results: Bioinformatic characterization of the predicted MGMT exon 2 promoter showed several consensus TATA box and INR motifs and the absence of CpG islands in contrast to the established TATA-less, CpG-rich, and GAF-bindable exon 1 promoter. RT-PCR showed very weak MGMT-E1 expression in MGMT-proficient SF188 and T98G GBM cells, compared to active transcription of MGMT-E2. In the MGMT-deficient SNB-19 cells, the expression of both exons remained weak. The RT q-PCR revealed that MGMT-E2 and MGMT-E5 expression was about 80- to 175-fold higher than that of E1 in SF188 and T98G cells. Nuclear run-on transcription assays using bromo-uridine immunocapture followed by RT q-PCR confirmed the exceptionally lower and higher transcription rates for MGMT-E1 and MGMT-E2, respectively. Conclusions: The results provide the first evidence for transcriptional pausing at the promoter 1- and non-coding exon 1 junction of the human MGMT gene and its activation/elongation through the protein-coding exons 2 through 5, possibly mediated by a second promoter. The findings offer novel insight into the regulation of MGMT transcription in glioma and other cancer types.

show abstract

Graded methylation in the promoter and body of the O6-methylguanine DNA methyltransferase (MGMT) gene correlates with MGMT expression in human glioma cells.

Cited by 173 publications

References 31 publications

The Implications of Heterogeneous DNA Methylation for The Accurate Quantification of Methylation

The Implications of Heterogeneous DNA Methylation for The Accurate Quantification of Methylation

Cis-Acting Factors Causing Secondary Epimutations: Impact on the Risk for Cancer and Other Diseases

Transcriptional Pausing and Activation at Exons-1 and -2, Respectively, Mediate the MGMT Gene Expression in Human Glioblastoma Cells

Contact Info

Product

Resources

About