The hypermethylation of the O⁶‐methylguanine‐DNA methyltransferase gene promoter in gliomas—correlation with array comparative genome hybridization results and IDH1 mutation

Abstract

The use of molecular markers in the diagnostics of gliomas aids histopathological diagnosis and allows their further classification into clinically significant subgroups. The aim of this study was to characterize the methylation pattern of the O 6 -methylguanine-DNA methyltransferase (MGMT) promoter, gene copy number aberrations, and isocitrate dehydrogenase I (IDH1) mutation in gliomas. We studied 51 gliomas (15 oligodendrogliomas, 18 oligoastrocytomas, 3 astrocytomas, and 15 glioblastomas) by pyrosequencing, array comparative genome hybridization (CGH), and immunohistochemistry. MGMT hypermethylation was observed in 100% of oligoastrocytomas, 93% of oligodendrogliomas, and 47% of glioblastomas. The most frequently altered chromosomal regions were deletions of 1p31.1/21.1-22.2 and 19q13.3qter in oligodendroglial tumors, and losses of 9p21.3, 10q25.3qter, and 10q26.13-26.2 in glioblastomas. Deletions on 9p and 10q, and gain of 7p were associated with the unmethylated MGMT phenotype, whereas deletion of 19q and oligodendroglial morphology was associated with MGMT hypermethylation. IDH1 mutation showed positive correlation with MGMT hypermethylation and loss of 1p/19q. Our results suggest that MGMT promoter methylation, analyzed by pyrosequencing, is a frequent event in oligodendroglial tumors, and it correlates with IDH1 mutation and 19q loss in gliomas. Pyrosequencing proved a good method for assessing the degree of MGMT methylation in formalin-fixed paraffin-embedded glioma samples. However, further studies are needed to confirm a clinically relevant cut-off point for MGMT methylation in gliomas.

Loss of heterozygosity and uniparental disomy of chromosome region 10q23.3–26.3 in glioblastoma

“…Some studies have not detected any significant association between these events in glioblastomas . In contrast, Tuononen et al demonstrated a negative correlation between MGMT hypermethylation and losses of 10q26.13–26.2 ( P < 0.05) and 10q25.3qter (including the MGMT gene locus; P < 0.01), resuming that more studies are needed to study the significance of this association and the effect of other possible mechanisms on MGMT dysregulation, such as mutations and miRNA expression . Our study adds yet another event to this list of possible MGMT dysregulation mechanisms, namely, UPD ( vs deletion).…”

Clinical Neuropathology practice news 1-2014: Pyrosequencing meets clinical and analytical performance criteria for routine testing of MGMT promoter methylation status in glioblastoma

“…We use in our laboratories the pyrosequencing device and kits commercialized by Qiagen, which have been proved to be easy to establish and use. It must be noted, however, that other pyrosequencing kits, both commercialized and non-commercialized, have been and are currently in use and may be equivalent alternatives for clinical applications, although conclusive comparative analyses are missing [11, 13, 15, 17, 18, 22, 23]. …”

Somatostatin receptor subtype 2 in high-grade gliomas: PET/CT with 68Ga-DOTA-peptides, correlation to prognostic markers, and implications for targeted radiotherapy

“…Antibodies for IHC are listed in Table 2 . MGMT promoter methylation was studied by pyrosequencing [ 14 ], 1p/19q co-deletion by fluorescent in situ hybridization, and EGFR amplification by silver in situ hybridization [ 15 ].…”