Evaluation of MGMT Gene Methylation in Neuroendocrine Neoplasms

Abstract

Unresectable neuroendocrine neoplasms (NENs) often poorly respond to standard therapeutic approaches. Alkylating agents, in particular temozolomide, commonly used to treat high-grade brain tumors including glioblastomas, have recently been tested in advanced or metastatic NENs, where they showed promising response rates. In glioblastomas, prediction of response to temozolomide is based on the assessment of the methylation status of the MGMT gene, as its product, O-6-methylguanine-DNA methyltransferase, may counteract the damaging effects of the alkylating agent. However, in NENs, such a biomarker has not been validated yet. Thus, we have investigated MGMT methylation in 42 NENs of different grades and from various sites of origin by two different approaches: in contrast to methylation-specific PCR (MSP), which is commonly used in glioblastoma management, amplicon bisulfite sequencing (ABS) is based on high resolution next-generation sequencing and interrogates several additional CpG sites compared to those covered by MSP. Overall, we found MGMT methylation in 74% (31/42) of the NENs investigated. A higher methylation degree was observed in well-differentiated tumors and in tumors originating in the gastrointestinal tract. Comparing MSP and ABS results, we demonstrate that the region analyzed by the MSP test is sufficiently informative of the MGMT methylation status in NENs, suggesting that this predictive parameter could routinely be interrogated also in NENs

A Rare Adult Primary Intracranial Sarcoma, DICER1-Mutant Identified by Epigenomic Profiling: A Case Report

“…In accordance with the frequent CNV alterations described in primary intracranial sarcomas, DICER1-mutant [6], and with the observed high Ki67 index (Figure 3), we found, in both cancer lesions, 1q and 9p chromosome deletions and high amplification of the CCND2 gene encoding for the D2-type cyclin protein, a strong regulator of cell cycle onset and, thus, of proliferation (Figure 4A). MGMT promoter methylation analysis by Methylation Specific PCR (MSP) [12] showed that the MGMT promoter was not methylated.…”

MGMT and Whole-Genome DNA Methylation Impacts on Diagnosis, Prognosis and Therapy of Glioblastoma Multiforme

“…MSP can rapidly assess the methylation status of any CpG site within a CpG island [22,23]. In a first step, DNA is treated with sodium bisulfite, resulting in the conversion of unmethylated cytosine into uracil while the methylated cytosine, resistant to bisulfite, remains unaltered.…”

Epigenetic alterations in glioblastomas: Diagnostic, prognostic and therapeutic relevance

“…Methylation of O6‐methylguanine‐DNA methyltransferase (MGMT) has been extensively investigated as a biomarker for prediction of pharmacological response to temozolomide in patients affected by GBM 21,22 . MGMT gene is located on chromosome 10q26.3 23‐25 . The expression of MGMT gene is mainly regulated by epigenetic mechanisms.…”

“…To evaluate the methylation status of target genes, it is possible to also perform Amplicon Bisulfite sequencing (ABS) based on NGS technology 94 . This technique allows one to study the methylation status of a target gene with high sequencing depth, but, also in this case, the costs of the technology are quite high and thus not routinely used in clinical practice 25 …”