# MGMT promoter methylation

Source: https://onco.cc/terms/mgmt/  
OnCo record `mgmt` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A chemical switch that turns off a DNA-repair gene. When it is off, temozolomide works much better.

## Summary

O6-methylguanine-DNA methyltransferase repairs the lesion temozolomide creates; promoter methylation silences it in ~40% of glioblastomas. Methylated: median OS ~23 months with chemoradiation; unmethylated: ~13 months with minimal temozolomide benefit, so unmethylated patients are the priority for novel-agent trials (e.g., CheckMate 498, which failed). Assay (MSP, pyrosequencing, methylation array) and cut-off variability persist.

## Fields

- Kind: Term
- Last checked: 2026-09-06

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/O-6-methylguanine-DNA_methyltransferase
- Wikipedia: https://en.wikipedia.org/wiki/O-6-methylguanine-DNA_methyltransferase

## Connected records

- cancers: [Astrocytoma, IDH-mutant (grades 2 to 4)](https://onco.cc/cancers/idh-mutant-astrocytoma/), [Glioma & glioblastoma](https://onco.cc/cancers/glioblastoma/), [Pituitary tumours (pituitary neuroendocrine tumours) and pituitary carcinoma](https://onco.cc/cancers/pituitary-tumours/)
- technologies: [DNA methylation profiling](https://onco.cc/technologies/methylation-profiling/)
- drugs: [Capecitabine + temozolomide (CAPTEM)](https://onco.cc/drugs/capecitabine-temozolomide/), [Temozolomide](https://onco.cc/drugs/temozolomide/)
- trials: [CCTG CE.6 / EORTC 26062-22061 (Perry trial)](https://onco.cc/trials/cctg-ce6/), [CheckMate 498](https://onco.cc/trials/checkmate-498/), [CheckMate 548](https://onco.cc/trials/checkmate-548/), [EORTC 26981 / NCIC CE.3 (Stupp trial)](https://onco.cc/trials/eortc-26981/)
- bottlenecks: [The brain: barrier and sanctuary](https://onco.cc/bottlenecks/b-brain-delivery/)
- pathways: [Base excision repair, PARP & alkylation damage](https://onco.cc/pathways/base-excision-repair-parp/), [Epigenetic reprogramming](https://onco.cc/pathways/epigenetic-reprogramming/), [Mutagenesis & mutational signatures](https://onco.cc/pathways/mutagenesis-signatures/), [The blood-brain barrier & brain metastasis](https://onco.cc/pathways/blood-brain-barrier-metastasis/)
- collections: [National Brain Tumor Society (NBTS)](https://onco.cc/collections/national-brain-tumor-society/)
- terms: [1p/19q codeletion](https://onco.cc/terms/1p19q-codeletion/), [DNA methylation arrays and beta values (450k, EPIC)](https://onco.cc/terms/methylation-arrays/), [SDH deficiency (SDHB immunohistochemistry loss)](https://onco.cc/terms/sdh-deficiency/)
- targets: [MGMT (O6-methylguanine-DNA methyltransferase)](https://onco.cc/targets/mgmt-protein/)
- biomarkers: [MGMT promoter methylation](https://onco.cc/biomarkers/mgmt-promoter-methylation/)

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JSON: https://onco.cc/api/v1/entities/mgmt.json