Methylguanine-DNA methyltransferase (MGMT)

O6-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme which is important in predicting the effects of alkylating chemotherapeutic agents (e.g. temozolomide) in the treatment of glioblastomas (GBM).

MGMT methylation is very common in low-grade gliomas (80%) 2 and is almost invariably present in low-grade tumours with IDH mutations 3. In contrast, MGMT methylation is far less common in higher grade gliomas (WHO grade III and IV), found in only 35-45% of such tumours 2

Assessment

MGMT methylation can be assessed with numerous techniques and no uniform consensus has been reached in regards to which technique is the most appropriate in clinical practice. Immunohistochemistry, nonquantitative methylation-specific polymerase chain reaction (MSP) and sequencing have all been used. 

Viable (non-necrotic) tissue must be sampled to avoid false negative results 2

Prognostic impact

High activity of MGMT (i.e. unmethylated) results in reduced efficacy of alkylating agents, and thus is a poor prognostic factor 1,2

On the other hand, when the MGMT promoter is methylated, there is decreased activity of MGMT and thus alkylating agents are more effective. In other words, identification of methylated-MGMT is a positive prognostic factor 1. It is also predictive of pseudoprogression following Stupp protocol 2

 

Astrocytic tumour
Share article

Article information

rID: 32837
Synonyms or Alternate Spellings:
  • MGMT
  • O6-Methylguanine-DNA methyltransferase (MGMT)
  • O6-Methylguanine-DNA methyltransferase
  • Methylguanine-DNA methyltransferase

Support Radiopaedia and see fewer ads

Updating… Please wait.
Loadinganimation

Alert accept

Error Unable to process the form. Check for errors and try again.

Alert accept Thank you for updating your details.