MGMT promoter methylation

What it is

MGMT promoter methylation is a chemical modification (methylation) that switches off the MGMT gene. Because the MGMT gene normally produces a protein that repairs the DNA damage caused by certain chemotherapy, silencing it makes a tumor — particularly glioblastoma — more responsive to the chemotherapy drug temozolomide.

Understanding MGMT promoter methylation

The MGMT protein repairs a specific type of DNA damage. Temozolomide works by causing that very damage in tumor cells. When the MGMT gene is methylated (silenced), the tumor cannot repair the damage as effectively, so temozolomide works better — making MGMT methylation a predictive marker (it predicts response to temozolomide). It is also a prognostic marker (methylated tumors tend to have better outcomes). In glioblastoma, MGMT status is commonly tested and can influence treatment decisions, particularly in older patients (where it may guide whether to use temozolomide, radiation, or both). Understanding MGMT promoter methylation clarifies a key marker that predicts how well glioblastoma responds to chemotherapy.

Why it matters

Understanding MGMT promoter methylation helps patients and families see why this test matters — a methylated (silenced) MGMT gene makes glioblastoma more responsive to temozolomide and tends to predict a better outcome.