Status of O6-methylguanine-DNA methyltransferase [MGMT] gene promoter methylation among patients with glioblastomas from India

Background: O-6-methylguanine DNA methyltransferase [MGMT] gene promoter methylation has emerged as a promising marker in determining resistance to temozolomide, used in the treatment of patients with glioblastomas. Aim: To determine the frequency of MGMT promoter methylation among patients with glioblastomas using methylation-specific polymerase chain reaction (MSP) and compare it to the results obtained by bisulfite sequencing of a subset of samples. Materials and Methods: DNA obtained from the frozen tissue of 27 samples of glioblastomas and three other gliomas, were analyzed for MGMT promoter methylation using a nested MSP assay. Sixteen samples were also subjected to bisulfite sequencing to determine the methylation status of 27 CpG sites within the sequenced region of the MGMT promoter. Data with respect to radiation, chemotherapy and survival outcome was also collected. Results: MGMT promoter methylation was seen in 67% of the cases included in the study using frozen tissues by MSP analysis, while 62% were methylated among glioblastomas alone. There was a 100% concordance between the results obtained by MSP analysis and bisulfite sequencing. Clinical outcome was known among 67% of cases and methylation was higher among those patients who had no recurrence, though it was not statistically significant [P=0.44]. Conclusion: The frequency of methylation seen in this study concurs with that reported earlier from the country. MSP was easy to perform and interpret. However, the utility of this testing system in a routine diagnostic setting is still being debated.