Hypermethylation of MGMT Gene Promoter in Peripheral Blood Mononuclear Cells as a Noninvasive Biomarker for Colorectal Cancer Diagnosis

Background: Early colorectal cancer (CRC) diagnosis can drastically reduce CRC-related morbidity and mortality. In this regard, increasing attention is now being directed to DNA-based tests, especially the evaluation of methylation levels, to prioritize high-risk suspected persons for colonoscopy examination. Therefore, we aimed to assess the accuracy of MGMT gene promoter methylation levels in peripheral blood mononuclear cells (PBMCs) for distinguishing CRC patients from healthy people. Materials and Methods: For this study, a total of seventy individuals with CRC and 75 healthy individuals from Iran were included. The methylation level of MGMT in the DNA isolated from PBMCs was evaluated using the methylation quantification endonuclease-resistant DNA technique. To assess the diagnostic capability of the MGMT promoter methylation level, a receiver operating characteristic (ROC) curve was generated. Results: The mean promoter methylation level of MGMT in the CRC and control groups was, respectively, 27.83 +/- 22.80 vs. 12.36 +/- 14.48. The average percentage of methylation of the MGMT promoter between the CRC and control groups was significantly different (P < 0.001). Also, the MGMT promoter was more hypermethylated in female patients than in males. ROC analyses indicated that the diagnostic power of the MGMT promoter methylation level for CRC was 0.754, with a sensitivity of 81.43% and a specificity of 75.71%, indicating a good biomarker for CRC diagnosis. Conclusion: Methylation evaluation of MGMT in PBMCs could be utilized as a diagnostic biomarker with high accuracy for prioritizing suspected CRC patients before colonoscopy.