Limited Role of Promoter Methylation of MGMT and C13ORF18 in Triage of Low-Grade Squamous Intraepithelial Lesion.

Background: Promoter methylation of MGMT and C13ORF18 has been confirmed as a potential biomarker for early diagnosis of cervical cancer. The aim of this study was to evaluate the performance of MGMT and C13ORF18 promoter methylation for triage of cytology screening samples and explore the potential mechanism.

Methods: Methylation-sensitive high-resolution melting was used to detect promoter methylation of MGMT and C13ORF18 in 124 cervical samples. High-risk human papillomavirus (HR-HPV) was detected by the Digene Hybrid Capture 2® . Gene methylation frequencies in relation to cervical intraepithelial neoplasia (CIN) were analyzed. Frequencies were compared by Chi-square tests. The expression of gene biomarkers and methylation regulators was analyzed by immunohistochemical staining, real-time fluorescence quantitative polymerase chain reaction, and Western blot.

Results: For triage of low-grade squamous intraepithelial lesion (LSIL), gene methylation increased specificity from 4.0% of HR-HPV detection to 30.8% of MGMT (χ2 = 9.873, P = 0.002) and to 50.0% of C13ORF18 (χ2 = 21.814, P = 0.001). For triage of atypical squamous cells of undetermined significance, HR-HPV detection had higher positive predictive value of 54.8%. Either MGMT or C13ORF18 methylation combined with HR-HPV increased the negative predictive value to 100.0% (χ2 = 9.757, P = 0.002). There was no relationship between MGMT and C13ORF18 expression and DNA methylation (χ2 = 0.776, P = 0.379 and χ2 = 1.411, P = 0.235, respectively). MBD2 protein level in cervical cancer was relatively lower than normal cervical tissue (t = 4.11, P = 0.006).

Conclusions: HR-HPV detection is the cornerstone for triage setting of CIN. Promoter methylation of MGMT and C13ORF18 plays a limited role in triage of LSIL. Promoter methylation of both genes may not be the causes of gene silence.