Background: Methylation of the HPV DNA has been proposed as a novel biomarker. Here, we correlated the mean methylation level of 12 CpG sites within L1 gene, to the histological grade of cervical precancer and cancer. We assessed whether HPV L1 gene methylation can predict the presence of high-grade disease at histology in women testing positive for HPV 16 genotype.
Methods: Pyrosequencing was used for DNA methylation quantification and 145 women were recruited.
Results: We found that the L1 HPV16 mean methylation (+/-SD) significantly increased with disease severity [CIN3=17.9%(±7.2) vs CIN2=11.6%(±6.5), p<0.001 or vs CIN1 =9.0%(±3.5), p<0.001). Mean methylation was a good predictor of CIN3+ cases; the Area Under the Curve (AUC) was higher for sites 5611 in the prediction of CIN2+ and higher for position 7145 for CIN3+. The evaluation of different methylation thresholds for the prediction of CIN3+, showed that the optimal balance of sensitivity and specificity (75.7% and 77.5%, respectively), PPV and NPV (74.7% and 78.5%, respectively) was achieved for a methylation of 14.0% with overall accuracy of 76.7%.
Conclusion: Elevated methylation level is associated with increased disease severity and has good ability to discriminate HPV16 positive women that have high-grade disease or worse.