Alterations of PTEN and SMAD4 methylation in diagnosis of breast cancer: implications of methyl II PCR assay

Background: Diagnosis of breast cancer is more complicated due to lack of minimal invasive biomarker with sufficient precision. DNA methylation is a promising marker for cancer diagnosis. In this study, authors evaluated methylation patterns for PTEN and SMAD4 in blood samples using EpiTect Methyl II QPCR assay quantitative PCR technology.

Results: Methylation status for PTEN and SMAD4 were statistically significant as breast cancer patients reported hypermethylation compared to benign and control groups (77.1 ± 17.9 vs. 24.9 ± 4.5 and 15.1 ± 1.4 and 70.1 ± 14.4 vs. 28.2 ± 0.61 and 29.5 ± 3.6, respectively). ROC curve analysis revealed that both PTEN (AUC = 0.992) and SMAD4 (AUC = 0.853) had good discriminative power for differentiating BC from all non-cancer individuals (benign and healthy combined) compared to routine tumor markers CEA (AUC = 0.538) and CA15.3 (AUC = 0.686). High PTEN methylation degree was associated with late stages (84.2 ± 17.4), positive lymph node (84.2 ± 18.5), positive ER (81.3 ± 19.7), positive PgR (79.5 ± 19.1), and positive HER2 (80.7 ± 19.0) vs. 67.4 ± 13.8, 70.6 ± 14.8, 72.8 ± 14.9, 72.5 ± 14.7, and 70.2 ± 13.5 in early stages, negative lymph node, negative ER, negative PgR, and negative HER2, respectively. Similar results were obtained regarding SMAD4 methylation. Sensitivity, specificity, positive and negative predictive values, and accuracy for methylated PTEN were 100%, 95%, 99.1%, 100%, and 95%, respectively when differentiated BC from all-non cancer controls. Interestingly, PTEN could distinguish early BC stages with good sensitivity 84.4%, 51.4%, 69.1%, 72%, and 70%, respectively.

Conclusion: Methylation status of PTEN and SMAD4 is a promising blood marker for early detection of breast cancer. Future studies are needed for their role as prognostic markers.