RUNX3 site-specific hypermethylation predicts papillary thyroid cancer recurrence.

Papillary thyroid cancer (PTC) is the most common epithelial thyroid tumor, accounting for more than 80% of all thyroid cancers. Although PTC shows an indolent character and excellent prognosis, patients with aggressive characteristics are more likely to have a disease recurrence and die in the end. The aim of this study was to analyze BRAF(V600E) mutation and methylation levels of CpG sites in the promoters of CDH1, DAPK, RARβ and RUNX3 genes in a cohort of PTCs, and investigate their association with tumor recurrence. In this study, we used pyrosequencing method to individually quantified methylation levels at multiple CpG sites within each gene promoter, and detect BRAF(V600E) mutation in 120 PTCs and 23 goiter tissues as normal control. Moreover, appropriate cut-off values for each CpG site were set up to predict disease recurrence. Our data showed that overall average methylation levels of CDH1 and RUNX3 genes were significantly higher in PTCs than that in control subjects. Conversely, overall average methylation levels of DAPK promoter were significantly lower in PTCs than that in control subjects. Moreover, BRAF(V600E) mutation and overall average methylation levels of all these genes were not significant difference between recurrent and non-recurrent cases. However, we found that hypermethylation of RUNX3 at CpG sites -1397, -1406, -1415 and -1417 significantly increased the risk of of disease recurrence by using appropriate site-specific cut-off values. Collectively, our findings suggest RUNX3 site-specific hypermethylation may offer value in predicting or monitoring postoperative recurrence of PTC patients.