DNA methylation of RUNX3 in papillary thyroid cancer

Runt-related transcription factor 3, mediated by DNA-methyltransferase 1, regulated Schwann cell proliferation and myelination during peripheral nerve regeneration via JAK/STAT signaling pathway

Schwann cells (SCs) play a crucial role in peripheral nerve injury and regeneration. Recently, RUNX3 was found to be linked with neurological dysfunction. We examined the RUNX3 expression in sciatic nerve stumps with peripheral nerve injury of rats, cyclic adenosine monophosphate (cAMP)-induced SCs. MTT assay was applied to determine the proliferation of SCs. Cell migration and apoptosis were assessed using wound healing assay and flow cytometry. Subsequently, we detected the methylation level of RUNX3 using Methylation-specific PCR assay and verified its regulation by DNMT1. The RUNX3 expressions were increased in sciatic nerve stumps with peripheral nerve injury and cAMP-induced SCs differentiation, which were related to demethylation of its promoter region regulated by DNMT1. RUNX3 knockdown notably suppressed the proliferation and migration, and induced the cell apoptosis of SCs. Silencing of RUNX3 inhibited the cAMP-induced morphological changes of SCs and the increase of myelin-related proteins induced by cAMP in SCs, while RUNX3 overexpression exerted opposite effects. Besides, the overexpression of RUNX3 promoted the activation of JAK/STAT signaling to regulate SCs proliferation and myelination. Meanwhile, DNMT1 overexpression inhibited the expression of RUNX3, and cell proliferation and myelination. In conclusion, RUNX3 mediated by DNMT1 regulated SC proliferation and myelination via JAK/STAT signaling pathway.

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.