Unfavorable clinical implications for hypermethylation of RUNX3 in patients with salivary gland adenoid cystic carcinoma.

To elucidate the potential etiological role of RUNX3 in the development of salivary gland adenoid cystic carcinoma (ACC), we analyzed the methylation status of RUNX3 in a series of 114 ACC tissues and 3 ACC cell lines. Results showed that the methylated rate of RUNX3 was 50.9 and 3.5% in the 114 ACC samples and the corresponding normal salivary glands, respectively, achieving a significant difference (P<0.001). There was a significant correlation between RUNX3 methylation and various clinicopathological parameters of ACCs, such as perineural invasion, lymph node involvement, T-stage and distant metastasis (P<0.001). RUNX3 methylation was a significant predictor of the 5-year disease-free survival in ACC patients after surgery. Partial methylation was found in all 3 ACC cell lines, and the reactivation and more potent expression of RUNX3 was induced by 5-triazole-2-deoxycytidine. Our findings indicate that RUNX3 methylation may occur as a common event in the development of ACC and that methylation may be a major mechanism for inactivation of RUNX3 in ACC.