Loss of RUNX3 is significantly associated with advanced tumor grade and stage in endometrial cancers

Loss of runt-related transcription factor 3 (RUNX3) has been reported in various cancers, and one of the mechanisms mediating loss of RUNX3 expression is DNA methylation. However, the role of RUNX3 expression and its DNA methylation status as prognostic factors in endometrial cancer remain unclear. In the present study, the expression and promoter methylation of RUNX3 was examined in endometrial cancer tissues and cell lines, as well as their association with endometrial cancer prognosis. Fifty-five endometrial cancer tissues and two endometrial cancer cell lines (HEC1- and Ishikawa) were studied. RUNX3 expression and promoter methylation were examined using reverse transcription-polymerase chain reaction (RT-PCR), methylation specific PCR (MS-PCR), and immunohistochemical staining. The demethylating agent 5-aza-2-deoxycytidine (ADC) was used to reverse the methylation of the RUNX3 promoter. Loss of RUNX3 expression was observed in 50.9% (27/53) of endometrial cancer tissues and in the HEC1- cell line by immunohistochemistry and RT-PCR, respectively. Methylation of the RUNX3 promoter was observed in 62.2% (33/53) of endometrial cancer tissues, 12.5% (1/8) of normal endometrial tissues, and the HEC1- cell line by MS-PCR. Tumor grade and stage were significantly correlated with loss of RUNX3 expression. The expression of RUNX3 was restored by treatment with ADC and resulted in growth inhibition in HEC1- cells. The present results suggested that methylation may serve a critical role in the silencing of RUNX3 and loss of RUNX3 expression may serve as a prognostic marker in endometrial cancer.