SOX11 hypermethylation as a tumor biomarker in endometrial cancer

We previously reported that SOX4 is overexpressed in endometrial cancer and that it partially contributes to hypermethylation of miR-129-2 and miR-203. The current study seeks to identify methylation and expression levels of the SOX gene family in endometrial carcinomas. Methylation levels of the 16 SOX gene family members were measured by combining bisulfite restriction analysis (COBRA), MassARRAY, and pyrosequencing assays of cell lines and endometrial cancer samples. Gene expression was determined by RT-qPCR. The methylation level of the SOX11 locus was correlated with clinicopathologic factors in primary endometrial tumors and in TCGA endometrial cohort. It was also examined in DNA of serum and endometrial specimens from a longitudinal cohort of early stage endometrial cancer patients. COBRA assays indicated that hypermethylation of SOX1, SOX2, SOX11, SOX14, SOX15, SOX17, and SOX18 was present in endometrial cancer cell lines and not in the normal control. SOX11 expression was reactivated only by a DNA methylation inhibitor. Moreover, aberrant DNA methylation of SOX11 was detected in the majority of endometrioid endometrial carcinomas (n=114) and none of the 22 adjacent normal endometrial samples (P<0.0001). The methylation status of SOX11 associated significantly with microsatellite instability and MLH1 methylation in endometrial tumors (P<0.0001), and this finding was validated in TCGA endometrial cohort. Furthermore, SOX11 was not hypermethylated in serum DNA from early stage endometrial cancer patients. This study found that hypermethylation of SOX11 is common in endometrial carcinomas and strongly associates with microsatellite instability and MLH1 methylation.