Estrogen upregulates DNMT1 and leads to the hypermethylation of RUNX3 in the malignant transformation of ovarian endometriosis

Abstract Research Question: What is the mechanism of  hypermethylation of RUNX3 in the eutopic endometrium of endometriosis as biomarker in the malignant transformation of endometriosis. Design: MSP was used to analyze the methylation status of RUNX3 in endometriosis-associated ovarian cancer (EAOC). Primary eutopic endometrial stromal cells (ESCs) were isolated from the uteri of patients with ovarian endometriosis. After RUNX3 knockdown by RNA interference technology or ESCs treated with estradiol , the proliferation and invasion ability were evaluated in ESCs by using MTT and transwell assays. Results: we found that the frequency of methylation of RUNX3 in neoplastic tissue in the EAOC group was significantly higher than that in the ectopic endometrium of the endometriosis (EMs) group. And the frequency of methylation of RUNX3 in the eutopic endometrium of the EAOC group was significantly higher than that in the EMs group. However, there was no significant difference in the eutopic endometrium when compared between the EMs group and the control endometrium (CEs) group. Silencing the RUNX3 promoted the proliferation and invasion of ESCs. Following intervention with estrogen, we observed that the E2 group showed higher levels of RUNX3 methylation and DNMT1 mRNA and protein, and lower levels of RUNX3 mRNA and protein when compared with the ESCs group. Conclusion: This study demonstrated that the hypermethylation of the RUNX3  was related to the malignant transformation of endometriosis and that this process was related to corresponding changes in the eutopic endometrium. Furthermore, the “estrogen-DNMT1” signaling pathway may induce the hypermethylation of RUNX3 to promote the malignant transformation of endometriosis.