Estradiol induces global changes in miRNA expression in endometrial cancer cells and upregulates oncogenic miR-182

Endometrial cancer (EC) occurs mainly in perimenopausal age. Risk factors are associated with unopposed estrogen stimulation of the endometrium. There are two main types of EC, EC1 and EC2. The pathogenesis of EC1 is estrogen-dependent. MiRNAs are small RNAs that regulate gene expression posttranscriptionally. They are induced by estrogens in different hormone-dependent neoplasias including breast cancer. However, little is known regarding their role in EC. Thus, this study aims to assess the role of the miRNA-estrogen axis in endometrial cancer cells. Estrogen-dependent endometrial cancer cell line Ishikawa was used in the study. Cells were incubated with estradiol, followed by RNA isolation. We used the microarray method to identify estradiol-induced miRNAs in EC cells. Then, we analyzed tissues derived from 45 patients (18 EC1, 12 EC2, and 15 healthy endometrium (HE)) that were cut using the Laser Capture Microdissection method. The expression of selected miRNAs and their targets was assessed using the RT-qPCR method. Ishikawa cells were transfected with miRNA mimic, miRNA inhibitor (anti-miRNA), and their scrambled controls. We identified 66 estrogen-upregulated miRNAs in endometrial cancer cells. Out of them, miR-182 was upregulated in EC1 compared to HE. We found that miR-182 is an oncomiR in EC since its increased expression promoted the proliferation of EC cells and decreased expression of miR-182 was associated with the inhibition of cancer cell proliferation. Moreover, miR-182 inhibition upregulated SMAD4 expression. Our study allowed us to better understand the role of estrogen in the pathogenesis of EC.