MicroRNA-126-5p downregulates BCAR3 expression to promote cell migration and invasion in endometriosis

Endometriosis (EMs) is an estrogen-dependent multifactorial disease. Inhibition of estrogen in endometrial cells contributes to their failure to form lesions in ectopic sites. However, whether reducing or suppressing the inhibitory effect of estrogen results in the establishment of ectopic lesions remains unclear. The BCAR3 gene induces estrogen resistance in estrogen-dependent breast cancer cells and promotes cell migration, invasion, and epithelial-mesenchymal transition (EMT). However, the expression of BCAR3 in endometriosis and its effect on endometrial cell function and the anti-estrogen effect of endometriosis have not been reported. These issues are addressed in the present study.

The study included 32 cases of ectopic endometrium and eutopic endometrium in patients with endometriosis and 31 cases of normal endometrium as controls. The expression of BCAR3 and microRNA (miR)-126-5p was detected by real-time PCR, immunohistochemistry, and western blotting. The effects of BCAR3 and miR-126-5p on the morphology and biological behavior of eutopic endometrial cells were verified using lentivirus overexpression and a vector knockdown model, the CCK-8 assay, Transwell experiments, and estrogen intervention experiments using primary cultures of epithelial and stromal cells.

The BCAR3 gene was highly expressed in ectopic endometrium and the eutopic endometrium of patients with endometriosis, and the expression level was higher in stage III-IV patients than in stage I-II patients. In vitro cell experiments showed that miR-126-5p negatively regulated the expression of BCAR3 and its effect on the migration and invasion of stromal cells. Low expression of miR-126-5p and high expression of BCAR3 promoted endometriosis stromal cell migration and invasion. Assessment of EMT in endometriosis compared with eutopic endometrium showed that the expression of vimentin was significantly increased and the expression of E-cadherin was significantly decreased in ectopic endometrium. Estrogen promoted EMT in eutopic endometrial epithelial cells and this effect was reversed by estrogen inhibitors. BCAR3 had no direct effect on EMT and did not act synergistically with estrogen on promoting EMT.

miR-126-5p negatively regulated BCAR3 expression in eutopic endometriosis, enhanced the migration and invasion of endometrial cells, and promoted the occurrence of endometriosis. BCAR3 did not induce EMT and had no synergistic effect with estrogen, but its inhibition of anti-estrogen function may provide new insight into the mechanism of local estrogen action in endometriosis.