miR-191/DAB2 axis regulates the tumorigenicity of estrogen receptor-positive breast cancer.

Disabled-2 (DAB2) has been shown to be downregulated in a variety of human cancer types including breast tumors. However, the role of DAB2 in estrogen receptor positive (ER+) breast cancer cells has not been reported. In this context, we demonstrated that DAB2 expression was significantly decreased in ER+ breast cancer cell lines and ER+ clinical specimens, compared with ER- breast cancer cell lines and ER- tissues, respectively. Depletion of estrogen significantly elevated DAB2 expression in ER+ MCF7 and T-47D cells. Treatment with estradiol (E2) reduced the expression of DAB2 and administration of tamoxifen upregulated DAB2 expression in a dose-dependent manner. Functionally, silencing of DAB2 in hormone-starved MCF7 and T-47D cells promoted cellular proliferation and enforced expression of DAB2 in normal-cultured or E2-treated cells suppressed cellular proliferation. Mechanistically, estrogen-induced miR-191 was identified as a direct upstream regulator of DAB2 in ER+ cells. Luciferase reporter assay indicated that miR-191 inhibited DAB2 expression by directly targeting the 3'-UTR of DAB2. Importantly, the expression and function of miR-191 showed the opposite tendency with DAB2 in ER+ cells. In vivo, inhibition of miR-191 significantly suppressed the xenograft growth induced by E2, and silencing of DAB2 could restored the growth arrest induced by miR-191 inhibition. Taken together, our data unveil that the miR-191-DAB2 axis seems to be an important pathway associated with estrogen signaling in breast cancer and may serve as a potential diagnostic biomarker and a powerful therapeutic target for ER+ breast cancer patients.