MiR-214 negatively regulates proliferation and WNT/β-catenin signaling in breast cancer

OBJECTIVE: To analyze the function and mechanism of miR-214 in regulating breast cancer cell proliferation. MATERIALS AND METHODS: MiR-214 expression level was measured by quantitative reverse transcription Polymerase Chain Reaction (qRT-PCR). The protein level of beta-catenin, PCNA and WNT targets (cyclin D1 and c-Myc) was evaluated by Western blot analysis. The effects of miR-214 on cell proliferation and cisplatin sensitivity were assessed by Cell Counting Kit-8 (CCK-8) assay and/or 5-bromo-2'-deoxyuridine (BrdU) assay. The effect of miR-214 on beta-catenin and WNT signaling activity was tested by luciferase reporter assay. RESULTS: MiR-214 was significantly downregulated in breast cancer tissues and was inversely correlated with beta-catenin expression. Forced expression of miR-214 in breast cancer cell line MCF-7 led to a decrease in cell proliferation and an increase in cisplatin sensitivity. Moreover, forced expression of miR-214 decreased the activity of WNT luciferase reporter and the luciferase reporter containing the 3'-untranslated region (3'UTR) of beta-catenin, whereas antisense inhibitor of miR-214 showed an opposite effect. Finally, miR-214 decreased the expression of beta-catenin and multiple WNT target genes. CONCLUSIONS: MiR-214 is downregulated and serves as a novel tumor suppressor in breast cancer. Forced expression of miR-214 in breast cancer cells diminished cancer cell survival possibly through inhibiting WNT signaling by direct repression of beta-catenin.