There is increasing evidence demonstrating that disorders affecting microRNAs (miRs) influence tumorigenesis and progression, which results in a poor prognosis in patients with breast cancer (BC). In the present study, the precise molecular mechanism underlying the role of miR-320 in the progression of BC was investigated. Reverse transcription-quantitative PCR was conducted to determine mRNA expression, and western blot analysis was used to test protein levels. An MTT assay was conducted to detect cell viability and Transwell assays were used to analyze cell migration and invasion abilities. Furthermore, E74-like factor 3 (ELF3) protein density was tested via immunohistochemistry. Tumor volume was detected by xenograft tumor formation assay. The current results indicated that miR-320 expression was downregulated in BC tissues and cells, and was associated with a poor prognosis of patients with BC. Overexpression of miR-320 inhibited cell proliferation, migration and invasion via inhibition of the epithelial-mesenchymal transition and the PI3K/AKT signaling pathway in BC cells. Furthermore, it was revealed that the tumor size and weight were smaller in nude mice that had been transfected to overexpress miR-320. The luciferase reporter assay demonstrated the direct binding of miR-320 to the 3' untranslated region of ELF3 mRNA, which may further downregulate ELF3. Overall, the present results provided evidence that miR-320 may be a tumor suppressor in BC, and that the miR-320/ELF3 axis regulated tumor progression via the PI3K/AKT signaling pathway, which may represent a novel treatment strategy for BC.
Keywords: E74-like factor 3; PI3K/AKT; breast cancer; microRNA-320.
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