MiR-216b modulates cisplatin resistance and stem cell-like features in breast cancer cells by targeting E2F4

Purpose: To study the influence of miR-216b expression in breast cancer (BC), and the underlying mechanism(s) of action. Methods: Viability of BC cell lines was determined using CCK-8 as well as colony formation assays, while the abundance of mRNAs of key genes was assessed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Western blot assay was utilized to measure protein expressions of E2F4 and stem cell markers. Bioinformatics and dual-luciferase procedures were deployed to predict the targets of miR-216b on 3 '-UTR of E2F4. Results: MiR-216b was reduced in BC tissues and mammary carcinoma cell line, MCF-7, relative to those in paracancerous tissue and normal breast cell line, MCF-10A (p < 0.05). Compared with miR-NC group, cell viability, median inhibitory concentration (IC50), and potential to form colonies in cisplatin-insensitive cell line MCF-7/DDP were reduced by miR-216b. Moreover, MiR-216b suppressed stem cell characteristics and decreased the expressions of ALDH1 and Oct-4 in BC cells. Inhibition of miR-216b resulted in significant increase in microsphere formation and expressions of ALDH1 and Oct-4, when compared with NC-inhibitor group. In addition, E2F transcription factor 4 (E2F4) was identified as the downstream gene of miR-216b. Knockdown of E2F4 annulled the influence of miR-216b on insensitivity to cisplatin and stem cell likeness of MCF-7/DDP. Conclusion: MiR-216b induces increase in BC response to cisplatin and suppressed stem cell characteristics by regulating E2F4. This finding may be useful for developing strategies aimed at reversing cisplatin insensitivity in BC.