ELF3 is a target of miR-320 in BC cells. (A) Binding sites of miR-320 and ELF3 were predicted using TargetScanHuman 7.1. (B) Luciferase activities in MCF-7 and SK-BR-3 cells were downregulated after co-transfection with miR-320 mimic and ELF3-3′-UTR-wild type. (C) Expression levels of miR-320 in MCF-7 and SK-BR-3 cell lines were measured by reverse transcription-quantitative PCR following transfection with miR-320 mimic, miR-320 inhibitor, control mimic and control inhibitor. (D) ELF3 protein level and (E) ELF3 mRNA expression were downregulated or upregulated in MCF-7 and SK-BR-3 cells after treatment with miR-320 mimic or inhibitor. (F) ELF3 expression and miR-320 expression in BC tissues (n=52) were negatively correlated (R=−0.6769; P<0.0001). *P<0.05, **P<0.01 vs. normal tissues. BC, breast cancer; miR, microRNA; ELF3, E74-like factor 3; 3′UTR, 3′ untranslated region