The 3′ UTRs fragments of human BECN1, ATG16L1 or SQSTM1 genes were cloned into pRL-TK luciferase vector (Promega, Madison, WI, USA), the resulting plasmids were called wild-type reporters (WT). To ablate the miR-20 bindings sites, we used site-directed mutagenesis kit (Takara, Kusatsu, Japan) to generate mutated vectors (Mut). MCF7 cells were transfected with luciferase vectors and miR-20a or NC using Lipofectamine 2000 (Invitrogen). Luciferase activity was measured and normalized by protein concentration.