miR-339-5p inhibits breast cancer through targeting CDK2. (A) Top10 miR-339-5p target gene enrichment pathways according to fold enrichment in descending order and p value in ascending order. (B) The intersection of the Venn plot of genes that three pathways contained shown two target genes. (C) Expression of CDK2 in 50 breast tumors compared with para-carcinoma tissues *p<0.05. (D–E) The mRNA and protein levels of CDK2 in T47D and MCF-7 cells after being transfected with miR-339-5p mimics or NC mimics. (F) Bioinformatic analysis revealing the presence of complementary binding sites for miR-339-5p with CDK2 in RNA22. (G) Luciferase activity cotransfected with miR-339-5p and luciferase reporters containing pmirGLO-CDK2-WT or pmirGLO-CDK2-MUT in T47D/MCF-7 cells. (H, I) Knockdown of CDK2 abolished the miR-339-5p inhibitor induced cell growth shown by MTT assay and colony formation assay. (J–K) The cell cycle distribution and apoptosis of T47D and MCF-7 cells.