miR-770-5p downregulates endogenous HIPK1 expression in HT-29 cells. (A) Sites at 2,359-2,365 of the HIPK1 3′UTR were predicted to be the potential binding sites of miR-770-5p by the MiRanda, MiRwalk, and TargetScan software. (B) PCR results of the measurement of HIPK1 mRNA expression in HT-29 cells transfected with miR-770-5p mimics or mimic control. (C) Luciferase activity detected in miR-770-5p-transfected HT-29 cells co-transfected with psiCHECK2-3′UTR or psiCHECK2-3′UTR-mutation. (D) PCR results of the measurement of HIPK1 mRNA expression in HT-29 cells transfected with miR-770-5p inhibitors or inhibitor control. (E) HT-29 cells were transfected with siRNA targeting HIPK1 or siRNA control for 24 h and treated with MTX for 5 days. Cell viability was detected by Cell Counting Kit-8 assay. (F) Western blot analysis of the protein expression levels of HIPK1 in HT-29 cells transfected with miR-770-5p mimics or mimic control. (G) Western blot analysis of the protein expression levels of HIPK1 in HT-29 cells transfected with miR-770-5p inhibitors or inhibitor control. Results are presented as the mean ± standard deviation. s**P<0.01. MTX, methotrexate; 3′UTR, 3′-untranslated region; HIPK1, homeodomain-interacting protein kinase 1; siRNA, small interfering RNA; miR, microRNA; WT, wild type; mut, mutant; hsa, Homo sapiens; CNT, control untreated.