SOX4 was directly targeted and inhibited by miR-145-5p. (a) The mRNA and protein levels of SOX4 in bladder cancer tissues (n = 36) and normal tissues (n = 36) were detected by RT-qPCR and western blot. (b) The mRNA and protein levels of SOX4 in SV-HUC-1, T24, and J82 cells were measured by RT-qPCR. (c) The putative or mutant miR-145-5p binding sites in the 3′UTR of SOX4 were predicted by Targetscan tool. (d) 293T cells were co-transfected with NC-mimic or miR-145-5p mimic and SOX4 3′UTR wt or SOX4 3′UTR mut, and the luciferase activity was detected. (e) T24 and J82 cells were transfected with NC-mimic, miR-145-5p mimic, NC inhibitor, or miR-145-5p inhibitor, respectively. And the expression level of SOX4 was examined by western blot. *P < 0.05.