Objective To investigate the effects of let-7f-5p targeting DARS2 on the viability, invasion and apoptosis of bladder cancer (BC) cells and its underlying mechanism.

Methods Normal human bladder epithelial cells SV-HUC-1 were used as control, the mRNA expression of let-7f-5p and DARS2 in BC cells 5637 and T24 were detected by qRT-PCR, and the protein expression of DARS2 was detected by western blot. Dual luciferase reporting assay was used to detect the targeting relationship between let-7f-5p and DARS2. Let-7f-5p mimic and DARS2 overexpression plasmid were transfected into bladder cancer cell T24. Cell viability was detected by CCK-8 method. Cell invasion was measured by transwell assay. Cell apoptosis was detected by flow cytometry. The expression of MAPK pathway proteins were detected by western blot.

Results Compared with SV-HUC-1 group, the expression of let-7f-5p was significantly decreased, the mRNA and protein expression of DARS2 were significantly increased in bladder cancer cells 5637 and T24 (P ＜ 0.05). Luciferase assay results showed that let-7f-5p directly targeted the 3'-UTR of DARS2. Overexpression of let-7f-5p significantly decreased the cell viability and invasion, promoted apoptosis, and inhibited the protein expression of p-p38 MAPK and p-ERK1/2 in T24 cells (P ＜ 0.05). After DARS2 expression was restored, cell viability and invasion were significantly increased, cell apoptosis was decreased, and the protein expressions of p-p38 MAPK and p-ERK1/2 were significantly increased in T24 cells (P ＜ 0.05).

Conclusion Let-7f-5p reduces T24 cell viability and invasion, promotes cell apoptosis by targeting DARS2 and inhibiting MAPK signaling pathway.