Objective To investigate the effect of overexpression of miR-218-5p and inhibition of TDP1 expression on rotenone-induced apoptosis of gastric cancer cells, and to elucidate its possible mechanism.

Methods The expression levels of miR-218-5p and TDP1 in human normal gastric epithelial cells and four gastric cancer cells were detected by RT-PCR, and their correlation was analyzed. The targeting regulation of miR-218-5p on TDP1 was verified by dual luciferase reporter gene assay. Gastric cancer cell injury model was induced by 1.0 μmol/L rotenone. Cell cycle and apoptotic rate were detected by flow cytometry. TDP1 level in mitochondria and the expression of Bax and Cyt-c protein were detected by Western blot.

Results The expression of miR-218-5p was low in gastric cancer cells (P < 0.05), and TDP1 was high (P < 0.01). There was a negative correlation between the expression of miR-218-5p and TDP1 (R²=0.9580, P=0.0212). Compared with the control group, SGC-7901 cells in the injured group developed G₁ phase arrest and the apoptotic rate increased (P < 0.01). After transfection of miR-218-5p-mimic, the cell arrest and apoptotic rate further increased (P < 0.01), the expression of Bax and Cyt-c increased (P < 0.01), while the level of TDP1 in mitochondria decreased (P < 0.01). The G₁ phase arrest of cells in TDP1 overexpression group was relieved, the apoptotic rate was decreased (P < 0.01), the level of TDP1 in mitochondria was increased (P < 0.01), and Bax and Cyt-c expression were decreased (P < 0.01).

Conclusion MiR-218-5p can target TDP1 expression and induce apoptosis of gastric cancer cells. Its mechanism may be related to inhibiting mitochondrial DNA damage repair and function maintenance and activating mitochondrial endogenous apoptosis pathway.