ABSTRACT
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.
ABSTRACT
PURPOSE: Lung adenocarcinoma (LA) is one of the major types of lung cancer. MicroRNAs (miRNAs) play an essential role in regulating responses of natural killer (NK) cells to cancer malignancy. However, the mechanism of miR-218-5p involved in the killing effect of NK cells to LA cells remains poorly understood. MATERIALS AND METHODS: The expression of miR-218-5p was examined by quantitative real-time polymerase chain reaction (qRT-PCR). Serine hydroxymethyl transferase 1 (SHMT1) level was detected by qRT-PCR or western blots. Cytokines production of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) were detected by ELISA. The killing effect of NK cells to LA cells was investigated using lactate dehydrogenase cytotoxicity assay kit. The interaction of miR-218-5p and SHMT1 was probed by luciferase activity assay. Xenograft model was established to investigate the killing effect of NK cells in vivo. RESULTS: miR-218-5p was enhanced and SHMT1 was inhibited in NK cells of LA patients, whereas stimulation of interleukin-2 (IL-2) reversed their abundances. Addition of miR-218-5p reduced IL-2-induced cytokines expression and cytotoxicity in NK-92 against LA cells. Moreover, SHMT1 was negatively regulated by miR-218-5p and attenuated miR-218-5p-mediated effect on cytotoxicity, IFN-γ and TNF-α secretion in IL-2-activated NK cells. In addition, miR-218-5p exhaustion inhibited tumor growth by promoting killing effect of NK cells. CONCLUSION: miR-218-5p suppresses the killing effect of NK cells to LA cells by targeting SHMT1, providing a potential target for LA treatment by ameliorating NK cells function.