ABSTRACT
Objective To explore the effects of miR-221 on tumor cell proliferation, migration and invasion in nonsmall cell lung cancer (NSCLC) xenograft model mice, and to preliminarily analyze its possible mechanism of regulating Akt/ mammalian target of rapamycin(mTOR) signaling pathway by targeting tissue inhibitor of metalloproteinase-2 (TIMP-2) on tumor cells in non-small cell lung cancer (NSCLC) through tumor-bearing nude mice. Methods The A549 cells were divided into control group, mimic group, TIMP-2 group and mimic+TIMP-2 group. The mimic group and TIMP-2 group were transfected with miR-221 mimic and TIMP-2 overexpression plasmids, respectively. The mimic + TIMP-2 group was simultaneously transfected with miR-221 mimic and TIMP-2 overexpression plasmids. The control group was transfected with the same amount of negative control plasmid. After transfection, the cells of each group were injected subcutaneously into the left forelimb to construct the corresponding 4 groups of NSCLC mouse models. The proliferation-related protein (Ki67) was detected by immunohistochemical staining to detected the effect of cell proliferation ability. Matrix metalloproteinase-2 (MMP-2) and N-cadherin proteins in each group were tested by Western blotting to assess and compare the abilities of migration and invasion. The levels of miR-221, TIMP-2 and Akt/ mTOR pathways in bone marrow and tumor tissues were detected by Real-time PCR and Western blotting. Results When co-transfected with wild type(WT)-TIMP-2 and miR-221 mimic, the relative luciferase activity in the cells reduced significantly (P<0. 05). Compared with the control group, the tumor mass, volume, Ki67, MMP-2 and N-cadherin protein expression levels, miR-221 and Akt/ mTOR pathway levels were increased significantly, while the levels of TIMP-2 mRNA and protein were significantly reduced in the mimic group (P<0. 05). Compared with the control group, the levels of TIMP-2 mRNA and protein in the TIMP-2 group increased significantly, while the other indicators decreased significantly (P<0. 05). Tumor tissue mass, volume, Ki67, MMP-2, Ncadherin, miR-221 and Akt/ mTOR pathway levels in mimic+TIMP-2 group were significantly lower than those in the mimic group and significantly higher than those in the TIMP-2 group, while TIMP-2 mRNA and protein levels were significantly higher than those in the mimic group and significantly lower than those in the TIMP-2 group (P<0. 05). Conclusion In the NSCLC transplanted tumor mouse model, miR-221 may mediate the Akt/ mTOR pathway by targeting the expression of TIMP-2 protein to promote cell proliferation, migration and invasion.