MicroRNA-9-5p exerts its effects on the invasive ability of triple-negative breast cancer cells by targeting leucine zipper tumor suppressor 2
Objective To observe the regulatory effect of microRNA(miRNA,miR)-9-5p on leucine zipper tumor suppressor 2(LZTS2)in triple negative breast cancer(TNBC)cells,as well as its impact on the invasive ability of these TNBC cells.Methods The specimens of triple-negative breast cancer and adjacent tissues were collected from the Department of Breast Surgery,Fourth Hospital of Hebei Medical University,from April 2019 to April 2020.The real-time fluorescent quantitative polymerase chain reaction(PCR)was used to detect the expression levels of miR-9-5p and LZTS2 genes in triple-negative breast cancer tissues.MDA-MB-231 cells were divided into a negative control group and a miR-9-5p mimics group,and whether LZTS2 was a target gene of miR-9-5p was analyzed using a dual luciferase reporter gene experiment.MDA-MB-231 cells were divided into a negative control group and a miR-9-5p inhibitor group,and the effect of miR-9-5p on LZTS2 protein expression was detected using Western blotting.The effect of miR-9-5p inhibitor on cell invasion capability was assessed using a cell invasion assay.Subsequently,MDA-MB-231 cells were divided into miRNA negative control+empty vector group and a miR-9-5p mimics+LZTS2 group,and cell invasion experiments were used to analyze whether the effect of miR-9-5p on cell invasion ability was related to LZTS2 expression.The comparison between the two groups was performed using t-test.Results The real time quantitative PCR showed that the expression of miR-9-5p in TNBC tis-sues(4.45±0.68)was significantly higher than that in adjacent tissues(1.02±0.07,t=8.691,P＜0.05).The expression of LZTS2 in TNBC tissues(0.35±0.11)was significantly lower than that in adjacent tissues(1.01±0.05,t=9.365,P＜0.05).The correlation analysis showed that the expression of miR-9-5p and LZTS2 was negatively correlated(r=-0.472,P＜0.05).The analysis of reporter gene showed that the co-transfection of miR-9-5p mimic and LZTS2 3'untranslated regions(3'UTR)wild-type vector group resulted in significantly lower reporter gene activity(0.35±0.02)than the control group(1.02±0.04,t=14.980,P＜0.05).The results of Western blotting showed that the expression level of LZTS2 protein in the miR-9-5p inhibitor transfection group(1.28±0.05)was significantly higher than that in the negative control group(0.23±0.01,t=17.50,P＜0.05).The results of the cell invasion assay showed that the number of inva-sive cells in the miR-9-5p inhibitor transfection group(121.00±9.89)was significantly lower than that in the negative control group(300.00±9.89,t=12.79,P＜0.05).However,after co-transfection with LZTS2 overexpression plasmid,there was no significant difference in the number of invasive cells between the miR-9-5p mimic+LZTS2 group(306.50±7.77)and the miRNA negative control+empty vector group(310.50±7.78,t=0.363,P＞0.05).Conclusion MiR-9-5p can inhibit the invasion capability of triple-negative breast cancer cells by targeting the LZTS2 gene.
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