miRNA-9 Inhibits Proliferation and Migration of Lung Squamous Cell Carcinoma Cells by Regulating NRSF/EGFR

Background: To investigate the mechanism of microRNA9 in inhibiting proliferation and migration of lung squamous cell carcinoma cells via neuron-restricted silencing factor/epidermal growth factor receptor. Material and Methods: Detection of microRNA9, neuron-restricted silencing factor, and epidermal growth factor receptor expression levels in lung cancer patients' tissues and lung cancer cells by Western blotting and quantitative polymerase chain reaction. Detection of cell proliferation by colony formation assay and cell counting kit-8 assay. Detection of cell migration by wound-healing assay and Transwell assay. And detection of the regulatory effect between neuron-restricted silencing factor and epidermal growth factor receptor by Luciferase reporter gene system. Subcutaneous implantation mouse models of NCI-H520 cells were constructed to detect cell proliferationin vivo, and Kaplan-Meier method calculated patient survival. Results: The expression of microRNA9 and epidermal growth factor receptor was higher in lung cancer tissues than in normal lung tissues, while the expression of neuron-restricted silencing factor was lower in lung cancer tissues than in normal lung tissues. MicroRNA9 higher expression was strongly related to tumor size, and TNM stage and predicted showed reduced overall survival in patients with lung cancer. Further loss of function and enhancement experiments revealed that inhibition of microRNA9 could significantly inhibit lung squamous carcinoma cell proliferation and migration. Luciferase reporter assay demonstrated that microRNA9 could bind to NRSF messenger RNA and inhibit its expression, neuron-restricted silencing factor overexpression also exerted inhibitory effects on cell proliferation and migration. Moreover, Luciferase reporter assay showed that neuron-restricted silencing factor downregulate epidermal growth factor receptor expression levels by binding to epidermal growth factor receptor promoter regions, and Pearson's correlation analysis indicated that the levels of microRNA9 in lung cancer tissues were correlated with neuron-restricted silencing factor and epidermal growth factor receptor. Combined microRNA9 with neuron-restricted silencing factor or epidermal growth factor receptor to predict the prognosis of patients with lung cancer may be more accurate. Conclusion: MicroRNA9 inhibits proliferation and migration of lung squamous cell carcinoma cells by inhibiting neuron-restricted silencing factor/epidermal growth factor receptor axis. MicroRNA9 can be a new prognostic marker and therapeutic target for lung squamous cell carcinoma.