Objective:To investigate the relationship between the methylation status of Septin9 gene in peripheral blood of patients with lung cancer and the clinicopathological characteristics, and its effect on the biological behavior of human lung cancer A549 cells. Methods:One hundred and four patients with lung cancer and 96 healthy people were respectively divided into research group and control group. The methylation-specific PCR method was used to detect the methylation of Septin9 gene in the peripheral blood of the two groups, and the positive rate of Septin9 gene methylation was calculated. The relationship between the positive rate of Septin9 gene methylation and the clinicopathological characteristics of lung cancer was analyzed. The human lung cancer cell line A549 was treated with 5, 10, and 20 μmol·L-1 5-aza-dC, and the normally cultured A549 cells were used as controls. Real-time fluorescent quantitative PCR and Western blot were used to detect the expression of Septin9 mRNA and protein in cells. Cell proliferation activity, cell apoptosis and cell migration and invasion ability were detected by MTT method, flow cytometry and Transwell experiment respectively. Results:Compared with the control group, the positive rate of Septin9 gene methylation in peripheral blood of lung cancer patients was significantly increased, which was related to the TNM stage, degree of differentiation and lymph node metastasis, while it was not related to the gender and age of lung cancer patients. After 5-aza-dC treatment, the expression levels of Septin9 mRNA and protein in A549 cells were significantly up-regulated in a concentration-dependent manner. 5-aza-dC could significantly inhibit the proliferation of A549 cells in a concentration- and time-dependent manner. After 5-aza-dC treatment, the apoptotic rate of A549 cells was significantly increased in a concentration-dependent manner and at the same time, 5-aza-dC significantly inhibited the migration and invasion, all being concentration-dependent. Conclusion:The positive rate of methylation of Septin9 gene in peripheral blood of lung cancer is increased, which is related to tumor stage, degree of differentiation and lymph node metastasis. 5-aza-dC treatment can inhibit lung cancer cell proliferation, invasion and migration by restoring Septin9 expression in A549 cells, and induce cell apoptosis.
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