Correlation and clinical significance of methyltransferases SETDB1 and SPG20 methylation in lung adenocarcinoma

Abstract

Objective: The incidence of primary lung adenocarcinoma is increasing year by year in worldwide, and it has surpassed squamous cell carcinoma to become the most common pathological type of lung cancer. Advances in medical technology have made the overall survival rate of lung cancer patients improve, but it is still very low. In the study, we investigated the methyltransferase SETDB1 expression and the methylation level of SPG20, and analyzed the correlation and its clinical significance in the pathogenesis of lung adenocarcinoma. Methods: 60 lung adenocarcinoma and normal lung tissues were selected.The expression of SPG20 and SETDB1 mRNA was examined by RT-qPCR; Protein expression of SPG20 and SETDB1 was determined by immunohistochemistry(SP) and immune protein imprinting(Western blot);Methylation level of SPG20 gene was determined by pyrosequencing. Correlation between SETDB1 and SPG20 methylation levels and both and clinical case characteristics was analysed by statistics. Western blot detection of SETDB1 and SPG20 protein expression in lung adenocarcinoma cells and normal bronchial mucosal epithelial cells.The small interfering RNA of SETDB1 was transfected into lung adenocarcinoma A549 cells by liposome-mediated method, the mRNA and protein expression levels of SETDB1 were detected by RT-qPCR and Wesrern blot, and the methylation level of SPG20 gene was detected by pyrosequencing. Results:Relative expression of SPG20 mRNA was significantly lower in lung adenocarcinoma tissue than in normal lung tissue, while relative SETDB1 mRNA expression was higher in cancer tissue than in normal lung tissue. SETDB1 protein expression was significantly higher in lung adenocarcinoma tissue than in normal lung tissue, while SPG20 protein showed lower expression in cancer tissue than in normal lung tissue. The methylation rate of the SPG20 gene was significantly higher in cancerous tissues than in normal lung tissue, the difference was statistically significant. SPG20 methylation in cancer tissues showed a correlation with SETDB1 and showed a positive correlation; SPG20 methylation and SETDB1 are closely related with TNM stage, tissue differentiation, and lymph node metastasis in lung adenocarcinoma. The vitro experiments showed that SETDB1 was highly expressed, while SPG20 was lowIn lung adenocarcinoma cells, SETDB1 was low and SPG20 was high in normal bronchial epithelial cells. RNA interference with SETDB1 could significantly reduce the mRNA and protein expression of SETDB1 in A549 cells, the methylation rate of SPG20 gene was significantly decreased, and the protein expression was increased. Conclusion:There is a significant correlation between methyltransferases SETDB1 and SPG20 methylation in lung adenocarcinoma, and high SETDB1 expression may be the upstream molecule of SPG20 methylation, working together in promoting the occurrence and development of lung adenocarcinoma.