Mechanism Of Candidate Tumor Suppressor Gene PRDM5 In The Progression Of Lung Adenocarcinoma

Objectives: Lung cancer is one of the most common malignancies in the world.Non-small cell lung cancer accounts for 85% of the total incidence of lung cancer,of which about 50% is lung adenocarcinoma.Because the cause of lung adenocarcinoma is still unclear and lacking of obvious clinical symptoms make it easy to be ignored.The treatment is still based on surgical resection,supplemented by radiotherapy and chemotherapy.It can be seen that the study of the molecular mechanism of the development of lung adenocarcinoma and the search for suitable gene targets are of great significance for the early diagnosis and treatment of lung adenocarcinoma.In recent years,studies have shown that PRDM5 is silenced in various cancers due to hypermethylation of Cp G islands in the promoter region,including breast cancer,ovarian cancer,colorectal cancer,gastric cancer and lung cancer.According to the results of previous experiments,the microarray results showed that expression of PRDM5 was downregulated in lung adenocarcinoma tissues.However,it is unclear whether PRDM5 acts as a tumor suppressor gene in the development of lung adenocarcinoma.Therefore,this study explores the effects of PRDM5 on the biological behavior and related signaling pathways of lung adenocarcinoma cells by constructing a PRDM5-associated lung adenocarcinoma model,aiming at providing early diagnosis and finding a therapy target for lung adenocarcinoma.Methods: Our study consists of three parts.In the first part,the expression of PRDM5 in normal lung bronchial epithelial cells and several lung adenocarcinoma cell lines was detected by Western blot and real-time quantitative PCR.The expression of PRDM5 in lung adenocarcinoma tissues and adjacent tissues was analyzed by using related databases.Kaplan–Meier survival rate analysis clarified the correlation between PRDM5 and the prognosis of lung adenocarcinoma In the second part,we constructed PRDM5-overexpressing stable A549 and H1975 cells lines using a lentiviral expression vector.In the A549 cells and H1299 cells which have high PRDM5 gene expression levels,RNA interference technology was used to knock down the expression of PRDM5.The proliferation of lung adenocarcinoma cell line was examined by CCK8 assay and plate cloning assay.In the third part,A549 cells overexpressing PRDM5 were screened for differential expressed genes compared with control cells by RNA-seq technology.The differential expressed genes and relevant signal pathways influenced by PRDM5 were detected by Western blotting,q PCR,and GLuc-ON Promoter Reporter assays.Results: In the first part,compared with human normal bronchial epithelial cells BEAS-2B,the m RNA and protein levels of PRDM5 in lung adenocarcinoma cell lines from different sources were significantly decreased.Statistical analysis of GEO database showed lower expression of PRDM5 in lung adenocarcinoma tissues compared with normal lung tissues.Kaplan–Meier survival curve results showed that the expression level of PRDM5 is positively correlated with the survival rate of patients with lung adenocarcinoma.In the second part,we successfully constructed a recombinant lentiviral plasmid overexpressing PRDM5 protein,which can stably express PRDM5 in A549 and H1975 cells.Overexpression of PRDM5 inhibited the proliferation of A549 and H1975 cells,while knockdown of PRDM5 in A549 and H1299 cells promoted cell proliferation.In the third part,analysis from RNA-seq technique,GO functional enrichment and KEGG signaling pathway showed that SOCS1 may be a downstream target of PRDM5.The results show that PRDM5 promote SOCS1 expression in m RNA level.We also found that PRDM5 enhanced the promoter activity of SOCS1 by GLuc-On-promoter reporter assay.Beside of SOCS1 overexpression,the expression of phosphate-JAK2 and phosphate-STAT3 in PRDM5 overexpressed cells decreased markedly than control A549 cells.Conclusions: PRDM5 expression is downregulated in lung adenocarcinoma tissues and cell lines.Overexpression of PRDM5 can inhibit the proliferation of lung adenocarcinoma cells,while knockdown of PRDM5 can promote the proliferation of lung adenocarcinoma cells.PRDM5 is able to activate the expression of SOCS1 by regulating the promoter activity of SOCS1,while inhibits the activation of the JAK/STAT signaling pathway.PRDM5 may suppress JAK/STAT pathway by upregulating SOCS1 expression in lung adenocarcinoma cells.The results of our studies will provide new ideas for targeted therapy of lung adenocarcinoma based on PRDM5.