The Mechanism Of LncRNAs On The Malignant Progression Of Lung Adenocarcinoma

Backgrounds:Human lung cancer is one of the most common aggressive malignancies in the world.Lung cancer mainly contains two types:small cell lung cancer(SCLC)and non-small-cell lung cancer(NSCLC),accounting for 15%and 85%of total lung cancer diagnoses,respectively.Even though there has been great improvement on traditional treatments,a considerable number of patients with lung adenocarcinoma(LAC),as the most widespread histological type of NSCLC,are diagnosed at the advanced stages,and the prognosis of these patients is still poor.Therefore,it is extremely necessary to identify novel biomarkers used as therapeutic targets for human LAC.With the research and development of the human genome,98%of the genome do not code for protein function,the lack of protein coding functions of RNA are known as non-coding RNAs(non-coding RNAs,ncRNAs),it is divided into short chain(<200 nt)and long chain(>200 nt)according to the length.LncRNAs belong to a novel heterogeneous class of ncRNAs,and are involved in various biological processes,including imprinting,histone?code regulation and proliferation of cancer cells,through regulation of gene expression.Lots of studies have demonstrated that lncRNAs play an important role in multiple cancers,which has given rise to be targets for therapeutic research.What kind of role the lncRNAs play in LAC,whether they can serve as valuable biomarkers of LAC and whether they can be effective therapeutic targets of LAC,these questions are of great value for the patients and cancer therapy,which remains unclear.Objectives:In this study,we focused on investigating the role and the underlying molecular machanism of two lncRNAs(lncRNA-LET and lncRNA AK001796)on malignant progression and drug resistance of LAC.Methods:Part 1:The expression levels of lncRNA-LET and NONO were dectected in LAC tissues using qRT-PCR.Stable clones with up-regulation of lncRNA-LET were generated with plasmid via lentivirus technology.Knock-down of lncRNA-LET was generated via small hairpin RNA technology.Cell migration,invasion,proliferation,cell cycle and apoptosis were investigated using wound healing,transwell,MTT and flow cytometry assays.Bioinformatics analysis was used to predict and verify the regulatory function of lncRNA-LET on its RNA-binding gene NONO.The expression levels of EMT markers were examined using western blot.The effect of lncRNA-LET on tumor growth in vivo was assessed by xenograft model.Part 2:The expression of lncRNA AK001796 was detected in A549 and/or A549/DDP cells using qRT-PCR.Knock-down of lncRNA AK001796 was generated via small interference RNA technology.IC50,cell proliferation,cell cycle and apoptosis were investigated by MTT and flow cytometry assays.The expression levels of cell apoptosis-associated proteins(CCNC and BIRC5)and cell cycle-associated proteins(CDK1 and GTSE1)were measured by western blot.Results:Part 1:The expression of lncRNA-LET was decreased in LAC tissues compared with matched paracarcinoma tissues.Low lncRNA-LET expression was associated with histological grade,tumor stage and lymph node metastasis of LAC.Overexpression of lncRNA-LET could inhibit cell proliferation,migration,invasion and attenuate EMT process,while the effect of lncRNA-LET down-regulation was reverse.Meanwhile,Overexpression of lncRNA-LET could induce cell cycle arrest at the G0/G1 phase,while the effect of lncRNA-LET down-regulation was reverse.Besides,NONO was the RNA-binding gene of lncRNA-LET,and restoration of NONO partially rescued the tumor suppressive role of lncRNA-LET.Furthermore,lncRNA-LET attenuated tumor growth in vivo via interacting with NONO partially.Part 2:The expression levels of lncRNA AK001796 were significantly higher in cisplatin?resistant A549/DDP cells,compared with those in parental A549 cells.Furthermore,down-regulation of lncRNA AK001796 was able to re?sensitize A549/DDP cells to cisplatin.Meanwhile,down-regulation of IncRNA AK001796 could inhibit cell proliferation,promote cell apoptosis and induce cell cycle arrest at the G0/G1 phase.The results also demonstrated that the lncRNA AK001796?mediated chemosensitivity enhancement was related to the regulation of cell apoptosis-associated proteins and cell cycle-associated proteins,at least partially.Conclusion:In summary,these results indicate that:(1)Overexpression of lncRNA-LET attenuates EMT process and represses the malignant process of LAC via interacting with NONO;(2)Overexpression of lncRNA-LET can repress NONO expression directly,and downregulated NONO can prolong the overall survival rate of patients with LAC;(3)LncRNA AK001796 may play a crucial role in the development of cisplatin resistance in LAC.