Linc00173 Is Involved In Chemoresistance Of Small Cell Lung Cancer

Background:Lung cancer is now the most common tumor in the world and statistics show that small cell lung cancer(SCLC)constitutes 13-15%of lung cancers worldwide and constitutes the sixth leading cause of cancer-related deaths.A key barrier to the treatment of small-cell lung cancer is that chemoresistance always occurs during the course of the treatment,and in the past three decades,the survival expectation and the standard treatment of the SCLC patients have not been changed.Therefore,it is very important to understand the molecular mechanism of SCLC chemoresistance for developing new therapeutic targets.Purpose:We found that long non-coding RNA Linc00173 was highly expressed in drug resistant SCLC cell lines by microarray.It was found that Linc00173 was closely related to chemoresistance of small cell lung cancer which the molecular mechanism is not clear.Bioinformatics prediction shows that microRNA-218 has binding sites with Linc00173 and Etk,a drug resistant factor in small cell lung cancer.Therefore,we intend to explore the mechanism that Linc00173 may act as a ceRNA.In addition,it was found by RNA-Pulldown experiments that Linc00173 can bind to the hnRNPA2B1 and hnRNPI.RNA-Seq and coexpression analysis were used to find out the cell cycle factor CHK2,which is regulated by Linc00173,hnRNPA2B1 and hnRNPI.The study will explore the mechanism of Linc00173 binding with RNA binding proteins to regulate downstream then induce drug resistance.Experimental design:QRT-PCR was used to detect the expression of Linc00173 in clinical specimen.The impact of Linc00173 on chemoresistance of SCLC was studied in vitro and in vivo.Luciferase assay,RIP,and RNA-pulldown assay were performed to validate that Linc00173 acts as a endogeneous sponge to absord miR-218 and decrease the degration of Etk.The downstream molecules of Etk was found by microarray analysis and confirmed by qRT-PCR,Western blotting assays.PDX model was used to show that Ibrutinib can promote chemosensitivity.Mass spectrometry followed by RNA-pulldown assay found the combination between hnRNPA2B1 and hnRNPI and Linc00173.RIP-Seq and coexpression analysis were used to find that Linc00173 can regulate CHK2 with hnRNPA2B1 and hnRNPI and which was validated by qRT-PCR and Western blot.Result:Elevated Linc00173 expression correlates with poor survival and chemotherapy response in SCLC patients.Linc00173 can increase the IC50 values of SCLC cells to various chemotherapeutic drugs and inhibit the apoptosis,affect cell cycle,promote cell proliferation,migration and invasion of small cell lung cancer.The luciferase activity of Linc00173 and Etk was regulated by miR-218,and the three genes were combined with Ago2.Linc00173 can regulate the expression of NDRG1 and GSKIP through Etk and lead to the translocateion of β-catenin from cytoplasm to nucleus.Ibrutinib can specifically target Etk and alleviate drug resistance in small cell lung cancer in vitro and in PDX model.Linc00173 can bind to hnRNPA2B1 and hnRNPI and regulate the expression of CHK2 then p53.Conclusions:Linc00173 can act as a competitive endogenous RNA binding miR-218 to promote Etk expression and can interact with hnRNPA2B1 and hnRNPI then regulate CHK2,thus contributing to the drug resistance of small cell lung cancer.