The Research Of Function And Mechanism Of Long Noncoding RNA LINC01234 In Non-small Cell Lung Cancer

Background and Objectives:Recent large-scale RNA profiling efforts have revealed that>75%of the human genome is actively transcribed,but only 1.2%of human genome can be translated into proteins[1],most of the rest are non-coding RNAs,long noncoding RNAs(lncRNAs)are non-coding RNAs that length are greater than 200nt,IncRNAs were previously considered as "noise" or "trash" in process of transcription,people thought they were by-products of transcription by RNA polymerase Ⅱ(pol Ⅱ)and have no biological functions[2].However,more and more studies have shown that IncRNAs play important roles in cancer progression.LncRNAs have been found involved in many biological processes including chromatin modification,regulation of transcription of target genes,alterative splicing and stability of mRNA,modulation of protein activity,alternation of protein localization[3].According to the latest global cancer statistics 2018,lung cancer is the most commonly malignant tumor and leading cancer incidence and mortality among males,closely followed by female breast cancer,the cancer incidence followed by breast cancer and colorectal cancer among females[4].Lung cancer can be divided into small cell lung cancer(SCLC)and non-small cell lung cancer(NSCLC),in which NSCLC accounts for about 80%-85%,and the five-year survival rate is less than 20%.Therefore,the study of non-small cell lung cancer will be very important for clinical treatment[5].Scholars from home and abroad have found that many IncRNAs are closely related to tumors,not only in lung cancer,but also in tumors such as breast cancer,colorectal cancer,gastric cancer,liver cancer and prostate cancer.More and more experiments have showed that IncRNAs play many important roles in the occurrence and development of tumors[2].At present,the most commonly used methods for the treatment of non-small cell lung cancer are surgical resection,chemotherapy and chest radiotherapy,so it is particularly important to find an effective target for the treatment of non-small lung cancer.Existing studies have found that IncRNAs can play its corresponding biological functions at the epigenetic level,transcriptional level,posttranscriptional level and posttranslational level[6].In this study,long noncoding RNA LINC01234,which is highly expressed in non-small cell lung cancer(NSCLC),was selected as object of study to explore its role in the occurrence and development of non-small cell lung cancer in different cell lines.Finally,we hope to provide a potential new target for clinical diagnosis and treatment of non-small cell lung cancer.Methods and Results:First of all,we found that the expression level of LINC01234 in lung adenocarcinoma was significantly higher than that in normal tissues.In addition,we analyzed the clinical data from KMplot website and found that patients with high expression of LINC01234 in lung adenocarcinoma had worse prognosis than those with low expression of LINC01234.These clinical data suggest that LINC01234 may act as an oncogene play an important role in the occurrence and development of non-small cell lung cancer,and it is of great significance as a target for the treatment of non-small cell lung cancer.Then we explored the fundamental structure,secondary structure and coding potentiality of LINC01234,and found that LINC01234 is a kind of long noncoding RNA with polyadenylated tail,complex secondary structure and no coding potentiality.In order to study the function of LINC01234,we detected the subcellular localization of LINC01234 in some non-small cell lung cancer cell lines by subcellular fractionation,and the results showed that its distribution is mainly in cytoplasm.We then detected the expression level of LINC01234 in a series of non-small cell lung cancer cell lines,we found that LINC01234 was generally highly expressed in non-small cell lung cancer,so we selected some cell lines to knockdown and activate or interfere the transcription of LINC01234 by shRNA and CRISPRa or CRISPRi,and we found that LINC01234 knockdown resulted in down-regulation of cell proliferation,migration and sphere formation of non-small cell lines by colony formation assay,sphere formation assay,MTT assay,wound healing and transwell assay,and we found that LINC01234 can increase the phosphorylation of Smad3,which is a component downstream of the active TGFβ-Smad signal pathway,the results may be related to the promotion of cell migration by LINC01234.Conclusion:1、LINC01234 is highly expressed in lung adenocarcinoma and is associated with poor prognosis;2、LINC01234 is a kind of long noncoding RNA with polyadenylated tail,complex secondary structure and no coding potentiality,its subcellular localization is mainly in cytoplasm;3、LINC01234 promote cell migration in non-small lung cancer,knockdown or interfere the transcription of LINC01234 can inhibit cell ability of proliferation,migration and sphere formation,and these effects are cell line dependent;4、LINC01234 can significantly increase the phosphorylation of Smad3 in TGFβ-Smad signal pathway.