Effect Of Long Non-coding RNA LncRNA55 Regulated By C-Myc On Proliferation Of Tongue Cancer Cells

Backgroud Tongue squamous cell carcinoma(TSCC)is one of the most common malignant tumor and has high mortality.Long non-coding RNAs(IncRNAs)play critical roles in carcinogenesis.Serveral researchs showed that some IncRNAs regulated by oncogene c-Myc was involved in tumorigenesis and progression.In previous studies,we found a IncRNA called lncRNA55 which is regulated by c-Myc.The aim of this study was to determine the role of lncRNA55 in the progression of TSCC.Objective We try to illuminate the correlation between the expression of long non-coding RNA(IncRNA)lncRNA55 and oncogene c-Myc,and investigate the effect of lncRNA55 knockdown on proliferation of SCC3 tongue cancer cells.Methods Infecting SCC3 cells with lentiviral vector carrying flag-c-Myc or plko.l-shc-Myc;Then detected the expression of c-Myc protein by western blot analysis and lncRNA55 mRNA level by real-time quantitative PCR(qRT-PCR)after transfection;Based on this,vector carrying shlncRNA55 was constructed and transfected into SCC3 cells,the transfection efficiency was evaluated using qRT-PCR;Then detected the cell proliferation of SCC3 by MTT and colony formation assays;In addition,we explored the subcellular distribution of lncRNA55 by fluorescence in situ hybridization.Results The c-Myc protein expression was significantly downregulated whereas lncRNA55 mRNA level was increased after plko.l-shc-Myc transfection(P<0.05);The expression of c-Myc protein was upregulated and lncRNA55 mRNA level was evidently decreased after flag-shc-Myc transfection(P<0.05);The lncRNA55 level was obviously inhibited after transfection with shlncRNA55(P<0.05);The inhibition of lncRNA55 significantly increased the cell viability and colony-formation ability(P<0.05);And we found that lncRNA55 resides mainly in the cytoplasm.Conclusion LncRNA55 may be negatively regulated by c-Myc,IncRNA55 knockdown can promote SCC3 cell proliferation.This will provide a new gene target for the treatment of tongue squamous cell carcinoma.