Long non-coding RNA TUG1-mediated downregulation of KLF4 contributes to metastasis and the epithelial-to-mesenchymal transition of colorectal cancer by miR-153-1

Abstract

Introduction: Taurine up-regulated 1 (TUG1) was reported to be over-expressed and involved in various human malignancies. However, its expression status and mechanistic importance in colorectal cancer (CRC) were yet to be defined. Methods: Relative expressions of TUG1, miR-153-1 and Kruppel-like factor 4 (KLF4) were analyzed by real-time PCR. The potential influences of TUG1-proficiency and miR- 153-1-deficiency on cell proliferation, migration and viability were determined by colony formation, wound healing and CCK-8 assays, respectively. Cell invasion was evaluated by transwell chamber assay. The regulatory effect of KLF4 on miR-153-1 was interrogated by luciferase reporter assay. Direct association between KLF4 and miR-153-1 promoter was measured by chromatin immunoprecipitation (ChIP) assay. Subcellular localization of TUG1 was determined by fractionization PCR. Enrichment of EZH2 on KLF4 promoter was analyzed by ChIP-PCR. The pro-tumoral activity of TUG1 was determined using xenograft tumor model. Results: We demonstrated the over-expression of TUG1 and down-regulation of miR-153-1 in CRC. Knockdown of TUG1 or ectopic over-expression of miR-153-1 in SW480 significantly suppressed cell proliferation, migration and viability. TUG1 negatively modulated miR- 153-1 expression, and simultaneous expression of TUG1 completely abolished the anti-tumor effect of miR-153-1.We further identified KLF4 as a transcription factor of miR-153-1, which was negatively regulated by TUG1 along with EZH2. Conclusion: Our study unravels the critical involvement of TUG1/KLF4/miR-153-1 axis in CRC.