TUG1 promotes osteosarcoma tumorigenesis by upregulating EZH2 expression via miR-144-3p
- Jiaqing Cao
- Xinyou Han
- Xin Qi
- Xiangyun Jin
- Xiaolin Li
Affiliations: Department of Orthopedic Surgery, The Sixth People's Hospital Affiliated to Shanghai Jiao Tong University, Shanghai 200233, P.R. China
- Published online on: August 30, 2017 https://doi.org/10.3892/ijo.2017.4110
Copyright: © Cao
et al. This is an open access article distributed under the
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lncRNA-TUG1 (Taurine upregulated 1) is upregulated and highly correlated with poor prognosis and disease status in osteosarcoma. TUG1 knockdown inhibits osteosarcoma cell proliferation, migration and invasion, and promotes apoptosis. However, its mechanism of action has not been well addressed. Growing evidence documented that lncRNA works as competing endogenous (ce)RNAs to modulate the expression and biological functions of miRNA. As a putative combining target of TUG1, miR-144-3p has been associated with the progress of osteosarcoma. To verify whether TUG1 functions through regulating miR-144-3p, the expression levels of TUG1 and miR-144-3p in osteosarcoma tissues and cell lines were determined. TUG1 was upregulated in osteosarcoma tissues and cell lines, and negatively correlated with miR-144-3p. TUG1 knockdown induced miR-144-3p expression in MG63 and U2OS cell lines. Results from dual luciferase reporter assay, RNA-binding protein immunoprecipitation (RIP) and applied biotin-avidin pull-down system confirmed TUG1 regulated miR-144-3p expression through direct binding. EZH2, a verified target of miR-144-3p was upregulated in osteosarcoma tissues and negatively correlated with miR-144-3p. EZH2 was negatively regulated by miR-144-3p and positively regulated by TUG1. Gain-and loss-of-function experiments were performed to analyze the role of TUG1, miR-144-3p and EZH2 in the migration and EMT of osteosarcoma cells. EZH2 overexpression partly abolished TUG1 knockdown or miR-144-3p overexpression induced inhibition of migration and EMT in osteosarcoma cells. In addition, TUG1 knockdown represses the activation of Wnt/β-catenin pathway, which was reversed by EZH2 overexpression. The activator of Wnt/β-catenin pathway LiCl could partially block the TUG1-knockdown induced osteosarcoma cell migration and EMT inhibition. In conclusion, our results showed that TUG1 plays an important role in osteosarcoma development through miRNA-144-3p/EZH2/Wnt/β-catenin pathway.