Long non-coding RNA TUG1 promotes progression of oral squamous cell carcinoma through upregulating FMNL2 by sponging miR-219.

Oral squamous cell carcinoma (OSCC) is a prevalent oral disease with a high morbidity and mortality rate. Several long non-coding RNAs (lncRNAs) were identified as important regulators of carcinogenesis. However, the pathogenic implications of TUG1 in OSCC are still unclear. In the present study, the expression of TUG1 was increased in OSCC cells. Knockdown of TUG1 inhibited cell proliferation, migration, and invasion, and induced cell cycle arrest at G0/G1 phase, whereas overexpression of TUG1 exerted the opposite effect on OSCC cells. A reciprocal repressive interaction between TUG1 and miR-219 was found, and miR-219 inhibition abolished the tumor-suppressive effect of TUG1 knockdown on cell growth and motility. Furthermore, bioinformatics analysis and luciferase reporter assay showed that FMNL2 was a direct target of miR-219. Restoration of FMNL2 abrogated the miR-219-induced inhibition of cell proliferation, cell cycle progression, migration, and invasion. Besides, overexpression of TUG1 promoted tumor growth and metastasis in vivo. Clinically, the expression of TUG1 and FMNL2 were increased, but miR-219 was decreased in primary tumors compared to non-tumor tissues. Both the upregulated TUG1, and FMNL2 and the downregulated miR-219 was associated with advanced stage of OSCC and poor overall survival. Notably, multivariate analyses confirmed that FMNL2 was an independent risk factor for OSCC. In conclusion, our data revealed that TUG1 confers oncogenic function in OSCC and TUG1/miR-219/FMNL2 axis may be a novel therapeutic strategy in this disease.