Long Non-Coding RNA TTN-AS1 Serves as a Competing Endogenous RNA of miR-195 to Facilitate Clear Cell Renal Cell Carcinoma Progression

INTRODUCTION: Clear cell renal cell carcinoma (ccRCC) is an aggressive human malignancy. Long non-coding RNAs (lncRNAs) are critical regulators in many malignant tumors, including ccRCC. The aim of this study is to investigate the expression, functions and molecular mechanisms of lncRNA TTN-AS1 in ccRCC. METHODS: A total of 145 paired cancer and normal tissues were collected from patients with ccRCC. The expression levels of TTN-AS1 and miR-195 in the tissues or cells were measured by RT-qPCR analysis. The expression levels of cyclin D1 protein were measured by Western blot analysis. Cell proliferation and cell cycle distribution were detected by MTT assay and flow cytometer analysis, respectively. The binding relationship between miR-195 and TTN-AS1 or cyclin D1 mRNA was validated by dual-luciferase reporter assay. RESULTS: Our results revealed that TTN-AS1 expression levels in human ccRCC tissues and cell lines were markedly increased. High expression of TTN-AS1 was closely associated with adverse clinicopathological characteristics of ccRCC patients. Gain- and loss-of-function experiments showed that TTN-AS1 overexpression promoted the proliferation and cell cycle transition of ccRCC cells, while the malignant traits were obviously suppressed after TTN-AS1 knockdown. Mechanistically, miR-195 was found to bind with and to be negatively regulated by TTN-AS1 in ccRCC cells. Further, we showed that cyclin D1 is a direct target of miR-195 in ccRCC, and rescue assays verified that restoration of miR-195 expression partially blocked the oncogenic effects of TTN-AS1 in ccRCC cells. CONCLUSION: Our study provides a novel mechanism of TTN-AS1/miR-195/cyclin D1 regulatory axis in ccRCC, which may become a breakthrough for ccRCC therapy in the future.