Circular RNA TLK1 Exerts Oncogenic Functions in Hepatocellular Carcinoma by Acting as a ceRNA of miR-138-5p

Mounting evidence has shown that circular RNAs (circRNAs) function as key regulators in carcinogenesis and cancer progression, and this study is aimed at investigating the regulatory functions of circRNA TLK1 (circ-TLK1) in hepatocellular carcinoma (HCC). We observed that circ-TLK1 was highly expressed in HCC samples, and its high expression was closely associated with poor clinicopathological variables of HCC patients. The results of functional experiments revealed that knockdown of circ-TLK1 remarkably inhibited the proliferation, migration, invasion, and EMT of HCC cells, while circ-TLK1 overexpression promoted these malignant behaviors. Moreover, we noted that circ-TLK1 was capable of binding to miR-138-5p and upregulating its target gene, SOX4 in HCC. Based on rescue assays, miR-138-5p inhibition partially suppressed the effects of circ-TLK1 knockdown on the malignant behaviors of HCC cells. In short, this study is the first to indicate that circ-TLK1 functions as an oncogene in HCC progression partly through acting as a ceRNA of miR-138-5p, which may be a promising target for HCC therapy.