Long non-coding RNA CARLo-5 expression is associated with disease progression and predicts outcome in hepatocellular carcinoma patients

Recently, many studies show that long non-coding RNAs (lncRNAs) play important roles in cancer biology. Although its expression was reported dysregulated during tumorigenesis, the contributions of lncRNAs to hepatocellular carcinoma (HCC) are still largely unknown. In particular, the lncRNA CARLo-5 has a functional role in cell-cycle regulation in colon cancer, while the clinical significance and biological function of CARLo-5 in HCC remain unelucidated. In order to fill those study blanks, the expression level of CARLo-5 in human HCC specimens was tested, and its correlation with clinicopathologic features as well as the prognosis for patients with HCC was analyzed. Additionally, MTT, wound healing and transwell assays were employed to investigate the biological function of CARLo-5. The results showed that CARLo-5 levels were significantly overexpressed in HCC tissues compared to ANLT. Besides, high expression of CARLo-5 was associated with liver cirrhosis (P = 0.001), tumor number (P < 0.001), vascular invasion (P = 0.001), capsular formation (P = 0.014) and Edmondson–Steiner grade (P < 0.001), which proved that CARLo-5 was an independent risk factor for overall survival and disease-free survival. In addition, in highly metastatic HCC cell lines (HCCLM3 and MHCC97-L), CARLo-5 was up-regulated, but in lowly metastatic HCC cell lines (HepG2, SNU387), it showed down-regulated. Besides, by using gain and loss of function experiments in HCC cell lines (HCCLM3 and HepG2), the results showed that CARLo-5 overexpression significantly enhanced cell proliferation, migration and invasion in vitro. Our study also revealed that CARLo-5 was prominently up-regulated in HCC specimens and its high expression was associated with poor prognosis of HCC patients. Totally, those findings together indicate that CARLo-5 promotes proliferation and metastasis of HCC and potentially emerged as a novel therapeutic target.