Decreased expression of a novel lncRNA CADM1-AS1 is associated with poor prognosis in patients with clear cell renal cell carcinomas.

The clear cell renal cell carcinoma (ccRCC) is the most common subtype in renal cell carcinomas. Rapidly accumulating studies show that the long non-coding RNAs (lncRNAs) may play essential roles in cancers. In this study, we investigated the expression pattern of a novel lncRNA CADM1-AS1 in ccRCC by quantitative real time PCR. The results showed that CADM1-AS1 expression was down-regulated in tumor tissues in 64 patients with ccRCC compared with adjacent non-tumor tissues. Furthermore, the expression of CADM1-AS1 was positively correlated with the expression of mRNA CADM1 in ccRCC specimens (R = 0.611, P <0.0001). Decreased CADM1-AS1 expression was correlated with the progression of AJCC stage (P = 0.039) and worse survival of ccRCC patients (P <0.05). Also, multivariate analysis identified low CADM1-AS1 expression as an independent prognostic factor for ccRCC (P <0.001, HR = 0.211, 95% CI = 0.088-0.504). In addition, we used small interfering RNA (siRNA) to evaluate the biological function of CADM1-AS1 in vitro. The results showed that CADM1-AS1 expression was positively associated with CADM1 mRNA expression in 786-O cells and ACHN cells. Functional experiments demonstrated markedly enhanced ability of growth and migration, and reduced apoptotic rate in CADM1-AS1 knocking down in 786-O cells. Conversely, overexpression of CADM1-AS1 showed a significant decrease in growth and migration, along with an increase in apoptotic rate in ACHN cells. In conclusion, our data demonstrated CADM1-AS1 is a new tumor suppressor in ccRCC which regulates cell proliferation, apoptosis and migration via the expression pattern of "CADM1-AS1/CADM1 mRNA gene pairs". CADM1-AS1 may be a potential biomarker and therapeutic target in patients with ccRCC.