GAS5 functions as a ceRNA to regulate hZIP1 expression by sponging miR-223 in clear cell renal cell carcinoma

Several studies have shown that low expression of hZIP1 is closely associated with many human cancers, including clear cell renal cell carcinoma (ccRCC). In this study, we aimed to explore the potential mechanism responsible for hZIP1 silencing and revealed a novel regulatory pathway in the pathogenesis of ccRCC. Here, miR-223 was predicted and experimentally validated to be a regulator of hZIP1, and its expression was negatively correlated with the mRNA levels of hZIP1 in primary tumors. Upregulation of hZIP1 inhibited cell proliferation, cell cycle progression, and invasion and induced apoptosis, while inhibition of miR-223 showed the opposite effect on cellular processes. Moreover, GAS5 interacted with miR-223 and was markedly downregulated in tumors. Knockdown of GAS5 partially reversed the effect of the miR-223 inhibitor on cell proliferation, cell cycle distribution, apoptosis and invasion. In addition, GAS5 acted as a molecular sponge to positively regulate the mRNA and protein levels of hZIP1 via regulating miR-223. The tumorigenicity of ccRCC cells was enhanced by silencing GAS5 but diminished by overexpression of hZIP1 in vivo. Clinically, the low expression of hZIP1 was significantly correlated with advanced clinical stage and Fuhrman stage. Downregulation of GAS5 indicated tumor progression and recurrence and was independently associated with disease-free survival of patients. Taken together, our results suggest that GAS5 may act as a competing endogenous RNA (ceRNA) to regulate hZIP1 by sponging miR-223 in the progression of ccRCC and that targeting the GAS5/miR-223/hZIP1 axis may serve as a therapeutic strategy for patients.