Circular RNA circ-ZKSCAN1 inhibits bladder cancer progression through miR-1178-3p/p21 axis and acts as a prognostic factor of recurrence

BACKGROUND: Circular RNAs (circRNAs) represent a subclass of regulatory RNAs that have been shown to have significant regulatory roles in cancer progression. However, the biological functions of circRNAs in bladder cancer (BCa) are largely unknown. METHODS: Cell invasion models were established, and invasion-related circRNAs were detected by qPCR. Using above method, circ-ZKSCAN1 was picked out for further study. Circ-ZKSCAN1 expression and survival analyses were performed through qPCR. The survival curves were generated by the Kaplan-Meier method, and the log-rank test was used to assess the significance. Cell proliferation, migration and invasion were examined to investigate the function of circ-ZKSCAN1. Tumorigenesis in nude mice was assessed to determine the effect of circ-ZKSCAN1 in bladder cancer. Biotin-coupled probe pull-down assays, FISH and luciferase reporter assays were conducted to confirm the relationship between circ-ZKSCAN1 and microRNA. RNA-seq revealed different molecular changes in downstream genes. RESULTS: Here, we found that circ-ZKSCAN1 was downregulated in BCa tissues and cell lines. Circ-ZKSCAN1 levels were associated with survival, tumor grade, pathological T stage and tumor recurrence. Overexpressed circ-ZKSCAN1 inhibits cell proliferation, migration, invasion and metastasis in vitro and in vivo. Mechanistically, we demonstrated that circ-ZKSCAN1 upregulated p21 expression by sponging miR-1178-3p, which suppressed the aggressive biological behaviors in bladder cancer. CONCLUSIONS: These results reveal that Circ-ZKSCAN1 acts as a tumor suppressor via a novel circ-ZKSCAN1/miR-1178-3p/p21 axis, which have the important role in the proliferation, migration and invasion ablitities of BCa cells and provide a novel perspective on circRNAs in BCa progression. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12943-019-1060-9) contains supplementary material, which is available to authorized users.