Circular RNA circSLC8A1 acts as a sponge of miR-130b/miR-494 in suppressing bladder cancer progression via regulating PTEN

BACKGROUND: Circular RNAs (circRNAs) are a novel class of endogenous noncoding RNAs formed by a covalently closed loop, and increasing evidence has revealed that circRNAs play crucial functions in regulating gene expression. CircSLC8A1 is a circRNA generated from the SLC8A1 gene. Currently, the role and underlying molecular mechanisms of circSLC8A1 in bladder cancer remain unknown. METHODS: The differentially expressed circRNAs were identified from RNA-sequencing data, and circSLC8A1 was determined as a new candidate circRNA. qRT-PCR was used to detect the expression of circRNAs, miRNAs and mRNAs in human tissues and cells. RNA pull-down assay and luciferase reporter assay were used to investigate the interactions between the specific circRNA, miRNA and mRNA. The effects of circSLC8A1 on bladder cancer cells were explored by transfecting with plasmids in vitro and in vivo. The expression of PTEN was detected by Western blot. The biological roles were measured by wound healing assay, transwell assay, and CCK-8 assay. RESULTS: In the present study, we found that circSLC8A1 was down-regulated in bladder cancer tissues and cell lines, and circSLC8A1 expression was associated with the pathological stage and histological grade of bladder cancer. Over-expression of circSLC8A1 inhibited cell migration, invasion and proliferation both in vitro and in vivo. Mechanistically, circSLC8A1 could directly interact with miR-130b/miR-494, and subsequently act as a miRNA sponge to regulate the expression of the miR-130b/miR-494 target gene PTEN and downstream signaling pathway, which suppressed the progression of bladder cancer. CONCLUSIONS: CircSLC8A1 acts as a tumor suppressor by a novel circSLC8A1/miR-130b, miR-494/PTEN axis, which may provide a potential biomarker and therapeutic target for the management of bladder cancer. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12943-019-1040-0) contains supplementary material, which is available to authorized users.