Abnormal expression of non-coding circular RNAs (circRNAs) have been reported in many types of tumors. circRNA have been suggested to be an ideal candidate biomarker for diagnostic and therapeutic implications in cancers. The aim of this study was to assess the circRNA expression profile of laryngeal squamous cell carcinomas (LSCC). The biopsy samples from patients with LSCC were obtained intra-operatively. The circRNA expression was performed using secondary sequencing. Among 10 patients with LSCC, 2 were well differentiated, 3 were moderately differentiated and 5 were adjunctive samples with normal and LSCC tissues. A total of 21,444 distinct circRNA candidates were detected. Among them, we defined the statistical criteria for selecting aberrant-expressed circRNA using a q-value of < 0.001 with a fold change of > 2.0 or < 0.5. A total of 29 circRNA were upregulated and 19 circRNA were downregulated significantly in the LSCC tissues. The intersection of these dysregulated circRNAs of normal-well differentiated set and normal-moderately differentiated set was then assessed to narrow the upregulated and downregulated circRNAs down to 18 and 5 respectively. Furthermore, an association of the circRNA-miRNA-mRNA was investigated, showing that 20 dysregulated circRNA successfully predicted an interaction with several cancer-related miRNAs. Finally, a further KEGG analysis showed that PPAR, Axon guidance, Wnt and Cell cycle signaling pathway were key putative pathways in the process of LSCC. hsa_circ:chr20:31876585–31,897,648 was found to be able to differentiate most of LSCC from the matching normal tissues. This observational study demonstrated dysregulation of circRNA in LSCC, which may have an impact on development of potential biomarkers in this disease. Validation of down-regulation of hsa_circ:chr20:31876585–31,897,648 in LSCC compared to each adjunctive tissue by Q-RT-PCR, indicating that hsa_circ:chr20:31876585–31,897,648 may be a novel promising tumor suppresser in LSCC.Electronic supplementary materialThe online version of this article (10.1186/s12943-018-0833-x) contains supplementary material, which is available to authorized users.

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Our previous studies have confirmed that α2δ1 has the potential to function as a cancer stem cell marker, and CACNA2D1 is the coding gene of α2δ1. But it is unclear how microRNAs regulate the expression of the CACNA2D1 gene in laryngeal cancer cells. We detected the expressions of α2δ1 protein, microRNA-107, and CACNA2D1 in 40 pairs of laryngeal cancer tissues and adjacent normal tissues. Laryngeal squamous cell carcinoma cells, TU212 and TU686, were cultured and transfected in the blank control group, the agomiR negative control group, the agomiR-107 group, the antagomiR negative control group, or the antagomiR-107 group, and the dual-luciferase reporter assay was employed to assess the regulatory effect of microRNA-107 on CACNA2D1. Then, the effects of microRNA-107 on the biological function of laryngeal squamous cell carcinoma cells were detected by qRT-PCR, Western blot, MTT, cell migration/invasion assay, and cell colony-formation assay. Our data suggested that the protein level of α2δ1, encoded by CACNA2D1, in laryngeal carcinoma tissues was higher than that in adjacent normal tissues, while the expression of microRNA-107 was significantly decreased in laryngeal carcinoma tissues. The dual-luciferase reporter gene assay confirmed that microRNA-107 bound to the 3′-UTR two positions (202-209, 902-908) of CACNA2D1 mRNA. Moreover, the expression of CACNA2D1 and α2δ1 protein were significantly decreased in TU212 and TU686 cells transfected with microRNA-107 expression vectors (P < 0.05), and proliferation, clone formation, migration, and invasion of these cells were also reduced. Furthermore, after knocking down microRNA-107, exactly opposite results were obtained. Overexpression of microRNA-107 can inhibit the proliferation and invasion of laryngeal carcinoma cells in vitro.