A novel circ_0000654/miR-375/E2F3 ceRNA network in esophageal squamous cell carcinoma

The competing endogenous RNA (ceRNA) activity of circular RNAs (circRNAs) has been implicated in the pathogenesis of cancers, including esophageal squamous cell carcinoma (ESCC). Here, we identified the ceRNA mechanism of circ_0000654 regulation in ESCC.

The levels of circ_0000654, E2F transcription factor 3 (E2F3), and microRNA (miR)-375 were gauged by quantitative real-time PCR (qRT-PCR) and western blot. Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and 5-ethynyl-2'-deoxyuridine (EdU) assays. Cell apoptosis was detected by flow cytometry. Cell colony formation was tested by colony formation assay. Dual-luciferase reporter, RNA pull-down and RNA immunoprecipitation (RIP) assays were performed to confirm the direct relationship between miR-375 and circ_0000654 or E2F3. Xenograft model assays were used to evaluate the effect of circ_0000654 in vivo.

Circ_0000654 and E2F3 were upregulated in ESCC. Circ_0000654 depletion enhanced cell apoptosis and hindered cell proliferation and glycolysis in vitro, as well as weakened tumor growth in vivo. Increased expression of E2F3 counteracted the effects of circ_0000654 depletion. Mechanistically, E2F3 was a target of miR-375, and circ_0000654 modulated E2F3 expression through sequestering miR-375. Furthermore, miR-375 upregulation phenocopied circ_0000654 knockdown in inhibiting ESCC progression.

Our findings identify a new circ_0000654/miR-375/E2F3 ceRNA crosstalk for the oncogenic role of circ_0000654 in ESCC and establish a notion that targeting circ_0000654 and its pathways may have the potential to improve ESCC outcome.