Circular RNA hsa_circ_0000654 promotes esophageal squamous cell carcinoma progression by regulating the miR‐149‐5p/IL‐6/STAT3 pathway

Abstract Circular RNAs (circRNAs) are novel noncoding RNAs (ncRNAs) with covalently closed‐loop structures that play an essential regulatory role in diverse malignancies, including esophageal squamous cell cancer (ESCC). Circ_0000654 expression in ESCC and its mechanism of action remains unclear. Real‐time PCR (RT‐PCR) was employed to detect circ_0000654 and miR‐149‐5p expression in ESCC tissues. Circ_0000654 and miR‐149‐5p expression in ESCC cells was selectively regulated. Furthermore, interleukin 6 (IL‐6) and signal transducer and activator of transcription 3 (STAT3) expression in cells was detected by RT‐PCR and western blot analysis, while CCK8, BrdU, flow cytometry, and transwell assays were used to monitor cell proliferation, apoptosis, migration and invasion, respectively. The dual‐luciferase reporter assay and RIP assay were used to verify the targeting relationship between circ_0000654 and miR‐149‐5p, miR‐149‐5p and IL‐6. The function of circ_0000654 on ESCC cell proliferation and metastasis in vivo was examined using a subcutaneous xenograft model and a tail intravenous injection model in nude mice. Circ_0000654 was significantly upregulated in ESCC tissues and cell lines, and its high expression was remarkably associated with an increased T stage and local lymph node metastasis in ESCC patients. Circ_0000654 overexpression and knockdown experiments revealed that circ_0000654 regulated ESCC cell proliferation, migration, invasion, and apoptosis in vitro. Circ_0000654 was identified as a sponge of miR‐149‐5p and facilitated ESCC progression by indirectly activating the IL‐6/STAT3 signaling pathway. Additionally, knocking down circ_0000654 strikingly repressed ESCC growth and metastasis in vivo. In summary, circ_0000654 functions as an oncogenic circRNA in ESCC and accelerates ESCC progression via adsorbing miR‐149‐5p and activating the IL‐6/STAT3 signaling pathway.