Circ-FNDC3B Functions as an Oncogenic Factor in Esophageal Squamous Cell Carcinoma via Upregulating MYO5A by Absorbing miR-136-5p and miR-370-3p.

Circular RNAs (circRNAs) are a class of key regulators in cancers via regulating gene levels by acting as sponges of miRNAs. This study was devoted to explore the functional mechanism of circRNA fibronectin type III domain-containing protein 3B (circ-FNDC3B) in esophageal squamous cell carcinoma (ESCC). RNA levels were examined via reverse transcription-quantitative polymerase chain reaction assay. Cell viability detection was performed using Cell Counting Kit-8 assay. The proliferation ability was determined through colony formation assay and EDU assay. Flow cytometry was applied for analysis of apoptosis. Invasion ability was assessed via transwell assay. Target binding was analyzed by dual-luciferase reporter assay. The protein expression was measured using western blot. In vivo research was conducted via xenograft model in mice. Circ-FNDC3B exhibited significant upregulation in ESCC tissues and cells. Downregulation of circ-FNDC3B inhibited ESCC cell proliferation and invasion but accelerated cell apoptosis. Circ-FNDC3B interacted with miR-136-5p or miR-370-3p. The function of circ-FNDC3B was achieved by sponging miR-136-5p or miR-370-3p. Myosin VA (MYO5A) acted as a downstream target of miR-136-5p or miR-370-3p. MYO5A reversed miR-136-5p/miR-370-3p-induced tumor inhibition in ESCC cells. Circ-FNDC3B targeted miR-136-5p or miR-370-3p to affect MYO5A expression. Circ-FNDC3B knockdown reduced tumor growth in vivo by inhibiting miR-136-5p or miR-370-3p-mediated MYO5A expression. These findings demonstrated that circ-FNDC3B contributed to malignant progression of ESCC cells via miR-136-5p/MYO5A or miR-370-3p/MYO5A axis.