Circular RNA circ_0000615 knockdown suppresses the development of nasopharyngeal cancer through regulating the miR-338-3p/FGF2 axis

Nasopharyngeal cancer (NPC) is a type of head and neck cancer with a high rate of metastasis. Circular RNAs (circRNAs) were reported to be related to the development of human cancers. This research aimed to investigate the functional mechanism of circRNA circ_0000615 in NPC. The gene expression was examined by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was employed to assess cell proliferation ability. Transwell assay was used to measure cell migratory and invasive abilities. Furthermore, the interaction between miR-338-3p and circ_0000615 or fibroblast growth factor 2 (FGF2) was predicted by starBase v.2.0 and then confirmed by the dual-luciferase reporter assay. Besides, the mouse xenograft experiment was carried out to explore the effect of circ_0000615 on tumor growth in vivo. We detected increased levels of circ_0000615 and FGF2, along with a decreased level of miR-338-3p in NPC tissues and cells. Circ_0000615 knockdown suppressed the proliferation, migration, invasion, and EMT of NPC cells. Interestingly, circ_0000615 interacted with miR-338-3p, and miR-338-3p targeted FGF2. Circ_0000615 inhibited miR-338-3p expression to upregulate the FGF2 level. Furthermore, both miR-338-3p depletion and FGF2 overexpression weakened the effect of circ_0000615 knockdown on NPC cell progression. Besides, circ_0000615 knockdown repressed tumor growth in vivo. In conclusion, our findings demonstrated that circ_0000615 knockdown suppressed the growth of NPC cells via modulating miR-338-3p/FGF2 axis, providing a theoretical basis for the treatment of NPC.