Circular RNA (circRNA) is involved in the occurrence of many cancers. Nonetheless, the mechanism of circ₀003998 in non-small cell lung cancer (NSCLC) needs to be studied in depth. Real-time quantitative PCR (RT-qPCR) was carried out to check the expression of circ₀003998, microRNA-330-5p (miR-330-5p), chemokine (C-X-C motif) ligand 3 (CXCL3) and methyltransferase-3 (METTL3) in NSCLC tissues and cells. CXCL3, Vimentin and E-cadherin protein levels were measured by western blot. The functions of circ₀003998 in NSCLC cell proliferation, apoptosis, angiogenesis, migration and invasion were tested by clone formation assay, flow cytometry, tube formation assay, wound healing assay, and transwell assay in vitro. The dual-luciferase reporter assay was made to verify the relationship between miR-330-5p and circ₀003998 or CXCL3. Finally, animal experiment was made to further research the function of circ₀003998 on tumor formation in vivo. The interaction between circ₀003998 and METTL3 was analyzed by RNA Immunoprecipitation (RIP) assay, methylated RNA Immunoprecipitation (MeRIP) assay and dual-luciferase reporter assay. In NSCLC tissue and cells, circ₀003998 was markedly overexpressed. Circ₀003998 suppression inhibited NSCLC cell growth, angiogenesis, migration and invasion. Circ₀003998 sponged miR-330-5p, and miR-330-5p inhibitor could reverse the suppression effect of circ₀003998 knockdown on NSCLC cell behaviors. CXCL3 was a downstream target gene of miR-330-5p, and CXCL3 overexpression also reversed the suppressive effect of miR-330-5p on NSCLC cell behaviors. Interference of circ₀003998 reduced NSCLC tumorigenesis by regulating miR-330-5p/CXCL3 axis. Also, METTL3 promoted the expression of circ₀003998 by m6A modification. METTL3-modified circ₀003998 promoted NSCLC cell malignancy through miR-330-5p/CXCL3 axis, suggesting that circ₀003998 might be a new treatment strategy for NSCLC.
Liu et al. (Fri,) studied this question.