circ_0007385 served as competing endogenous RNA for miR-519d-3p to suppress malignant behaviors and cisplatin resistance of non-small cell lung cancer cells.

BACKGROUND Circular RNAs (circRNAs) have been closely implicated in competing endogenous RNA (ceRNA) network among human cancers including non-small cell lung cancer (NSCLC). However, the role of most circRNAs in NSCLC remains to be determined. Here, we aimed to investigate the role of hsa_circ_0007385 (circ_0007385) in NSCLC cells. METHODS Expression of hsa_circ_0007385 (circ_0007385), miRNA (miR)-519d-5p and high-mobility group box 1 (HMGB1) was measured by real-time quantitative PCR and western blotting. Functional experiments were evaluated by cell counting kit (CCK)-8, flow cytometry, fluorescein active caspase-3 staining kit, transwell assays, western blotting, and xenograft experiment. The relationship among circ_0007385,miR-519d-5p and HMGB1 was testified by dual-luciferase reporter assay. Kaplan-Meiersurvival curve identified overall survival in NSCLC patients. RESULTS circ_0007385 expression was higher in NSCLC tissues and cell lines, and was associated with poor overall survival. Silencing circ_0007385 could suppress cell proliferation, migration and invasion in A549 and H1975 cells, as well as cisplatin (DDP) resistance. Moreover, circ_0007385 silence retarded tumor growth of A549 cells in vivo. Molecularly, there was a direct interaction between miR-519d-3p and either circ_0007385 or HMGB1; expression of miR-519d-3p was downregulated in NSCLC tumors in a circ_0007385-correlated manner, and circ_0007385 could indirectly regulate HMGB1 via miR-519d-3p. Functionally, both inhibiting miR-519d-3p and restoring HMGB1 could overturn the suppressive effect of circ_0007385 knockdown on cell proliferation, migration, invasion, and DDP resistance. CONCLUSIONS Collectively, circ_0007385 deletion could function anti-tumor role in NSCLC by suppressing malignant behaviors and DDP resistance in vitro and in vivo via circ_0007385/miR-519d-3p/HMGB1 axis. These outcomes might enhance our understanding of the molecular mechanisms underlying the malignant progression of NSCLC. KEY POINTS SIGNIFICANT FINDINGS OF THE STUDY: circ_0007385 was upregulated in NSCLC tissues and cells, and was associated with poor overall survival. Silenced circ_0007385 suppressed NSCLC cell proliferation, migration, invasion, and DDP resistance in vitro, and tumor growth in vivo. circ_0007385 was upregulated in NSCLC tissues and cells, and was associated with poor overall survival. WHAT THIS STUDY ADDS miR-519d-3p could directly interact with circ_0007385 and HMGB1 in NSCLC cells. A promising circ_0007385/miR-519d-3p/HMGB1 regulatory pathway was determined in NSCLC cells.