Background: The present study is to investigate the biological functions and mechanisms of circular RNA_0000523 (circ_0000523) in nasopharyngeal carcinoma (NPC).

Methods: Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was conducted to examine the expression levels of circ_0000523 and microRNA-1184 (miR-1184) in NPC tissues and cells. Collagen type 1 alpha 1 chain (COL1A1) expression was assessed by qRT-PCR and immunohistochemistry (IHC) assay. Cell proliferation, cell cycle progression, migration and invasion were examined by cell counting kit-8 (CCK-8), 5-bromo-2'-deoxyuridine (BrdU), flow cytometry and Transwell assays. Xenograft nude mouse models were used to investigate the metastatic potential of NPC cells in vivo. The binding relationships between circ_0000523 and miR-1184, and between miR-1184 and COL1A1 were detected by dual-luciferase reporter gene assay. The protein expressions of COL1A1, phosphatidylinositol 3-kinase (p85), phosphorylated (p)-p85, protein kinase B (Akt) and p-Akt were detected through Western blot. The DAVID database was used for the enrichment analysis of the potential targets of miR-1184.

Results: Circ_0000523 and COL1A1 mRNA expressions were significantly increased in NPC tissues and cell lines. Circ_0000523 overexpression promoted NPC cell proliferation and accelerated cell cycle progression, whereas miR-1184 overexpression reversed these effects; circ_0000523 knockdown suppressed NPC cell proliferation and induced cell cycle arrest, while miR-1184 inhibition counteracted these effects. MiR-1184 was the downstream target of circ_0000523, and COL1A1 was the target gene of miR-1184 and could be positively modulated by circ_0000523. COL1A1 overexpression increased the expression levels of p-p85 and p-Akt, whereas knocking down COL1A1 repressed their expressions.

Conclusions: Circ_0000523 facilitates NPC progression through regulating the miR-1184/COL1A1 axis.