The POU2F1/miR-4490/USP22 Axis Regulates Cell Proliferation and Metastasis in Gastric Cancer

Background: Gastric cancer (GC) remains the fourth most common cancer and the miRNAs can function as tumor suppressors or oncogenes.The biological role of miR-4490 has not yet been reported in the context of cancer. Methods: To explore the function of miR-4490, we performed colony formation assays, EdU incorporation assays, qRT-PCR, Western blotting, In situ hybridization (ISH), immunohistochemistry (IHC), flow-cytometry assays, ChIP and dual-luciferase reporter assays. The growth, migration, and invasive capacity of GC cells were evaluated. Findings: microRNA-4490 (miR-4490) was significantly downregulated in GC tumor samples and cell lines compared with that in normal controls and that its expression level was negatively correlated with the aggressiveness of GC. Ectopic miR-4490 expression not only reduced cell-cycle transition and proliferation but also significantly inhibited GC cell migration, invasion, and epithelial-mesenchymal transition (EMT) in vitro. Mechanistically, we confirmed that miR-4490 directly targeted USP22, which mediates the inhibition of proliferation and EMT-induced metastasis in vitro and in vivo. Moreover, we determined through luciferase and ChIP assays that the transcription factor POU2F1 directly bound to potential POU2F1 binding sites in the miR-4490 promoters and modulated their transcription. Spearman's correlation analysis showed a positive correlation between USP22 and POU2F1 and negative correlations between miR-4490 and USP22 as well as between miR-4490 and POU2F1 expression in GC tissues. Interpretation: Our findings suggest that POU2F1/miR-4490/USP22 axis plays an important role in the development and progression of human GC. Funding: National Natural Science Funds of China (Nos.81672875 and 81772964). Declaration of Interest: The authors declare that they have no competing interests. Ethical Approval: This study was reviewed and approved by the Medical Ethics Committee of Nanfang Hosital (NFEC-2017-062), Southern Medical University, Guangzhou, China. All animal studies were approved by the Institutional Animal Care and Use Committee of Committee of Nanfang Hosital.