Silencing of circUSPL1 represses breast cancer progression by targeting miR-1296-5p/MTA1 axis.

Background: The effect of circular RNAs (circRNAs) is widely studied in various human cancers, including breast cancer (BC). Herein, circUSPL1 has been recognized as a new regulator for BC progression. However, the detailed biological function and molecular mechanism of circUSPL1 in BC remain vague.

Methods: The expression level of circUSPL1, miR-1296-5p and metastasis associated 1 (MTA1) was examined by quantitative reverse transcription PCR. BC cell proliferation, migration, invasion, apoptosis and aerobic glycolysis were analyzed by colony formation assay, 5-ethynyl-2'-deoxyuridine assay, wound healing assay, transwell assay, flow cytometry and glycolysis corresponding kits, respectively. The protein level of Bcl-2, Bax, HK2, GLUT1 and MTA1 was evaluated by western blot analysis. The relationship of miR-1296-5p and circUSPL1 or MTA1 was affirmed using dual-luciferase reporter or RIP assays. A murine xenograft model was conducted to analyze the tumor growth in vivo.

Results: CircUSPL1 and MTA1 expression level was increased, but miR-1296-5p was particularly reduced in BC tissues and cells. CircUSPL1 deficiency significantly inhibited BC cell proliferation, migration, invasion, glycolysis, and promoted cell apoptosis. In addition, circUSPL1 directly targeted miR-1296-5p, and downregulation of miR-1296-5p eliminated the inhibitory action of circUSPL1 knockdown. Additionally, overexpression of miR-1296-5p repressed cell malignant properties, while the suppressive effects were overturned by MTA1 elevation. Lastly, silencing of circUSPL1 inhibited tumor growth by sponging miR-1296-5p and regulating MTA1.

Conclusion: CircUSPL1 deficiency repressed BC cell malignant phenotypes through reducing MTA1 via targeting miR-1296-5p, which might provide a theoretical basis for BC treatment.