Circular RNA circ_0005774 contributes to proliferation and suppresses apoptosis of acute myeloid leukemia cells via circ_0005774/miR-192-5p/ULK1 ceRNA pathway.

Circular RNAs (circRNAs) and microRNAs (miRNAs) have been emerging as new players in acute myeloid leukemia (AML). Hsa_circ_0005774 (circ_0005774) is an upregulated circRNA in pediatric AML, while its role is uncovered. Thus, we intended to measure the function and mechanism of circ_0005774 in AML leukemogenesis. Real time-quantitative PCR revealed that circ_0005774 was highly expressed in blood of pediatric AML patients and AML cells (HL-60 and NB4), accompanied with downregulated miRNA-192-5p (miR-192-5p) which was a crucial tumor-associated and leukemia-related miRNA. Circ_0005774 was abundant in miRNA response element according to CSCD software, and miR-192-5p was identified as a target of circ_0005774, as evidenced by RNA immunoprecipitation and dual-luciferase reporter assays. Cell viability assay, flow cytometry and western blotting were performed to measure cell functions. Accordingly, blocking circ_0005774 and/or overexpressing miR-192-5p could enhance apoptosis rate of HL-60 and NB4 cells, but suppress cell viability and cell cycle entrance, accompanied with depression of proliferation markers including proliferating cell nuclear antigen (PCNA), CyclinD1 and B cell lymphoma 2 (Bcl-2). Meanwhile, depleting miR-192-5p counteracted the role of circ_0005774 knockdown in AML cells. Uncoordinated 51-like kinase 1 (ULK1) was previously demonstrated to be associated with diagnosis, prognosis and therapeutic strategy for AML, and restoring ULK1 could abrogate miR-192-5p overexpression-induced effects in HL-60 and NB4 cells. Notably, ULK1 was a downstream target of miR-192-5p and indirectly modulated by circ_0005774. In conclusion, circ_0005774 knockdown repressed cell proliferation and promoted apoptosis of AML cells partially through regulating miR-192-5p/ULK1 axis.