Background:Circular RNAs(circRNAs)are covalently closed single-stranded RNAs with multiple biological functions.CircRNA.0007127 is derived from the carbon catabolite repression 4-negative on TATA-less(CCR4-NOT)complex subunit 2(CNOT2),which was found to regulate tumor cell apoptosis through caspase pathway.Methods:Potential circRNA.0007127 target microRNAs(miRNAs)were analyzed by miRanda,TargetScan,and RNAhybrid software,and the miRNAs with binding sites for apoptosis-related genes were screened.The roles of circRNA.0007127 and its downstream target,microRNA(miR)-513a-5p,were validated by quantitative real-time polymerase chain reaction(qPCR),flow cytometry,mitochondrial membrane potential,immunofluorescence,western blot,and caspase-8(CASP8)protein activity in vitro in H2O2-induced K-562 cells.The circRNA.0007127-miR-513a-5p and CASP8-miR-513a-5p interactions were verified by luciferase reporter assays.Results:Silencing circRNA.0007127 decreased cell apoptosis by inhibiting CASP8 pathway activation in K-562 cells.Compared with the control group,the expression of CASP8 was reduced by 50％and the 43-kD fragment of CASP8 protein was significantly reduced(P≤0.05).The luciferase reporting assay showed that circRNA.0007127 combined with miR-513a-5p or CASP8,with extremely significant differences(P≤0.001).The overexpression of miR-513a-5p inhibited the gene expression level of CASP8 in a human myeloid leukemia cell model(75％change)and the level of a 43-kD fragment of CASP8 protein(P≤0.01).The rescue experiment showed that cotransfection with circRNA.0007127 small-interfering RNA(siRNA)and the miR-513a-5p inhibitor increased CASP8 gene expression and the apoptosis rate,suggesting that the miR-513a-5p inhibitor is a circRNA.0007127 siRNA antagonist.Conclusions:CircRNA.0007127 regulates K-562 cell apoptosis through the miR-513a-5p/CASP8 axis,which can serve as a novel powerful molecular target for K-562 cells.