Objective To study the effect of circular ArfGAP with FG repeats 1(CircAGFG1) on radiosensitivity of esophageal squamous cell carcinoma (ESCC) cells via miR-375/ubiquitin specific protease 22 (USP22) axis. Methods The expression of CircAGFG1, miR-375 and USP22 in human ESCC cell line KYSE150 and human ESCC radiation resistant cell KYSE150-R was detected by real-time fluorescent quantitative PCR and Western blot.The KYSE150-R cells cultured in vitro were randomly divided into control group, radiation group, radiation+negative control group, radiation+CircAGFG1 knockdown group, and radiation+CircAGFG1 knockdown+miR-375 inhibitor group,after transfection, the expression of CircAGFG1, miR-375 and USP22 in KYSE150-R cells of each group was detected by real-time fluorescent quantitative PCR and Western blot;the proliferation of KYSE150-R cells in each group was detected by CCK-8 method and plate colony formation test;the apoptosis of KYSE150-R cells was detected by flow cytometry;the ratio of apoptosis related protein Bax to Bcl-2 (Bax/Bcl-2) of KYSE150-R cells in each group was detected by immunofluorescence staining.The cells of each group were inoculated under the armpit of the right hind limb of nude mice to construct an ESCC transplanted tumor model,the tumor volume and weight of nude mice in each group were measured after 3 weeks of feeding.Double luciferase reporter gene experiment was used to detect the targeting regulation of CircAGFG1 on miR-375 and the targeting regulation of miR-375 on USP22 in KYSE150-R.Results Compared with KYSE150 cells, the expression of CircAGFG1, USP22 mRNA and protein in KYSE150-R cells increased (P＜0.05),the expression of miR-375 decreased (P＜0.05).Compared with the control group, the cell proliferation rate, colony generation rate, CircAGFG1 expression, USP22 mRNA and protein expression, tumor volume and tumor weight of nude mice in the radiation+CircAGFG1 knockdown group reduced(P＜0.05), the apoptosis rate, Bax/Bcl-2, miR-375 expression increased (P＜0.05);there was no obvious change in the cell indexes of the radiation group and the radiation+negative control group (P＞0.05).Compared with the radiation group, the cell proliferation rate, colony generation rate, CircAGFG1 expression, USP22 mRNA and protein expression, tumor volume and tumor weight of nude mice in the radiation+CircAGFG1 knockdown group reduced(P＜0.05), the apoptosis rate, Bax/Bcl-2, miR-375 expression increased (P＜0.05).Compared with the radiation+CircAGFG1 knockdown group, the cell proliferation rate, USP22 mRNA and protein expression, tumor volume and tumor weight of nude mice in the radiation+CircAGFG1 knockdown group increased (P＜0.05), the apoptosis rate, Bax/Bcl-2, miR-375 expression reduced(P＜0.05);in the radiation+negative control group, there was no significant change in the cell indexes (P＞0.05).CircAGFG1 was able to target and down regulate the expression of miR-375 in KYSE150-R cells, while miR-375 was able to target and down regulate the expression of USP22 in KYSE150-R cells.Conclusion Knocking down CircAGFG1 can reduce the expression of USP22 by up regulating miR-375, thereby enhancing the radiosensitivity of ESCC cells, enhancing the lethality of radiation to ESCC cells, and promoting their apoptosis