[The mechanism of circ_0023990/miR-873-5p/ANXA2 axis regulating radiosensitivity and development of thyroid carcinoma].

Objective: To explore the effect and possible mechanism of circ_0023990 on the radiosensitivity of thyroid cancer cells. Methods: qRT-PCR was used to detect the expression of circ_0023990 in the cancer tissues of 55 patients with thyroid cancer and thyroid cancer cell lines (TPC-1, KTC-1, FTC-133 and CAL-62), and the relationship between the expression of circ_0023990 in cancer tissues and the clinical characteristics of the patients were analyzed. Thyroid cancer cells TPC-1 and KTC-1 were divided into sh-circ_0023990 group, sh-NC group, sh-circ_0023990+anti-miR-873-5p group, sh-circ_0023990+anti-miR-NC group, miR-873-5p group, miR-NC group, miR-873-5p+pcDNA-ANXA2 group and miR-873-5p+pcDNA group, and then clone formation experiment was used to detect cell radiosensitivity. After each group of cells was irradiated with 4Gy radiation, the expression of γH2AX protein in the cells was detected by Western Blot. The dual luciferase reporter gene experiment verified the targeting relationship between circ_0023990 and miR-873-5p or miR-873-5p and ANXA2. Results: The expression of circ_0023990 in thyroid cancer tissues was higher than that in normal tissues (2.15±0.09 vs. 0.97±0.05, P<0.05), and its expression was closely related to tumor size, lymph node metastasis and TNM staging of patients with thyroid cancer (P<0.05). The expression of circ_0023990 in thyroid cancer cell lines (TPC-1, KTC-1, FTC-133 and CAL-62) were higher than that of normal thyroid cells HTori-3 (3.16±0.38, 2.63±0.28, 1.82±0.24, 1.71±0.22 vs. 1.00±0.10, all P<0.05). The survival scores of TPC-1 and KTC-1 cells in the sh-circ_0023990 group were significantly lower than those in the sh-NC group (P<0.05), and the sensitization ratios were 2.482, 1.643; The survival scores of TPC-1 and KTC-1 cells in the sh-circ_0023990+anti-miR-873-5p group were higher than those in the sh-circ_0023990+anti-miR-NC group (P<0.05), and the sensitization ratios were 0.305, 0.441, respectively. The survival scores of TPC-1 and KTC-1 cells in the miR-873-5p group were lower than those in the miR-NC group (P<0.05), and the sensitization ratios were 2.044, 1.653 respectively. The survival scores of TPC-1 and KTC-1 cells in the miR-873-5p+pcDNA-ANXA2 group was higher than that in the miR-873-5p+pcDNA group (P<0.05), and the sensitization ratios were 0.496, 0.686, respectively. The expression of γH2AX protein in TPC-1 and KTC-1 cells of the 4 Gy+sh-circ_0023990 group were higher than that in the 4 Gy+sh-NC group (2.68±0.27 vs. 1.87±0.25, 2.46±0.19 vs. 1.77±0.14; all P<0.05), but the expression of γH2AX protein in TPC-1 and KTC-1 cells of the 4 Gy+sh-circ_0023990+anti-miR-873-5p group were lower than that in the 4 Gy+sh-circ_0023990+anti-miR-NC group (1.13±0.09 vs. 1.69±0.09, 1.11±0.08 vs. 1.60±0.08; both P<0.05). The expression of γH2AX protein in TPC-1 and KTC-1 cells in the 4 Gy+miR-873-5p group were higher than that in the 4 Gy+miR-NC group (2.35±0.16 vs. 1.84±0.14, 2.26±0.12 vs. 1.77±0.13; both P<0.05), but the expression of γH2AX protein in TPC-1 and KTC-1 cells of the 4 Gy+miR-873-5p+pcDNA-ANXA2 group were lower than that in the 4 Gy+miR-873-5p+pcDNA group (1.96±0.12 vs. 2.41±0.12, 1.92±0.07 vs. 2.28±0.12; both P<0.05). circ_0023990 targeted the negative regulation of miR-873-5p, and ANXA2 was the target gene of miR-873-5p. Conclusion: circ_0023990 was highly expressed in thyroid cancer tissues and cell lines, and it may promote the radiotherapy resistance of thyroid cancer cells in vivo through regulating miR-873-5p/ANXA2 axis.