Objective:To investigate the effect of circ-PRKDC on lung cancer cell proliferation, apoptosis and radiosensitivity and its molecular mechanism.Methods:Normal lung epithelial cells BEAS-2B and lung cancer cell lines NCI-H1299, NCI-H2170, NCI-H1975 were cultured. NCI-H1299 cells were divided into the si-NC, si-PRKDC, pcDNA-NC, pcDNA-PRKDC, miR-NC, miR-505-3p, anti-miR-NC, anti-miR-505-3p, si-PRKDC+ anti-miR-NC and si-PRKDC+ anti-miR-505-3p groups. RT-qPCR was used to detect the expression levels of circ-PRKDC and miR-505-3p. Western blot was employed to measure the protein expression. MTT was used to detect cell proliferation. Flow cytometry was utilized to detect cell apoptosis. Plate clone formation assay was conducted to detect the cell radiosensitivity. Dual luciferase reporter assay was performed to analyze the targeting relationship between circ-PRKDC and miR-505-3p.Results:Compared with normal lung epithelial cells BEAS-2B, the expression levels of circ-PRKDC in the lung cancer cell lines NCI-H1299, NCI-H2170 and NCI-H1975 were significantly up-regulated (3.65, 3.10, 2.67 vs. 1.00, all P<0.05), whereas those of miR-505-3p were significantly down-regulated (0.42, 0.50, 0.54 vs. 1.02, all P<0.05). After low expression of circ-PRKDC, the expression level of CyclinD1 was significantly down-regulated (0.42 vs. 0.81, P<0.05), whereas those of Cleaved-caspase-3(0.71 vs. 0.33, P<0.05) and γ-H 2AX (0.89 vs. 0.46, P<0.05) were significantly up-regulated, the cell A value was significantly decreased (0.413 vs. 0.839, P<0.05), cell apoptosis rate was significantly increased (20.35 vs. 6.21, P<0.05), cell survival fraction was significantly decreased ( P<0.05), and β-catenin expression was significantly down-regulated (0.35 vs. 0.73, P<0.05). After high expression of miR-505-3p, the expression level of CyclinD1 was significantly down-regulated (0.34 vs. 0.83, P<0.05), those of Cleaved-caspase-3(0.65 vs. 0.32, P<0.05) and γ-H 2AX (0.96 vs. 0.45, P<0.05) were significantly up-regulated, the cell A value was significantly decreased (0.386 vs. 0.851, P<0.05), the apoptosis rate was significantly increased (16.38 vs. 6.20, P<0.05), and the cell survival fraction was significantly decreased ( P<0.05). Compared with miR-NC, the luciferase activity of miR-505-3p group transfected with circ-PRKDC wild-type reporter plasmid was significantly decreased (0.44 vs. 1.00, P<0.05). Down-regulation of miR-505-3p could reverse the effect of low expression of circ-PRKDC on the proliferation, apoptosis, radiosensitivity and β-catenin expression of NCI-H1299 cells. Conclusion:Low expression of circ-PRKDC may inhibit lung cancer cell proliferation, promote cell apoptosis and enhance cell radiosensitivity by up-regulating miR-505-3p, which is probably associated with the Wnt/β-catenin signaling pathway.

Objective:To evaluate the effect of circLPAR3 on the radiosensitivity of esophageal cancer cells and investigate its mechanism.Methods:The cancer tissues and and adjacent tissues of 37 patients with esophageal cancer were collected, and esophageal cancer cell lines Eca-109, EC9706 and KYSE30 and esophageal epithelial cells HET-1A were cultured in vitro. The expression levels of circLPAR3 and miR-1238 in the tissues and cells were measured by RT-qPCR. Eca-109 cells were transfected with circLPAR3 siRNA and miR-1238 mimics or co-transfected with circLPAR3 siRNA and miR-1238 inhibitor. Cell cloning experiment was conducted to evaluate the effects of silencing circLPAR3, overexpressing miR-1238, or silencing both circLPAR3 and miR-1238 on the radiosensitivity of Eca-109 cells. After Eca-109 cells that silenced circLPAR3, overexpressed miR-1238 or silenced both circLPAR3 and miR-1238 were exposed to 4 Gy irradiation, CCK-8 assay (A value), flow cytometry and Western blot were employed to assess the effects of silencing circLPAR3, overexpressing miR-1238, or silencing both circLPAR3 and miR-1238 combined with 4 Gy irradiation on the proliferation and apoptosis of Eca-109 cells and the expression levels of CyclinD1, p21, Bcl-2 and Bax proteins. Dual luciferase reporter gene experiment and RNA pull down experiment were performed to verify the regulatory relationship between circLPAR3 and miR-1238. Results:Compared with adjacent tissues, the expression level of circLPAR3 was up-regulated in the esophageal cancer tissues ( P<0.05), while that of miR-1238 was down-regulated ( P<0.05). Compared with HET-1A cells, the expression levels of circLPAR3 were up-regulated in the esophageal cancer cell lines Eca-109, EC9706 and KYSE30(all P<0.05), whereas those of miR-1238 were down-regulated (all P<0.05). Silencing circLPAR3 or overexpressing miR-1238 reduced the survival fraction of Eca-109 cells (all P<0.05), and the sensitization ratio was 1.21 and 1.75, respectively. Silencing circLPAR3 or overexpressing miR-1238 decreased the A value of Eca-109 cells and the expression levels of CyclinD1 and Bcl-2 proteins (all P<0.05), while increased the apoptosis rate of Eca-109 cells and the expression levels of p21 and Bax proteins (all P<0.05). After silencing circLPAR3 or overexpressing miR-1238 combined with 4 Gy irradiation, the A value of Eca-109 cells and the expression levels of CyclinD1 and Bcl-2 proteins were decreased (all P<0.05), while Eca-109 cell apoptosis rate and the expression levels of p21 and Bax proteins were increased (all P<0.05). circLPAR3 targeted and negatively regulated the expression level of miR-1238 in Eca-109 cells. After silencing miR-1238 and circLPAR3 simultaneously, the survival fraction of Eca-109 cells was higher than that when only silencing circLPAR3, and the sensitization ratio was 0.59. Silencing miR-1238 reversed the effects of silencing circLPAR3 combined with 4 Gy irradiation on the proliferation and apoptosis of Eca-109 cells. Conclusion:circLPAR3 is highly expressed in esophageal cancer tissues and cell lines, and silencing the expression of circLPAR3 can inhibit the proliferation of esophageal cancer Eca-109 cells, promote their apoptosis, and enhance cell radiosensitivity by up-regulating miR-1238.

Objective: To investigate the mechanism of miR-31-5p/tension protein 1 gene (TNS1) axis modulating radiotherapy resistance in breast cancer. Methods: The breast cancer tissues and corresponding para-cancerous tissues of 21 patients with breast cancer, who underwent surgical resection at Department of Cancer Radiotherapy of Nanyang Central Hospital from July 2017 to December 2017, were collected for this study; breast cancer cell lines (MCF-7，MDA-MB-23 and SKBR-3) were also collected; qPCR was applied to detect the expression level of miR-31-5p in breast cancer tissues and cell lines. The radiation resistant cell line MCF-7R was constructed by using 6 MV-X ray radiotherapy treatment. Subsequently, the influence of over-expression/kockdown of miR-31-5p on radiation sensitivity of MCF-7 and MCF-7R cells were detected by colony formation assay, Transwell assay and Annexin V-FITC/PI double staining flow cytometry assay, respectively. Moreover, luciferase reporter assay was used to verify whether TNS1 was a target gene of miR-31-5p. Results: Compared with para-cancerous tissues, normal mammary epithelial MCF-10A cells and MCF-7 cells, miR-31-5p was low-expressed in breast cancer, cell lines and MCF-7R (all P<0.01). Over-expression of miR-31-5p resulted in inhibited invasion and promoted apoptosis of MCF-7R cells (P<0.01), whereas miR-31-5p knockdown got opposite results in MCF-7 cells. Moreover, luciferase reporter assay confirmed that TNS1 was a target gene of miR-31-5p. Over-expression of miR-31-5p inhibited invasion and increased radio-sensitivity, apoptosis of MCF-7R cell via targeting TNS1 (P<0.01), whereas knockdown of miR-31-5p significantly promoted the invasion but reduced apoptosis of MCF-7R cells (all P<0.01), and further up-regulated the radio-sensitivity of MCF-7R cells. Conclusion: miR-31-5p/TNS1 axis regulates the radiotherapy resistance of breast cancer, and over-expression of miR-31-5p may reverse the resistance of MCF-7R to radiotherapy.