Objective To investigate the effect of ubiquitin-like with PHD and ring finger domains 1 (UHRF1) on the radiosensitivity of esophageal squamous carcinoma cells and explore its mechanism. Methods The shRNA sequence was designed with human UHRF1 as the target, and the UHRF1-shRNA was transfected into Eca-109 cells mediated by lentivirus. The expressions of UHRF1 mRNA and protein before and after transfection were determined by fluorescence quantitative PCR and Western blotting. The radiosensitivity of Eca-109 cells after down-regulation of UHRF1 gene was assessed by colony formation assay. The effect of silencing UHRF1 on the apoptosis of Eca-109 cells before and after X-ray irradiation was detected by flow cytometry. Western blotting was used to detect the effects of UHRF1 silencing and X-ray irradiation on the expressions of apoptosis-related proteins Bcl-2, caspase-3 and proteins related to AKT/mTOR signaling pathway in Eca-109 cells. Results We successfully constructed an Eca-109 shUHRF1 cell line with UHRF1 stablely down-regulated. Colony formation assays showed that the radiosensitivity of Eca-109 cells was increased after down-regulation of UHRF1 expression compared with the NC group. The proportion of apoptotic cells in Eca-109 cells was increased, while this change was more obvious after irradiation. Compared with NC group, down-regulation of UHRF1 expression increased the level of active caspase-3 protein and decreased the level of the apoptosis inhibitory protein Bcl-2; the expression levels of p-AKT and p-mTOR protein were decreased. The changes in these four proteins in Eca-109 cells with down-regulation of UHRF1 combined with 6 Gy X-ray irradiation were more obvious compared with the NC group. Conclusion UHRF1 knock-down increased the radiosensitivity of ESCC via inhibiting the Akt/mTOR signaling pathway activity and inducing the apoptosis of the cells.

【Objective】 To investigate setup and respiratory movement residual error with the guidance of online four-dimensional cone beam computed tomography (4DCBCT) and the impact on margins required to internal target volume (ITV) margin during stereotactic body radiotherapy (SBRT) of lung tumor in the middle or lower lobe. 【Methods】 Twenty SBRT treatment patients with lung tumor in the middle or lower lobe were enrolled for treatment residual error retrospective analysis. Thermoplastic masks were used as immobilization devices during SBRT treatment. ITV was determined by 4DCBCT simulation. A total of 76 4DCBCT scans before the treatment were recorded to determine the setup and respiratory residual error for ITV margins. 【Results】 The setup and respiratory movement error were significantly reduced with the guidance of online 4DCBCT during radiotherapy. The setup residual errors were respectively (0.07±0.12)cm, (0.03±0.29)cm and (0.04±0.14)cm in right-left (RL), superior-inferior (SI) directions and anterior-posterior (AP) directions. The respiratory movement residual errors were respectively (-0.06±0.07)cm, (0.02±0.26)cm and (0.02±0.11)cm in RL, AP, and SI directions. Based on setup and respiratory movement residual errors, the PTV margins of NSCLC were reduced from 1.13 cm, 2.15 cm and 0.90 cm to 0.50 cm, 0.59 cm and 0.56 cm in RL, AP and SI directions, respectively, calculated with recipe by VanHerk. 【Conclusion】 With the guidance of online 4DCBCT, the setup and respiratory movement residual error cannot be ignored during SBRT of lung tumor in the middle or lower lobe. The ITV margin required after online 4DCBCT correction for the patients enrolled in the study would be approximatively 0.6 cm around to ensure an accurate dose to the target tumor and reduce the dose to normal tissues.