Objective:To explore the effects of estrogen receptor α (ERα) encoded by protein encoding gene ESR1 on the radiation resistance of breast cancer cells and their molecular mechanisms.Methods:The ESR1 overexpression plasmid was transfected into estrogen receptor (ER)-negative breast cancer cells. Then, the shRNA-ESR1 vector was introduced into ER-positive cell to establish models with different phenotype. The ATG5 mRNA level and protein expression levels of LC3B-I, LC3B-II, P62, FIP200, ATG5, ATG7, ATG12, Beclin1, ULK1 were detected using qPCR and Western blot techniques. Cell death was measured using flow cytometry. The radiation sensitivity was determined through the colony formation assay. The mortality of breast cancer cells under the autophagy gene knockdown and overexpression or treated with estrogen receptor inhibitor (TAM) combined with ionizing radiation were detected by trypan blue staining.Results:Under the condition of 8 Gy X-ray irradiation, the knockdown of ESR1 in ER-positive ZR75 breast cancer cells promoted cell death ( t = 3.49, 3.13, P < 0.05), while the overexpression of ESR1 in ER-negative MDA-MB-231 breast cancer cells inhibited cell death ( t = 4.16, 7.48, P < 0.05). Compared to the control group, the treatment with chloroquine increased the number of formed colonies of ESR1 knockdown ZR75 cells ( t = 8.49, P < 0.05), and inhibiting autophagy could reduce the death of ZR75 cells caused by ESR1 silencing. Under the treatment with ionizing radiation, the overexpression of ESR1 in MDA-MB-231 cells promoted protective autophagy, which, however, was reduced after ESR1 knockdown in ZR75 cells. Furthermore, it was observed that the knockdown of ATG5 in ZR75 cells was associated with reduced autophagy and an increase in cell death ( t = 4.19, 6.39, P < 0.05). In contrast, the overexpression of ATG5 in ZR75 cells reversed the increase in cell death caused by ESR1 knockdown ( t = 1.70, 4.65, P < 0.05). After the treatment of ER-positive ZR75 breast cancer cells with TAM, the expressions of ATG5 and ATG12 decreased, suggesting inhibited autophagy and an increase in cell death ( t = 18.70, P < 0.05). Furthermore, these processes were promoted by ionizing radiation ( t = 16.82, P < 0.05). Conclusions:The estrogen receptor encoded by ESR1 promotes protective autophagy of ER-positive breast cancer cells by increasing ATG5, further leading to radiation resistance in ER-positive breast cancer cells. Treatment with tamoxifen combined with ionizing radiation can increase the radiation sensitivity of ER-positive breast cancer cells.

Objective: To evaluate the efficacy and safety of sofosbuvir (Nanjing Zhengda Tianqing Pharmaceutical Co., Ltd.) combined with ribavirin in patients with genotype 2 chronic hepatitis C virus infection. Methods: Treatment-naïve or treatment experienced genotype 2 chronic hepatitis C patients from sixteen research centers of China were screened. All subjects received once-daily dose of sofosbuvir (400 mg) combined with ribavirin (body weight < 75 kg, 1 000 mg/day, 400 mg in the morning and 600 mg in the evening; body weight > 75 kg, 1 200 mg/d, 600 mg in the morning and 600 mg in the evening) for 12 weeks. Patients were followed-up for a period of 12 weeks after discontinuation of treatment. Continuous variables were expressed as mean ± standard deviation. The proportion of subjects with virologic response at different follow-up time points and 95% confidence intervals were estimated by maximum likelihood ratio and Clopper-Pearson interval. Results: 132 cases with genotype 2 chronic hepatitis C virus infection from sixteen research centers of China were included, 12 cases of whom were associated with cirrhosis, and the remaining 120 cases were not associated with cirrhosis. One hundred and thirty-one cases completed the study, and one patient lost to follow-up at week 4 after the end of treatment. The sustained virological response rate was 96.2% (95% confidence interval: 92.37% - 99.16%) after 12 weeks of drug withdrawal. Virological relapse occurred in four cases. Of the 132 subjects enrolled in the study, 119 (90.2%) reported 617 adverse events during treatment, of which 359 (76.5%) were TEAE related to sofosbuvir and/or ribavirin. There were nine TEAEs of grade 3 and above, and six cases (4.5%) of them had six severe adverse events. Only one serious adverse event was associated with sofosbuvir and ribavirin (unstable angina pectoris). There were no adverse events leading to drug discontinuation or death. Conclusion Sofosbuvir combined with ribavirin has a high SVR rate in the treatment of genotype 2 chronic hepatitis C virus infection, and most of the adverse events occurred were mild with acceptable safety profile.