Effect of EBI3 on radiation-induced immunosuppression of cervical cancer HeLa cells by regulating Treg cells through PD-1/PD-L1 pathway.

This study aimed to investigate the effect of EBI3 on radiation-induced immunosuppression of cervical cancer HeLa cells by regulating Treg cells through PD-1/PD-L1 signaling pathway. A total of 43 adult female Wistar rats were selected and injected with HeLa cells in the caudal vein to construct a rat model of cervical cancer. All model rats were randomly divided into the radiotherapy group (n = 31) and the control group (n = 12). The immunophenotype of Treg cells was detected by the flow cytometry. The protein expressions of EBI3, PD-1, and PD-L1 in cervical cancer tissues were tested by the streptavidin-peroxidase method. HeLa cells in the logarithmic growth phase were divided into four groups: the blank, the negative control group, the EBI3 mimics group, and the EBI3 inhibitors group. Western blotting was used to detect PD-1 and PD-L1 protein expressions. MTT assay was performed to measure the proliferation of Treg cells. Flow cytometry was used to detect cell cycle and apoptosis, and CD4(+)/CD8(+)T cell ratio in each group. Compared with before and 1 week after radiotherapy, the percentages of CD4(+)T cells and CD8(+)T cells were significantly decreased in the radiotherapy group at 1 month after radiotherapy. Furthermore, down-regulation of EBI3 and up-regulation of PD-1 and PD-L1 were observed in cervical cancer tissues at 1 month after radiotherapy. In comparison to the blank and negative control groups, increased expression of EBI3 and decreased expressions of PD-1 and PD-L1 were found in the EBI3 mimics group. However, the EBI3 inhibitors group had a lower expression of EBI3 and higher expressions of PD-1 and PD-L1 than those in the blank and negative control groups. The EBI3 mimics group showed an increase in the optical density value (0.43 +/- 0.05), while a decrease in the optical density value (0.31 +/- 0.02) was found in the EBI3 inhibitors group. Moreover, compared with the blank and negative control groups, the apoptosis rates of Treg/CD4(+)T/CD8(+)T cells were decreased in the EBI3 mimics group, but the EBI3 inhibitors group exhibited an increase in apoptosis rate. In conclusion, over-expression of EBI3 could reduce the apoptosis of Treg/CD4(+)T/CD8(+)T cells and prevent radiation-induced immunosuppression of cervical cancer HeLa cells by inhibiting the activation of PD-1/PD-L1 signaling pathway.