The IL-6/STAT3 signaling pathway mediated by radiotherapy regulates the expression of PD-L1 and affects the biological functions of esophageal cancer cells.

e16531 Background: The mechanism by which radiotherapy regulates PD-L1 expression and affects the biological behavior of esophageal cancer cells is not clear.The IL-6 /STAT3 signaling pathway may be involved. Methods: After irradiation of different doses to the esophageal cancer cell lines (Eca109, KYSE150, and TE1), RT-PCR and Western blotting were used to detect PD-L1, STAT3 and P-STAT3, ELISA was performed to examine the effects on IL-6, CCK-8 assays were used to test the effects on the proliferation. After the optimal dose radiation, Transwell assays were used to detect the invasion and proliferation of cell clones, and cell cycle changes were detected by flow cytometry. Results: The mRNA and the protein expression of PD-L1 in the cancer cell lines was significantly higher than in the normal esophageal cell line HET-1A(P < 0.01). The PD-L1 mRNA levels first increased and then decreased, which peaked 12 hours after 3,6,9,12Gy irradiation and was significantly higher than in nonirradiated cells (P < 0.05). PD-L1 protein expression first increased and then decreased, which peaked 48 hours after 6 Gy irradiation (P < 0.05). P-STAT3 protein expression first increased and then decreased after 6Gy irradiation (P < 0.05), that the expression in Eca109 peaked 48 hours but in KYSE150 and TE1 peaked 24 hours (P < 0.05). IL-6 protein expression peaked 12 hours and decreased gradually after irradiation (P < 0.05). The proliferation levels of the the cancer cell lines decreased after irradiation, and the inhibitory force increased with the increase in dose and time after radiotherapy (P < 0.05). The clone formation ability of the cancer cell lines was inhibited to varying degrees 14 days after irradiation with 6 Gy(P < 0.05). After 48 hours irradiation with 6 Gy, and the invasion ability of the cancer cell lines was lower than that of the nonirradiated cell lines (P < 0.05), and the proportion of cells in G2/M phase was higher in exposed cells than in nonexposed cells (P < 0.05), while the proportion of cells in S phase did not change significantly. Conclusions: PD-L1, IL-6 and STAT3 protein expression in the esophageal cancer cell lines first increased and then decreased consistency after irradiation, radiotherapy could regulate PD-L1 expression through the IL-6/STAT3 signaling pathway and affect the biological functions of esophageal cancer.