EGFR Confers Radioresistance In Human Oropharyngeal Carcinoma By Activating Endoplasmic Reticulum Stress Signaling PERK-eIF2?-GRP94 And IRE1?-XBP1-GRP78

Objective: Epidermal growth factor receptor(EGFR)is overexpressed in many tumors.The activation of EGFR is associated with radioresistance in malignant tumors.Specifically,radiation can destroy endoplasmic reticulum(ER)homeostasis to induce ER stress(ERS)and confers radioresistance.However,the effect of EGFR?mediated regulation of ERS signaling pathway on radiosensitivity has not yet been reported.Methods: This research adopts the method of siRNA transfection to silence EGFR,and epidermal growth factor(EGF)pretreatment to activate EGFR.Original oropharyngeal cancer cell line(FaduP,Detroit562P),and their radioresistant cell line(FaduR,Detroit562 R is used in our study.Clone formation experiments are used to test the effect of EGFR silence and EGFR activation on radiosensitivity.Western blot is used to detect the activation of ERS-related protein expression in oropharyngeal cancer cells after silencing EGFR or activating EGFR when combined with irradiation.Immunofluorescence and Western blot were used to detect the activation of autophagy,DNA double-strand repair and apoptosis-related proteins after silencing EGFR when combined with radiotherapy.Immunohistochemistry was used to detect EGFR and PERK expression in 80 patients with oropharyngeal cancer.Kaplan-meier method was used to analyze the correlation of EGFR and PERK with prognosis in oropharyngeal cancer patients.Results: The present study showed that irradiation could activate the expression of EGFR in both radioresistant and radiosensitive OSCC cell lines.Silencing EGFR increased radiosensitivity of both radiosensitive and radioresistant oropharyngeal squamous cell carcinoma(OSCC)cells by inhibiting ER stress signaling(PERK?eIF2??GRP94 and IRE1??XBP1?GRP78).This effect was abolished by pretreatment with EGF,however.In addition,knockdown of EGFR in OSCC cells inhibited DNA double?stand break repair and autophagy while increased radiation?induced apoptosis.Immunohistochemical analysis of 80 tissue samples from OSCC patients showed that co?expression of EGFR and PERK was associated with poor prognosis(P<0.05).Conclusion: EGFR confers radioresistance in OSCC by activating ER stress signaling.The specific mechanism is related to the inhibition of autophagy,DNA damage repair,and the increase of apoptosis mediated by them.