Cellular proteomic profiling of esophageal epithelial cells cultured under physioxia or normoxia reveals high correlation of radiation response

Objective: To investigate the radiation response and proteomic profiling of esophageal epithelial cells cultured under physioxia and normoxia. Methods: The human immortalized normal esophageal epithelial cell line SHEE cells were cultured under normoxia (21%) and physioxia (4%), respectively. A clonogenic assay was performed to evaluate the radiation response of SHEE cells. Cellular proteomic profiling of SHEE cells maintained under physioxia and normoxia was conducted to determine the differentially expressed proteins. Then, the identified differentially expressed proteins were validated by Western blot. Results: SHEE cells exposed to normoxia showed an increased radiation response compared to physioxia (irradiation dose ≥10 ​Gy, P< 0.05). Over 1200 non-redundant proteins were identified in the collected samples. Protein expression was compared between physioxia and normoxia, 42 proteins were downregulated and 45 proteins upregulated, in which oxidative phosphorylation was the most significantly enriched pathway. When cells were cultured under normoxia conditions, the induction of antioxidant genes appeared to contribute to form a phenotype adapted to the environment with high oxygen-content. Further analysis validated NRF2, BIP, VCP, SOD1, and YAP1 were the key regulators of this phenotype. Conclusions: Compared with physioxia, normoxic cell culture condition can enhance the radiation response. This study could stimulate in vivo microenvironment, and provide a basis for radiation-induced normal tissue damage.