Abstract: Objective To detect proteins differentially expressed between radiosensitive and radioresistant nasopharyngeal carcinoma xenografts exposed to 10 Gy X-irradiation in an effort to identify proteins related to radiotherapy resistance.Methods Xenograft tumors of radiosensitive CNE-2 cells or radioresistant CNE-2R cells were established in nude mice. Proteins were extracted，digested into peptides，and labeled using the iTRAQ kit. Peptide mixtures were separated by 2D-HPLC，then analyzed by LTQ-Orbitrap massspectrometry. Differentially expressed proteins were classified according to gene ontology analysis. Results A total of 61 differentially expressed proteins were identified，of which 17 were up-regulated and 44 were down-regulated. GO analysis showed these proteins to
be involved in key biological processes such as cell cycle regulation，catabolism，signaling pathway regulation，response to pressure tress and redox reactions. Conclusion MudPIT analysis identified the following 7 proteins that may help render nasopharyngeal tumor issue radioresistant: Annexin2，PDIA3，Ubiquitin，CKAP4，HSPA8，14-3-3δ/ζ，and NLRC4.

Key words: Nasopharyngeal neoplasm, Transplantation tumor, Radiation resistance, Proteins, Differentially expressed