Blockade of Radiation-induced EGFR Nuclear Transport Enhances Radiosensitivity of Human Cervical Cancer

Objective To investigate whether the inhibition of EGFR nuclear transport could reduce the radioresistance of human cervical cancer cells. Methods Human cervical cancer CaSki and HeLa cells were exposed to radiation treated with or without Thr654 inhibitory peptide, cetuximab and gefitinib. The expression levels of pEGFR-T654 and pDNA-PK-T2609 were determined using Western blot. The survival fraction (SF2) was determined by colony formation and the dose-survival curve was fitted with a singlehit multi-target model to calculate the radiosensitization ratio (SER). Results After 4 Gy irradiation, EGFR expression in the nuclear of CaSki and HeLa cells were up-regulated in a time-dependent manner. Compared with the control peptide, Thr654 inhibitory peptide significantly reduced the expression levels of pEGFR-T654, DNA-PK and pDNA-PK-T2609 in the nucleus of CaSki and HeLa cells; compared with irradiation alone, cetuximab combined with irradiation significantly reduced the expression levels of EGFR, pEGFR-T654 and DNA-PK-T2609 in the nucleus of CaSki cells, as well as clone formation rate and survival fraction (SF2=31.030), and increased the radiosensitivity (SER=2.34). Conclusion Radiationinduced pEGFR-T654 nuclear translocation mediates the activation of pDNA-PK-T2609, and the inhibition of pEGFR-T654 nuclear transport by cetuximab reduces DNA-PK-mediated radiation resistance of cervical squamous cell carcinoma.