Expression of EGFR variant vIII promotes both radiation resistance and hypoxia tolerance.

Abstract

EGFRvIII has been described to function as an oncoprotein with constitutive activation promoting neoplastic transformation and tumorigenicity. The present study was undertaken to test whether EGFRvIII also contributes to hypoxia tolerance. The human glioma cell line U373 was genetically modified to stably express EGFRvIII. Western blotting and immunohistochemistry verified the expression of EGFRvIII. Tumour xenografts were produced by injecting U373 control and EGFRvIII positive cells subcutaneously into the lateral flank of recipient mice. Colony formation assays were performed after ionizing radiation at 4Gy and after exposure to anoxia for 1-4 days. EGFRvIII accelerated tumour growth leading to a 3.5-fold increase in tumour size compared to control tumours at 40 days after cell injection. EGFRvIII promoted clonogenic survival by almost 2-fold and 4-fold after 4Gy and 4 days of anoxia, respectively. EGFRvIII was also associated with a substantially bigger colony size after anoxic treatment. EGFRvIII expression stimulates the growth of tumour xenografts and strongly promotes survival after irradiation and under hypoxic stress.