A minority subpopulation of CD133+/EGFRvIII+/EGFR- cells acquires stemness and contributes to gefitinib resistance

Abstract

Aims: To study the contribution of epidermal growth factor receptor variant III (EGFRvIII) to glioblastoma multiforme (GBM) stemness and gefitinib resistance. Methods: CD133+ and CD133- cells were separated from EGFRvIII+ clinical specimens of three patients with newly diagnosed GBM. Then, RT-PCR was performed to evaluate EGFRvIII and EGFR expression in CD133+ and CD133- cells. The tumorigenicity and stemness of CD133+ cells was verified by intracranial implantation of 5 × 103 cells into immunodeficient NOD/SCID mice. Finally, cells were evaluated for their sensitivity to EGFR tyrosine kinase inhibition by gefitinib. Results: RT-PCR results showed that the sorted CD133+ cells expressed EGFRvIII exclusively, while the CD133- cells expressed both EGFRvIII and EGFR. At 6-8 weeks postimplantation, CD133+/EGFRvIII+/EGFR- cells formed intracranial tumors. Cell counting kit-8 results showed that the IC50 values of the three isolated EGFRvIII+ cell lines treated with gefitinib were 14.44, 16.00, and 14.66 μM, respectively, whereas the IC50 value of an isolated EGFRvIII- cell line was 8.57 μM. Conclusions: EGFRvIII contributes to the stemness of cancer stem cells through coexpression with CD133 in GBMs. Furthermore, CD133+/EGFRvIII+/EGFR- cells have the ability to initiate tumor formation and may contribute to gefitinib resistance. © 2013 John Wiley & Sons Ltd.