A Novel EGFR Extracellular Domain Mutant, EGFRΔ768, Possesses Distinct Biological and Biochemical Properties in Neuroblastoma.

UNLABELLED: EGFR is a popular therapeutic target for many cancers. EGFR inhibitors have been tested in children with refractory neuroblastoma. Interestingly, partial response or stable disease was observed in a few neuroblastoma patients. As EGFR mutations are biomarkers for response to anti-EGFR drugs, primary neuroblastoma tumors and cell lines were screened for mutations. A novel EGFR extracellular domain deletion mutant, EGFRΔ768, was discovered and the biologic and biochemical properties of this mutant were characterized and compared with wild-type and EGFRvIII receptors. EGFRΔ768 was found to be constitutively active and localized to the cell surface. Its expression conferred resistance to etoposide and drove proliferation as well as invasion of cancer cells. While EGFRΔ768 had similarity to EGFRvIII, its biologic and biochemical properties were distinctly different from both the EGFRvIII and wild-type receptors. Even though erlotinib inhibited EGFRΔ768, its effect on the mutant was not as strong as that on wild-type EGFR and EGFRvIII. In addition, downstream signaling of EGFRΔ768 was different from that of the wild-type receptor. In conclusion, this is the first study to demonstrate that neuroblastoma express not only EGFRvIII, but also a novel EGFR extracellular domain deletion mutant, EGFRΔ768. The EGFRΔ768 also possesses distinct biologic and biochemical properties which might have therapeutic implications for neuroblastoma as well as other tumors expressing this novel mutant. IMPLICATIONS: Neuroblastoma expressed a novel EGFR mutant which possesses distinct biologic and biochemical properties that might have therapeutic implications. Mol Cancer Res; 14(8); 740-52. ©2016 AACR. ©2016 American Association for Cancer Research.