Epidermal growth factor receptor variant III mutations in lung tumorigenesis and sensitivity to tyrosine kinase inhibitors

Abstract

The tyrosine kinase inhibitors gefitinib (Iressa) and erlotinib (Tarceva) have shown anti-tumor activity in the treatment of non-small cell lung cancer (NSCLC). Dramatic and durable responses have occurred in NSCLC tumors with mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR). In contrast, these inhibitors have shown limited efficacy in glioblastoma, where a distinct EGFR mutation, the variant III (vIII) in-frame deletion of exons 2-7, is commonly found. In this study, we determined that EGFRvIII mutation was present in 5% (3͞56) of analyzed human lung squamous cell carcinoma (SCC) but was not present in human lung adenocarcinoma (0͞123). We analyzed the role of the EGFRvIII mutation in lung tumorigenesis and its response to tyrosine kinase inhibition. Tissue-specific expression of EGFRvIII in the murine lung led to the development of NSCLC. Most importantly, these lung tumors depend on EGFRvIII expression for maintenance. Treatment with an irreversible EGFR inhibitor, HKI-272, dramatically reduced the size of these EGFRvIII-driven murine tumors in 1 week. Similarly, Ba͞F3 cells transformed with the EGFRvIII mutant were relatively resistant to gefitinib and erlotinib in vitro but proved sensitive to HKI-272. These findings suggest a therapeutic strategy for cancers harboring the EGFRvIII mutation.irreversible inhibitor ͉ lung cancer ͉ lung squamous cell carcinoma E pidermal growth factor receptor (EGFR) is commonly overexpressed and mutated in many human malignancies and is often associated with aggressive phenotypes (1-3). Before the recent discovery of the somatic mutations in the EGFR kinase domain (4-8) in non-small cell lung cancers (NSCLC), deletions of the extracellular domain were considered the most frequent EGFR mutations in the different tumor types (9-13). These deletions have an activating effect on the receptor, giving cells expressing these truncated receptors a proliferative advantage. The most common truncated receptor is the variant III EGFR deletion mutant (EGFRvIII, delta 801EGFR, del2-7 EGFR), containing an inframe deletion of exons 2-7 (801 bp) from the extracellular domain, initially characterized at the genomic level in glioblastoma.Studies using immunohistochemical assays with EGFRvIII mutant-specific antibodies suggest that this mutation is present in multiple other tumor types, including NSCLC (10,11,14). However, because of EGFR's large and complex genomic structure (28 exons spanning Ϸ190 kb) and its large intron 1 (123 kb) where genomic deletions frequently occur, it has been difficult to assess and verify the existence of the EGFRvIII mutations at the genomic level. EGFRvIII mutations have been well demonstrated in glioblastoma, where they are present in Ͼ50% of glioblastomas with amplification of EGFR gene locus (12, 15, 16), but no genomic evidence for the existence of EGFRvIII mutations has been reported in NSCLC. Furthermore, the role of EGFRvIII mutation in the potential pathogenesis of NSCLC is unclear.Here, we report that the EGFRvIII mut...

Molecular pathology of lung cancer: key to personalized medicine

“…The information concerning whether EGFRvIII mutation is associated with specific histological types of lung cancer is conflicting, although most studies have indicated that EGFRvIII is associated with squamous cell carcinoma. 98,99 In the study by Sasaki et al, 97 EGFRvIII mutation was detected in 3% (8/ 252) of non-selected lung cancer patients. All patients bearing a EGFRvIII mutation were male, smokers, and seven had squamous cell carcinoma, whereas one had poorly differentiated adenocarcinoma.…”

“…EGFRvIII mutations were found in 5% of human lung squamous cell carcinomas (also see prior discussion) (Figure 4). 98,99 The advent of targeted therapy based on driver mutations in lung adenocarcinoma has countered the notion that non-small cell lung cancer (NSCLC) is a distinct clinical entity. Current information indicates that distinguishing a tumor as NSCLC alone is no longer sufficient for patient management and the term 'non-small cell lung cancer (NSCLC)' should be abandoned.…”

Genomics of Squamous Cell Lung Cancer

“…Decreased response to therapy with cisplatin and cetuximab was reported in head and neck SQCCs (HNSCCs) harboring this variant [104]. Evidence from a cell line study also suggests that EGFR vIII harboring tumors are relatively resistant (Ͼ40 fold more resistant compared with L858R variant) to gefitinib and erlotinib [102]. Although strategies capable of targeting this variant have been described in the literature, none are currently available for clinical use [105].…”

The ErbB signalling pathway: protein expression and prognostic value in epithelial ovarian cancer

“…We performed RT -PCR separately for EGFRvIII and the housekeeping gene GAPDH. Primers were 5 0 -GGGCTCTGGAGGAAAAGAAA-3 0 and 5 0 -AGGCC CTTCGCACTTCTTAC-3 0 for amplifying EGFRvIII and wtEGFR (Ji et al, 2006), and 5 0 -CACCCACTCCTCCACCTTTG-3 0 and 5 0 -CCAC CACCCTGTTGCTGTAG-3 0 for amplifying GAPDH. The protocol was as follows: initial denaturation at 951C for 10 min, followed by 30 (EGFRvIII) or 25 cycles (GAPDH) of amplification (1 min at 951C, 1 min at 561C for EGFRvIII and at 601C for GAPDH, and 90 s at 721C) and a final extension step at 721C for 7 min.…”