Kinetic Analysis of Epidermal Growth Factor Receptor Somatic Mutant Proteins Shows Increased Sensitivity to the Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor, Erlotinib

Abstract

We show that two commonly occurring epidermal growth factor receptor (EGFR) somatic mutations, L858R and an in-frame deletion mutant, Del(746-750), exhibit distinct enzymatic properties relative to wild-type EGFR and are differentially sensitive to erlotinib. Kinetic analysis of the purified intracellular domains of EGFR L858R and EGFR Del(746-750) reveals that both mutants are active but exhibit a higher K M for ATP and a lower K i for erlotinib relative to wild-type receptor. When expressed in NR6 cells, a cell line that does not express EGFR or other ErbB receptors, both mutations are ligand dependent for receptor activation, can activate downstream EGFR signaling pathways, and promote cell cycle progression. As expected from the kinetic analysis, the EGFR Del(746-752) is more sensitive to erlotinib inhibition than the EGFR L858R mutant. Further characterization shows that these mutations promote ligand-dependent and anchorageindependent growth, and cells harboring these mutant receptors form tumors in immunocompromised mice. Analysis of tumor lysates reveals that the tumorigenicity of the mutant EGFR cell lines may be due to a differential pattern of mutant EGFR autophosphorylation as compared with wild-type receptor. Significant inhibition of tumor growth, in mice harboring wild-type EGFR receptors, is only observed at doses of erlotinib approaching the maximum tolerated dose for the mouse. In contrast, the growth of mutant tumors is inhibited by erlotinib treatment at approximately one third the maximum tolerated dose. These findings suggest that EGFR somatic mutations directly influence both erlotinib sensitivity and cellular transformation. (Cancer Res 2006; 66(16): 8163-71)

Comment on prognostic value of epidermal growth factor receptor mutation subtypes in surgically resected non-small cell lung cancer

“…In this study, pathologic N status (N1 or N2) or pathologic stage (stage II or III) were determined to not be statistically informative prognostic factors for DFS using multivariate analysis (HR 1.71; P=0.353, or HR 0.75; P=0.627, respectively). Additionally, patients with Ex21 tumors (12). This data might support the results and hypothesis of Isaka's study.…”

Comparison of the efficacy of icotinib in patients with non-small-cell lung cancer according to the type of epidermal growth factor receptor mutation

“…A European phase III randomized controlled trial of erlotinib (Tarceva ® ) vs. chemotherapy (EURTAC trial) demonstrated that NSCLC patients with exon 19 deletion have a more favorable response rate, PFS and OS compared with patients with exon 21 L858R mutation (9). Based on in vitro cell cultures, another study demonstrated that exon 19 deletion may have a greater affinity for TKIs and display a higher sensitivity to treatment compared with exon 21 L858R mutation (15). However, a retrospective clinical study by Igawa et al (10) revealed no significant differences in RR, PFR or OS between patients with exon 19 deletion and those with exon 21 L858R mutation after receiving gefitinib, which is consistent with the stratification analysis results of another two large, randomized, phase III trials [NEJ002 (12) and WJTOG3405 (13)].…”

The Role of Smoking Status on the Progression-Free Survival of Non-Small Cell Lung Cancer Patients Harboring Activating Epidermal Growth Factor Receptor (EGFR) Mutations Receiving First-Line EGFR Tyrosine Kinase Inhibitor Versus Platinum Doublet Chemotherapy: A Meta-Analysis of Prospective Randomized Trials

“…We did not include IPASS [18] or First-SIGNAL [19] trials because both trials mainly enrolled never-smokers, the analysis of the EGFRm subgroup was retrospective, and a significant amount of Finally, this meta-analysis also demonstrates that EGFR TKI is significantly more effective in conferring PFS benefit against exon 19 deletion than against L858R substitution when compared with platinum-doublet chemotherapy. In vitro data have demonstrated that gefitinib and erlotinib both have a higher affinity for the exon 19 deletion than L858R mutation [20], resulting in inhibition of the kinase activity of mutated exon 19 deletion EGFR much faster and tighter with both EGFR TKIs [21]. As early as in 2006, clinical observations have reported that exon 19 deletion seems to derive longer PFS from EGFR TKI than L858R substitution [22,23].…”