Novel D761Y and Common Secondary T790M Mutations in Epidermal Growth Factor Receptor–Mutant Lung Adenocarcinomas with Acquired Resistance to Kinase Inhibitors

Abstract

Purpose: In patients whose lung adenocarcinomas harbor epidermal growth factor receptor (EGFR) tyrosine kinase domain mutations, acquired resistance to the tyrosine kinase inhibitors (TKI) gefitinib (Iressa) and erlotinib (Tarceva) has been associated with a second-site EGFR mutation, which leads to substitution of methionine for threonine at position 790 (T790M). We aimed to elucidate the frequency and nature of secondary EGFR mutations in patients with acquired resistance toTKI monotherapy. Experimental Design: Tumor cells from patients with acquired resistance were examined for secondary EGFR kinase domain mutations by molecular analyses. Results: Eight of 16 patients (50% observed rate; 95% confidence interval, 25-75%) had tumor cells with second-site EGFR mutations. Seven mutations were T790M and one was a novel D761Y mutation found in a brain metastasis. When combined with a drug-sensitive L858R mutation, the D761Y mutation modestly reduced the sensitivity of mutant EGFR to TKIs in both surrogate kinase and cell viability assays. In an autopsy case, theT790M mutation was found in multiple visceral metastases but not in a brain lesion. Conclusions: TheT790M mutation is common in patients with acquired resistance. The limited spectrum of TKI-resistant mutations in EGFR, which binds to erlotinib in the active conformation, contrasts with a wider range of second-site mutations seen with acquired resistance to imatinib, which binds to ABL and KIT, respectively, in closed conformations. Collectively, our data suggest that the type and nature of kinase inhibitor resistance mutations may be influenced by both anatomic site and mode of binding to the kinase target.

Epidermal growth factor receptor mutations detected by denaturing high‐performance liquid chromatography in nonsmall cell lung cancer

“…The secondary EGFR mutation, T790M, results in the substitution of methionine for threonine in the tyrosine kinase domain of EGFR, disrupting normal binding of erlotinib. 38 Jackman et al have hypothesized that T790m mutations may occur more frequently with L585R mutations than with exon 19 deletions. 25 In 2 Japanese prospective trials, the response rates for both mutations were not significantly different.…”

Molecular pathology of lung cancer: key to personalized medicine

“…15,67 The most important mutation in exon 20 is T790M, which is associated with a small fraction of adenocarcinomas with primary resistance to EGFR TKI and over one-half of the patients with acquired resistance to EGFR TKI ( Figure 2). 12,[67][68][69][70][71] A comprehensive literature review by Yamamoto et al 33 indicated that 569 mutations were found in 2880 lung cancer patients (20%). The distribution of EGFR mutations was as follows: 48% in exon 19, 43% in exon 21, 4% in exon 20, and 3% in exon 18.…”

“…Exons 18-21 in the tyrosine kinase region of the EGFR gene are scaled up; a detailed list of EGFR mutations in these exons associated with sensitivity (green) or resistance (orange) to EGFR TKI. 6,12,[67][68][69][70][71][80][81][82][83][84]195 The frequency of the mutations is labeled to the side of the color-coded bars. The most prevalent EGFR mutations are in-frame deletions of exon 19 (45%), followed by L858R substitution in exon 21 (41%).…”

“…The incidences of mutations were as follows: KRAS 25%, EGFR 23%, ALK rearrangements 6%, BRAF 3%, PIK3CA 3%, MET amplifications 2%, ERBB2 1%, MAP2K1 0.4%, NRAS 0.2%, and AKT1 0% (Figure 3). 12,[67][68][69][70][71] It is noteworthy that 95% of molecular lesions were mutually exclusive. 79 EGFR mutations are responsible for the constitutive activation of the tyrosine kinase receptor.…”

“…70,[179][180][181] Clinically, patients with EGFR exon 20 mutations do not respond to gefitinib. 67 Moreover, the appearance of a secondary mutation in exon 20 (T790M) accounts for B50% of acquired drug resistance.…”