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1.  Acquired Resistance to EGFR Kinase Inhibitors Associated with a Novel T854A Mutation in a Patient with EGFR-Mutant Lung Adenocarcinoma 
Somatic mutations in the tyrosine kinase domain of EGFR are associated with sensitivity of lung adenocarcinomas to the EGFR tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib. Acquired drug resistance is frequently associated with a secondary somatic mutation that leads to substitution of methionine for threonine at position 790 (T790M). We aimed to identify additional second-site alterations associated with acquired resistance.
Experimental Design
Tumor samples were obtained from 48 patients with acquired resistance. Tumor cell DNA was analyzed for EGFR kinase domain mutations. Molecular analyses were then performed to characterize biological properties of a novel mutant EGFR allele.
A previously unreported mutation in exon 21 of EGFR, which leads to substitution of alanine for threonine at position 854 (T854A), was identified in one patient with a drug-sensitive EGFR L858R-mutant lung adenocarcinoma after long-term treatment with TKIs. The T854A mutation was not detected in a pretreatment tumor sample. Crystal structure analyses of EGFR suggest that the T854 side chain is within contact distance of gefitinib and erlotinib. Surrogate kinase assays demonstrate that the EGFR T854A mutation abrogates inhibition of tyrosine phosphorylation by erlotinib. Such resistance appears to be overcome by a new irreversible dual EGFR/HER2 inhibitor, BIBW 2992.
The T854A mutation is the second reported second-site acquired resistance mutation that is within contact distance of gefitinib and erlotinib. These data suggest that acquired resistance to ATP-mimetic EGFR kinase inhibitors may often be associated with amino acid substitutions that alter drug contact residues in the EGFR ATP-binding pocket.
PMCID: PMC2596620  PMID: 19010870
2.  Frequency and Distinctive Spectrum of KRAS Mutations in Never Smokers with Lung Adenocarcinoma 
KRAS mutations are found in ~ 25% of lung adenocarcinomas in Western countries and, as a group, have been strongly associated with cigarette smoking. These mutations are predictive of poor prognosis in resected disease as well as resistance to treatment with erlotinib or gefitinib.
Experimental Design:
We determined the frequency and type of KRAS codon 12 and 13 mutations and characterized their association with cigarette smoking history in patients with lung adenocarcinomas.
KRAS mutational analysis was performed on 482 lung adenocarcinomas, 81 (17%) of which were obtained from patients who had never smoked cigarettes. KRAS mutations were found in 15% (12/81; 95% CI 8%-24%) of tumors from never smokers. Similarly, 22% (69/316; 95% CI 17%-27%) of tumors from former smokers, and 25% (21/85; 95% CI 16%-35%) of tumors from current smokers had KRAS mutations. The frequency of KRAS mutation was not associated with age, gender, or smoking history. The number of pack years of cigarette smoking did not predict an increased likelihood of KRAS mutations. Never smokers were significantly more likely than former or current smokers to have a transition mutation (G→A) rather than the transversion mutations known to be smoking related (G→T or G→C; p<0.0001).
Based upon our data, KRAS mutations are not rare among never smokers with lung adenocarcinoma and such patients have a distinct KRAS mutation profile. The etiologic and biological heterogeneity of KRAS mutant lung adenocarcinomas is worthy of further study.
PMCID: PMC2754127  PMID: 18794081
3.  Novel MEK1 Mutation Identified by Mutational Analysis of Epidermal Growth Factor Receptor Signaling Pathway Genes in Lung Adenocarcinoma 
Cancer research  2008;68(14):5524-5528.
Genetic lesions affecting a number of kinases and other elements within the epidermal growth factor receptor (EGFR) signaling pathway have been implicated in the pathogenesis of human non–small-cell lung cancer (NSCLC). We performed mutational profiling of a large cohort of lung adenocarcinomas to uncover other potential somatic mutations in genes of this pathway that could contribute to lung tumorigenesis. We have identified in 2 of 207 primary lung tumors a somatic activating mutation in exon 2 of MEK1 (i.e., mitogen-activated protein kinase kinase 1 or MAP2K1) that substitutes asparagine for lysine at amino acid 57 (K57N) in the nonkinase portion of the kinase. Neither of these two tumors harbored known mutations in other genes encoding components of the EGFR signaling pathway (i.e., EGFR, HER2, KRAS, PIK3CA, and BRAF). Expression of mutant, but not wild-type, MEK1 leads to constitutive activity of extracellular signal–regulated kinase (ERK)-1/2 in human 293T cells and to growth factor–independent proliferation of murine Ba/F3 cells. A selective MEK inhibitor, AZD6244, inhibits mutant-induced ERK activity in 293T cells and growth of mutant-bearing Ba/F3 cells. We also screened 85 NSCLC cell lines for MEK1 exon 2 mutations; one line (NCI-H1437) harbors a Q56P substitution, a known transformation-competent allele of MEK1 originally identified in rat fibroblasts, and is sensitive to treatment with AZD6244. MEK1 mutants have not previously been reported in lung cancer and may provide a target for effective therapy in a small subset of patients with lung adenocarcinoma.
PMCID: PMC2586155  PMID: 18632602
4.  Mutational Analysis of EGFR and Related Signaling Pathway Genes in Lung Adenocarcinomas Identifies a Novel Somatic Kinase Domain Mutation in FGFR4 
PLoS ONE  2007;2(5):e426.
Fifty percent of lung adenocarcinomas harbor somatic mutations in six genes that encode proteins in the EGFR signaling pathway, i.e., EGFR, HER2/ERBB2, HER4/ERBB4, PIK3CA, BRAF, and KRAS. We performed mutational profiling of a large cohort of lung adenocarcinomas to uncover other potential somatic mutations in genes of this signaling pathway that could contribute to lung tumorigenesis.
Methodology/Principal Findings
We analyzed genomic DNA from a total of 261 resected, clinically annotated non-small cell lung cancer (NSCLC) specimens. The coding sequences of 39 genes were screened for somatic mutations via high-throughput dideoxynucleotide sequencing of PCR-amplified gene products. Mutations were considered to be somatic only if they were found in an independent tumor-derived PCR product but not in matched normal tissue. Sequencing of 9MB of tumor sequence identified 239 putative genetic variants. We further examined 22 variants found in RAS family genes and 135 variants localized to exons encoding the kinase domain of respective proteins. We identified a total of 37 non-synonymous somatic mutations; 36 were found collectively in EGFR, KRAS, BRAF, and PIK3CA. One somatic mutation was a previously unreported mutation in the kinase domain (exon 16) of FGFR4 (Glu681Lys), identified in 1 of 158 tumors. The FGFR4 mutation is analogous to a reported tumor-specific somatic mutation in ERBB2 and is located in the same exon as a previously reported kinase domain mutation in FGFR4 (Pro712Thr) in a lung adenocarcinoma cell line.
This study is one of the first comprehensive mutational analyses of major genes in a specific signaling pathway in a sizeable cohort of lung adenocarcinomas. Our results suggest the majority of gain-of-function mutations within kinase genes in the EGFR signaling pathway have already been identified. Our findings also implicate FGFR4 in the pathogenesis of a subset of lung adenocarcinomas.
PMCID: PMC1855985  PMID: 17487277

Results 1-4 (4)