Acquired Resistance of Lung Adenocarcinomas to Gefitinib or Erlotinib Is Associated with a Second Mutation in the EGFR Kinase Domain

Abstract

BackgroundLung adenocarcinomas from patients who respond to the tyrosine kinase inhibitors gefitinib (Iressa) or erlotinib (Tarceva) usually harbor somatic gain-of-function mutations in exons encoding the kinase domain of the epidermal growth factor receptor (EGFR). Despite initial responses, patients eventually progress by unknown mechanisms of “acquired” resistance.Methods and FindingsWe show that in two of five patients with acquired resistance to gefitinib or erlotinib, progressing tumors contain, in addition to a primary drug-sensitive mutation in EGFR, a secondary mutation in exon 20, which leads to substitution of methionine for threonine at position 790 (T790M) in the kinase domain. Tumor cells from a sixth patient with a drug-sensitive EGFR mutation whose tumor progressed on adjuvant gefitinib after complete resection also contained the T790M mutation. This mutation was not detected in untreated tumor samples. Moreover, no tumors with acquired resistance had KRAS mutations, which have been associated with primary resistance to these drugs. Biochemical analyses of transfected cells and growth inhibition studies with lung cancer cell lines demonstrate that the T790M mutation confers resistance to EGFR mutants usually sensitive to either gefitinib or erlotinib. Interestingly, a mutation analogous to T790M has been observed in other kinases with acquired resistance to another kinase inhibitor, imatinib (Gleevec).ConclusionIn patients with tumors bearing gefitinib- or erlotinib-sensitive EGFR mutations, resistant subclones containing an additional EGFR mutation emerge in the presence of drug. This observation should help guide the search for more effective therapy against a specific subset of lung cancers.

Everolimus restores gefitinib sensitivity in resistant non-small cell lung cancer cell lines

“…The H1975 cell line carrying the L858R and T790M mutations was resistant to gefitinib [7]; the H1650 cell line, despite harboring a delE746_A750 activating mutation in the exon 19 of the EGFR gene, was resistant to gefitinib and erlotinib as previously reported [28][29][30]; K-RAS mutations were found in four of the tested resistant cell lines.…”

“…By contrast, acquired resistance to EGFR TKIs involves in same cases the recurrent T790M mutation, which affects the catalytic domain of the kinase weakening the interaction of the inhibitor with its target [7]. Tumor cells can develop other mechanisms of resistance to EGFR TKIs such as the activation of alternative tyrosine kinase receptors (IGF-1R), amplification of the MET gene and constitutive activation of signaling pathways downstream of EGFR (i.e.…”

Molecular pathology of lung cancer: key to personalized medicine

“…208 KRAS mutations are almost exclusively detected in codons 12 and 13 of exon 2, resulting in EGFR independent intracellular signal transduction activation. In the study of Eberhard et al, 11 EGFR exons 18 through 21 and KRAS exon 2 mutations were investigated via sequencing in tumors of 274 patients.…”

“…110 Substitution of this residue in EGFR with a bulky methionine may cause resistance by steric interference with binding of TKIs, including gefitinib and erlotinib. 182,208,243 This mutation confers a survival advantage to the tumor and is selected while the patient is receiving anti-EGFR TKI treatment. 82,179 This secondary mutation is quite prevalent, being found in up to 50% of EGFR-mutant tumors treated with first-generation EGFR TKIs.…”

“…82,179 This secondary mutation is quite prevalent, being found in up to 50% of EGFR-mutant tumors treated with first-generation EGFR TKIs. 182,208 Arcila et al 244 recently analyzed sensitizing EGFR mutations in 121 lung cancer patients, but only 104 (86%) cases were tested successfully. Most test failures were related to low-tumor content in the tested samples.…”