Article

Lung cancers with acquired resistance to EGFR inhibitors occasionally harbor BRAF gene mutations but lack mutations in KRAS, NRAS, or MEK1

Division of Hematology-Oncology, Department of Medicine, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 07/2012; 109(31):E2127-33. DOI: 10.1073/pnas.1203530109
Source: PubMed

ABSTRACT

Acquired resistance to EGF receptor (EGFR) tyrosine kinase inhibitors (TKIs) is inevitable in metastatic EGFR-mutant lung cancers. Here, we modeled disease progression using EGFR-mutant human tumor cell lines. Although five of six models displayed alterations already found in humans, one harbored an unexpected secondary NRAS Q61K mutation; resistant cells were sensitive to concurrent EGFR and MEK inhibition but to neither alone. Prompted by this finding and because RAS/RAF/MEK mutations are known mediators of acquired resistance in other solid tumors (colon cancers, gastrointestinal stromal tumors, and melanomas) responsive to targeted therapies, we analyzed the frequency of secondary KRAS/NRAS/BRAF/MEK1 gene mutations in the largest collection to date of lung cancers with acquired resistance to EGFR TKIs. No recurrent NRAS, KRAS, or MEK1 mutations were found in 212, 195, or 146 patient samples, respectively, but 2 of 195 (1%) were found to have mutations in BRAF (G469A and V600E). Ectopic expression of mutant NRAS or BRAF in drug-sensitive EGFR-mutant cells conferred resistance to EGFR TKIs that was overcome by addition of a MEK inhibitor. Collectively, these positive and negative results provide deeper insight into mechanisms of acquired resistance to EGFR TKIs in lung cancer and inform ongoing clinical trials designed to overcome resistance. In the context of emerging knowledge about mechanisms of acquired resistance to targeted therapies in various cancers, our data highlight the notion that, even though solid tumors share common signaling cascades, mediators of acquired resistance must be elucidated for each disease separately in the context of treatment.

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Available from: Panos Fidias, Sep 25, 2014
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    • "While the role of MUT KRAS in primary resistance to EGFR-TKIs in molecularly unselected NSCLC is quite well established[29,30], its development and role in acquired resistance to EGFR-TKIs in MUT EGFR patients has not been explored in detail. In a previous work on a large collection of NSCLC tissues from patients with acquired EGFR-TKI resistance, MUT NRAS or MUT KRAS were not demonstrated[10]. However, comparison with the present results is not possible because detailed information were not provided neither on the timing of sampling with respect of development of TKI resistance nor on the type of tissue analysed. "
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    ABSTRACT: Introduction: KRAS oncogene mutations (MUTKRAS) drive resistance to EGFR inhibition by providing alternative signaling as demonstrated in colo-rectal cancer. In non-small cell lung cancer (NSCLC), the efficacy of treatment with EGFR tyrosine kinase inhibitors (EGFR-TKIs) depends on activating EGFR mutations (MUTEGFR). However, inhibition of EGFR may select resistant cells displaying alternative signaling, i.e., KRAS, or restoration of EGFR activity due to additional MUTEGFR, i.e., the c.2369C > T (p.T790MEGFR). Aim: The aim of this study was to investigate the appearance of MUTKRAS during EGFR-TKI treatment and their contribution to drug resistance. Methods: This study used cell-free circulating tumor DNA (cftDNA) to evaluate the appearance of codon 12 MUTKRAS and p.T790MEGFR mutations in 33 advanced NSCLC patients progressing after an EGFR-TKI. Results: p.T790MEGFR was detected in 11 (33.3%) patients, MUTKRAS at codon 12 in 3 (9.1%) while both p.T790MEGFR and MUTKRAS codon 12 were found in 13 (39.4%) patients. Six patients (18.2%) were KRAS wild-type (WTKRAS) and negative for p.T790MEGFR. In 8 subjects paired tumor re-biopsy/plasma samples were available; the percent concordance of tissue/plasma was 62.5% for p.T790MEGFR and 37.5% for MUTKRAS. The analysis of time to progression (TTP) and overall survival (OS) in WTKRAS vs. MUTKRAS were not statistically different, even if there was a better survival with WTKRAS vs. MUTKRAS, i.e., TTP 14.4 vs. 11.4 months (p = 0.97) and OS 40.2 vs. 35.0 months (p = 0.56), respectively. Conclusions: MUTKRAS could be an additional mechanism of escape from EGFR-TKI inhibition and cftDNA is a feasible approach to monitor the molecular development of drug resistance.
    Full-text · Article · Jan 2016 · Oncotarget
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    • "This incomplete therapy response results in residual disease that enables the emergence of acquired resistance in patients, often a lethal event. Although many mechanisms of either innate or acquired resistance have been deciphered (Bivona et al., 2011; Engelman et al., 2007; Ercan et al., 2012; Ng et al., 2012; Ohashi et al., 2012, 2013; Sequist et al., 2011; Takezawa et al., 2012; Turke et al., 2010; Yu et al., 2013; Zhang et al., 2012), the molecular basis of incomplete response and residual disease during initial EGFR TKI therapy is poorly understood. Filling this knowledge gap is essential to identify therapeutic strategies to combat tumor cell adaptation and survival during initial treatment and induce complete responses in patients. "

    Full-text · Dataset · Apr 2015
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    • "This incomplete therapy response results in residual disease that enables the emergence of acquired resistance in patients, often a lethal event. Although many mechanisms of either innate or acquired resistance have been deciphered (Bivona et al., 2011; Engelman et al., 2007; Ercan et al., 2012; Ng et al., 2012; Ohashi et al., 2012, 2013; Sequist et al., 2011; Takezawa et al., 2012; Turke et al., 2010; Yu et al., 2013; Zhang et al., 2012), the molecular basis of incomplete response and residual disease during initial EGFR TKI therapy is poorly understood. Filling this knowledge gap is essential to identify therapeutic strategies to combat tumor cell adaptation and survival during initial treatment and induce complete responses in patients. "
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    ABSTRACT: Although oncogene-targeted therapy often elicits profound initial tumor responses in patients, responses are generally incomplete because some tumor cells survive initial therapy as residual disease that enables eventual acquired resistance. The mechanisms underlying tumor cell adaptation and survival during initial therapy are incompletely understood. Here, through the study of EGFR mutant lung adenocarcinoma, we show that NF-κB signaling is rapidly engaged upon initial EGFR inhibitor treatment to promote tumor cell survival and residual disease. EGFR oncogene inhibition induced an EGFR-TRAF2-RIP1-IKK complex that stimulated an NF-κB-mediated transcriptional survival program. The direct NF-κB inhibitor PBS-1086 suppressed this adaptive survival program and increased the magnitude and duration of initial EGFR inhibitor response in multiple NSCLC models, including a patient-derived xenograft. These findings unveil NF-κB activation as a critical adaptive survival mechanism engaged by EGFR oncogene inhibition and provide rationale for EGFR and NF-κB co-inhibition to eliminate residual disease and enhance patient responses. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Full-text · Article · Apr 2015 · Cell Reports
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