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A mechanism of resistance to gefitinib mediated by cellular reprogramming and the acquisition of an FGF2-FGFR1 autocrine growth loop

ABSTRACT: Despite initial and often dramatic responses of epidermal growth factor receptor (EGFR)-addicted lung tumors to the EGFR-specific tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib, nearly all develop resistance and relapse. To explore novel mechanisms mediating acquired resistance, we employed non-small-cell lung cancer (NSCLC) cell lines bearing activating mutations in EGFR and rendered them resistant to EGFR-specific TKIs through chronic adaptation in tissue culture. In addition to previously observed resistance mechanisms including EGFR-T790M 'gate-keeper' mutations and MET amplification, a subset of the seven chronically adapted NSCLC cell lines including HCC4006, HCC2279 and H1650 cells exhibited marked induction of fibroblast growth factor (FGF) 2 and FGF receptor 1 (FGFR1) mRNA and protein. Also, adaptation to EGFR-specific TKIs was accompanied by an epithelial to mesenchymal transition (EMT) as assessed by changes in CDH1, VIM, ZEB1 and ZEB2 expression and altered growth properties in Matrigel. In adapted cell lines exhibiting increased FGF2 and FGFR1 expression, measures of growth and signaling, but not EMT, were blocked by FGFR-specific TKIs, an FGF-ligand trap and FGFR1 silencing with RNAi. In parental HCC4006 cells, cell growth was strongly inhibited by gefitinib, although drug-resistant clones progress within 10 days. Combined treatment with gefitinib and AZD4547, an FGFR-specific TKI, prevented the outgrowth of drug-resistant clones. Thus, induction of FGF2 and FGFR1 following chronic adaptation to EGFR-specific TKIs provides a novel autocrine receptor tyrosine kinase-driven bypass pathway in a subset of lung cancer cell lines that are initially sensitive to EGFR-specific TKIs. The findings support FGFR-specific TKIs as potentially valuable additions to existing targeted therapeutic strategies with EGFR-specific TKIs to prevent or delay acquired resistance in EGFR-driven NSCLC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE79688 | GEO | 2016/03/29

SECONDARY ACCESSION(S): PRJNA316712

REPOSITORIES: GEO

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Project description:Despite initial and often dramatic responses of epidermal growth factor receptor (EGFR)-addicted lung tumors to the EGFR-specific tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib, nearly all develop resistance and relapse. To explore novel mechanisms mediating acquired resistance, we employed non-small-cell lung cancer (NSCLC) cell lines bearing activating mutations in EGFR and rendered them resistant to EGFR-specific TKIs through chronic adaptation in tissue culture. In addition to previously observed resistance mechanisms including EGFR-T790M 'gate-keeper' mutations and MET amplification, a subset of the seven chronically adapted NSCLC cell lines including HCC4006, HCC2279 and H1650 cells exhibited marked induction of fibroblast growth factor (FGF) 2 and FGF receptor 1 (FGFR1) mRNA and protein. Also, adaptation to EGFR-specific TKIs was accompanied by an epithelial to mesenchymal transition (EMT) as assessed by changes in CDH1, VIM, ZEB1 and ZEB2 expression and altered growth properties in Matrigel. In adapted cell lines exhibiting increased FGF2 and FGFR1 expression, measures of growth and signaling, but not EMT, were blocked by FGFR-specific TKIs, an FGF-ligand trap and FGFR1 silencing with RNAi. In parental HCC4006 cells, cell growth was strongly inhibited by gefitinib, although drug-resistant clones progress within 10 days. Combined treatment with gefitinib and AZD4547, an FGFR-specific TKI, prevented the outgrowth of drug-resistant clones. Thus, induction of FGF2 and FGFR1 following chronic adaptation to EGFR-specific TKIs provides a novel autocrine receptor tyrosine kinase-driven bypass pathway in a subset of lung cancer cell lines that are initially sensitive to EGFR-specific TKIs. The findings support FGFR-specific TKIs as potentially valuable additions to existing targeted therapeutic strategies with EGFR-specific TKIs to prevent or delay acquired resistance in EGFR-driven NSCLC. Examination of mRNA levels in DMSO and gefitinib-resistant cultures of HCC4006 and HCC827. Each group has two replicates.

Project description:Introduction: The clinical benefit of EGFR tyrosine kinase inhibitor (TKI) treatment in non-small cell lung cancer (NSCLC) patients with activating EGFR mutations is temporary, as virtually all patients develop acquired EGFR TKI resistance that occurs via diverse mechanisms. Here, we identified increased FGFR1 expression as such a resistance mechanism and using pathways analysis and drug combination testing we identified a novel combination treatment to control growth of these resistant tumors. Methods: Novel erlotinib-resistant NSCLC cell lines were generated and analyzed by mass spectrometry-based proteomics to identify altered pathways associated with erlotinib resistance. The altered pathways were further analyzed in gefitinib and osibenib resistant cell lines. Small molecule inhibitor combinations were used to block the altered pathways and investigate growth reduction in vitro and in two xenograft mouse models. FGFR1 mRNA levels were examined in pre- and (post?)- EGFR TKI treatment clinical tumor samples. Results: Proteomic analysis revealed increased expression of FGFR1 and AXL as well as increased Akt and ERK1/2 activation in a panel of novel erlotinib-resistant HCC827 cell lines. Combined treatment with erlotinib or osimertinib and a panel of small molecule inhibitors targeting AXL/MET, FGFRs, Akt, PI3K/mTOR, MEK or ERK1/2 showed that the most prominent re-sensitization to EGFR TKI occurred with the pan-FGFR inhibitor, PD173074. Interestingly, simultaneous blockade of components of the Akt pathway using specific Akt or dual PI3K-mTOR inhibitors combined with inhibitors targeting the FGFR family exhibited the most efficient growth inhibition of FGFR1 overexpressing EGFR TKI-resistant cell lines. Phosphorylation of proteins downstream of Akt, including PRAS40, FOXO and S6 ribosomal protein, were completely abrogated by PD173074 combined with the Akt inhibitor GSK2141795 . Combination treatment with PD173074 and an Akt inhibitor exhibited synergistic growth inhibition in vivo in two FGFR1 overexpressing NSCLC EGFR TKI-resistant animal models. Conclusion: The significant growth inhibition in vitro and in vivo observed with PD173074 combined with Akt compared to either drug alone imply that inhibition of several key targets may be beneficial in controlling erlotinib-resistant NSCLC. The complete abrogation of PRAS40, FOXO and S6 phosphorylations by PD173074 combined with an Akt inhibitor indicates that the Akt pathway is no longer active.

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A mechanism of resistance to gefitinib mediated by cellular reprogramming and the acquisition of an FGF2-FGFR1 autocrine growth loop

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