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S. Kim



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    MINI 09 - Drug Resistance (ID 107)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      MINI09.07 - Activation of the MET Kinase Confers Acquired Resistance to FGFR-Targeted Therapy in FGFR-Dependent Squamous Cell Carcinoma of the Lung (ID 1212)

      17:20 - 17:25  |  Author(s): S. Kim

      • Abstract
      • Presentation
      • Slides

      Background:
      Fibroblast growth factor receptor (FGFR) tyrosine kinase plays a crucial role in cancer cell growth, survival, and resistance to chemotherapy. FGFR1 amplification occurs at a frequency of 10-20% and is a novel druggable target in squamous cell carcinoma of the lung (SCCL). A number of FGFR-targeted agents are currently being developed in SCCL harboring FGFR alterations. The aim of the study is to evaluate the activity of selective FGFR inhibitors (AZD4547, BAY116387) and the mechanisms of intrinsic and acquired resistance to these agents in SCCL.

      Methods:
      The antitumor activity of AZD4547 and BAY116387 was screened in a panel of 12 SCCL cell lines, among which 4 cell lines harbored FGFR1 amplification. To investigate mechanisms of acquired resistance, FGFR1-amplified H1581 cells which were exquisitely sensitive to FGFR inhibitors, were exposed to AZD4547 or BAY116387 to generate polyclonal resistant clones (H1581-AR, H1581-BR). Characterization of these resistant clones was performed using receptor tyrosine kinase (RTK) array, immunoblotting and microarray. Migration and invasion assays were also performed.

      Results:
      Among 12 SCCL cell lines, two FGFR1-amplified cells, H1581 and DMS114, were sensitive to FGFR inhibitors (IC~50~<250 nmol/L). Compared with resistant cells, sensitive cells showed increased phosphorylation of FRS2 and PLC-γ, but decreased phosphorylation of STAT3. There was no noticeable difference in FGFR1-3 protein expression level between sensitive and resistant cells. Importantly, phosphorylation of ERK1/2 was significantly suppressed upon treatment of FGFR inhibitors only in sensitive cells, suggesting phospho-ERK1/2 as a pharmacodynamic marker of downstream FGFR signaling. RTK array and immunoblots demonstrated strong overexpression and activation of MET in H1581-AR and H1581-BR, in comparison to almost nil expression in parental cells. Four different SCCL cells with intrinsic resistance to FGFR inhibitors also showed intermediate to high MET expression, suggesting that MET may be involved in both intrinsic and acquired resistance to FGFR inhibitors. Gene-set enrichment analysis against KEGG database showed that cytokine-cytokine receptor interaction pathway was significantly enriched, with MET contributing significantly to the core enrichment, in H1581-AR and H1581-BR, as compared with parental cells. Stimulation with HGF strongly activated downstream FGFR signaling or enhanced cell survival in the presence of FGFR inhibitors in both acquired and intrinsic resistant cells. Quantitative PCR on genomic DNA and fluorescent in situ hybridization revealed MET amplification in H1581-AR, but not in H1581-BR. MET amplification led to acquired resistance to AZD4547 in H1581-AR by activating ERBB3. The combination of FGFR inhibitors with ALK/MET inhibitor, crizotinib, or small interfering RNA targeting MET synergistically inhibited cell proliferation in both H1581-AR and H1581-BR, whereas it resulted in additive effects in SCCL cells with intrinsic resistance to FGFR inhibitors. Acquisition of resistance to FGFR inhibitors not only led to a morphologic change, but also promoted migration and invasion of resistant clones via inducing epithelial to mesenchymal transition phenotype, as documented by a decrease in E-cadherin and an increase in N-cadherin and vimentin.

      Conclusion:
      MET activation is sufficient to bypass dependency on FGFR signaling and concurrent inhibition of these two pathways may be desirable when targeting FGFR-dependent SCCL.

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