Kinase switching in mesenchymal-like non-small cell lung cancer lines contributes to EGFR inhibitor resistance through pathway redundancy

• Published in: Clinical & experimental metastasis 2008-12, Vol.25 (8), p.843-854
• Main Authors: Thomson, Stuart, Petti, Filippo, Sujka-Kwok, Izabela, Epstein, David, Haley, John D.
• Format: Article
• Language: English
• Subjects: Benzimidazoles - pharmacology; Biomedical and Life Sciences; Biomedicine; Cancer Research; Carcinoma, Non-Small-Cell Lung - drug therapy; Carcinoma, Non-Small-Cell Lung - metabolism; Carcinoma, Non-Small-Cell Lung - pathology; Cell Proliferation - drug effects; Chromatography, Liquid; Drug Resistance, Neoplasm; Erlotinib Hydrochloride; Hematology; Humans; Immunoblotting; Lung cancer; Lung Neoplasms - drug therapy; Lung Neoplasms - metabolism; Lung Neoplasms - pathology; Mesoderm - cytology; Mesoderm - metabolism; Mitogen-Activated Protein Kinase Kinases - genetics; Mitogen-Activated Protein Kinase Kinases - metabolism; Mitogen-Activated Protein Kinases - genetics; Mitogen-Activated Protein Kinases - metabolism; Oncology; Phosphorylation - drug effects; Protein Kinase Inhibitors - pharmacology; Protein-Tyrosine Kinases - genetics; Protein-Tyrosine Kinases - metabolism; Proto-Oncogene Proteins c-akt - genetics; Proto-Oncogene Proteins c-akt - metabolism; Pyrimidines - pharmacology; Quinazolines - pharmacology; Quinolines - pharmacology; Receptor, Epidermal Growth Factor - antagonists & inhibitors; Receptor, Epidermal Growth Factor - genetics; Receptor, Epidermal Growth Factor - metabolism; Receptor, ErbB-2 - genetics; Receptor, ErbB-2 - metabolism; Receptor, ErbB-3 - genetics; Receptor, ErbB-3 - metabolism; Receptors, Fibroblast Growth Factor - genetics; Receptors, Fibroblast Growth Factor - metabolism; Receptors, Platelet-Derived Growth Factor - genetics; Receptors, Platelet-Derived Growth Factor - metabolism; Research Paper; Respiratory Mucosa - cytology; Respiratory Mucosa - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; Signal Transduction - drug effects; Spectrometry, Mass, Electrospray Ionization; Surgical Oncology; Thiophenes - pharmacology; Transforming Growth Factor beta - metabolism; Tumor Cells, Cultured
• ISSN: 0262-0898; 1573-7276
• DOI: 10.1007/s10585-008-9200-4

NSCLC cells with a mesenchymal phenotype have shown a marked reduction in sensitivity to EGFR inhibitors, though the molecular rationale has remained obscure. Here we find that in mesenchymal-like tumor cells both tyrosine phosphorylation of EGFR, ErbB2, and ErbB3 signaling networks and expression of EGFR family ligands were decreased. While chronic activation of EGFR can promote an EMT-like transition, once having occurred EGFR family signaling was attenuated. We investigated the mechanisms by which mesenchymal-like cells bypass EGFR signaling and acquire alternative routes of proliferative and survival signaling. Mesenchymal-like NSCLC cells exhibit aberrant PDGFR and FGFR expression and autocrine signaling through these receptors can activate the MEK-ERK and PI3K pathways. Selective pharmacological inhibition of PDGFR or FGFR receptor tyrosine kinases reduced cell proliferation in mesenchymal-like but not epithelial NSCLC cell lines. A metastable, reversible EMT-like transition in the NSCLC line H358 was achieved by exogenous TGFβ, which served as a model EMT system. The H358/TGFβ cells showed many of the attributes of established mesenchymal-like NSCLC cells including a loss of cell-cell junctions, a loss of EGF-family ligand expression, a loss of ErbB3 expression, increased EGFR-independent Mek-Erk pathway activation and reduced sensitivity to EGFR inhibition. Notably an EMT-dependent acquisition of PDGFR, FGFR and TGFβ receptors in H358/TGFbeta cells was also observed. In H358/TGFbeta cells both PDGFR and FGFR showed functional ligand stimulation of their intrinsic tyrosine kinase activities. The findings of kinase switching and acquired PDGFR and FGFR signaling suggest investigation of new inhibitor combinations to target NSCLC metastases.