Characterization of epidermal growth factor receptor (EGFR) P848L, an unusual EGFR variant present in lung cancer patients, in a murine Ba/F3 model

• Published in: FEBS open bio Vol. 9; no. 10; pp. 1689 - 1704
• Main Authors: Sarcar, Bhaswati, Gimbrone, Nicholas T., Wright, Gabriela, Remsing Rix, Lily L., Gordian, Edna R., Rix, Uwe, Chiappori, Alberto A., Reuther, Gary W., Santiago‐Cardona, Pedro G., Muñoz‐Antonia, Teresita, Cress, William Douglas
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.10.2019; John Wiley and Sons Inc; Wiley
• Subjects: Amino acids; Animals; Antibodies; Ba/F3 cells; Biotechnology; Bone cancer; Bone marrow; Bone tumors; Cell Proliferation - drug effects; Cell Survival - drug effects; Cells; Cells, Cultured; Clonal deletion; Cytokines; Disease Models, Animal; Drug resistance; EGFR mutation; Epidermal growth factor; Epidermal growth factor receptors; ErbB Receptors - genetics; ErbB Receptors - metabolism; exons; Extracellular signal-regulated kinase; Gene deletion; Genetic Variation - genetics; germ cells; HEK293 Cells; Humans; Insertion; Janus kinase; Janus kinase inhibitor; Kinases; Lung cancer; lung neoplasms; Lung Neoplasms - genetics; Lung Neoplasms - metabolism; Lymphocytes B; MAP kinase; Mice; Mice, Transgenic; Microscopy, Fluorescence; Mutation; non-specific protein-tyrosine kinase; Penicillin; Protein Kinase Inhibitors - pharmacology; Protein-tyrosine kinase; Proteins; proto-oncogenes; Pyrazoles - pharmacology; Pyrimidines - pharmacology; Tumors; Tyr 1045; tyrosine; tyrosine kinase inhibitor; Tyrosine kinase inhibitors; viability; Florida; United States > US; EGFR mutation; lung cancer; tyrosine kinase inhibitor; Tyr 1045; Ba/F3 cells; Janus kinase inhibitor
• ISSN: 2211-5463; 2211-5463
• DOI: 10.1002/2211-5463.12702

Lung cancer patients with mutations in epidermal growth factor receptor (EGFR) benefit from treatments targeting tyrosine kinase inhibitors (TKIs). However, both intrinsic and acquired resistance of tumors to TKIs are common, and EGFR variants have been identified that are resistant to multiple TKIs. In the present study, we characterized selected EGFR variants previously observed in lung cancer patients and expressed in a murine bone marrow pro‐B Ba/F3 cell model. Among these EGFR variants, we report that an exon 20 deletion/insertion mutation S768insVGH is resistant to erlotinib (a first‐generation TKI), but sensitive to osimertinib (a third‐generation TKI). We also characterized a rare exon 21 germline variant, EGFR P848L, which transformed Ba/F3 cells and conferred resistance to multiple EGFR‐targeting TKIs. Our analysis revealed that P848L (a) does not bind erlotinib; (b) is turned over less rapidly than L858R (a common tumor‐derived EGFR mutation); (c) is not autophosphorylated at Tyr 1045 [the major docking site for Cbl proto‐oncogene (c‐Cbl) binding]; and (d) does not bind c‐Cbl. Using viability assays including 300 clinically relevant targeted compounds, we observed that Ba/F3 cells transduced with EGFR P848L, S768insVGH, or L858R have very different drug‐sensitivity profiles. In particular, EGFR P848L, but not L858R or S768insVGH, was sensitive to multiple Janus kinase 1/2 inhibitors. In contrast, cells driven by L858R, but not by P848L, were sensitive to multikinase MAPK/extracellular‐signal‐regulated kinase (ERK) kinase and ERK inhibitors including EGFR‐specific TKIs. These observations suggest that continued investigation of rare TKI‐resistant EGFR variants is warranted to identify optimal treatments for cancer. We find that a rare germline epidermal growth factor receptor (EGFR) variant, P848L, signals Ba/F3 cells for growth independent of ligand in a manner that is resistant to erlotinib and gefitinib, but sensitive to osimertinib. Growth signaling in this system appears primarily dependent on the activation of Janus kinase/signal transduction and activator of transcription signaling, associated with the phosphorylation of EGFR Tyr 1173.