Novel SEC61G - EGFR Fusion Gene in Pediatric Ependymomas Discovered by Clonal Expansion of Stem Cells in Absence of Exogenous Mitogens

• Published in: Cancer research (Chicago, Ill.) Ill.), 2017-11, Vol.77 (21), p.5860-5872
• Main Authors: Servidei, Tiziana, Meco, Daniela, Muto, Valentina, Bruselles, Alessandro, Ciolfi, Andrea, Trivieri, Nadia, Lucchini, Matteo, Morosetti, Roberta, Mirabella, Massimiliano, Martini, Maurizio, Caldarelli, Massimo, Lasorella, Anna, Tartaglia, Marco, Riccardi, Riccardo
• Format: Article
• Language: English
• Subjects: AKT protein; Amino Acid Sequence; Animals; Cancer; Cell culture; Cell Line, Tumor; Cell proliferation; Cell Proliferation - drug effects; Cell Proliferation - genetics; Central nervous system; Child; Children; Clone Cells; Ependymoma - genetics; Ependymoma - metabolism; Ependymoma - pathology; Epidermal growth factor receptors; Fibroblast growth factor 2; Fusion protein; Gene Expression Regulation, Neoplastic; Humans; Kaplan-Meier Estimate; Male; Mice, Nude; Mitogens; Mitogens - pharmacology; Mutants; Mutation; Nervous system; Polymerase chain reaction; Protein Kinase Inhibitors - pharmacology; Protein-tyrosine kinase; Receptor, Epidermal Growth Factor - antagonists & inhibitors; Receptor, Epidermal Growth Factor - genetics; Receptor, Epidermal Growth Factor - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Rodents; SEC Translocation Channels - genetics; SEC Translocation Channels - metabolism; Stat3 protein; Stem cell transplantation; Stem cells; Stem Cells - drug effects; Stem Cells - metabolism; Transplantation, Heterologous; Tumorigenicity; Tumors; Xenografts
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.CAN-17-0790

The basis for molecular and cellular heterogeneity in ependymomas of the central nervous system is not understood. This study suggests a basis for this phenomenon in the selection for mitogen-independent (MI) stem-like cells with impaired proliferation but increased intracranial tumorigenicity. MI ependymoma cell lines created by selection for EGF/FGF2-independent proliferation exhibited constitutive activation of EGFR, AKT, and STAT3 and sensitization to the antiproliferative effects of EGFR tyrosine kinase inhibitors (TKI). One highly tumorigenic MI line harbored membrane-bound, constitutively active, truncated EGFR. Two EGFR mutants (ΔN566 and ΔN599) were identified as products of intrachromosomal rearrangements fusing the 3' coding portion of the gene to the 5'-UTR of the , yielding products lacking the entire extracellular ligand-binding domain of the receptor while retaining the transmembrane and tyrosine kinase domains. EGFR TKI efficiently targeted ΔN566/ΔN599-mutant-mediated signaling and prolonged the survival of mice bearing intracranial xenografts of MI cells harboring these mutations. RT-PCR sequencing of 16 childhood ependymoma samples identified chimeric mRNAs in one infratentorial ependymoma WHO III, arguing that this fusion occurs in a small proportion of these tumors. Our findings demonstrate how culture selections applied to genetically heterogeneous tumors can help identify focal mutations that are potentially pharmaceutically actionable in rare cancers. .