title: Effects of epidermal growth factor receptor blockade on ependymoma stem cells in vitro and in orthotopic mouse models.
abstract: Some lines of evidence suggest that tumors, including ependymoma, might arise from a subpopulation of cells, termed cancer stem cells (CSCs), with self-renewal and tumor-initiation properties. Given the strict dependence of CSCs on epidermal growth factor (EGF) through EGF receptor (EGFR), we investigated the effects of EGFR inhibitors in ependymoma-stem cells (SCs) in vitro and in orthotopic mouse models. We established two ependymoma-SC lines from two recurrent pediatric ependymoma. Both lines expressed markers of radial glia--the candidate SCs of ependymoma--and showed renewal ability, multipotency, and tumorigenicity after orthotopic implantation, despite markedly different expression of CD133 (94 vs. 6%). High phosphorylated-EGFR/EGFR ratio was detected, which decreased after differentiation. EGFR inhibitors (gefitinib and AEE788) reduced clonogenicity, proliferation and survival of ependymoma-SC lines dose-dependently, and blocked EGF-induced activation of EGFR, Akt and extracellular signal-regulated kinase 1/2. Overall, AEE788 was more effective than gefitinib. EGFR blockade as well as differentiation strongly reduced CD133 expression. However, ex vivo treatment with AEE788 did not impair orthotopic tumor engraftment, whereas ex vivo differentiation did, suggesting that CD133 does not absolutely segregate for tumorigenicity in ependymoma-SCs. Orally administered AEE788 prolonged survival of mice bearing ependymoma-SC-driven orthotopic xenografts from 56 to 63 days, close to statistical significance (log-rank p=0.06). Our study describes for the first time EGFR signaling in ependymoma-SCs and the effects of EGFR blockade in complementary in vitro and in vivo systems. The experimental models we developed can be used to further investigate the activity of EGFR inhibitors or other antineoplastic agents in this tumor.
authors: Department of Pediatric Oncology, Catholic University, Rome, Italy. tservidei@rm.unicatt.it
authors: Tiziana
authors: T
authors: Servidei
authors: Daniela
authors: D
authors: Meco
authors: Nadia
authors: N
authors: Trivieri
authors: Valentina
authors: V
authors: Patriarca
authors: Valerio Gaetano
authors: VG
authors: Vellone
authors: Gian Franco
authors: GF
authors: Zannoni
authors: Giuseppe
authors: G
authors: Lamorte
authors: Roberto
authors: R
authors: Pallini
authors: Riccardo
authors: R
authors: Riccardi
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002648:Child; D004806:Ependymoma / Q000188:drug therapy*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D000077156:Gefitinib; D006801:Humans; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D051379:Mice; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D011687:Purines / Q000627:therapeutic use*; D011799:Quinazolines / Q000627:therapeutic use*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D011687:Purines; D011799:Quinazolines; D012333:RNA, Messenger; D066246:ErbB Receptors; C489254:AEE 788; D000077156:Gefitinib