title: Resistance to chemotherapy mediated by TrkB in neuroblastomas.
abstract: Neuroblastoma is a common childhood tumor derived from the peripheral nervous system. Favorable neuroblastomas usually express TrkA, the receptor for nerve growth factor (NGF), whereas unfavorable, MYCN-amplified neuroblastomas usually express TrkB and its ligand, brain-derived neurotrophic factor (BDNF). Here, we provide evidence that the TrkB-BDNF pathway is associated with enhanced survival and resistance to chemotherapy in neuroblastoma. We transfected the neuroblastoma line SH-SY5Y, which has endogenous expression of BDNF, with a full-length TrkB expression vector, and obtained clones with moderate or high levels of expression. Cells were exposed in vitro to chemotherapy agents used to treat neuroblastomas: doxorubicin, etoposide (VP16), and cisplatin. Chemoresistance was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cell survival and by ELISA for cell death. In all cases, the TrkB-expressing subclones were more resistant to treatment than the parent line. Furthermore, when the TrkB tyrosine kinase was blocked with the Trk-specific inhibitor CEP-2563, or by neutralizing antibody to BDNF, sensitivity to chemotherapy was significantly increased. We also found constitutive phosphorylation of AKT at the Ser-473 site in TrkB transfectants, whereas there was only a minimal level of constitutive phosphorylation of AKT in SY5Y cells. These results show that the TrkB-BDNF pathway provides a survival advantage when exposed to DNA-damaging reagents, and, therefore, this autocrine pathway may play an important role in mediating the drug-resistant phenotype associated with TrkB-expressing neuroblastomas. Activation of PI3K/AKT survival pathway may contribute to the increased drug resistance in TrkB-expressing neuroblastomas.
authors.affiliation: Division of Oncology, the Children's Hospital of Philadelphia and the University of Pennsylvania, Philadelphia, Pennsylvania 19104-4318, USA.
authors.forename: Ruth
authors.initials: R
authors.lastname: Ho
authors.forename: Angelika
authors.initials: A
authors.lastname: Eggert
authors.forename: Tomoro
authors.initials: T
authors.lastname: Hishiki
authors.forename: Jane E
authors.initials: JE
authors.lastname: Minturn
authors.forename: Naohiko
authors.initials: N
authors.lastname: Ikegaki
authors.forename: Patricia
authors.initials: P
authors.lastname: Foster
authors.forename: Anna Marie
authors.initials: AM
authors.lastname: Camoratto
authors.forename: Audrey E
authors.initials: AE
authors.lastname: Evans
authors.forename: Garrett M
authors.initials: GM
authors.lastname: Brodeur
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D019208:Brain-Derived Neurotrophic Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D002945:Cisplatin / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000502:physiology*; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D009447:Neuroblastoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D020813:Receptor, trkB / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000906:Antibodies; D019208:Brain-Derived Neurotrophic Factor; D004791:Enzyme Inhibitors; D005047:Etoposide; D004317:Doxorubicin; D011505:Protein-Tyrosine Kinases; D020813:Receptor, trkB; D002945:Cisplatin