1. ¹University Children's Hospital of Essen, Germany
2. ²Institute of Cell Biology, University of Essen, Germany
3. ³Division of Intelligent Bioinformatic Systems, DKFZ Heidelberg, Germany
4. ⁴The Children's Hospital of Philadelphia, Philadelphia, PA, USA
5. ⁵University Children's Hospital of Göttingen, Germany

Correspondence: A Eggert, Division of Oncology, University Children's Hospital of Essen, Hufelandstr. 55, 45122 Essen, Germany. E-mail: angelika.eggert@uni-essen.de

⁶These authors contributed equally to this work

Received 3 March 2004; Revised 10 June 2004; Accepted 22 June 2004; Published online 8 November 2004.

Abstract

Expression of neurotrophin receptors of the tyrosine kinase receptor (Trk) family is an important prognostic factor in solid tumors including neuroblastoma. High expression of TrkA (NTRK1) is associated with a favorable biology and outcome of neuroblastoma, whereas TrkB (NTRK2) is expressed on aggressive neuroblastomas with unfavorable outcome. To gain new insights into the global gene expression program resulting in these divergent biological phenotypes, we stably expressed either TrkA or TrkB in the human SH-SY5Y neuroblastoma cell line. Gene expression profiles were obtained from parental cells and transfectants activated by their ligands in a time course over 24 h using oligonucleotide microarrays. Basal activation of Trk receptors in the absence of exogenous ligand was sufficient to induce broad and divergent genetic changes. Global gene regulation following external ligand stimulation was surprisingly similar in SY5Y-TrkA and SY5Y-TrkB cells except for the differential expression of distinct novel target genes. Consistent with their divergent biological phenotype, SY5Y-TrkA cells were characterized by upregulation of proapoptotic genes and angiogenesis inhibitors, whereas SY5Y-TrkB cells demonstrated upregulation of genes involved in invasion or therapy resistance. We suggest that the transcriptional program of neuroblastoma cells is modulated by Trk-receptor expression and basal activation rather than by ligand-induced activation. Fine-tuning of the malignant phenotype may be achieved by additional ligand stimulation with subsequent activation of a few specific genes.