title: Insulin-like growth factor binding protein 5: contribution to growth and differentiation of neuroblastoma cells.
abstract: Neuroblastoma (NB) is a childhood tumor that depends on insulin-like growth factors (IGFs) for its growth and metastatic spread. Some metastatic NBs acquire independence from the paracrine support of IGF by activating autocrine production of IGF-2. Insulin-like growth factor binding protein-5 (IGFBP-5), a member of the IGF binding protein family, is able to optimize binding between IGF itself and its receptor. NB cell lines retain the ability to differentiate in vitro toward neuronal, schwann-like or melanocytic phenotypes upon treatment with retinoic acid (RA). Retinoids are currently used in NB therapy to achieve a mature postmitotic phenotype. Here, we present evidence that the expression of IGFBP-5 is a common feature of neuroblastoma cell lines and that IGFBP-5 acts in concert with IGF-2 in inducing cell proliferation. RA-induced differentiation causes a sharp increase of IGFBP-5. Functional assays carried out in differentiating conditions demonstrate that IGFBP-5 transcription is sensitive to RA treatment. We show that the effect of RA on the IGFBP-5 promoter is exerted, at least in part, through a proximal 5'-CACCC-3' tandem repeat (-147 bp to -137 bp from the transcription start site) that has previously been described as a cis-acting element involved in the progesterone-mediated response in osteoblasts. Given the relevance of IGF-2 in determining the proliferative and metastatic behavior of NB, the role of IGFBP-5 as a modulator of the IGF signal transduction pathway should be studied further for potential therapeutic applications.
authors.affiliation: ENEA Centro Ricerche Casaccia, 00060, Rome, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Cesi
authors.forename: Roberta
authors.initials: R
authors.lastname: Vitali
authors.forename: Barbara
authors.initials: B
authors.lastname: Tanno
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Giuffrida
authors.forename: Fabiola
authors.initials: F
authors.lastname: Sesti
authors.forename: Camillo
authors.initials: C
authors.lastname: Mancini
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Raschellà
mesh_terms: D015153:Blotting, Western; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D017931:DNA Primers / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D006801:Humans; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000235:genetics* / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008938:Mitosis; D008957:Models, Genetic; D009154:Mutation; D009447:Neuroblastoma / Q000378:metabolism*; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014162:Transfection; D014212:Tretinoin / Q000378:metabolism / Q000494:pharmacology
chemical_list: D017931:DNA Primers; D018975:Insulin-Like Growth Factor Binding Protein 5; D011994:Recombinant Proteins; D014212:Tretinoin; D007335:Insulin-Like Growth Factor II; D008156:Luciferases