title: Identification of phosphoproteins as possible differentiation markers in all-trans-retinoic acid-treated neuroblastoma cells.
abstract: BACKGROUND
  Neuroblastic tumors account for 9-10% of pediatric tumors and neuroblastoma (NB) is the first cause of death in pre-school age children. NB is classified in four stages, depending on the extent of spreading. A fifth type of NB, so-called stage 4S (S for special), includes patients with metastatic tumors but with an overall survival that approximates 75% at five years. In most of these cases, the tumor regresses spontaneously and regression is probably associated with delayed neuroblast cell differentiation.
  
  
  RESULTS
  In order to identify new early markers to follow and predict this process for diagnostic and therapeutics intents, we mimicked the differentiation process treating NB cell line SJ-NK-P with all-trans-retinoic acid (ATRA) at different times; therefore the cell proteomic pattern by mass spectrometry and the phosphoproteomic pattern by a 2-DE approach coupled with anti-phosphoserine and anti-phosphotyrosine western blotting were studied.
  
  
  CONCLUSIONS
  Proteomic analysis identified only two proteins whose expression was significantly different in treated cells versus control cells: nucleoside diphosphate kinase A (NDKA) and reticulocalbin-1 (RCN1), which were both downregulated after 9 days of ATRA treatment. However, phosphoproteomic analysis identified 8 proteins that were differentially serine-phosphorylated and 3 that were differentially tyrosine-phosphorylated after ATRA treatment. All proteins were significantly regulated (at least 0.5-fold down-regulated). Our results suggest that differentially phosphorylated proteins could be considered as more promising markers of differentiation for NB than differentially expressed proteins.
authors.affiliation: Dipartimento di Genetica, Biologia e Biochimica, Università di Torino, Torino, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Mandili
authors.forename: Cristina
authors.initials: C
authors.lastname: Marini
authors.forename: Franco
authors.initials: F
authors.lastname: Carta
authors.forename: Cristina
authors.initials: C
authors.lastname: Zanini
authors.forename: Mauro
authors.initials: M
authors.lastname: Prato
authors.forename: Amina
authors.initials: A
authors.lastname: Khadjavi
authors.forename: Franco
authors.initials: F
authors.lastname: Turrini
authors.forename: Giuliana
authors.initials: G
authors.lastname: Giribaldi
mesh_terms: D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D013058:Mass Spectrometry; D008858:Microscopy, Phase-Contrast; D054778:NM23 Nucleoside Diphosphate Kinases / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D002135:Calcium-Binding Proteins; D054778:NM23 Nucleoside Diphosphate Kinases; D010750:Phosphoproteins; C078865:reticulocalbin; D014212:Tretinoin