title: PBX1 is a favorable prognostic biomarker as it modulates 13-cis retinoic acid-mediated differentiation in neuroblastoma.
abstract: OBJECTIVE
  Neuroblastoma is an embryonic childhood cancer with high mortality. 13-cis retinoic acid (13-cisRA) improves survival for some patients, but many recur, suggesting clinical resistance. The mechanism of resistance and the normal differentiation pathway are poorly understood. Three-amino-acid loop extension (TALE) family genes are master regulators of differentiation. Because retinoids promote differentiation in neuroblastoma, we evaluated TALE family gene expression in neuroblastoma.
  
  
  METHODS
  We evaluated expression of TALE family genes in RA-sensitive and -resistant neuroblastoma cell lines, with and without 13-cisRA treatment, identifying genes whose expression correlates with retinoid sensitivity. We evaluated the roles of one gene, PBX1, in neuroblastoma cell lines, including proliferation and differentiation. We evaluated PBX1 expression in primary human neuroblastoma samples by qRT-PCR, and three independent clinical cohort microarray datasets.
  
  
  RESULTS
  We confirmed that induction of PBX1 expression, and no other TALE family genes, was associated with 13-cisRA responsiveness in neuroblastoma cell lines. Exogenous PBX1 expression in neuroblastoma cell lines, mimicking induced PBX1 expression, significantly impaired proliferation and anchorage-independent growth, and promoted RA-dependent and -independent differentiation. Reduced PBX1 protein levels produced an aggressive growth phenotype and RA resistance. PBX1 expression correlated with histologic neuroblastoma subtypes, with highest expression in benign ganglioneuromas and lowest in high-risk neuroblastomas. High PBX1 expression is prognostic of survival, including in multivariate analysis, in the three clinical cohorts.
  
  
  CONCLUSIONS
  PBX1 is an essential regulator of differentiation in neuroblastoma and potentiates retinoid-induced differentiation. Neuroblastoma cells and tumors with low PBX1 expression have an immature phenotype with poorer prognosis, independent of other risk factors.
authors.affiliation: Center for Childhood Cancer and Blood Diseases, The Research Institute of Nationwide Children's Hospital and The Ohio State University College of Medicine, Columbus, Ohio; nshahnb@gmail.com.
authors.forename: Nilay
authors.initials: N
authors.lastname: Shah
authors.affiliation: Oncogenomics Section, Advanced Technology Center, Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, NIH, Gaithersburg, Maryland;
authors.forename: Jianjun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Center for Childhood Cancer and Blood Diseases, The Research Institute of Nationwide Children's Hospital and The Ohio State University College of Medicine, Columbus, Ohio;
authors.forename: Julia
authors.initials: J
authors.lastname: Selich-Anderson
authors.affiliation: Department of Oncology, Lombardi Comprehensive Cancer Center; and.
authors.forename: Garrett
authors.initials: G
authors.lastname: Graham
authors.affiliation: Center for Childhood Cancer and Blood Diseases, The Research Institute of Nationwide Children's Hospital and The Ohio State University College of Medicine, Columbus, Ohio;
authors.forename: Hasan
authors.initials: H
authors.lastname: Siddiqui
authors.affiliation: Department of Biostatistics, Bioinformatics and Biomathematics, Georgetown University, Washington, D.C.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: Oncogenomics Section, Advanced Technology Center, Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, NIH, Gaithersburg, Maryland;
authors.forename: Javed
authors.initials: J
authors.lastname: Khan
authors.affiliation: Department of Oncology, Lombardi Comprehensive Cancer Center; and.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Toretsky
mesh_terms: D000293:Adolescent; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects*; D015331:Cohort Studies; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003879:Dermatologic Agents / Q000494:pharmacology*; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005500:Follow-Up Studies; D006801:Humans; D015474:Isotretinoin / Q000494:pharmacology*; D008297:Male; D009367:Neoplasm Staging; D009447:Neuroblastoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011379:Prognosis; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015996:Survival Rate; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D003879:Dermatologic Agents; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; C083400:PBX1 protein, human; D015474:Isotretinoin