title: Combined RAR alpha- and RXR-specific ligands overcome N-myc-associated retinoid resistance in neuroblastoma cells.
abstract: Retinoids induce human neuroblastoma cells to undergo growth inhibition and neuritic differentiation in vitro, through interactions with nuclear retinoid receptor proteins. In this study, we found that three different neuroblastoma cell lines exhibited wide variation in their responsiveness to the growth inhibitory effects of the retinoic acid receptor (RAR) agonist, all-trans-retinoic acid (aRA). Resistance to the growth inhibitory effect of aRA correlated with the presence of N-myc gene amplification and not aRA-induced RAR beta levels. Over-expression of N-myc in a neuroblastoma cell line with no endogenous N-myc expression caused a marked reduction in retinoid-induced growth inhibition. Combination of receptor-specific retinoid agonists for RXR and RAR alpha significantly enhanced the sensitivity of N-myc-amplified neuroblastoma cells to the growth inhibitory effects of aRA. Our results indicate that combination receptor-specific retinoid therapy can overcome N-myc-mediated retinoid resistance and may be a more effective chemo-preventive strategy in the disease.
authors.affiliation: Children's Cancer Institute Australia for Medical Research, P.O. Box 81, Randwick, NSW 2031, Australia.
authors.forename: Tue
authors.initials: T
authors.lastname: Nguyen
authors.forename: Jayne E
authors.initials: JE
authors.lastname: Hocker
authors.forename: Wayne
authors.initials: W
authors.lastname: Thomas
authors.forename: Stewart A
authors.initials: SA
authors.lastname: Smith
authors.forename: Murray D
authors.initials: MD
authors.lastname: Norris
authors.forename: Michelle
authors.initials: M
authors.lastname: Haber
authors.forename: Belamy
authors.initials: B
authors.lastname: Cheung
authors.forename: Glenn M
authors.initials: GM
authors.lastname: Marshall
mesh_terms: D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D019281:Dimerization; D006801:Humans; D008024:Ligands; D009447:Neuroblastoma / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014212:Tretinoin / Q000378:metabolism* / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D008024:Ligands; D016271:Proto-Oncogene Proteins c-myc; C000607071:RARA protein, human; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D014157:Transcription Factors; C082925:retinoic acid receptor beta; D014212:Tretinoin; D012313:RNA