title: Deoxyhypusine synthase (DHPS) inhibitor GC7 induces p21/Rb-mediated inhibition of tumor cell growth and DHPS expression correlates with poor prognosis in neuroblastoma patients.
abstract: OBJECTIVE
  Neuroblastoma (NB) is an aggressive pediatric malignancy that typically occurs in infants and children under the age of 5 years. High-stage tumors relapse frequently even after aggressive multimodal treatment, resulting in therapy resistance and eventually in patient death. Clearly, new biologically-targeted drugs are needed that more efficiently suppress tumor growth and prevent relapse. We and others previously showed that polyamines such as spermidine play an essential role in NB tumorigenesis and that DFMO, an inhibitor of the central polyamine synthesis gene ODC, is effective in vitro and in vivo, prompting its evaluation in NB clinical trials. However, the specific molecular actions of polyamines remain poorly defined. Spermidine and deoxyhypusine synthase (DHPS) are essential components in the hypusination-driven post-translational activation of eukaryotic initiation factor 5A (eIF5A).
  
  
  METHODS
  We assessed the role of DHPS in NB and the impact of its inhibition by N(1)-guanyl-1,7-diaminoheptane (GC7) on tumor cell growth using cell proliferation assays, Western blot, immunofluorescence microscopy, and Affymetrix micro-array mRNA expression analyses in NB tumor samples.
  
  
  RESULTS
  We found that GC7 inhibits NB cell proliferation in a dose-dependent manner, through induction of the cell cycle inhibitor p21 and reduction of total and phosphorylated Rb proteins. Strikingly, high DHPS mRNA expression correlated significantly with unfavorable clinical parameters, including poor patient survival, in a cohort of 88 NB tumors (all P < 0.04).
  
  
  CONCLUSIONS
  These results suggest that spermidine and DHPS are key contributing factors in NB tumor proliferation through regulation of the p21/Rb signaling axis.
authors.affiliation: Department of Pharmaceutical Sciences, The Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo, 34 Rainbow Drive, Hilo, HI, 96720, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bandino
authors.forename: Dirk
authors.initials: D
authors.lastname: Geerts
authors.forename: Jan
authors.initials: J
authors.lastname: Koster
authors.forename: André S
authors.initials: AS
authors.lastname: Bachmann
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D008856:Microscopy, Fluorescence; D009447:Neuroblastoma / Q000201:enzymology* / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011379:Prognosis; D016160:Retinoblastoma Protein / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; C100667:N(1)-guanyl-1,7-diaminoheptane; D016160:Retinoblastoma Protein; D006147:Guanine; D000587:Oxidoreductases Acting on CH-NH Group Donors; C063507:deoxyhypusine synthase