title: Sensitivity to gemcitabine and its metabolizing enzymes in neuroblastoma.
abstract: OBJECTIVE
  We examined the activity of gemcitabine against neuroblastoma in vitro and in vivo. In addition, we investigated the cellular mechanisms of high sensitivity to the agent in neuroblastoma cells.
  
  
  METHODS
  We examined 11 neuroblastoma cell lines for sensitivity to gemcitabine and other chemotherapeutic agents used clinically for neuroblastoma. The in vivo sensitivity of neuroblastoma to gemcitabine was determined in xenograft models. Furthermore, the major metabolic enzymes of gemcitabine were assessed and compared in leukemia and carcinoma cells. Apoptosis and mitochondrial membrane potentials were also evaluated.
  
  
  RESULTS
  The IC50s for gemcitabine in 11 neuroblastoma lines ranged between 3 nmol/L and 4 micromol/L. The high activity of gemcitabine against neuroblastoma was confirmed in animal models. Interestingly, enzymes in neuroblastoma cells involved in the metabolism of deoxycytidine analogue have unique characteristics among solid tumors. The median of deoxycytidine kinase activity in neuroblastoma lines was similar to that in leukemia lines, which have low IC50s for cytarabine. Cytidine deaminase (CDA) activity in neuroblastoma was hardly detectable and significantly lower than that in carcinoma. The defect of CDA activity was associated with negative expression of mRNA. Furthermore, gemcitabine-induced apoptosis was observed irrespective of the caspase-8 status of neuroblastoma cells, which indicates that apoptosis depends on the mitochondrial pathway.
  
  
  CONCLUSIONS
  Neuroblastoma is highly sensitive to gemcitabine. Although the cellular mechanism involved in sensitivity to gemcitabine is multifactorial, low CDA activity may contribute high sensitivity in neuroblastoma cells. These results suggest that clinical application of gemcitabine to the treatment of neuroblastoma is warranted.
authors.affiliation: Department of Pediatrics, Mie University School of Medicine, Tsu, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ogawa
authors.forename: Hiroki
authors.initials: H
authors.lastname: Hori
authors.forename: Takuya
authors.initials: T
authors.lastname: Ohta
authors.forename: Kaori
authors.initials: K
authors.lastname: Onozato
authors.forename: Masazumi
authors.initials: M
authors.lastname: Miyahara
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Komada
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003564:Cytidine Deaminase / Q000235:genetics / Q000378:metabolism; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology* / Q000627:therapeutic use; D003842:Deoxycytidine Kinase / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009447:Neuroblastoma / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D012333:RNA, Messenger; D003841:Deoxycytidine; D003842:Deoxycytidine Kinase; D003564:Cytidine Deaminase; D000093542:Gemcitabine