Use of the ornithine decarboxylase promoter to achieve N-MYC-mediated overexpression of a rabbit carboxylesterase to sensitize neuroblastoma cells to CPT-11

Mol Ther. 2000 May;1(5 Pt 1):457-63. doi: 10.1006/mthe.2000.0064.


Overexpression of specific transcription factors by tumor cells can be exploited to regulate expression of proteins that induce apoptosis or activate prodrugs, thereby producing tumor-selective toxicity. A majority of advanced-stage neuroblastomas overexpress the transcription factor N-MYC, and this overexpression is associated with poor prognosis. This study describes regulation of expression by N-MYC, via the ornithine decarboxylase (ODC) promoter, of a rabbit liver carboxylesterase (CE) that activates the prodrug CPT-11. Chloramphenicol acetyltransferase reporter assays and CE activity assays in transiently transfected neuroblastoma cell lines (SJNB-1, SJNB-4, NB-1691) and rhabdomyosarcoma cell lines (JR1neo20, JR1Nmyc6, JR1Nmyc9) support this approach as a potential method for sensitizing tumor cells to CPT-11. Clonogenic assays with IMR32 human neuroblastoma cells which express N-MYC and that had been stably transfected with a plasmid containing an ODC promoter/CE cassette corroborated results of enzyme activity assays. Specifically, IMR32.ODC.CE cells expressed approximately eightfold more CE activity than IMR32.CMV.neo cells; and 5 microM CPT-11 reduced the clonogenic potential of IMR32.ODC.CE cells to zero, while 50 microM CPT-11 was required to produce the same effect with IMR32.CMV.neo cells. Current experiments focus on adenoviral delivery of an ODC promoter/CE cDNA cassette for potential virus-directed enzyme prodrug therapy applications.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blotting, Northern
  • Blotting, Southern
  • Blotting, Western
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacology*
  • Carboxylesterase
  • Carboxylic Ester Hydrolases / biosynthesis*
  • Chloramphenicol O-Acetyltransferase / biosynthesis
  • Dose-Response Relationship, Drug
  • Genetic Vectors
  • Humans
  • Irinotecan
  • Neuroblastoma / drug therapy*
  • Neuroblastoma / enzymology
  • Ornithine Decarboxylase / genetics*
  • Promoter Regions, Genetic / genetics*
  • Proto-Oncogene Proteins c-myc / metabolism*
  • Rabbits
  • Rhabdomyosarcoma / drug therapy
  • Rhabdomyosarcoma / enzymology
  • Transfection
  • Tumor Cells, Cultured


  • Proto-Oncogene Proteins c-myc
  • Irinotecan
  • Chloramphenicol O-Acetyltransferase
  • Carboxylic Ester Hydrolases
  • Carboxylesterase
  • Ornithine Decarboxylase
  • Camptothecin