title: Gene therapy for cancer using tumour-specific prodrug activation.
abstract: Current treatments for metastatic malignant disease are often ineffective. One of the most promising of the selective genetic strategies against cancer is VDEPT (virally directed enzyme prodrug therapy). This uses a viral vector to carry a prodrug-activating enzyme gene into both tumour and normal cells. By linking the foreign gene downstream of tumour-specific transcription units, tumour-specific expression of the foreign enzyme gene can be achieved. We have developed a genetic therapy strategy using VDEPT against cancers that overexpress the oncogene ERBB2. This occurs in approximately one-third of breast and pancreatic tumours (and in a smaller proportion of other tumours) and involves transcriptional up-regulation of the ERBB2 gene with or without gene amplification. We have constructed a chimeric minigene consisting of the proximal ERBB2 promoter linked to the gene encoding cytosine deaminase, an enzyme that can deaminate the prodrug 5-fluorocytosine (5-FC) to form cytotoxic 5-fluorouracil (5-FU). We have constructed a double-copy recombinant retrovirus to deliver the enzyme gene under the control of the ERBB2 promoter into a panel of ERBB2 expression-positive (ERBB2+) and -negative (ERBB2-) pancreatic and breast cell lines. Cytosine deaminase activity was high in ERBB2+ transduced cells but was not detected in ERBB2- transduced cells. Significant cell death was observed in ERBB2+ transduced cells treated with 5-FC whereas ERBB2- cells were not affected. Hence we present a novel gene therapy strategy that is potentially tumour-specific and could be used against a range of tumour types that overexpress the ERBB2 oncogene.
authors.affiliation: Imperial Cancer Research Fund Oncology Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK.
authors.forename: J D
authors.initials: JD
authors.lastname: Harris
authors.forename: A A
authors.initials: AA
authors.lastname: Gutierrez
authors.forename: H C
authors.initials: HC
authors.lastname: Hurst
authors.forename: K
authors.initials: K
authors.lastname: Sikora
authors.forename: N R
authors.initials: NR
authors.lastname: Lemoine
mesh_terms: D001483:Base Sequence; D001711:Biotransformation; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000628:therapy; D043525:Cytosine Deaminase; D017931:DNA Primers / Q000235:genetics; D005260:Female; D005437:Flucytosine / Q000493:pharmacokinetics / Q000627:therapeutic use*; D005472:Fluorouracil / Q000493:pharmacokinetics / Q000627:therapeutic use; D018734:Genes, erbB-2; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000628:therapy*; D009700:Nucleoside Deaminases / Q000235:genetics; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000628:therapy; D010957:Plasmids / Q000235:genetics; D011355:Prodrugs / Q000493:pharmacokinetics / Q000627:therapeutic use*; D012190:Retroviridae / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D017931:DNA Primers; D011355:Prodrugs; D005437:Flucytosine; D009700:Nucleoside Deaminases; D043525:Cytosine Deaminase; D005472:Fluorouracil