title: Cytosine deaminase versus thymidine kinase: a comparison of the antitumor activity.
abstract: The efficacy of single and combination suicide gene therapy was evaluated using a Herpes simplex virus thymidine kinase/ganciclovir system and Escherichia coli cytosine deaminase/5-fluorocytosine system on the rat prostate tumor cell line R3327 AT-1. The wild-type R3327 AT-1 cell line was transfected with a bifunctional fusion gene CDglyTK, which had the advantage that the resulting R3327 AT-1/CDglyTK cell line has the same amount of cytosine deaminase and thymidine kinase molecules. The percentage of viable R3327 AT-1/CDglyTK cells after 96 h incubation with 0.1 micro g/ml ganciclovir or 10 micro g/ml 5-fluorocytosine were 85% and 52% of controls, respectively. The cell viability when both suicide genes systems were activated was 43%. For in vivo analysis, Copenhagen rats were injected subcutaneously with R3327 AT-1 or R3327 AT-1/CDglyTK cells and treated with 30 mg/kg ganciclovir, 500 mg/kg 5-fluorocytosine, or both prodrugs together. A survival of 83% with the thymidine kinase/ganciclovir and 57% with the CD/5-FC could be observed. Only co-administration of thymidine kinase- and cytosine deaminase-specific prodrugs resulted in a 100% recurrence-free survival of the Copenhagen rats with a Dunning R3327 AT-1/CDglyTK prostate tumor and showed an additive cytotoxic effect. Calculation of the degree of activation and the potential of activation can be used to predict the success of a suicide gene therapy. In our case, the cytosine deaminase/5-fluorocytosine system had a low degree of activation (value 40), which is also found in the low response to 5- fluorocytosine in vivo (57% tumor free).
authors.affiliation: Klinische Kooperationseinheit Strahlentherapeutische Onkologie, Deutsches Krebsforschungszentrum, 101949-69009 Heidelberg, Germany. h.corban-wilhelm@dkfz.de
authors.forename: H
authors.initials: H
authors.lastname: Corban-Wilhelm
authors.forename: G
authors.initials: G
authors.lastname: Becker
authors.forename: U
authors.initials: U
authors.lastname: Bauder-Wüst
authors.forename: D
authors.initials: D
authors.lastname: Greulich
authors.forename: J
authors.initials: J
authors.lastname: Debus
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use*; D043525:Cytosine Deaminase / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005472:Fluorouracil / Q000627:therapeutic use; D015774:Ganciclovir / Q000627:therapeutic use*; D015316:Genetic Therapy / Q000379:methods; D018259:Herpesvirus 1, Human / Q000201:enzymology / Q000235:genetics*; D008297:Male; D011471:Prostatic Neoplasms / Q000235:genetics / Q000628:therapy*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013937:Thymidine Kinase / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000998:Antiviral Agents; D011993:Recombinant Fusion Proteins; D013937:Thymidine Kinase; D043525:Cytosine Deaminase; D015774:Ganciclovir; D005472:Fluorouracil