Potential of Varicella zoster virus thymidine kinase as a suicide gene in breast cancer cells.
To investigate the potential of the thymidine kinase gene from Varicella zoster virus (VZVtk) to act as a suicide gene, VZVtk was transferred via a dicistronic retroviral construct into MCF7, T-47D and MDA-MB-435 human breast cancer cells. The cytotoxicity of antiviral drugs was then evaluated in vitro on the wild-type and transduced cells. Acyclovir and ganciclovir did not show any selective toxicity for the modified cells. In contrast, (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) was extremely toxic for the VZVtk expressing cells, with IC50 values of 0.6 microM, 0.1 microM and 0.06 microM for MCF7, T-47D and MDA-MB-435 cells, respectively. The selectivity index of BVDU (ie the IC50 value ratio of the wild-type to the VZVtk cells) was 400 for MCF7, 750 for T-47D and 2000 for MDA-MB-435 cells. To test the system in vivo, VZVtk carrying MDA-MB-435 cells were inoculated subcutaneously into nude mice. An intraperitoneal treatment with BVDU administered at the emergence of the tumors, led to a prolonged arrest of the tumor growth and a reduced tumor mass. This effect was BVDU dose-dependent. No bystander effect of BVDU killing could be demonstrated in vitro on mixed populations of VZVtk positive and negative MDA-MB-435 cells. However, an important bystander effect was observed in identical experiments performed on 9L rat gliosarcoma cells infected with the VZVtk-carrying vector. These results demonstrate the efficiency of VZVtk as a suicide gene when BVDU is used as prodrug. The bystander effect measured in vitro, depends however on the tumoral cell type used.
Grignet-Debrus
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Laboratory of Fundamental Virology and Immunology, University of Liège, Sart-Tilman, Belgium.
Calberg-Bacq
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D016475:3T3 Cells; D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000628:therapy*; D001973:Bromodeoxyuridine / Q000031:analogs & derivatives / Q000627:therapeutic use; D003131:Combined Modality Therapy; D005260:Female; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D014645:Herpesvirus 3, Human / Q000201:enzymology*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D051381:Rats; D013937:Thymidine Kinase / Q000235:genetics*; D014407:Tumor Cells, Cultured
D000998:Antiviral Agents; C020235:brivudine; D013937:Thymidine Kinase; D001973:Bromodeoxyuridine