title: Glioma cells transduced with an Escherichia coli CD/HSV-1 TK fusion gene exhibit enhanced metabolic suicide and radiosensitivity.
abstract: To ascertain whether concomitant expression of Escherichia coli deaminase (CD) and herpes simplex virus type-1 thymidine kinase (HSV-1 TK) could mediate greater levels of cytotoxicity beyond that observed with either suicide gene alone, 9L gliosarcoma cells were transduced with a retrovirus encoding a CD/HSV-1 TK fusion gene. The resultant CD/HSV-1 TK fusion protein (CDglyTK) was found to be bifunctional via CD and HSV-1 TK enzymatic assays, and conferred upon cells prodrug sensitivities equivalent to or better than that observed for each enzyme independently (ganciclovir [GCV] and bromovinyldeoxyuridine [BVdU] for HSV-1 TK and 5-fluorocytosine [5-FC] for CD). Simultaneous treatment of CDglyTK-expressing cells with prodrugs specific for HSV-1 TK and CD (GCV/5-FC or BVdU/5-FC) resulted in slight synergistic toxicity, two- to three-fold greater than that expected if the cytotoxic effects of each prodrug were purely additive. More importantly, co-treatment with HSV-1 TK- and CD-specific prodrugs was found to increase greatly the radiosensitivity of CDglyTK-expressing cells. Sensitivity enhancement ratios of 2.44 (GCV/5-FC) and 3.90 (BVdU/5-FC) were achieved. The results suggest that double suicide gene therapy, using a bifunctional CD/HSV-1 TK fusion gene, coupled with radiotherapy may provide a highly efficient means of selectively treating cancer.
authors.affiliation: Henry Ford Health System, Department of Radiation Oncology, Detroit, MI 48202-4689, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Rogulski
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: S O
authors.initials: SO
authors.lastname: Freytag
mesh_terms: D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000031:analogs & derivatives / Q000494:pharmacology / Q000633:toxicity; D003596:Cytosine / Q000378:metabolism; D043525:Cytosine Deaminase; D003857:Deoxyuridine / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000633:toxicity; D004926:Escherichia coli / Q000201:enzymology; D005437:Flucytosine / Q000494:pharmacology / Q000633:toxicity; D015774:Ganciclovir / Q000494:pharmacology / Q000633:toxicity; D015967:Gene Expression Regulation, Viral / Q000235:genetics*; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics; D018316:Gliosarcoma / Q000378:metabolism*; D006801:Humans; D009700:Nucleoside Deaminases / Q000235:genetics / Q000378:metabolism; D011355:Prodrugs / Q000494:pharmacology / Q000633:toxicity; D011836:Radiation Tolerance / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D018139:Simplexvirus / Q000201:enzymology; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D004791:Enzyme Inhibitors; D011355:Prodrugs; D011993:Recombinant Fusion Proteins; C020235:brivudine; D003596:Cytosine; D005437:Flucytosine; D013937:Thymidine Kinase; D009700:Nucleoside Deaminases; D043525:Cytosine Deaminase; D001973:Bromodeoxyuridine; D015774:Ganciclovir; D003857:Deoxyuridine