title: The thymidine kinase/ganciclovir-mediated "suicide" effect is variable in different tumor cells.
abstract: The herpes simplex virus thymidine kinase (HSV-TK) converts ganciclovir (GCV) into a toxic product and allows selective elimination of TK+ cells in vitro and in vivo. It is currently being used in clinical gene therapy trials as a therapeutic gene or as a safety marker. We have analyzed the susceptibility of different tumor cell lines to the TK/GCV-mediated "suicide" effect. Therefore, tumor cells TSA, J558L, EB, and ESB and, as a control, NIH-3T3 cells were infected with a retrovirus containing a hygromycin/TK fusion gene. All cell lines were sensitive to GCV in vitro; however, the concentration of GCV and the time needed to eliminate tumor cells completely considerably varied between different tumor cell lines. TSA-TK cells were completely eliminated within 10 days in 1 microg/ml GCV, whereas ESB-TK cells required 22 days in 10 microg/ml GCV. When two cell lines were examined, the differing sensitivity to GCV in vitro correlated with the ability to eradicate TK+ tumors in vivo. TSA-TK tumors could be eliminated in almost all animals by systemic GCV administration, whereas ESB-TK tumors were completely resistant. Different sensitivity to GCV was not due to different TK expression levels because the cells were similarly resistant to hygromycin, and Western blot analysis with an anti-TK antiserum revealed similar protein amounts in TSA/TK and ESB-TK cells. Together, the results demonstrate that tumor cells are highly different concerning the susceptibility to the TK/GCV effect, which, however, may be tested for in vitro.
authors.affiliation: Robert-Rössle Klinik, Virchow Klinikum der Medizinichen Fakultät der Humboldt Universität Berlin, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Beck
authors.forename: S
authors.initials: S
authors.lastname: Cayeux
authors.forename: S D
authors.initials: SD
authors.lastname: Lupton
authors.forename: B
authors.initials: B
authors.lastname: Dörken
authors.forename: T
authors.initials: T
authors.lastname: Blankenstein
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000493:pharmacokinetics / Q000494:pharmacology*; D001711:Biotransformation; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D005260:Female; D015774:Ganciclovir / Q000493:pharmacokinetics / Q000494:pharmacology*; D015316:Genetic Therapy; D051379:Mice; D008807:Mice, Inbred BALB C; D008811:Mice, Inbred DBA; D018139:Simplexvirus / Q000201:enzymology*; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D000964:Antimetabolites, Antineoplastic; D013937:Thymidine Kinase; D015774:Ganciclovir