Enhanced tumor cell killing in the presence of ganciclovir by herpes simplex virus type 1 vector-directed coexpression of human tumor necrosis factor-alpha and herpes simplex virus thymidine kinase.
Past studies have documented the promise of herpes simplex virus type 1 (HSV-1) thymidine kinase (TK) suicide gene therapy as a potential antitumor treatment. HSV-TK converts the pro-drug ganciclovir (GCV) into a toxic nucleotide analogue, the incorporation of which into cellular DNA blocks cell proliferation. In this report, we have examined the hypothesis that the effectiveness of HSV-TK suicide gene therapy can be enhanced by coexpression of the antitumor cytokine human tumor necrosis factor-alpha (TNF-alpha) from the same replication-defective HSV-1 vector. In vitro testing demonstrated that TNF-alpha expression from this vector potentiated the killing of both TNF-alpha-sensitive L929 tumor cells and TNF-alpha-resistant U-87 MG cells in the presence of GCV. Furthermore, treatment of established intradermal L929 tumors in vivo with the TNF-alpha/TK vector and GCV resulted in prolonged animal survival compared with treatment with parental HSV-TK vector in the presence or absence of GCV. Treatment of intracerebral U-87 MG tumors showed a clear benefit of TK therapy, but a significant further increase in survival using the TNF-alpha vector could not be demonstrated. We found that potentiation of cell killing in vitro required intracellular TNF-alpha because purified protein added to the culture medium of cells infected with HSV-TK vector failed to have the same effect. Accordingly, potentiation in vivo should depend on efficient infection, but immunohistochemical analysis indicated that virus administration by U-87 MG intratumoral injection was inadequate, resulting in an estimated <1% infection of all tumor cells. Moreover, the majority of infected tumor cells were localized at the tumor margin. Together, these results suggest that TNF-enhanced tk gene therapy should provide a useful treatment for TNF-alpha-sensitive tumors and perhaps also for TNT-alpha-resistant tumors if vector delivery can be improved to increase the percentage of transduced tumor cells.
Moriuchi
S
S
Department of Molecular Genetics, University of Pittsburgh School of Medicine, Pennsylvania 15261, USA.
Oligino
T
T
Krisky
D
D
Marconi
P
P
Fink
D
D
Cohen
J
J
Glorioso
J C
JC
D000818:Animals; D002522:Chlorocebus aethiops; D019008:Drug Resistance, Neoplasm; D005069:Evaluation Studies as Topic; D015316:Genetic Therapy; D005822:Genetic Vectors; D005909:Glioblastoma / Q000628:therapy; D018259:Herpesvirus 1, Human / Q000201:enzymology / Q000235:genetics*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D013937:Thymidine Kinase / Q000235:genetics; D014161:Transduction, Genetic; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics* / Q000627:therapeutic use
D014409:Tumor Necrosis Factor-alpha; D013937:Thymidine Kinase