Topoisomerase inhibitors enhance the cytocidal effect of AAV-HSVtk/ganciclovir on head and neck cancer cells.
Adeno-associated virus (AAV) is a non-pathogenic virus with a single-strand DNA genome. AAV vectors have several unique properties suited for gene therapy applications. However, an obstacle to their application is a low efficiency of transgene expression, mainly due to a limited second-strand synthesis. Previously, we reported that gamma-rays enhanced the transduction efficiency and cytocidal effect of AAV vector harboring the herpes simplex virus-thymidine kinase (AAVtk) and ganciclovir (GCV) system. In the present study, we investigated whether topoisomerase inhibitors (etoposide and camptothecin) enhance the AAV vector-mediated transgene expression and the killing effect by AAVtk/GCV system. The enhancement of transgene expression was observed in a concentration-dependent manner on human laryngeal carcinoma cells (HEp-2 cells) and HeLa cells. Southern analysis confirmed that etoposide enhanced the double-strand synthesis of the AAV vector genome in HEp-2 cells and HeLa cells. The cells were efficiently killed by AAVtk/GCV system, as expected. More importantly, both etoposide and camptothecin augmented the cytocidal effect of the AAVtk/GCV system. These findings suggest that the combination of AAV-mediated suicide gene therapy and treatment with topoisomerase inhibitors may have synergistic therapeutic effects in the treatment of cancers.
Division of Genetic Therapeutics, Center for Molecular Medicine, Jichi Medical School, 3311-1 Yakushiji Minamikawachi, Tochigi 329-0498, Japan.
Takeharu
T
Kanazawa
Hiroaki
H
Mizukami
Hiroshi
H
Nishino
Takashi
T
Okada
Yutaka
Y
Hanazono
Akihiro
A
Kume
Ken
K
Kitamura
Keiichi
K
Ichimura
Keiya
K
Ozawa
D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D002166:Camptothecin / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000229:Dependovirus / Q000187:drug effects / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D005047:Etoposide / Q000494:pharmacology; D015774:Ganciclovir / Q000627:therapeutic use*; D015870:Gene Expression; D041722:Genes, Transgenic, Suicide; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000628:therapy*; D006801:Humans; D013937:Thymidine Kinase / Q000235:genetics* / Q000378:metabolism; D059004:Topoisomerase I Inhibitors
D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D059004:Topoisomerase I Inhibitors; D005047:Etoposide; D013937:Thymidine Kinase; D015774:Ganciclovir; D002166:Camptothecin