[Herpes simplex virus type 1 thymidine kinase/ganciclovir (HSV(1)-TK/GCV) system as an effective "in vivo death switch" of live tumor vaccines].
OBJECTIVE
Live tumor vaccines could achieve better immunotherapeutic effects than irradiated tumor vaccines; however, the tumorigenicity is the crucial drawback incurred by the current procedures for vaccine preparation. This study was to explore the application of herpes simplex virus type 1 thymidine kinase/ganciclovir (HSV1-TK/GCV) system as "in vivo death switch" to control the survival status of cancer vaccines under certain circumstances.


METHODS
Suicide gene HSV(1)-TK was transferred into ovarian cancer cell line NuTu-19 with a retrovirus vector, followed by G418 selection to obtain HSV(1)-TK-transfected NuTu-19 cells (NuTu-19/TK). Dendritic cells (DCs) derived from Fischer344 rat bone marrow were fused with NuTu-19/TK cells to construct live tumor vaccine FC/TK. The expression of HSV(1)-TK in FC/TK cells was determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The cytotoxic efficacy of GCV on FC/TK cells was evaluated by XTT assay. The apoptosis of FC/TK cells was analyzed by flow cytometry and Hoechst33258 staining after GCV treatment. Rats were vaccinated with FC/TK cells and divided into 2 groups: GCV group (5 rats) were intraperitoneally treated with GCV for 7 days, control group (5 rats) were treated with normal saline. The tumorigenesis and tumor metastasis in the rats were observed 90 days after inoculation.


RESULTS
HSV1-TK was specifically expressed in FC/TK cells. GCV showed in vitro cytotoxicity to FC/TK cells in a dose-dependent manner, and 86.25% of the FC/TK cells were killed by GCV at a concentration of 100 microg/ml; the apoptosis rate of FC/TK cells was over 80%, and apoptotic morphology, including cell shrinkage, chromatin condensation, was observed. In the rat models, the tumor was developed at the injection site in 3 rats of control group, while no tumor was observed in the rats of GCV group.


CONCLUSIONS
HSV(1)-TK/GCV could act as the "death switch" of tumor vaccines by triggering apoptosis of tumor vaccines both in vitro and in vivo.
Kang
Yu
Y
Department of Obstetrics and Gynecology, Obstetrics and Gynecology Hospital, Fudan University, Shanghai 200011, P. R. China.
Xu
Cong-Jian
CJ
Liu
Xi-Shi
XS
Wu
Chao-Qun
CQ
Zhong
Cui-Ping
CP
Gu
Jian-Ren
JR
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D019496:Cancer Vaccines; D002459:Cell Fusion; D003713:Dendritic Cells / Q000166:cytology / Q000201:enzymology; D005260:Female; D015774:Ganciclovir / Q000494:pharmacology*; D041722:Genes, Transgenic, Suicide; D005822:Genetic Vectors; D018259:Herpesvirus 1, Human / Q000201:enzymology* / Q000235:genetics; D016233:Immunotherapy, Active; D010051:Ovarian Neoplasms / Q000201:enzymology / Q000473:pathology*; D051381:Rats; D011916:Rats, Inbred F344; D012190:Retroviridae / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D019496:Cancer Vaccines; D013937:Thymidine Kinase; D015774:Ganciclovir