[The mechanism of bystander effect in herpes simplex virus thymidine kinase/ganciclovir-mediated gene therapy].
OBJECTIVE
To study the mechanism of bystander effect in herpes simplex virus thymidine kinase (HSV-TK)/Ganciclovir (GCV)-mediated gene therapy.


METHODS
Recombinant retroviral vectors expressing HSV-TK and beta-Galactosidase (Lac Z) genes were constructed and transferred into pancreatic carcinoma cell line respectively. Cell counting was used to detect the growth inhibition rate of HSV-TK-transduced cells in presence of GCV. Taking Lac Z-transduced cells as bystander cells, the bystander effect was detected by MTT method, and its mechanism was studied by the experiments of supernatant shifting, Verapamil inhibition and ultrastructural observation.


RESULTS
The growth inhibition rate of the HSV-TK-transduced cells in the presence of GCV was 92.1%, which was obviously 4.9% and 3.2% higher than of the non-and control vector-transduced cells. Mixed cells containing only 10% of HSV-TK-transduced cells showed 39.0% reduction of the proliferation, which meant there was an obvious bystander effect in the system. However this effect disappeared when transferring GCV-containing supernatant of HSV-TK-transduced cells to the parent cells and could be reduced significantly when verapamil was added in the medium, indicating that this bystander effect requires cell-cell contact. Gap junctions were observed existing between PC-2 cells by electron microscopy.


CONCLUSIONS
The bystander effect in HSV-TK/GCV-mediated gene therapy occurs by transfer of GCV metabolite from cell to cell through gap junction.
Zhang
L
L
Department of Pathology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730.
Liu
T
T
Cui
Q
Q
Gao
J
J
D000998:Antiviral Agents / Q000494:pharmacology; D024201:Bystander Effect; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D018920:Coculture Techniques; D015774:Ganciclovir / Q000494:pharmacology; D005822:Genetic Vectors / Q000235:genetics; D018259:Herpesvirus 1, Human / Q000201:enzymology*; D006801:Humans; D007763:Lac Operon / Q000235:genetics; D012190:Retroviridae / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics*; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000473:pathology
D000998:Antiviral Agents; D013937:Thymidine Kinase; D015774:Ganciclovir