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Suicide gene therapy for human uterine adenocarcinoma cells using herpes simplex virus thymidine kinase
I Kunishige1, Y Samejima, Y Shiki
1Department of Obstetrics and Gynecology, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka, 565, Japan.
Abstract:
In gene therapy, the herpes simplex virus thymidine kinase (HSV-tk) gene is widely used as a suicide agent. Tumor cells expressing HSV-tk are sensitive to nucleoside analogs such as ganciclovir (GCV). An advantage of this system is the bystander killing effect whereby HSV-tk-positive cells exposed to GCV are lethal to surrounding HSV-tk-negative cells. We transfected the HSV-tk gene into a human cervical adenocarcinoma cell line, BU25TK-, and a human endometrial adenocarcinoma cell line, HHUA, by the Lipofectine method. The sensitivity of HSV-tk-positive cells to GCV and bystander killing effect on HSV-tk-negative cells were examined in vitro. HSV-tk-positive cells were sensitive to GCV at concentrations of 1 to 100 microg/ml in a dose- and time-dependent manner. The growth of HSV-tk-negative cells was inhibited when the population of cultured cells contained more than about 3% HSV-tk-positive cells. Moreover, for BU25TK- cells, HSV-tk-positive cells were injected into SCID mice subcutaneously and the effects of GCV therapy and bystander killing at a daily concentration of 25 mg/kg for 14 days were examined. HSV-tk-positive tumors transduced into SCID mice almost disappeared upon GCV treatment. Furthermore, tumor reduction was observed when mixtures of HSV-tk-negative cells containing more than 20% HSV-tk-positive cells were injected into SCID mice. In conclusion, the HSV-tk/GCV system might be applied to both cervical and endometrial adenocarcinoma.
Insights
The herpes simplex virus thymidine kinase (HSV-tk) suicide gene therapy effectively kills tumor cells and surrounding cancer cells when treated with ganciclovir (GCV). This gene therapy shows promise for treating cervical and endometrial adenocarcinomas.
Area of Science:
- Gene Therapy
- Cancer Research
- Molecular Biology
Background:
- The herpes simplex virus thymidine kinase (HSV-tk) gene is a key suicide agent in gene therapy.
- Tumor cells expressing HSV-tk become sensitive to ganciclovir (GCV), a nucleoside analog.
- The bystander effect allows HSV-tk-positive cells to eliminate nearby HSV-tk-negative cells.
Purpose of the Study:
- To evaluate the efficacy of the HSV-tk/GCV system in human cervical and endometrial adenocarcinoma cell lines.
- To assess the in vitro sensitivity of HSV-tk-positive cells to GCV.
- To examine the bystander killing effect on HSV-tk-negative cells and in vivo tumor suppression.
Main Methods:
- Transfection of the HSV-tk gene into human cervical (BU25TK-) and endometrial (HHUA) adenocarcinoma cell lines using Lipofectine.
- In vitro assessment of GCV sensitivity and bystander effect.
- In vivo studies using SCID mice with subcutaneous tumors, evaluating GCV therapy and bystander killing.
Main Results:
- HSV-tk-positive cells demonstrated sensitivity to GCV (1-100 microg/ml) in a dose- and time-dependent manner.
- In vitro, bystander killing inhibited HSV-tk-negative cell growth when positive cells comprised over 3% of the population.
- In vivo, GCV treatment led to near-complete disappearance of HSV-tk-positive tumors in SCID mice, with significant reduction observed when positive cells were 20% of mixtures.
Conclusions:
- The HSV-tk/GCV system exhibits significant potential as a gene therapy for both cervical and endometrial adenocarcinomas.
- The study confirms the dose-dependent sensitivity to GCV and the potent bystander effect in vitro and in vivo.
- Successful tumor suppression in animal models suggests clinical applicability for these cancer types.