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Targeted gene therapy of ovarian cancer using an ovarian-specific promoter
Rudi Bao1, Muthu Selvakumaran, Thomas C Hamilton
1Ovarian Cancer Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Objectives:
The "suicide" gene therapy of cancer using promoters such as cytomegalovirus could cause severe toxicity to normal tissues due to a lack of specificity of prodrug activation. Therefore, we investigated gene therapy of ovarian cancer using ovarian-specific promoter (OSP1) to limit the synthesis of the prodrug activating enzyme HSVtk to ovarian cancer cells.
Methods:
The HSVtk expressing plasmid pOSP1-HSVtk was created and transfected into an ovarian cancer cell line OVCAR3. The ganciclovir (GCV) sensitivity of the stable transfectants was evaluated with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Tissue specificity of this promoter was evaluated by comparing the sensitivity to GCV between ovarian and nonovarian cancer cell lines after they were transfected with pOSP1-HSVtk. One transfectant sensitive to GCV was implanted intraperitoneally to immunocompromised mice which were treated subsequently with GCV. Furthermore, this ovarian cancer survival model was used to evaluate the in vivo efficacy of cationic lipid mediated pOSP1-HSVtk gene delivery followed by GCV treatment.
Results:
Stable transfectants of OVCAR3 cells bearing OSP1-HSVtk became more sensitive to GCV treatment compared to the parental cell line and vector transfected OVCAR3 cell line. OSP1-HSVtk could specifically sensitize the OVCAR3 ovarian cancer cell line to GCV. SCID mice transplanted with the OVCAR3 transfectant and treated with GCV survived longer than the mice without GCV treatment (P = 0.032). In vivo gene delivery mediated by a cationic lipid (GL67) followed by GCV treatment yielded a longer survival in the OVCAR3 survival model (P = 0.016).
Conclusions:
The OSP1 promoter can selectively direct suicide gene therapy of ovarian cancer and the in vivo efficacy is improved by using a cationic lipid GL67 as delivery vehicle as opposed to the direct injection of plasmid.
Insights
Ovarian cancer suicide gene therapy using the OSP1 promoter and ganciclovir (GCV) demonstrated improved specificity and efficacy. Cationic lipid GL67 enhanced in vivo gene delivery, leading to longer survival in ovarian cancer models.
Area of Science:
- Oncology
- Gene Therapy
- Molecular Biology
Background:
- Traditional "suicide" gene therapy for cancer faces toxicity issues due to non-specific prodrug activation.
- Cytomegalovirus promoters lack the specificity required for targeted cancer treatment.
Purpose of the Study:
- To investigate ovarian cancer gene therapy using an ovarian-specific promoter (OSP1) to restrict prodrug-activating enzyme synthesis to ovarian cancer cells.
- To evaluate the efficacy of OSP1-driven gene therapy in an ovarian cancer model.
Main Methods:
- Constructed and transfected the pOSP1-HSVtk plasmid into OVCAR3 ovarian cancer cells.
- Assessed ganciclovir (GCV) sensitivity of transfectants in vitro and in vivo.
- Evaluated tissue specificity of the OSP1 promoter by comparing GCV sensitivity across different cell lines.
- Utilized a cationic lipid (GL67) for in vivo gene delivery in an ovarian cancer mouse model.
Main Results:
- Stable OVCAR3 transfectants expressing OSP1-HSVtk showed increased sensitivity to GCV.
- The OSP1 promoter specifically sensitized ovarian cancer cells to GCV.
- Mice with ovarian tumors treated with GCV survived significantly longer (P = 0.032).
- In vivo gene delivery with cationic lipid GL67 and GCV treatment resulted in prolonged survival (P = 0.016).
Conclusions:
- The OSP1 promoter enables selective suicide gene therapy for ovarian cancer.
- Cationic lipid GL67 improves the in vivo efficacy of OSP1-mediated gene therapy compared to direct plasmid injection.