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Preclinical testing of recombinant adenoviral herpes simplex virus-thymidine kinase gene therapy for central nervous
A J Vincent1, M C Esandi, C J Avezaat
1Department of Neurosurgery, University Hospital Rotterdam, The Netherlands.
Objectives:
Adenoviral gene transfer and killing efficiency using the thymidine kinase (TK)/ganciclovir (GCV) mechanism was evaluated in human cancer cells occurring as central nervous system tumors. The effectiveness of this approach was tested in vitro and in experimental models for brain tumor and leptomeningeal metastases in rats in vivo. Recombinant adenoviruses with different promoters were compared.
Methods:
Adenoviral vectors harboring a marker (lacZ) or a TK gene were constructed. Transcription of genes was under the control of either the adenovirus Type 2 major late promoter (MLP) or the human cytomegalovirus (CMV) immediate early gene promoter. lacZ expression and GCV killing efficiency after TK gene transfer in several human tumor cells was evaluated in vitro. The 9L rat brain tumor and leptomeningeal metastases models were used to determine the effectiveness of adeno-TK and subsequent GCV treatment in vivo. MLP and CMV containing adenoviral vectors were compared.
Results:
Gene expression and the killing of tumor cells were very efficient in all human tumor cell lines tested. The adenovirus containing the CMV promoter showed cytopathic effects in cultured tumor cells at high multiplicity of infections but also greater cell killing efficiency after TK/GCV treatment, as compared to the MLP promoter. Although both the MLP and CMV vectors showed a significant dose-dependent therapeutic effect, animals treated with recombinant adenovirus containing the CMV promoter showed significantly longer survival time (brain tumors) or symptom-free periods (leptomeningeal metastases).
Conclusion:
This study demonstrates the therapeutic efficiency and feasibility of the TK/GCV approach in experimental brain tumors and leptomeningeal metastases. It also demonstrates that the promoter driving the transgene in an adenoviral vector influences toxicity and efficiency of treatment.
Insights
Adenoviral gene therapy using thymidine kinase (TK)/ganciclovir (GCV) effectively targets brain tumors and leptomeningeal metastases. The cytomegalovirus (CMV) promoter enhanced treatment efficiency and survival in experimental models.
Area of Science:
- Oncolytic virology
- Gene therapy
- Cancer research
Background:
- Central nervous system (CNS) tumors, including brain tumors and leptomeningeal metastases, present significant therapeutic challenges.
- The thymidine kinase (TK)/ganciclovir (GCV) system offers a potential suicide gene therapy approach for cancer treatment.
Purpose of the Study:
- To evaluate the efficiency of adenoviral gene transfer and TK/GCV-mediated killing in human CNS cancer cells.
- To compare the effectiveness of different adenoviral promoters (MLP and CMV) in vitro and in vivo for experimental brain tumor and leptomeningeal metastases models.
Main Methods:
- Construction of adenoviral vectors carrying a marker gene (lacZ) or the TK gene.
- Utilizing adenovirus Type 2 major late promoter (MLP) and human cytomegalovirus (CMV) immediate early gene promoter for gene transcription.
- In vitro assessment of gene expression and GCV killing efficiency in human tumor cell lines.
- In vivo evaluation using 9L rat brain tumor and leptomeningeal metastases models.
Main Results:
- Adenoviral TK gene transfer and GCV treatment demonstrated efficient tumor cell killing across tested human cell lines.
- The CMV promoter-driven adenoviral vector exhibited greater cell killing efficiency and cytopathic effects compared to the MLP promoter.
- Both MLP and CMV vectors showed dose-dependent therapeutic effects, with the CMV promoter leading to significantly longer survival and symptom-free periods in vivo.
Conclusions:
- The TK/GCV approach is a feasible and therapeutically efficient strategy for experimental brain tumors and leptomeningeal metastases.
- The choice of promoter significantly impacts the toxicity and therapeutic efficacy of adenoviral vectors in gene therapy for CNS cancers.