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Selective elimination of long INterspersed element-1 expressing tumour cells by targeted expression of the HSV-TK
Mariam Chendeb1, Robert Schneider1,2, Irwin Davidson1,3
1Department of Functional Genomics and Cancer, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Illkirch, Cédex, France.
Abstract:
In gene therapy, effective and selective suicide gene expression is crucial. We exploited the endogenous Long INterspersed Element-1 (L1) machinery often reactivated in human cancers to integrate the Herpes Simplex Virus Thymidine Kinase (HSV-TK) suicide gene selectively into the genome of cancer cells. We developed a plasmid-based system directing HSV-TK expression only when reverse transcribed and integrated in the host genome via the endogenous L1 ORF1/2 proteins and an Alu element. Delivery of these new constructs into cells followed by Ganciclovir (GCV) treatment selectively induced mortality of L1 ORF1/2 protein expressing cancer cells, but had no effect on primary cells that do not express L1 ORF1/2. This novel strategy for selective targeting of tumour cells provides high tolerability as the HSV-TK gene cannot be expressed without reverse transcription and integration, and high selectivity as these processes take place only in cancer cells expressing high levels of functional L1 ORF1/2.
Insights
This study introduces a novel gene therapy approach using the Long INterspersed Element-1 (L1) machinery to selectively deliver the Herpes Simplex Virus Thymidine Kinase (HSV-TK) suicide gene into cancer cells. Ganciclovir treatment then specifically eliminates cancer cells expressing L1 proteins, sparing healthy cells.
Area of Science:
- Gene Therapy
- Molecular Biology
- Oncology
Background:
- Effective and selective suicide gene expression is critical for successful gene therapy.
- Long INterspersed Element-1 (L1) retrotransposons are often reactivated in human cancers.
Purpose of the Study:
- To develop a novel gene therapy strategy for selective cancer cell targeting.
- To exploit the endogenous L1 machinery for targeted suicide gene delivery.
Main Methods:
- A plasmid-based system was engineered to direct Herpes Simplex Virus Thymidine Kinase (HSV-TK) expression.
- The system relies on reverse transcription and integration mediated by endogenous L1 ORF1/2 proteins and an Alu element.
- Cancer cells were treated with Ganciclovir (GCV) post-delivery of the constructs.
Main Results:
- Selective mortality of cancer cells expressing L1 ORF1/2 proteins was induced by Ganciclovir treatment.
- Primary cells lacking L1 ORF1/2 expression remained unaffected.
- The HSV-TK gene expression was contingent upon reverse transcription and integration via L1 machinery.
Conclusions:
- This novel strategy offers high tolerability and selectivity for targeting tumor cells.
- The reliance on cancer-specific L1 activity ensures minimal impact on healthy tissues.
- This approach represents a promising advancement in targeted cancer gene therapy.