Related Experiment Videos
Caspase-8 gene therapy using the human telomerase reverse transcriptase promoter for malignant glioma cells
Tadashi Komata1, Yasuko Kondo, Takao Kanzawa
1The Center for Surgery Research and Department of Neurosurgery, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
Abstract:
Telomerase is a distinctive candidate for targeted gene therapy of malignant gliomas, because the vast majority of malignant gliomas express telomerase activity while normal brain tissues do not. Recently, we developed a telomerase-specific expression system of caspase-8 gene using the promoter of the human telomerase reverse transcriptase (hTERT) gene. However, the transcriptional activity of hTERT-181 promoter (a 181-base pair [bp] region upstream of the transcription start site) was relatively lower in malignant glioma cells than in other tumors such as prostate cancer cells. To establish the hTERT/caspase-8 construct as a novel therapy for malignant gliomas, we need to increase the transcriptional activity of the hTERT promoter in malignant glioma cells. In the present study, we demonstrate that the transcriptional activity of hTERT-378 promoter (a 378-bp region) was 2- to 40-fold higher in hTERT-positive malignant glioma cells (A172, GB-1, T98G, U87-MG, U251-MG, and U373-MG) than that of hTERT-181. We further demonstrate that by using the hTERT-378/caspase-8 construct, apoptosis was restricted to malignant glioma cells, and was not seen in astrocytes or fibroblasts lacking hTERT. Moreover, the growth of subcutaneously established U373-MG tumors in mice was significantly inhibited by seven daily intratumoral injections of hTERT-378/caspase-8 construct and its inhibitory effect persisted during 3 additional weeks without additional treatment. These results suggest that the telomerase-specific expression of caspase-8 under hTERT-378 promoter is a novel targeting approach for the treatment of telomerase-positive malignant gliomas.
Insights
This study enhances gene therapy for malignant gliomas by using a stronger human telomerase reverse transcriptase (hTERT) promoter to drive caspase-8 expression, specifically targeting cancer cells and inhibiting tumor growth.
Area of Science:
- Oncology
- Gene Therapy
- Molecular Biology
Background:
- Malignant gliomas express telomerase, making it a target for gene therapy.
- Previous hTERT promoter constructs showed limited activity in glioma cells.
Purpose of the Study:
- To enhance the transcriptional activity of the hTERT promoter for improved glioma gene therapy.
- To develop a novel therapeutic strategy targeting telomerase-positive malignant gliomas.
Main Methods:
- Utilized a 378-bp region of the hTERT promoter (hTERT-378) to drive caspase-8 expression.
- Tested the hTERT-378/caspase-8 construct in various malignant glioma cell lines, astrocytes, and fibroblasts.
- Evaluated tumor growth inhibition in a mouse xenograft model.
Main Results:
- The hTERT-378 promoter exhibited 2- to 40-fold higher activity than hTERT-181 in glioma cells.
- Caspase-8-induced apoptosis was specific to hTERT-positive glioma cells, sparing normal cells.
- Intratumoral injection of the hTERT-378/caspase-8 construct significantly inhibited tumor growth in mice.
Conclusions:
- The hTERT-378 promoter significantly enhances telomerase-specific gene expression in malignant gliomas.
- This improved construct offers a promising targeted gene therapy approach for telomerase-positive malignant gliomas.