A novel treatment of human malignant gliomas in vitro and in vivo: FADD gene transfer under the control of the human telomerase reverse transcriptasegene promoter

Telomerase activity has a close relationship with malignancies in many cell types and it is tightly regulated at the transcriptional level of human te lomerase reverse transcriptase (hTERT). Utilizing the hTERT promoter, the a uthors developed a gene delivery system of Fas associated protein with deat h domain (FADD) (hTERT/FADD). FADD is a protein which plays an important ro le in the apoptotic pathway of Fas. Overexpression of FADD induces apoptosi s in the cells regardless of Fas expression on the cell surface. We hypothe sized that we might be able to restrict the expression of FADD in malignant glioma cells if we use the gene transfer system under the control of hTERT promoter. This study was designed to investigate whether the hTERT/FADD co nstruct induces apoptosis effectively in malignant glioma cells while keepi ng normal cells intact. First, using the reverse transcription-polymerase c hain reaction (RT-PCR) technique, we confirmed that hTERT mRNA was expresse d in human malignant glioma cells (U373-MG, A172 and GB-1), but not in cult ured astrocytes (TEN) or fibroblasts (MRC5). After transient transfection w ith the hTERT/FADD construct, a significant number of FADD-positive cells a nd apoptotic cells were detected in hTERT-positive malignant glioma cells. In contrast, hTERT-negative astrocytes and fibroblasts remained intact. Fur thermore, subcutaneously implanted U373-MG tumors treated with the hTERT/FA DD construct reduced in volume significantly C compared to the conrol treat ment (p=0.0001). Gene transfer of FADD under the control of the hTERT promo ter may be a novel and promising therapy to kill hTERT-positive malignant g lioma cells while sparing normal brain cells lacking hTERT.