Use of Transcriptional Regulatory Sequences of Telomerase (hTER and hTERT) for Selective Killing of Cancer Cells

Abstract

Telomerase (hTER and hTERT) plays a crucial role in cellular immortalization and carcinogenesis. Telomerase activity can be detected in about 85% of different malignant tumors, but is absent in most normal cells. In situ hybridization analysis showed that high levels of hTER and hTERT expression are present in bladder cancer, while no signal was detected in normal tissue. Therefore, in this work we propose to use hTER and hTERT transcriptional regulatory sequences to control the expression of a cytotoxic gene in bladder tumor cells, resulting in the selective destruction of this cell population. Expression vectors containing the diphtheria toxin A-chain (DT-A) gene were linked to hTER and hTERT transcriptional regulatory sequences, respectively. Inhibition of protein synthesis occurred in bladder and hepatocellular carcinoma cells transfected with the plasmids containing the DT-A gene under the control of the hTER or hTERT promoters in correlation with their activity. These studies support the feasibility of using hTER and hTERT transcriptional regulatory sequences for targeted patient-oriented gene therapy of human cancer.

Telomerase-dependent oncolytic adenovirus for cancer treatment

“…To address the issue of replication specificity, replication efficiencies of AdvTERTp-E1A and wt adenovirus were compared in both TERT-positive and -negative cell lines. [26][27][28] For every cell line, the relation between multiplicity of infection (MOI) and percentage of target cell infection was firstly determined using an E1A-deleted adenovirus expressing b-galactosidase. In the subsequent experiments, the MOI that led to 10% infection of target cells was used in order to be able to observe virus replication in vitro.…”

Characterisation of systemic dissemination of nonreplicating adenoviral vectors from tumours in local gene delivery

“…To reduce transgene expression in normal tissues, unique promoters have been integrated into viral vectors. These promoters can be activated only by specific stimuli in tumours that are either endogenous or applied externally (Vaupel et al, 1989;Gossen and Bujard, 1992;Garver et al, 1994;Harris et al, 1994;Hallahan et al, 1995;Kumagai et al, 1996;Jaggar et al, 1997;Jenster et al, 1997;Blackburn et al, 1998;Chung et al, 1999;Abdul-Ghani et al, 2000;Huang et al, 2000;Koshikawa et al, 2000;Pollock et al, 2000;Spitz et al, 2000). However, the control of transgene expression will not reduce the acute toxicity in normal tissues caused by viral proteins.…”

Tumor-specific adenoviral gene therapy: transcriptional repression of gene expression by utilizing p53-signal transduction pathways

“…[1][2][3][4][5][6][7][8][9][41][42][43][44][45][46] In Figure 6 Influence of orientation and distance of the expression cassettes for p53-dependent transcriptional repression in a double transgene adenoviral shuttle plasmid. (d) The CMV gal-5 luciferase reporter cassette and the transcriptional repressor cassettes (GAL4-KRAB-A and GAL4-SIN3B-SF) under control of prMin-RGC were cloned into the adenoviral shuttle plasmid in different orientations as indicated.…”

“…Besides retargeting adenoviral vectors by genetical modifications of the fiber protein, many attempts have been made to target therapy to cancer cells by using tumor selective promoters such as AFP-, CEA-, PSA-or hTERT-promoter. [1][2][3][4][5][6][7][8][9][10] Using this approach, tumor specificity has been achieved at the cost of 50-300-fold loss in transcriptional activity compared to the strong but nonselective CMV-promoter. Other important limitations of gene therapy targeting by tumor-specific promoters are the heterogenous strength of these promoters in different tumor cells within a tumor nodule and the wide variety of promoter activities in different tumors.…”