Gene transfer into human prostate adenocarcinoma cells with an adenoviral vector: Hyperthermia enhances a double suicide gene expression, cytotoxicity and radiotoxicity

Abstract

We have previously developed a recombinant adenovirus containing a fusion gene of Escherichia coli cytosine deaminase ( CD ) and herpes simplex virus type 1 thymidine kinase ( HSV -1 TK ) controlled by a cytomegalovirus ( CMV ) enhancer -promoter. This replication -incompetent adenovirus effectively transduced the CD -TK gene into human prostate adenocarcinoma DU -145 or PC -3 cells. Interestingly, heat shock at 418C for 4 hours elevated the level of CD -TK by approximately 5 -to 20 -fold at a multiplicity of infection ( MOI ) of 1. Heat -enhanced expression of CD -TK promoted cytotoxicity by 23 -, 9 -, or 47 -fold in the presence of 50 g / mL ganciclovir ( GCV ), 500 g / mL 5 -fluorocytosine ( 5 -FC ), or 50 g / mL GCV + 500 g / mL 5 -FC, respectively, at an MOI of 1. Moreover, there was an increase in radiosensitivity when adenovirus -infected cells were heated at 418C for 4 hours followed by irradiation in the presence of the prodrugs. Virus + heat + 1 g / mL GCV treatment increased radiosensitivity by a dose -modifying factor ( DMF ) of 2.2, whereas virus + heat + 10 g / mL 5 -FC exposure resulted in a DMF of 2.3. Radiosensitization was clearly enhanced as a result of combined prodrug exposure ( DMF = 4.4 ). Our results suggest that the efficiency in expression of suicide genes from an adenoviral vector used for cytotoxic anticancer therapy could be improved by combining heat treatment with radiation therapy.

Activation of the CMV-IE Promoter by Hyperthermia In Vitro and In Vivo: Biphasic Heat Induction of Cytosine Deaminase Suicide Gene Expression

“…This binding results in fast and efficient up-regulation of the respective gene expression, as is known for the heat induction of the human HSP70 promoter [27,28]. By contrast, the CMV-IE promoter of the human CMV does not harbor HSEs and is, therefore, unable to bind HSF-1 [9]. In result of this, the observed heat response of the CMV-IE promoter seems to recruit other pathways and transcription factors.…”

“…In another study, the CMV-IE promoter was used for heat-responsive expression of the HSV-tk/CD suicide fusion gene. Hyperthermia of 41°C applied to adenovirally transduced human prostate adenocarcinoma cell lines led to an up to 20-fold increase in CMV-IE promoter driven gene expression in vitro [9]. These studies support the heat responsiveness of the CMV-IE promoter; however they do not provide insights into possible mechanisms of this effect.…”

“…Some earlier reports describe heat induction of the CMV-IE promoter [7][8][9]. This resulted in the purposive use of the CMV-IE promoter for the expression of heat shock protein 28 (HSP28) cDNA [8].…”

PET imaging of heat-inducible suicide gene expression in mice bearing head and neck squamous cell carcinoma xenografts

“…Borrelli et al 11 investigated the time course of EGFP expression after infection of human prostate cancer cells with an adenovirus and heating at 41 °C. Lee et al 27,28 showed that the use of a selectively replicating adenovirus resulted in higher expression of the CD/TK fusion protein after heating at 41 °C compared to a nonreplicating adenovirus. These studies show that heat-specific expression of a target protein can be achieved in vitro using the HS promoter in the context of adenoviral vectors.…”

Suppression of murine melanoma growth by a vaccine of attenuated Salmonella carrying heat shock protein 70 and Herpes simplex virus-thymidine kinase genes

“…Thermal effects, heat shock protein (HSP) promoter and HSP can all boost the efficacy of suicide genes (3)(4)(5)(6)(7). With strong antigenicity, Mycobacterium tuberculosis heat shock protein 70 (mtHSP70) has become an important immunological adjuvant.…”