Heat-directed gene targeting of adenoviral vectors to tumor cells

Abstract

Targeting therapeutic gene expression to tumor cells represents a major challenge for cancer gene therapy. The strong transcriptional response exhibited by heat shock genes, along with the beneficial therapeutic effects of hyperthermia have led us to develop a heatdirected gene -targeting strategy for cancer treatment. Heat shock gene expression is mediated in large part by the interaction of heat shock factor 1 with specific binding sites ( heat shock elements; HSE ) found in the promoters of heat -inducible genes. Here we present a quantitative analysis of heat -inducible gene expression mediated by the wild -type hsp70b gene promoter, as well as a modified hsp70b promoter containing additional HSE sequences. -Galactosidase ( -gal ) expression was induced between 50 -and 800 -fold in a panel of human breast cancer cell lines infected with an adenoviral vector containing the wild -type hsp70b promoter ( Ad.70b. g ) following treatment at 438C for 30 minutes. Infection with an adenoviral vector containing the modified hsp70b promoter ( Ad.HSE.70b. g ) resulted in a 200 -to 950 -fold increase in -gal expression under the same conditions, and also provided a 1 ± 28C decrease in the threshold of activation. Significant increases in the heat responsiveness of the Ad.HSE.70b. g construct were observed in five of six tumor cell lines tested, as well as under thermotolerant conditions. Finally, we demonstrate that localized heating of a HeLa cell xenograft can effectively target -gal gene expression following intratumoral injection of Ad.70b. g. Adenoviral vectors incorporating heat -inducible therapeutic genes may provide useful adjuncts for clinical hyperthermia. Cancer Gene Therapy ( 2000 ) 7, 1566 ± 1574

Use of the human MDR1 promoter for heat‐inducible expression of therapeutic genes

“…15 Studies with the HSP promoter have shown in different studies that this promoter can permit induction rates of up to several hundred fold in response to hyperthermia in a range of 40 -45°C. 11,14 In contrast, our CAT-reporter assays revealed that the mdr1 promoter does not reach such heat-induction levels, indicating that further optimization of the promoter sequence maybe necessary to improve the heat-inducibility. In the light of the combined hyperthermia, chemotherapy and gene therapy, however, the observed increase of transgene expression might be 295 sufficient for improved tumor cell killing.…”

“…294 of these vector systems are based on the employment of the human heat shock protein 70 (HSP) promoter or of derivatives of this promoter to achieve heat-inducible gene expression at temperatures that are relevant for hyperthermic treatments of tumor patients. 11,13,14,29 In our study we were using a different human promoter, which is originally known to regulate the expression of the multidrug resistance gene mdr1. Because the mdr1 gene regulation responds to external stress stimuli such as UV irradiation, cytostatic drugs and also to hyperthermia, this promoter is an attractive candidate for the construction of hyperthermia-inducible vectors.…”

“…The wild type hsp70 promoter or modified variants of the promoter were shown to permit a heat-induction of transgene expression of up to 1,000-fold over background levels. 11,14 More importantly Huang et al 11 showed that hyperthermia-induced expression of IL-12 can lead to more efficient antitumor activity in a mouse melanoma model.…”

Heat-directed suicide gene therapy for breast cancer

“…We 6 and others [7][8][9][10][11][12] have been working to harness hyperthermia as a modality to target therapeutic gene expression to tumor cells. Studies to date have demonstrated that hyperthermia shows significant promise as a way to achieve treatment-targeted, spatiotemporal control of gene expression in vitro 6,[8][9][10][11][12][13] and in vivo.…”

“…Studies to date have demonstrated that hyperthermia shows significant promise as a way to achieve treatment-targeted, spatiotemporal control of gene expression in vitro 6,[8][9][10][11][12][13] and in vivo. 6,[8][9][10][11][12][13] LRBC is an excellent choice for the clinical application of heat-directed cancer gene therapy in that it is prevalent, responds to hyperthermia and is relatively uncomplicated in terms of treatment planning for heat dosimetry. It is also amenable to gene therapy because its superficial and localized nature renders it easily accessible for vector administration.…”