Heat-directed gene targeting of adenoviral vectors to tumor cells

Targeting therapeutic gene expression to tumor cells represents a major cha llenge for cancer gene therapy. The strong transcriptional response exhibit ed by heat shock genes, along with the beneficial therapeutic effects of hy perthermia have led us to develop a heat-directed gene-targeting strategy f or cancer treatment. Heat shock gene Expression is mediated in large part b y the interaction of heat shock factor 1 with specific binding sites (heat shock elements; HSE) found in the promoters of heat-inducible genes. Here w e present a quantitative analysis of heat-inducible gene expression mediate d by the wild-type hsp70b, gene promoter, as well as a modified hsp70b prom oter containing additional HSE sequences. beta -Galactosidase (beta -gal) e xpression was induced between 50- and 800-fold in a panel of human breast c ancer cell lines infected with an adenoviral vector containing the wild-typ e hsp70b promoter (Ad.70b.betag) following treatment at 43 degreesC for 30 minutes. infection with an adenoviral vector containing the modified hsp70b promoter (Ad.HSE.70b.betag) resulted in a 200- to 950-fold increase in bet a -gal expression under the same conditions, and also provided a 1-2 degree sC decrease in the threshold of activation. Significant increases in the he at responsiveness of the Ad.HSE.70b.betag construct were observed in five o f six tumor cell lines tested, as well as under thermotolerant conditions. Finally, we demonstrate that localized hearing of a HeLa cell xenograft can effectively target beta -gal gene expression following intratumoral inject ion of Ad.70b.betag, Adenoviral vectors incorporating heat-inducible therap eutic genes may provide useful adjuncts for clinical hyperthermia.