A method for controlling in vivo heat-inducible gene expression for provision of therapeutic polypeptide. The method includes the steps of: (a) providing a construct comprising a polynucleotide encoding a therapeutic polypeptide, wherein the polynucleotide is operatively linked to a heat-inducible promoter; (b) administering the construct to a warm-blooded vertebrate at a site at or near the tumor; and (c) applying heat to the site at or near the tumor to express the therapeutic polypeptide, whereby anti-tumor activity is observed.