Control of transgene expression using local hyperthermia in combination with a heat-sensitive promoter

Background Local production of therapeutic proteins, e.g. for cancer treatm ents, is based on gene therapy approaches and requires tight spatial and te mporal control of gene expression. Here we demonstrate the use of local hyp erthermia of varying intensity and duration to control the expression of a transgene under control of the thermoinducible hsp70 (heat shock protein) p romoter. Methods Heat-induced expression of the EGFP (green fluorescent protein) rep orter gene was characterized using a stably transfected glioma C6 cell line expressing the EGFP gene under control of the heat inducible minimal hsp70 promoter both in vitro and in vivo for subcutaneous tumors in immunodefici ent mice. Results A heat shock of 20-30 min at 43 degrees C in cell culture led to a maximum EGFP concentration at about 24 h. Heat treatments at higher tempera ture (up to 48 degrees C) but with shorter durations (down to 30 s) also in duced strong EGFP expression. Local heating in situ led to gradients in EGF P expression which decreased with increasing distance from the heat source. Conclusion Local hyperthermia, in combination with a heat sensitive promote r, represents a method for the spatial and temporal control of transgene ex pression. Copyright (C) 2000 John Wiley & Sons, Ltd.