Background: Local production of therapeutic proteins, e.g. for cancer treatments, is based on gene therapy approaches and requires tight spatial and temporal control of gene expression. Here we demonstrate the use of local hyperthermia of varying intensity and duration to control the expression of a transgene under control of the thermoinducible hsp70 (heat shock protein) promoter.
Methods: Heat-induced expression of the EGFP (green fluorescent protein) reporter 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 immunodeficient 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 temperature (up to 48 degrees C) but with shorter durations (down to 30 s) also induced strong EGFP expression. Local heating in situ led to gradients in EGFP expression which decreased with increasing distance from the heat source.
Conclusion: Local hyperthermia, in combination with a heat sensitive promoter, represents a method for the spatial and temporal control of transgene expression.