Oxygen tension and a pharmacological switch in the regulation of transgeneexpression for gene therapy

Background The combination of physiologically and pharmacologically control led elements may provide a means to ensure both the regulation and the safe ty of transgene expression - two major goals in gene therapy. Methods A two-gene modulation system was developed that uses the following three levels of control: (i) the hypoxia-responsive element directing the t ranscription of the tetracycline-controlled transactivator (tTA); (ii) part of the oxygen-degradation domain limiting the production of tTA in normoxi a; and (iii) the tetracycline switch of the transactivator activity (the te t-off system). Results This triple-control system allowed high expression of the gene of i nterest (luciferase or erythropoietin) by transfected cells upon hypoxia an d low expression under normoxia or in the presence of tetracycline. This co ntrol of transgene expression was also obtained in mouse tumors. Conclusions This multiple-control system is of interest for spatially restr icting transgene expression into hypoxic tumors, and for finely adjusting t he expression level of a therapeutic protein to the oxygen supply in medica l applications such as neoangiogenesis or the erythropoietin-mediated treat ment of anemia. Copyright (C) 2001 John Wiley & Sons, Ltd.