[Gene therapy: what is it and what is its use?].

Gene therapy has developed as a method of approach to the treatment of human diseases based on the transfer of genetic material to the cells of an individual. Normally, the aim of this transfer of genetic material is to re-establish a cellular function that has been abolished or is defective, to introduce a new function or to interfere with an existing function. Thus, the different gene therapy strategies are based on the combination of three key elements: the genetic material to be transferred, the method of transfer and the cellular type that will incorporate this genetic material. Attention was initially centred on the treatment of monogenic hereditary diseases, but subsequently the majority of clinical trials (over four hundred) have concerned the treatment of cancer. In China a genetic product has been approved for commercialisation: an adenovirus that transfers the correct version of the tumour suppressor gene p53. And, in the late 1990s, a group of children with severe combined immunodeficiency were successfully treated through the ex vivo transfer of the correct version of the altered gene to their bone marrow, although some of these children later developed lymphoproliferative syndromes due to the activation of an oncogen in the corrected cells. Human gene therapy is feasible and can be useful, but the tools need improving for it to become part of the therapeutic arsenal.