Gene therapy is the transfer of normal GENES into a patient to combat the eﬀects of abnormal genes which are causing disease(s). The GENETIC ENGINEERING technique used is SOMATIC cell gene therapy in which the healthy gene is put into somatic cells that produce other cells – for example, stem cells that develop into BONE MARROW. Descendants of these altered cells will be normal and, when suﬃcient numbers have developed, the patient’s genetic disorder should be remedied. The abnormal gene, however, will still be present in the treated individual’s germ cells (eggs or sperm) so he or she can still pass the inherited defect on to succeeding generations.
Gene therapy is currently used to treat disorders caused by a fault in a single recessive gene, when the defect can remedied by introducing a normal ALLELE. Treating disorders caused by dominant genes is more complicated. CYSTIC FIBROSIS is an example of a disease caused by a recessive gene, and clinical trials are taking place on the eﬀectiveness of using LIPOSOMES to introduce the normal gene into the lungs of someone with the disorder. Trials are also underway to test the eﬀectiveness of introducing tumour-suppressing genes into cancer cells to check their spread.
Gene therapy was ﬁrst used in 1990 to treat an American patient. Eleven European medical research councils (including the UK’s) recommended in 1988 that gene therapy should be restricted to correcting disease or defects, and that it should be limited to somatic cells. Interventions in germ-line cells (the sperm and egg) to eﬀect changes that would be inherited, though technically feasible, is not allowed (see CLONING; HUMAN GENOME).