ABSTRACT
Introduction Gene therapy encompasses a wide range of treatment types that all use genetic material to modify cells in the treatment of cancer. This may be by insertion of genes into cells or by the use of nucleic acid (either DNA or RNA) to influence protein formation. In theory, it is possible to transform either somatic or germline cells by gene therapy, and gene therapy can be performed ex vivo (modification of cells outside the body) or in vivo (in the body). Gene therapy can be used to:
Viral vectors The most common vector is a virus that has been genetically altered to carry the information of a human gene. Target cells are infected with the vector, which unloads the genetic material containing the therapeutic human gene into the target cell. Several viruses have been used to transfer genes into cells:
■ Retroviruses have RNA molecules as genetic material. They have reverse transcriptase to translate the RNA into DNA, and integrase to insert this newly formed DNA into host DNA. However, the insertion of this new DNA is uncontrolled and can take place everywhere in the genome. This problem might be overcome by using zinc finger nucleases or by including
certain sequences such as the β-globulin locus control region to direct the integration to specific chromosomal sites.
