The cancer patients who are not helped by these therapies may be treated by gene therapy. Gene therapy is the insertion of a functional gene into the cells of a patient to correct an inborn error of metabolism, to alter or repair an acquired genetic abnormality, and to provide a new function to a cell.here are several potential strategies for gene therapy in the treatment of cancer. 1  Enhancing the immunogenicity of the tumor, for example by introducing genes that encode foreign antigens. 2  Enhancing immune cells to increase anti-tumor activity, for example by introducing genes that encode cytokines.