Clinical applications of gene therapy for cancer

The number of gene therapy protocols for the treatment of cancer is growing rapidly. The most common type of approved clinical trial for cancer gene therapy involves the ex vivo gene transfer of cytokine genes (e.g., tumor necrosis factor, interleukin-2, granulocyte-macrophage colony-stimulating factor) into tumor cells. The idea behind this approach is to use gene transfer to induce a patient's tumor to become more immunogenic. The genetically altered tumor cells are reinjected into the patient in an effort to induce a systemic antitumor immune response against residual tumor cells. In other trials, investigators are using in situ gene transfer to selectively destroy cancer cells, sparing normal tissues. Continuing advances in molecular biology are likely to allow the development of new cancer treatments and methods of cancer prevention that will redefine cancer therapy.