Current status of gene therapy for cancers

Gene therapy with viral/unviral vectors is thought to be one of the most promising treatments for malignant diseases including cancers. The potential targeted genes researched are categorized into 2 groups: 1) those comprising oncogenes and oncosuppressor genes such as p 53 and E 1 A to directly kill tumors, and 2) others comprising immunoregulatory molecules such as TAA, cytokines, and T-cell costimulatory molecules to enhance anti-tumor immunity. These modalities have been intensively investigated for cancer treatment, and the anti-tumor efficacies are being shown in many preclinical studies using animal tumor models. To date, nevertheless, the clinical trials have not been successful overall. It is sometimes doubted whether this strategy with gene therapeutics is more beneficial than existing therapeutic modalities such as standard therapy with radiation and chemotherapeutics or immunotherapy with cytokines and immune cells to treat cancers. In fact,however,clinical responses of some targeted genes are now being revealed at higher levels of clinical trials, Phase II/III. Here, the genes targeted for cancer therapy and the current clinical trials are reviewed for a better understanding of cancer gene therapy.