Cancer gene therapy: challenges and opportunities.

Understanding the molecular basis of human disease has been the corner-stone of rationally designed molecular therapies. Medicine has a long history of treating patients with cell therapies (i.e., blood transfusions) and protein therapies (i.e., growth factors and cytokines). Gene therapies are the newest therapeutic strategy for treating human diseases. Where will gene therapy be in five years after the euphoria and frustrations of the last 14 years? This is a complex question, but the primary challenge for gene therapy will be to successfully deliver an efficacious dose of a therapeutic gene to the defective tissue. Will the delivery systems return to the early clinical trials of ex vivo gene therapy or will there still be a high demand for systemic therapy? Will systemic therapy continue to depend on viral vectors, or will non-viral and nano-particles become the new mode for gene delivery? The future success of gene therapy will be built on achievements in other fields, such as medical devices, cell therapy, protein therapy and nano-particle technology. This review describes the advances being made in the gene therapy field, as well as addressing the challenges of the near future for cancer gene therapy.