Figure 5.

Gene therapy strategies. (A) Targeting the tumor microenvironment: viruses carry enzymes that degrade ECM components or anti-angiogenic factors that reduce vascular support of tumor. (B) GBM cells receive suicide genes from local injection of a carrier, together with systemic delivery of a prodrug. The suicide gene converts the prodrug into cytotoxic agents that kill the recipient cell and non-transduced bystander tumor cells. (C) The gene for an immunomodulatory cytokine is delivered to the tumor cells by viruses. Cytokine expression increases tumor cell apoptosis and activates immune cells such as macrophages, natural killer cells, and T-cell lymphocytes. (D) Tumor cells receive the functional copy of a tumor suppressor gene, which subsequently induces apoptosis.