Suicide gene therapy involves delivering a gene product in proximity to the targeted cancer tissue through various targeted delivery methods followed by tissue/tumor-specific expression of the gene product which then converts a systemically available pro-drug into an active drug within the tumor locale. In suicide gene therapy, gap junctions allow local diffusion of the active drug resulting in an enhanced effect. In addition, a bystander effect can be mediated through the enhanced immune response as an effect of the resulting cancer necrosis which can sensitize the immune system independently from the expressed suicide gene. Suicide gene therapy is based on the introduction of genes into tumor tissue which ultimately results in cancer cell death. (Rajab K, Nelson P, Keung EZ, Conrad C, Suicide Gene Therapy against Cancer)