The engineered serotype 5 adenovirus (Ad5) provides selective viral replication and cytokine expression in tumor cells, controlled by a dual-promoter system: (1) E2F-1, a tumor-specific promoter, drives the expression of E1A, which is essential for viral replication leading to tumor cell lysis; and (2) E3, a promoter activated by E1A gene products that control the tumor-specific expression of GM-CSF to induce an anti-tumor immune response (Figure 3b) [48]. Here, E2F1 is linked to neoplasm.