TP53 and neoplasm: Finally, to constrain expression of these tumoricidal proteins to the tumor region, both p53 and Azurin expression by the carriers was engineered to be driven by a hypoxic promoter pflE. 52This approach exploits the hypoxic tumor microenvironment combined with purine-dependent motile carrier to achieve tumor-targeted expression of p53 and full-length Azurin to induce apoptosis of glioblastoma cells (Figure 1A).