Additionally, the vehicles of the gene therapy (e.g., viral vectors) can be designed to target specific tissues, directing the CYP enzyme expression directly to the tumor cells where prodrug metabolism will be most effective and, at the same time, reducing toxic effects of chemotherapeutic drugs on healthy tissue (Wang and Yuan, 2006; Capasso et al., 2013; Sun et al., 2020). This evidence concerns the gene PPIG and neoplasm.