To enhance the immunogenicity of DNA, vaccines encoding immunostimulatory RNA, such as double-stranded RNA or replicon RNA, were also generated [84] . [46] [47] [48] intradermal/EP prostate cancer; colon cancer [49, 50] gene gun cervical cancer [51, 52] tattoo perforating needle melanoma [53] intratumor melanoma; renal carcinoma [54, 55] high-pressure liquid delivery B-cell lymphoma; [50, 56] Engineering vaccine design for manipulating antigen presentation and processing pathways is one of the most important aspect that can be easily handled in the DNA vaccine technology. If an antibody response is the goal, it is clearly desirable to direct antigen expression to the endoplasmic reticulum (ER), in which folding and secretion can occur. An appropriate leader (signal) sequence can achieve this. (reviewed in [47] ). For induction of CTLs, addition of genes encoding molecules such as ubiquitin, aimed to enhance degradation and peptide production in the proteasome, can be effective (reviewed in [85] ). Similarly, targeting expression to different subcellular pathways such as the endosome or lysosome can amplify CD4 + T cell responses [85] . Thus, DNA vaccines can be designed to induce an appropriate effector pathway, including antibody against cell-surface antigens, or CTL response against intracellular antigens expressed only as MHC class I-associated peptides. Since tumor antigens are often weakly immunogenic and the immune repertoire in patients may have been tolerized, the central question is whether DNA vaccines can activate and maintain the high level of immunity required to suppress cancer cell growth.