Based on this evidence, we hypothesized that encoding ADA into OVs could exert pleiotropic antitumor benefits by: (i) depriving cancer cells of adenosinergic survival signaling; (ii) restoring antitumor functions of immune cell populations (T, NK, DC, APC); (iii) suppressing tolerogenic immune cells (Treg, MDSC, M2 macrophages) through eADO clearance; (iv) improving antigen presentation and Tfh cells by Tcell-to-DC crosslinking by CD26 and A2Ar [75,76,77,78,79,80]; (v) supplying intratumor inosine to reinforce antitumor T cell metabolism [81,82,83]. This evidence concerns the gene DPP4 and cancer.