The innate arm of immunity mediated by NK cells and adaptive immunity mediated by Th1 cytokines seemed to play an important role in this anti-tumor effect. The potential beneficial effects of supplementing rAAV-/rAdv-hTERTC27 gene therapy with other therapies for prevention and treatment of melanoma metastasis warrant further investigations. nhanced expression level of hTERTC27 likely played a role. As a universal tumor-associated antigen, TERT is an ideal Dinaciclib target for cancer therapy. Conceptually, three approaches have exploited TERT for cancer therapy: gene therapy, immunotherapy, and small-molecule inhibitors. Previously, rAAV-hTERTC27 was developed as a TERT-targeting gene therapy. Our study indicates that activation of NK cells by hTERTC27 is sufficient to inhibit melanoma growth in mouse model, pinpointing the importance of NK cell activation in cancer immunotherapy. These observations are consistent with our previous study that rAAV-hTERTC27 administration effectively inhibited glioblastoma growth in nude mice, where T cells are absent but NK cells are functional. Consistently, a previous study also indicated that activation of NK cells can provide effective innate immunotherapy of melanoma in mouse model. The NK activity-stimulating effect of rAAV-/rAdv-hTERTC27 represents a novel way to exploit the functions of TERT in cancer treatment. hTERTC27 contains two peptides, p973 and p988, both of which have been shown to induce TERT specific CTLs in vitro or in vivo to lyse TERT+ tumor cells, including melanoma B16 cells. It has also been reported that dendritic cells pulsed with peptide p540 can elicit CTLs ex vivo to lyse hTERT+ tumor cells, including human melanoma cells K029. DCs transfected with mTERT gene can also induce CTLs to lyse B16 cells and inhibit B16 melanoma metastasis. Apparently, the mechanism of hTERTC27-induced tumor suppression in our study is different from that of peptides or TERT gene transfected DCs reported in other studies. hTERTC27 may contain other unknown epitopes that have a tendency to induce a strong innate immune response other than an adaptive immune response. Not surprisingly, a single-peptide epitope tends to induce adaptive immunity because such single peptide is screened by CTL assay. However, subcutaneous injection of rAAV-/rAdv-hTERTC27 viral cocktail near tumor site produced the most significant antitumor effect. Although it is unclear what might have contributed to the differences of antitumor effect among these administration routes, it has been reported that the induction of immunity against the transgene product carried by rAAV depends on the routes of administration. Therefore, intratumoral, intravenous or subcutaneous administration of rAAV-/rAdv-hTERTC27 may preferentially enable the stimulation of innate anti-tumor immunity. It will be interesting to investigate the effect of different administration routes on NK cell population and activation. Our observation implies that careful selection of administration route may be important for cancer gene therapy.