NOS2 and neoplasm: In conclusion, our data reveal that Poly6 treatment elicits a strong antitumor immune response in mice, possibly via an IFN-I-dependent Tip-DC-inducing capacity, contributing to tumor clearance in two ways: direct cancer cell killing by Tip-DCs, which is iNOS-dependent and involves NO and peroxynitrite production, and indirect killing by CD8+ T cell-mediated CTL response via a CD40 activation, suggesting the potential use of Poly6 as an adjunct immunotherapy that can enhance the effect of immune checkpoints.