There is still much to do in terms of optimizing vaccine design, activation and selecting appropriate target antigens, improving immune recruitment, and delivery technology. Nevertheless, in the next years an increasing number of DNA vaccines will enter more advanced phases of human studies, aimed to establish their efficacy as real clinical products. Therapeutic regimens composed of optimal vaccine formulations with combinations of immunotherapy agents and delivery strategies could offer hope to patients suffering from incurable cancer that current standard therapies cannot provide alone. TLR agonist–Stat3 siRNA conjugates: cell-specific gene silencing and enhanced antitumor immune responses Efficient delivery of siRNA to specific cell populations in vivo remains a formidable challenge to its successful therapeutic application. We describe a novel siRNA-based approach – synthetically linking siRNA to an oligonucleotide TLR9 agonist – that targets and silences genes in TLR9(+) myeloid cells and B cells, both of which are key components of the tumor microenvironment. Because Stat3 in tumor-associated immune cells suppresses antitumor immune responses and hinders TLR9-induced immune stimulation, we tested CpG-Stat3siRNA conjugates for anti-tumor effects. When injected locally at the tumor site or systemically through an intravenous route, the CpG-Stat3siRNA conjugates access tumor-associated dendritic cells, macrophages and B cells, inhibit Stat3 expression, leading to activation of tumor-associated immune cells, and ultimately potent anti-tumor immune responses. Our findings demonstrate the potential of TLR agonist-siRNA conjugates for targeted gene silencing coupled with TLR stimulation and immune activation in the tumor microenvironment. siRNA conjugates for targeted gene silencing coupled with TLR stimulation and immune activation in the tumor microenvironment.