Abstract

A key phenomenon in cancer is the establishment of a highly immunosuppressive tumor microenvironment (TME). Despite advances in immunotherapy, where the purpose is to induce tumor recognition and hence hereof tumor eradication, the majority of patients applicable for such treatment still fail to respond. It has been suggested that high immunological activity in the tumor is essential for achieving effective response to immunotherapy, which therefore have led to exploration of strategies that triggers inflammatory pathways. Here activation of the stimulator of interferon genes (STING) signaling pathway has been considered an attractive target, as it is a potent trigger of pro-inflammatory cytokines and type I and III interferons. However, immunotherapy combined with targeted STING agonists has not yielded sustained clinical remission in humans. This suggest a need for exploring novel adjuvants to improve the innate immunological efficacy. Here, we demonstrate that extracellular vesicles (EVs), derived from activated CD4+ T cells (T-EVs), sensitizes macrophages to elevate STING activation, mediated by IFN{gamma} carried on the T-EVs. Our work support that T-EVs can disrupt the immune suppressive environment in the tumor by reprogramming macrophages to a pro-inflammatory phenotype, and priming them for a robust immune response towards STING activation.