Dendritic cell-derived exosomes for cancer immunotherapy: hope and challenges

Dendritic cells (DCs) are the most potent antigenpresenting cells in the human body. When primed with antigens, DCs activate both helper and killer T cells and B cells. In the past decade, DC-based vaccine has emerged as an important strategy for cancer immunotherapy (1). Several phase I or II clinical trials of DC-based immunotherapy to treat different cancers have been reported with increased survival and mild vaccination-related side effects (2,3). However, DC-based immunotherapy has several limitations. For example, molecular composition of DCs may change and is difficult to be defined (4). Tumor cells may secret soluble immunosuppressive cytokines that could convert immature DCs into tolerogenic DCs, which may activate Treg cells (5). Live DCs are inconvenient for storage (4) and have to be produced locally with quality control issues.