The 'kiss of death' by dendritic cells to cancer cells

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) specialized in the stimulation of naive T lymphocytes, which are key components of antiviral and antitumor immunity. DCs are 'sentinels' of the immune system endowed with the mission to (1) sense invading pathogens as well as any form of tissue distress and (2) alert the effectors of the immune response. They represent a very heterogeneous population including subsets characterized by their anatomical locations and specific missions. Beyond their unique APC features, DCs exhibit a large array of effector functions that play critical roles in the induction and regulation of the cell-mediated as well as humoral immune responses. In the course of the antitumor immune response, DCs are unique in engulfing tumor cells killed by natural killer (NK) cells and cross-presenting tumor-associated antigens to cytotoxic T lymphocytes (CTLs). However, while DCs mediate antitumor immune responses by stimulating tumor-specific CTLs and NK cells, direct tumoricidal mechanisms have been recently evoked. This review addresses the other face of DCs to directly deliver apoptotic signals to stressed cells, their role in tumor cell death, and its implication in the design of DC-based cancer immunotherapies.