PDCD1 and cancer: The current combined strategy of immunotherapy and locoregional treatments essentially aims to enhance the effects of immune checkpoint inhibitors (ICIs) that selectively target these immune checkpoints (PD-1/PD-L1 and CTLA-4); therefore, rather than stimulating new or different immune responses, ICIs can restore and unleash a preexisting immune reactivity to cancer which is being held in check by tumoral microenvironmental factors (Figure 2) [63,64].