Monotherapy with anti–PD-1 or anti–PD-L1 was not effective in preventing tumor development because the tumor size averaged 508 ± 356 mm3 and 500 ± 208 mm3, respectively, whereas mice receiving EV alone or in combination with checkpoint blockade antibodies had tumors with an average size smaller than 100 mm3. Here, PDCD1 is linked to neoplasm.