PDCD1 and neoplasm: The potential benefits of anti-tumor efficacy using anti-VISTA therapy (Figure 4) through the multiple anti-cancer mechanisms described above must be evaluated in the context of the risks of immune system stimulation, which could conceivably be amplified when combined with other checkpoint inhibitors (anti-CTLA-4 and anti-PD-1/PD-L1) already known to induce the immune system.