For example, although anti-PD-1 and anti-CTLA-4 monoclonal antibodies show spectacular clinical outcomes (>70% efficacy) against cancers such as melanoma, they can only achieve less than 20-30% efficacy in most other cancer types, exhibiting considerable variability among patient responses and often leading to relapse in initial responders (2, 3). This evidence concerns the gene PDCD1 and cancer.