PDCD1 and metastatic melanoma: In contrast, immunotherapy with checkpoint inhibitor antibodies such as anti-programmed cell death protein-1 (PD-1) (Nivolumab) and anti-cytotoxic T lymphocyte antigen-4 (CTLA-4) (Ipilimumab) seems to induce stronger anti-tumor immunity as post-surgical (adjuvant) therapy in patients with resectable metastatic melanoma and lung cancer when compared to neoadjuvant therapy; tumor mutational burden and T cell expansion were predictive of the anti-tumor response to checkpoint blockade [7,8].