Immunotherapeutic targeting of immune checkpoint molecules (such as PD-1, PD-L1 and CTLA-4) have been widely used for some human cancers in the last 7 years, particularly melanoma, with Ipilimumab (CTLA-4 monoclonal antibody) treatment improving overall survival in patients with previously treated metastatic melanoma [116]. Here, CTLA4 is linked to metastatic melanoma.