It has been demonstrated that this kind of combination has an additive therapeutic effect compared to treatments with either anti-CTLA-4 or anti-PD1 as it impedes tumors more efficiently from evading immune responses; however, the response is dependent on the level of expression of PD-1 by tumor cells and therefore cannot be considered as standard treatment for all melanoma patients (33–35). Here, PDCD1 is linked to melanoma.