CTLA4 and metastatic melanoma: CTLA-4 is an immune checkpoint receptor that downregulates the cellular immune response toward self-tissues and treatment of patients with anti-CTLA-4 antibodies, such as Ipilimumab, have demonstrated increased progression-free survival in late stage metastatic melanoma, when compared to traditional chemotherapeutics alone (Lipson and Drake, 2011; Walunas et al., 1994).