Antibodies blocking CTLA-4 or interfering with the PD-1/PD-L1 interaction have proven clinical efficacious in patients with metastatic malignant melanoma.34, 35, 36 Moreover, early studies have suggested clinical activity in cancers of the lung, kidney and other entities.37, 38 Although these examples follow different strategies to evoke a cancer-directed cellular immune response, they all rely on the susceptibility of cancer cells to the cellular immune effector mechanisms. Here, CTLA4 is linked to metastatic melanoma.