CTLA4 and melanoma: Immune checkpoint blockade (ICB), in particular blockade of the immune checkpoints cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and lymphocyte-activation gene 3 (LAG-3), has revolutionized the treatment of advanced melanoma with significantly improved therapy response and long-term survival (reviewed in: [1]).