CTLA4 and melanoma: Blockade of immune checkpoints, such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), PD-1, and PD-L1, has shown clinical activity not only in conventionally immune-responsive tumors such as melanoma and renal cell carcinoma, but also in non-small cell lung cancer (NSCLC) and prostate cancer16–18.