CTLA4 and melanoma: Especially, checkpoint inhibitors including anti-PD-1, anti-PD-L1, and anti-CTLA4 blocking inhibitory signaling in effector anti-tumor T cells are significantly effective in treating renal cell carcinoma, melanoma, non-small cell lung carcinoma, head and neck cancers, hepatocellular carcinoma, triple-negative breast cancer, and others (2, 4, 5).