CTLA4 and neoplasm: Immune checkpoints including cytotoxic T lymphocyte‐associated‐antigen 4 (CTLA‐4), programmed cell death protein‐1 (PD‐1), and programmed death ligand‐1 (PDL1) are critical mechanism for tumor cells to escape from immune system, therefore immune checkpoints blockade is used for the treatment of cancer in clinic.