By far, the best characterized immune checkpoint receptors are programmed cell death protein 1 (PD-1; also known as CD279), cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4; also known as CD152) and indoleamine 2,3-dioxygenase (IDO); agents targeting these molecules are either approved or being extensively tested in clinical trials for multiple solid or hematological cancers [9]. The gene discussed is PDCD1; the disease is hematopoietic and lymphoid cell neoplasm.