PDCD1 and neoplasm: For example, it has been reported that tumor-associated lymphocytes (TALs) or tumor-infiltrating lymphocytes (TILs), isolated from a mouse model of metastatic ovarian cancer or human ovarian cancer patients, simultaneously express several immune checkpoint inhibitory receptors, such as PD-1, LAG-3, and CTLA-4, that participate in creating an extremely immune-suppressed TME.