Tumor cell-intrinsic PD-1 has also been found in murine non-small cell lung20, hepatocellular24, glioblastoma23, and ovarian cancer lines7,12 and in human melanoma5,13–15,17–19, lung17,20,21, liver18,24–26, brain22,23, colorectal18,19,21, pancreatic17,27, gastric28, esophageal29–31, and thyroid tumors32,33. Here, PDCD1 is linked to neoplasm.