The lack of PD-L1 upregulation by either tumor cells or tumor-infiltrating immune cells has also been found in biopsies from patients with other types of cancer, such as melanoma, renal-cell carcinoma, colorectal cancer, gastric cancer, and head-and-neck squamous-cell carcinoma, which display patterns with little or no tumor-infiltrating immune cell action [43]. Here, CD274 is linked to head and neck squamous cell carcinoma.