A study evaluating samples from non-small-cell lung cancer, HNSCC and melanoma demonstrated that PD-1 and PD-L1 expression, together with 11 signatures including CD8+ and CD4+ T cell activation, NK cells, and interferon (IFN) activation, were associated with better disease control and PFS [99]. Here, PDCD1 is linked to head and neck squamous cell carcinoma.