In addition, analysis of E-cadherin, Vimentin, CD80, and CD155 proteins in cSCC patient samples shows their value as predictive biomarkers of anti-PD-1/PD-L1 response, which has also been corroborated in head and neck squamous cell carcinoma (HNSCC) and melanoma patient samples. The gene discussed is PDCD1; the disease is head and neck squamous cell carcinoma.