Several different tumor types were assessed and the highest percentage of DP CD8 TILs were found in melanoma and MSIhigh colon cancer, both tumors with high mutational burden that show the highest response rates to immunotherapy26,27, while intermediate percentages were found in HNSCC, lung, and ovarian cancer patients (all known to respond to PD-1 blockade but to a lesser extent than melanoma and MSIhigh colon cancer) (Fig. 1d). The gene discussed is PDCD1; the disease is head and neck squamous cell carcinoma.