Analyses of single-cell RNA sequencing (scRNA-seq) data of PBMCs from head and neck squamous cell carcinoma patients who received neoadjuvant ICI therapy19 revealed that the frequency of Treg cells expressing MKI67 (gene encoding Ki67) at baseline was notably higher in patients with disease progression (P = 0.044; Supplementary Fig. 7). This evidence concerns the gene MKI67 and head and neck squamous cell carcinoma.