PECAM1 and head and neck squamous cell carcinoma: On the basis of classical cell markers identified in prior studies (13–15), we manually annotated and merged these cell clusters on the basis of the specific cell markers expressed within each cluster and presented the primary markers within each corresponding cell type (Supplementary Table S3): HNSCC cells (KRT5, KRT6A, and PKP3), En (endothelial cells: VWF and PECAM1), Fib (fibroblasts: COL1A1 and ACTA2), SMC (smooth muscle cells: DES), Mac (macrophages: CD14 and CD163), DC (dendritic cells: CD1A and CD1C), ILC (innate lymphoid cells: ID2 and KIT), B cells (MS4A1, CD79A and CD79B), Naive.