CCL21 and head and neck squamous cell carcinoma: The chemokines CCL5, CCL19, and CXCL9 and the immune checkpoints CD40, IDO1, and LGALS9 were highly upregulated in cluster 1 of both CC and HNSCC, whereas CXCL10 was dominant in cluster 1 only in CC and CCL21 only in HNCC.