Immunofluorescence staining of tissue samples from five patients with HNSCC revealed that patients 1, 3, and 4 had higher protein expression levels of SPHK1, MMP1, and p-ERK1/2, whereas patients 2 and 5 had lower protein expression levels of these markers (Figure 4G). This evidence concerns the gene SPHK1 and head and neck squamous cell carcinoma.