Meanwhile, a higher expression level of these genes was observed in Stages 1–4 of HNSCCs than that in normal tissues, among which SMOX and DHPS mRNA expression was higher in advanced HNSCC (stage 3 and stage 4) than that in lower stages of HNSCC (stage 1 and stage 2) (Supplementary Fig. 1A–F). This evidence concerns the gene DHPS and head and neck squamous cell carcinoma.