SMOX and head and neck squamous cell carcinoma: In the present study, we performed TCGA analysis of the HNSCC dataset and found that the mRNA expression of EIF5A2 gene and several key enzyme genes involved in polyamine metabolism, including ODC1, SRM, SMOX, DHPS, and DOHH, was significantly upregulated in HNSCC tissues compared with those in adjacent normal tissues, which is positively correlated with disease stages and histological grades (Fig. 1 and Supplementary Fig. 1).