SRM and cancer: Due to the important role of polyamine-eIF5Ahpu axis in tumorigenesis and progression of a variety of cancers [27, 36], we initially performed TCGA data analysis using the UALCAN online tool to evaluate the expression of EIF5A2 and several key enzyme genes involved polyamine metabolism, including ODC1, SRM, SMOX, DHPS, and DOHH, in human HNSCC tissues (n = 520) and adjacent normal tissues (n = 44).