Moreover, apart from therapeutical purposes, the alteration of the genes/enzymes of the two metabolisms, should also be thoroughly evaluated as predictive biomarkers, since a 5-genes signature (TP63, PHGDH, PSAT1, PSPH) seems to correlate with HNSCC overall survival and considering the lack of effective predictive tools [81–83]. This evidence concerns the gene PSAT1 and head and neck squamous cell carcinoma.