RIPK2 and head and neck squamous cell carcinoma: In this investigation, an array analysis revealed that NOD1 and RIPK2 expressions in advanced HNSCC (cT3N3bM0, patient no. 2) were significantly up-regulated (> 2 times) above those in NCMT, being 5.4 and 2.1 times greater, respectively, but NOD2 was weakly expressed (1.4-fold) (Fig. 2c).