APP and head and neck squamous cell carcinoma: On the basis of the HPA database, the protein expression levels of CSRP2, CAV1, APP, TNFRSF12A, CAV2, PLAU, and LAMC2 were significantly higher in HNSCC tumor tissues than in normal tissues, whereas the protein expression levels of HMGA1, PRAME, and AREG were not significantly different between normal and tumor tissues (Fig. 8).