PDE4DIP and head and neck squamous cell carcinoma: The results showed that the expression of the PDE4DIP protein in PAAD, KIRC, and colon adenocarcinoma (COAD) (all p < 0.05) was significantly down-regulated compared with that in normal tissues, while it was significantly up-regulated in BRCA, glioblastoma multiforme (GBM), head and neck squamous cell carcinoma (HNSC), LIHC, LUAD, and UCEC (all p < 0.05) (Figure 2).