3.1 MUC18 serves as a Crucial Biomarker for Tumors
The expression difference of MUC18 between tumor and normal tissues was evaluated by pairing TCGA and GTEx data. MUC18 was upregulated in 8 cancers—head and neck squamous cell carcinoma (HNSC), kidney renal clear cell carcinoma (KIRC), lymphoid neoplasm diffuses large B-cell lymphoma (DLBC), cholangiocarcinoma (CHOL), glioblastoma multiforme (GBM), liver hepatocellular carcinoma (LIHC), pancreatic adenocarcinoma (PAAD), and thymoma (THYM)—compared with normal tissues (Figure 1A). Analysis of the pancancer cohort from the GEPIA2 database revealed that patients with high MUC18 expression in the Mesothelioma (MESO, HR=2.8), GBM (HR=1.5), Brain Lower Grade Glioma (LGG, HR=2.2), and Cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC, HR=1.6) cohorts had significantly reduced OS, and patients with high MUC18 expression in the Adrenocortical carcinoma (ACC, HR=2.8), Kidney Chromophobe (KICH, HR=12), LGG (HR=1.5), and Uveal Melanoma (UVM, HR=3.2) cohorts had significantly reduced DFS, suggesting that high MUC18 expression adversely affects the prognosis of patients with these tumors (Figure 1B).