PDCD2 and digestive system neoplasm: To investigate whether PDCD2 could act as a biomarker in solid cancers, the ROC curve analysis was conducted, and the results indicated that PDCD2 could be used as a high sensitivity and specificity biomarker (AUC > 0.75) for diagnosing digestive system tumors such as CHOL, COAD, STAD, PAAD, and READ (Fig. 3A), chest tumors including esophageal adenocarcinoma (ESAD), ESCA, and LUSC (Fig. 3B), nervous system tumor GBMLGG including GBM and LGG (Fig. 3C), and genitourinary system tumors including KICH, TGCT, and UCS (Fig. 3D).