The expression level of ACE2 was significantly higher in the tumor tissue of esophageal carcinoma (ESCA), kidney renal papillary cell carcinoma (KIRP), lung adenocarcinoma, rectum adenocarcinoma (READ), and uterine corpus endometrial carcinoma (UCEC), whereas lower in breast invasive carcinoma (BRCA), kidney chromophobe (KICH), liver hepatocellular carcinoma (LIHC), pancreatic adenocarcinoma (PAAD), prostate adenocarcinoma (PRAD), thyroid carcinoma (THCA), and stomach adenocarcinoma (STAD) compared with the adjacent normal tissue (Figure 1B). This evidence concerns the gene ACE2 and lung adenocarcinoma.