Nevertheless, compared with normal tissue, the downregulation of ACE2 has been identified in hepatocellular carcinoma (59), non-small cell lung cancer (NSCLC) (60), breast tumors (61), pancreatic ductal adenocarcinoma (62), and gallbladder cancer (63), while the upregulation of ACE2 and TMPRSS2 has been identified in colorectal tumors (64) and lung cancer (65). Here, TMPRSS2 is linked to lung cancer.