KLF3 and carcinoid tumor: Further analysis through the Human Protein Atlas (HPA) database revealed that the expression frequency of KLF3 protein was 100% in tumor types such as glioma (11/11), thyroid cancer (3/3), lung cancer (10/10), colorectal cancer (10/10), head and neck cancer (4/4), stomach cancer (12/12), urothelial cancer (12/12), cervical cancer (11/11), and pancreatic cancer (11/11), while the lowest expression frequency was observed in tumor types such as carcinoid (2/4), melanoma (6/11), and renal cancer (7/12) (Figure 1C).