KLF4 and esophageal squamous cell carcinoma: In the context of digestive system cancers, the vast majority of studies have revealed that KLF4 is decreased or absent with a bad clinical outcome, including esophagus squamous cell carcinoma (ESCC) [15, 16], gastric cancer (GC) [17–19], pancreatic ductal adenocarcinoma (PDAC) [20, 21], hepatocellular cancer (HCC) [22–24], and colorectal cancer (CRC) [25–27].