CKAP4 and esophageal squamous cell carcinoma: At present, there have been studies examining the serum levels of CKAP4 in various cancers (Table 3), including hepatocellular carcinoma (Li et al., 2016; Wang et al., 2019), lung cancer (Yanagita et al., 2018), pancreatic cancer (Kimura et al., 2019), and ESCC (Chen et al., 2018).