SFRP4 and esophageal adenocarcinoma: The association of loss or reduced expression of SFRP4 protein with tumor progression has been documented in esophageal adenocarcinoma (Zou et al., 2005), pancreatic cancer (Bu et al., 2008), mesothelioma (He et al., 2005) and pituitary adenoma (Wu et al., 2015).