PEBP1 and esophageal squamous cell carcinoma: Several studies on the promoter methylation have shown that the methylation status of the RKIP promoter is correlated with low RKIP expression levels in advanced stages of several tumors, including gastric adenocarcinomas, esophageal squamous cell carcinomas, and colorectal and breast cancers [62,73,101,102,103,104,105,106].