The finding that OPN is highly and frequently overexpressed in a large cohort of primary EACs at both the transcriptional and protein levels as reported here supports data from a previously reported expression profiling study of EAC and a multi-tumor analysis that included 10 cases of esophageal squamous carcinoma, 16 cases of pancreatic duct adenocarcinoma and 11 cases of gastric adenocarcinoma with OPN up-regulated in 70%, 81% and 100% of cases, respectively [48, 69]. This evidence concerns the gene SPP1 and pancreatic ductal adenocarcinoma.