Prior work has suggested S100A9 is downregulated in the progression from Barrett’s metaplasia to EAC but this only assessed expression at the mRNA level (67), in contrast in a further study, the protein has been found to be overexpressed in EAC in comparison to Barrett’s tissue samples and upregulated in serum in patients with EAC (68). This evidence concerns the gene S100A9 and Barrett esophagus.