Non-endoscopic screening biomarkers for Barrett's oesophagus: from microarray analysis to the clinic

Background and aims: Barrett's oesophagus predisposes to oesophageal adenocarcinoma but the majority of patients are undiagnosed. A novel non-endoscopic cytological screening device, called a capsule sponge, makes population-based screening for the disease a feasible option. However, due to the mixed cell population retrieved by the capsule sponge, biomarkers specific for Barrett's oesophagus are required. Methods: Three publically available microarray datasets were used to identify putative biomarkers present in Barrett's oesophagus but absent from normal oesophagus and gastric mucosa. Validation was performed by qPCR (n = 10 each of normal oesophagus, Barrett's oesophagus, gastric mucosa) and immunohistochemistry (normal oesophagus, n = 20; Barrett's oesophagus, n = 21; gastric mucosa, n = 24; duodenum, n = 18). The biomarker was then prospectively evaluated on capsule sponge specimens from 47 patients with Barrett's oesophagus and 99 healthy controls. Results: 2/14 genes identified, dopa decarboxylase (DDC) and Trefoil factor 3 (TFF3), were confirmed by qPCR to be upregulated in Barrett's oesophagus compared to normal oesophagus (p < 0.01) and gastric mucosa (p < 0.01 and p < 0.05, respectively). Immunohistochemistry confirmed that DDC protein expression was restricted to Barrett's oesophagus but was confined to < 1% of the cells within the crypt compartment. TFF3 protein was expressed to high levels at the luminal surface of Barrett's oesophagus compared to absent expression in normal oesophagus and gastric mucosa (p < 0.001). Using the capsule sponge 36/46 patients with Barrett's oesophagus (one inadequate sample) and 6/96 controls were positive for TFF3 giving a sensitivity of 78% and a specificity of 94%. Conclusions: TFF3 is a promising marker for Barrett's oesophagus screening since it is expressed at the luminal surface of Barrett's oesophagus but not in adjacent tissue types and may be applied to a non-endoscopic screening device.