Overexpression of long non coding RNA OR3A4 is associated with altered p38 signalling, morphological and phenotypic changes, and reduced immunogenicity in Barrett’s Oesophagus

Background: Barretts Oesophagus (BO) presents a particular pathological dilemma, in that patients who have no dysplasia within their BO experience a small but significant risk of malignant progression each year. Screening programmes have attempted to reduce the mortality from BO associated oesophageal adenocarcinoma but cannot predict which BO patients will progress to invasive malignancy. We have previously identified the long non coding RNA, OR3A4, is differentially hypomethylated in progressive BO. We aimed to understand its role in BO pathogenicity Methods: The stable BO cell line CP-A, as well as the oesophageal adenocarcinoma cells line OE-33 was transfected with a lentiviral OR3A4 over-expression vector, and underwent high resolution microscopy, immunofluorescence, RT-qPCR, RNA sequencing, and targeted drug screening with the p38-MAPK inhibitor domipramod to understand the effects of OR3A4 expression on progression. We then compared progressive vs. non-progressive BO samples using quantitative multi-fluorophore (Vectra) immunohistochemistry. Results: Over-expression of OR3A4 in CP-A lines resulted in a hyperproliferative, dysplastic cellular phenotype, with strong over-expression of MAPK and anti-apoptotic pathways at the RNA and protein level, which was sensitive to the p38-MAPK inhibitor domipramod. Vectra immunohistochemistry demonstrated that progressive BO had reduced visibility associated with a reduction in CD8+ T-cells and CD68+ macrophages and reduced CD4+ T-cells in the stomal compartment. Conclusion: The overexpression of OR3A4, which we have previously shown is associated with progressive BO leads to a proliferative dysplastic cellular phenotype associated with increased, reversible MAPK signalling and loss of immune visibility.