A51: Use of the PigA gene mutation assay as a novel blood-based biomarker for cancer progression in the Barrett’s oesophagus – oesophageal adenocarcinoma model
1Swansea University, Swansea, UK,2ABMU Health Board, Swansea, UK
There has been a 600% increase in the incidence of oesophageal adenocarcinoma (OA) over the last 30-years and given the poor survival associated with this cancer, intensified efforts to better risk stratify patients have been employed. Whilst regular endoscopic surveillance of its precursor Barretts oesophagus (BO) condition has been the mainstay, the cost implications of this and potential for patient harm warrant the investigation of adjunctive biomarkers.
The Pig-A gene mutation assay is a fast and reproducible method of assessing genomic instability through the measurement of fluorescently labeled antibodies to specific membrane proteins by flow-cytometric methodology.
We postulate that blood cells circulating through the inflamed oesophageal mucosa, exposed to mutagenic chemicals such as bile, accumulate mutations that can be investigated using this assay.
Blood based cell lines were exposed to physiological doses of refluxate constituents (mimicking the natural exposure to these noxious chemicals) and the Pig-A mutant frequency measured.
Subsequent ex-vivo analysis of blood was undertaken in patients attending endoscopy with symptoms of gastro-oesophageal reflux disease, GORD. Pig-A analysis of erythrocytes and leucocytes was performed and results correlated with histopathological analysis of oesophageal biopsies as well as a detailed lifestyle questionnaire.
In-vitro investigations confirmed the carcinogenicity of bile salts to blood based cell lines, (p<0.05).
Subsequent ex-vivo erythrocyte analysis of 121 patients was undertaken. Confounding variables such as smoking and increasing age were associated with higher mutant frequencies. Both univariate and multivariate analysis demonstrated statistically significant elevations in mutant frequency in OA patients compared to normal controls (p<0.01).
The application of this simple, blood-based assay in reflux sufferers demonstrates greater levels of DNA damage in OA patients compared to patients with Barretts or GORD alone.
The PigA gene mutation assay has the potential to be a biomonitoring tool in both Barretts oesophagus as well as other pre-malignant conditions.