Background

With only 17% of oesophageal adenocarcinoma (OAC) patients surviving 5 years post diagnosis (CRUK, 2017), there is an urgent need for improved diagnostic testing for this disease. Here we describe a novel blood-based biomarker for OAC based on the phosophatidylinositol glycan class A (PIG-A) mutation assay alongside the lymphocyte micronucleus assay with the hope of developing a less-invasive diagnostic tool for OAC.

Method

Blood samples were obtained from consenting healthy volunteers and patients attending endoscopy including patients with gastro-oesophageal reflux disease (GORD), Barrett’s metaplasia (BM) and treatment naïve OAC patients. The X-linked PIG-A gene encodes one of the enzymes responsible for the production of glycosyl phosphatidylinositol (GPI) anchors that tether cell signalling molecules to the extracellular surface. A finger-prick volume of whole blood was stained with antibodies targeting CD235a, an erythrocyte specific marker together with antibodies targeting 2 GPI linked proteins, CD55 and CD59. GPI anchor status was measured using the convenient, high throughput method of flow cytometry. An erythrocyte mutant frequency (EMF) was calculated which is the number of PIG-A mutant cells per million erythrocytes. The lymphocyte cytokinesis block micronucleus (L-CBMN) assay was also carried out on a number of samples. Lymphocytes were isolated, grown in culture for 4 days including 24hour treatment with cytochalasin-B (to block cytokinesis) and harvested. Micronucleated cells (evidence of chromosomal damage) were scored manually using light microscopy.

Results

OAC patients (n=84) had a three–fold increase in erythrocyte mutant frequency (EMF) compared to GORD patients (n=130) (p<0.001) and healthy volunteers (n=156) (p<0.001). In OAC patients, higher EMF was associated with worsening tumour staging (p=0.014), nodal involvement (p=0.019) and metastatic disease (p=0.008). In addition, preliminary analysis revealed that OAC patients appeared to have higher levels of micronucleated lymphocytes compared to controls (p<0.001).

Conclusion

Blood based mutation testing has the potential to be used as a less-invasive tool to identify patients with OAC and perhaps prioritise patients for endoscopy. Further work is required to continue test optimisation and investigate its specificity in other tumour types.

Impact statement

Less-invasive biomarkers could revolutionise cancer detection and improve patient outcomes, particularly for high-mortality malignancies such as oesophageal cancer.