Oral (15W199)

The expression of Dual Specificity Phosphatases (DUSP) 1, 5 and 6 is modulated by acid and bile acid exposure, and varies at different stages of oesophageal carcinogenesis.

Author(s)

McEnroy, D.M.1,2, Kirca M.1,2, MacGarrigal S.3, Zaheer A.1,2, Reynolds J.V.3, Duggan, S.P.4 & Kelleher, D.4

Department(s)/Institutions

1Dept. of Clinical Medicine, Trinity College Dublin, St. James’s Hospital, Dublin 8, Ireland 2Dept. of Gastroenterology, St. James’s Hospital, Dublin 8, Ireland 3Dept. of Surgery, Trinity College Dublin.

Introduction

Reflux damage caused by gastric / bile acids predisposes to the development of Oesophageal Adenocarcinoma (OAC) and its metaplastic precursor Barrett’s Oesophagitis (BO). During this process inflammatory and proliferative pathways regulated by ERK, AP-1 and NF-κB are known to be deregulated. Dual Specificity Phosphatases (DUSPs) play an important role in modulating inflammatory processes, cell proliferation and cell death through de-phosphorylation of mitogen-activated protein kinase ERK. DUSP expression has been found to differ between various other cancers and their more benign precursors (e.g. in the pancreas).

Aims/Background

The aims of this study were to ascertain the expression status of DUSPs 1, 5, and 6 in clinical samples of BO and OAC relative to normal squamous oesophageal samples, and to examine whether DUSP expression may be influenced by exposure to simulated reflux events in cell lines derived from normal squamous, dysplastic BO and adenocarcinomatous oesophageal tissues.

Method

DUSP1, 5 and 6 levels were compared in patient samples of OAC (n=21), BO (n=17) and normal squamous tissue (n=19) using RT-PCR. Cells from squamous (HET1A, HEEC), dysplastic (GOH-TRT), and adenocarcinoma (SKGT4) cell lines were exposed to varying concentrations of de-oxycholic acid (DCA) and pulses of HCl, and DUSP 1, 5 and 6 levels were compared with resting cells at different time-points using RT-PCR.

Results

Significant up-regulation of DUSPs 1 and 6 (p=0.02, p<0.0001) was observed in BO tissues but was surprisingly absent in the OAC patients. DUSP5 expression was significantly increased in the OAC patient cohort (p<0.0001) in contrast with its substantial down-regulation in the BO tissue (p<0.001). DCA exposure induced changes in DUSP expression in all of the cell lines tested. In cells treated with DCA concentration 250uM for 12 hours, DUSP6 was down-regulated in the squamous cell lines (HET1A log fold change (LFC) = 0.5, HEEC LFC = 0.4), was up-regulated in the dysplastic cells (GOH-TRT LFC = 12), and the magnitude of LFC was reduced in the cancer cell line (SK-GT4 LFC = 1.4). In cancer cell line SK-GT4, pulsatile exposure to acidic pH simulating reflux events induced increases in DUSP expression, which were still present 24 hours later (DUSP1 LFC = 1.4, p<0.01; DUSP5 LFC = 8.9, p<0.0001; DUSP6 LF = 14.5, p<0.001). Use of BCI, a chemical inhibitor of DUSPs 1 and 6, is associated with reduced cell proliferation in the dysplastic BO cell line GOH-TRT.

Conclusions

DUSP expression differs between the normal, BO and OAC tissues, and is altered in response to acid and bile acid exposure. Further work is ongoing to assess their potential as therapeutic targets in the prevention and treatment of oesophageal cancer.

Click to access the login or register cheese