Matrix metalloproteinase-7 in Barrett's oesophagus and oesophageal adenocarcinoma : expression, metabolism and functional significance

• Main Author: Garalla, H. M.
• Published: University of Liverpool 2017
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.733900

Oesophageal adenocarcinoma (OAC) is an entity of increasing clinical importance due to an unexplained rise in incidence in recent decades in most Western countries. The prognosis is dismal. The most important risk factor is Barrett’s oesophagus (BO) and so identifying those patients with BO at risk of progression to OAC becomes important. A growing body of evidence implicates MMP-7 in tumorigenesis in a number of different organs, including roles in cellular transformation, cell survival, tumour growth and angiogenesis. MMP-7 expression is typically associated with epithelial cells but the regulatory mechanisms remain uncertain. The objectives of this thesis were (a) to evaluate the pattern of expression of MMP-7 in OAC and BO, (b) to investigate the mechanisms regulating its expression in an OAC cell line, and its functional significance, (c) to assess the action of gastrin on MMP-7 secretion by oesophageal cancer cell lines and (d) to characterise interactions between OE33 cells and myofibroblasts cells in modulating MMP-7 secretion and metabolism. Expression of MMP-7 in all OAC cases was localized to carcinoma cells with relatively low expression in normal squamous oesophageal epithelium and progressively increased expression in BO, low grade dysplasia, high grade dysplasia and OAC with highest expression at the invasive front. In the stroma, myofibroblasts, identified as spindle-shaped cells, exhibited strong MMP-7 expression in the invasive part of the tumour. The data suggest that MMP-7 could be a novel predictive marker for progression of BO to OAC, as well as a potential target driving malignant transformation in BO. Western blotting and ELISA revealed OE33 but not OE21 or OE19 cells secreted abundant proMMP-7 that was insensitive to phorbol 12-myristate 13-acetate (PMA) and both classical (amidated) and non-classical forms of gastrin. Factors other than hypergastrinaemia are therefore likely to be responsible for the increased MMP-7 that occurs in BO and OAC. MMP-7 secretion was inhibited by brefeldin A in OE33-GR cells. Additionally, blocking PI3kinase signalling decreased the expression and secretion of MMP-7 in OE33 cells, while inhibition of protein kinase C or MAP kinase activation had no effect. Cultured cancer-associated myofibroblasts expressed MMP-7, but there was no evidence of secretion into the media. However, MMP-7 was cleaved in the presence of myofibroblasts. Finally, CAMs exhibited increased migration in response to conditioned medium from OE33 cells and the response was reversed by MMP-7 neutralising antibody. This work indicates that MMP-7 should now be formally evaluated as a marker for progression of BO to OAC. Increased expression in OAC may be attributable to enhanced PI3K signalling and may be functionally important in driving invasion and metastasis.