Introduction The incidence of oesophageal adenocarcinoma (AC) has increased at an alarming rate in the past few decades; the most important risk factor is Barrett’s oesophagus (BO). Matrix metalloproteinase (MMP)-7 has been linked to progression in this and many other epithelial cancers; expression of MMP-7 is typical associated with epithelial cells but the regulatory mechanisms remain uncertain. Our aim was to evaluate the pattern of expression of MMP-7 in AC and the mechanisms regulating its expression in an AC cell line.
Methods Surgically resected tumours and adjacent tissue from 14 patients with AC were stained with a mouse monoclonal anti-human MMP-7 antibody. Stromal and epithelial compartments were scored separately for staining intensity on a four point scale (0–3) and the percentage of stained cells at each intensity recorded. Western blot and indirect ELISA were applied to an oesophageal adenocarcinoma cell line (OE33 cells). Data are expressed as mean ± SE and comparisons were made by ANOVA or t test as appropriate.
Results MMP-7 was localised to carcinoma cells in all AC cases (80 ± 3% cells scored 2 for intensity), and was strongest in tumour cells at the invasive front (93 ± 1% cells scored 3). There was also expression in epithelial cells in adjacent premalignant lesions of BO (78 ± 4% cells scored 1), but <50% of normal epithelial cells were MMP-7 positive. In the stroma, putative myofibroblasts identified as spindle-shaped cells that expressed MMP-7 were abundant in the invasive part of the tumour (75 ± 7% cells scored 3) whereas they were scarce or absent in adjacent tissue. In OE33 cells, there was high constitutive secretion of MMP-7 that was inhibited by blocking vesicular trafficking with brefeldin A, but not by inhibitors of protein kinase C or MAP kinase activation. However, the phosphatidylinositol (PI) 3 kinase inhibitor, LY294002, significantly inhibited MMP-7 secretion detected by both Western blot and ELISA (secretion in 6 h: 0.7 ± 0.1 nM vs 0.40 ± 0.1 nM, p < 0.002). MMP-7 secretion was similarly inhibited by another PI 3 kinase inhibitor, TG100713 and by MK2206 which inhibits the downstream mediator of PI 3 kinase, Akt. However, the mTOR inhibitor, rapamycin, had no significant effect on MMP-7 expression.
Conclusion MMP-7 expression increases at the invasive front in AC where it is also expressed in stromal spindle-shaped cells. High constitutive expression of MMP-7 in an AC cell line is partly attributable to activation of PI 3 kinase and Akt.
Disclosure of Interest None Declared
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