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Open Access Research article

Inhibitory effects of prostaglandin E2 on collagen synthesis and cell proliferation in human stellate cells from pancreatic head adenocarcinoma

Ewa Pomianowska12*, Dagny Sandnes3, Krzysztof Grzyb4, Aasa R Schjølberg1, Monica Aasrum3, Ingun H Tveteraas3, Vegard Tjomsland12, Thoralf Christoffersen3 and Ivar P Gladhaug12

Author Affiliations

1 Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway

2 Department of Hepato-pancreato-biliary Surgery, Oslo University Hospital, Rikshospitalet, PO Box 4956, Nydalen 0424 Oslo, Norway

3 Department of Pharmacology, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway

4 Department of Pathology, Oslo University Hospital, Rikshospitalet, Oslo, Norway

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BMC Cancer 2014, 14:413  doi:10.1186/1471-2407-14-413

Published: 9 June 2014

Abstract

Background

Several studies have described an increased cyclooxygenase-2 (COX-2) expression in pancreatic cancer, but the role of COX-2 in tumour development and progression is not clear. The aim of the present study was to examine expression of COX-2 in cancer cells and stromal cells in pancreatic cancer specimens, and to explore the role of PGE2 in pancreatic stellate cell proliferation and collagen synthesis.

Methods

Immunohistochemistry and immunofluorescence was performed on slides from whole sections of tissue blocks using antibodies against COX-2 and α-smooth muscle actin (αSMA). Pancreatic stellate cells (PSC) were isolated from surgically resected tumour tissue by the outgrowth method. Cells were used between passages 4 and 8. Collagen synthesis was determined by [3H]-proline incorporation, or by enzyme immunoassay measurement of collagen C-peptide. DNA synthesis was measured by incorporation of [3H]-thymidine in DNA. Cyclic AMP (cAMP) was determined by radioimmunoassay. Collagen 1A1 mRNA was determined by RT-qPCR.

Results

Immunohistochemistry staining showed COX-2 in pancreatic carcinoma cells, but not in stromal cells. All tumours showed positive staining for αSMA in the fibrotic stroma. Cultured PSC expressed COX-2, which could be further induced by interleukin-1β (IL-1β), epidermal growth factor (EGF), thrombin, and PGE2, but not by transforming growth factor-β1 (TGFβ). Indirect coculture with the adenocarcinoma cell line BxPC-3, but not HPAFII or Panc-1, induced COX-2 expression in PSC. Treatment of PSC with PGE2 strongly stimulated cAMP accumulation, mediated by EP2 receptors, and also stimulated phosphorylation of extracellular signal-regulated kinase (ERK). Treatment of PSC with PGE2 or forskolin suppressed both TGFβ-stimulated collagen synthesis and PDGF-stimulated DNA synthesis.

Conclusions

The present results show that COX-2 is mainly produced in carcinoma cells and suggest that the cancer cells are the main source of PGE2 in pancreatic tumours. PGE2 exerts a suppressive effect on proliferation and fibrogenesis in pancreatic stellate cells. These effects of PGE2 are mediated by the cAMP pathway and suggest a role of EP2 receptors.

Keywords:
Pancreatic stellate cells; Prostaglandin E2; Cyclic AMP; DNA synthesis; Collagen synthesis