Proteinase-activated Receptor-2 Induces Cyclooxygenase-2 Expression through β-Catenin and Cyclic AMP-response Element-binding Protein

Abstract

Chronic inflammation of mucosae is associated with an increased cancer risk. Tumorigenesis in these tissues is associated with the activity of some proteinases, cyclooxygenase-2 (COX-2), and ␤-catenin. Serine proteinases participate in both inflammation and tumorigenesis through the activation of proteinase-activated receptor-2 (PAR 2 ), which up-regulates COX-2 by an unknown mechanism. We sought to determine whether ␤-catenin participated in PAR 2 -induced COX-2 expression and through what cellular mechanism. In A549 epithelial cells, we showed that PAR 2 activation increased COX-2 expression through the ␤-catenin/T cell factor transcription pathway. This effect was dependent upon ERK1/2 MAPK, which inhibited the ␤-catenin-regulating protein, glycogen synthase kinase-3␤, and induced the activity of the cAMP-response element-binding protein (CREB). Knockdown of CREB by small interfering RNA revealed that PAR 2 -induced ␤-catenin transcriptional activity and COX-2 expression were CREB-dependent. A co-immunoprecipitation assay revealed a physical interaction between CREB and ␤-catenin. Thus, PAR 2 up-regulated COX-2 expression via an ERK1/2-mediated activation of the ␤-catenin/Tcf-4 and CREB pathways. These findings reveal new cellular mechanisms by which serine proteinases may participate in tumor development and are particularly relevant to cancers associated with chronic mucosal inflammation, where serine proteinases are abundant and COX-2 overexpression is a common feature.Patients with chronic inflammatory diseases of mucosae, including those of the airway and intestine, have an increased risk for the development of cancer. Serine proteinases have been implicated as key factors in mucosal inflammation and the formation and metastasis of tumors. These proteinases trigger specific cellular responses through proteinase-activated receptors (PARs), 3 G-protein-coupled receptors that are activated by proteolytic cleavage of the extracellular N terminus at a specific amino acid sequence, revealing a new N-terminal "tethered ligand" that binds to and activates the receptor (1, 2). PAR 2 , one of the four members of this receptor family, can be activated by trypsin (3), tryptase (4), and the tumor-derived proteinase matriptase (5) to stimulate processes ranging from inflammation and pain perception to tumorigenesis (3, 7-9). Tumor cells, especially those of epithelial origin, express a high level of PAR 2 (10, 11). Trypsin and matriptase are commonly overexpressed in tumor cells and in their microenvironment at concentrations compatible with PAR 2 activation (12, 13).We have shown previously that the activation of PAR 2 stimulates COX-2 expression (14). COX-2 is expressed early in carcinogenesis and very likely plays a role in the development of cancer (15-17), as it correlates with tumor invasion and poor clinical outcome (18). The mechanisms by which PAR 2 activation induces the expression of COX-2 are still unclear. However, it is known that the cox2 gene can be induced by the transcriptional activity of ␤-catenin....

Proteinase-Activated Receptor-2–Triggered Prostaglandin E2 Release, but Not Cyclooxygenase-2 Upregulation, Requires Activation of the Phosphatidylinositol 3–Kinase / Akt / Nuclear Factor-κB Pathway in Human Alveolar Epithelial Cells

“…It has been demonstrated that activation of CREB downstream of ERK or p38MAPK might contribute to upregulation of COX-2 in certain cells including A549 cells (22,29,30). These reports are supported by our present findings that PAR2 stimulation actually induced phosphorylation of CREB in a manner dependent on the MEK / ERK pathway, but not the EGF receptor / p38MAPK pathway (see Fig.…”

“…Unfortunately, in the present study, we could not obtain direct evidence showing that CREB is upstream of the PAR2-triggered COX-2 upregulation. However, Wang et al have reported that in A549 cells, the same cell line of ours, COX-2 upregulation caused by activation of PAR2 was suppressed by knockdown of CREB with the siRNA (22), supporting possible involvement of the MEK / ERK / CREB pathway in the PAR2-triggered COX-2 upregulation in A549 cells. Considering the blockade of COX-2 induction by an inhibitor of JNK (see Fig.…”

“…Apart from NF-κB, CREB has been shown to be downstream of ERK or p38MAPK and mediate upregulation of COX-2 in various cells including A549 cells (22,29,30). In our experimental conditions, SLIGRL-NH 2 at 100 μM for 20 min caused phosphorylation of CREB, an effect suppressed by the MEK inhibitor U0126, but not by the p38MAPK inhibitor SB203580 (Fig.…”

“…Our signal transduction studies have shown that PAR2-triggered PGE 2 production involves formation of arachidonic acid via the MEK / ERK / cytosolic phospholipase A 2 (cPLA 2 ) pathway and upregulation of COX-2 via the Src / epidermal growth factor (EGF) receptor / p38 MAP kinase (p38MAPK) pathway in A549 cells (18,21). An independent study has also suggested possible involvement of the cAMP-response element-binding protein (CREB) pathway in the PAR2-mediated upregulation of COX-2 in the same cell line (22).…”

Protease-Activated Receptor–Stimulated Interleukin-6 Expression in Endometriosis-Like Lesions in an Experimental Mouse Model of Endometriosis

“…PAR1 has also been implicated in cancer cell invasion and tumor progression (36,38,39). PAR2 functions to increase PG and cytokine levels in epithelial cells (33,40). In the current study, the fact that such dramatic lesion formation was observed at the site of ovarian removal where bleeding was present during and after uOVX suggests that tissue damage and bleeding may trigger an inflammatory reaction via PAR activation in this model.…”