Epidermal growth factor receptor activation induces nuclear targeting of cyclooxygenase-2, basolateral release of prostaglandins, and mitogenesis in polarizing colon cancer cells

Abstract

Nonsteroidal antiinf lammatory drugs reduce the risk of colon cancer, possibly via cyclooxygenase (COX) inhibition. The growth factor-inducible COX-2, which is overexpressed in neoplastic colonic tissue, is an attractive target to mediate this effect. Herein we have exploited the ability of a human colon cancer cell line, HCA-7 Colony 29, to polarize when cultured on Transwell (Costar) filters to study COX-2 production and the vectorial release of prostaglandins (PGs). Administration of type ␣ transforming growth factor to the basolateral compartment, in which the epidermal growth factor receptor (EGFR) resides, results in a marked induction of COX-2 immunoreactivity at the base of the cells and the unexpected appearance of COX-2 in the nucleus. The increase in COX-2 protein is associated with a dose-and time-dependent increase in PG levels in the basolateral, but not apical, medium. Amphiregulin is the most abundantly expressed EGFR ligand in these cells, and the protein is present at the basolateral surface. EGFR blockade reduces baseline COX-2 immunoreactivity, PG levels, and mitogenesis in a concentration-dependent manner. Two specific COX-2 inhibitors, SC-58125 and NS 398, also, in a dose-dependent manner, attenuate baseline and type ␣ transforming growth factor-stimulated mitogenesis, although PG levels are decreased >90% at all concentrations of inhibitor tested. These findings show that activation of the EGFR stimulates COX-2 production and its translocation to the nucleus, vectorial release of PGs, and mitogenesis in polarized HCA-7 Colony 29 cells.In the gastrointestinal tract, prostaglandins (PGs) mediate important functions, including motility, vascular tone, angiogenesis, mucosal protection, and immune responsiveness (1). Inasmuch as epithelial cells are capable of PG synthesis, it is feasible that PGs synthesized in the gastrointestinal epithelium regulate these functions by paracrine pathways in response to luminal or serosal stimuli. Although data exist in support of vectorial release of PGs in the isolated rat colon (2), as well as in other tissues and polarized kidney-derived cells (3-5), regulatory mechanisms have not been defined more precisely.Cyclooxygenases (COXs) are key enzymes in the conversion of arachidonic acid (AA) to PGs and other eicosanoids. Two isoforms of the enzyme have been characterized. COX-1 in most cells is expressed constitutively, and a second inducible form known as COX-2 has been identified (refs. 6-8; for review see ref. 9). Recent observations indicate that many colonic polyps and cancers overexpress COX-2 (10-12) and that inhibition of this enzyme by nonsteroidal antiinflammatory drugs decreases the risk of colonic neoplasia (13-20), emphasizing the importance of defining potential autocrine and paracrine pathways for regulation of gastrointestinal epithelial growth by COX. Signaling through the epidermal growth factor receptor (EGFR) induces COX-2 expression, and unregulated overexpression of COX-2 results in a tumorigenic phenotype in the rat intestinal e...

Cyclooxygenase-2 overexpression abrogates the antiproliferative effects of TGF-β

“…So a direct effect of the overexpressed TGF-a on the EGF-receptor seems more likely. An interrelation between COX-2 and growth factors has been shown before for TGF-a and amphiregulin (Coffey et al, 1997;Shao et al, 2004). In this regard, it is interesting that TGF-a-stimulated cells have been used for the isolation and cloning of COX-2 (DuBois et al, 1994) and shows the close interrelation between both systems.…”

Prosurvival and antiapoptotic effects of PGE2in radiation injury are mediated by EP2receptor in intestine

“…In other cell types, including NIH3T3 cells, there is nuclear membrane localization of COX-1 and -2 and PGE 2 (52). In addition, a transporter has been identified that mediates the influx of prostanoids across the plasma membrane (23,29), and Ca-dependent cPLA 2 can be transported to the nuclear envelope (45), Finally, growth factor-induced translocation of COX-2 to the nuclear envelope has been described (8). Furthermore, functional EP 1 , EP 3 , and EP 4 are localized to the nucleus in porcine brain and rat liver (4).…”

Regulation of cyclooxygenase activity by metamizol

“…Cyclooxygenase-2 is induced in a variety of cell types by diverse stimuli including cytokines, growth factors, mito-Ž gens and tumour promoters Kujubu et al, 1991;Lee et al, 1992;DeWitt and Meade, 1993;Ristimaki et al, 1994; . Coffey et al, 1997 . In brain and spinal cord cyclooxy-Ž genase-2 is constitutively expressed McCormak, 1994;.…”