Loss of the EP2 Prostaglandin E2 Receptor in Immortalized Human Keratinocytes Results in Increased Invasiveness and Decreased Paxillin Expression

Abstract

Prostaglandin E(2) (PGE(2)) receptor subtype EP(2), which is coupled to cAMP metabolism, is known to mediate proliferation of primary human keratinocytes in vitro. The effect of gain or loss of EP(2) receptors in immortalized human keratinocytes (HaCat cells) was examined. HaCat keratinocytes were transfected with sense or anti-sense constructs of the EP(2) receptor. Loss or gain of EP(2) expression was documented by immunoblot and associated changes in agonist-stimulated cAMP production. Loss or gain of EP(2) receptor expression correlated with alterations in plating efficiencies but with modest affects on growth. When cell lines were studied in an organ culture model, anti-sense clones were highly invasive compared with vector controls and sense transfectants. A marked increase in prostaglandin production is commonly seen in malignant lesions. Because prostaglandin receptors are known to undergo ligand-induced receptor down-regulation, we sought to determine whether EP(2) receptor down-regulation results in increased invasiveness. In vector controls, invasiveness was reproduced by ligand-dependent EP(2) receptor down-regulation as assessed by immunohistochemistry. In addition, loss of EP(2) receptor expression was associated with decreased paxillin expression, a critical component of focal adhesion assembly. Thus, down-regulation of EP(2) receptors represents a potential mechanism for neoplastic progression to an invasive phenotype.

Increased sensitivity of asthmatic airway smooth muscle cells to prostaglandin E2 might be mediated by increased numbers of E-prostanoid receptors☆

“…Konger et al 24 found that a decrease in the number of EP2 receptors resulted in a lack of adhesion, and conversely, an increase in EP2 receptor numbers promoted cell adhesion in immortalized human keratinocytes.…”

Targeting Prostaglandin E EP Receptors to Inhibit Metastasis

“…Tumors arising in EP2À/À mice contain fewer CD31 + cells and more evidence of apoptosis, suggesting that PGE 2 -mediated signaling through EP2 drives tumor angiogenesis and apoptosis resistance. In direct contrast, however, loss of EP2 in immortalized keratinocytes was associated with increased invasiveness (20). Also unresolved is the role of EP3.…”

Expression of cyclooxygenase 2, microsomal prostaglandin E synthase 1, and EP receptors is increased in rat oesophageal squamous cell dysplasia and Barrett's metaplasia induced by duodenal contents reflux

“…33 In contrast, Konger et al reported that loss of EP 2 receptor in immortalised human keratinocytes resulted in increased invasiveness. 50 They suggested that this discrepancy may be caused by differences in cell or tissue type, and the presence of negative feedback loop.…”