E Series of Prostaglandin Receptor 2-Mediated Activation of Extracellular Signal-Regulated Kinase/Activator Protein-1 Signaling Is Required for the Mitogenic Action of Prostaglandin E₂in Esophageal Squamous-Cell Carcinoma

Abstract

The use of nonsteroidal anti-inflammatory drugs is associated with a lower risk for esophageal squamous cell carcinoma, in which overexpression of cyclooxygenase-2 (COX-2) is frequently reported. Prostaglandin E 2 (PGE 2 ), a COX-2-derived eicosanoid, is implicated in the promotion of cancer growth. However, the precise role of PGE 2 in the disease development of esophageal squamous cell carcinoma remains elusive. In this study, we investigated the effect of PGE 2 on the proliferation of cultured esophageal squamous cell carcinoma cells (HKESC-1). Results showed that HKESC-1 cells expressed all four series of prostaglandin (EP) receptors, namely, EP1 to EP4 receptors. In this regard, PGE 2 and the EP2 receptor agonist (Ϯ)-15-deoxy-16S-hydroxy-17-cyclobutyl PGE 1 methyl ester (butaprost) markedly increased HKESC-1 cell proliferation. Moreover, the mitogenic effect of PGE 2 was significantly attenuated by RNA interference-mediated knockdown of the EP2 receptor, indicating that this receptor mediated the mitogenic effect of PGE 2 . In this connection, PGE 2 and butaprost induced phosphorylation of extracellular signal-regulated kinases 1/2 (Erk1/2), whose down-regulation by RNA interference significantly attenuated PGE 2 -induced cell proliferation. In addition, PGE 2 and butaprost increased c-Fos expression and activator protein 1 (AP-1) transcriptional activity, which were abolished by the mitogen-activated protein kinase/Erk kinase inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto)-butadiene ethanolate (U0126). AP-1-binding inhibitor curcumin also partially reversed the mitogenic effect of PGE 2 . Taken together, these data demonstrate for the first time that the EP2 receptor mediates the mitogenic effect of PGE 2 in esophageal squamous cell carcinoma via activation of the Erk/AP-1 pathway. This study supports the growth-promoting action of PGE 2 in esophageal squamous cell carcinoma and the potential application of EP2 receptor antagonists in the treatment of this disease.Esophageal cancer is a highly aggressive malignant disease with a 5-year survival rate of 10 to 15% (Jemal et al., 2003). There are two major histological types of esophageal cancer, squamous cell carcinoma and adenocarcinoma, each of which has distinct etiological and pathological characteristics. Although esophageal adenocarcinomas are more prevalent in the West, esophageal squamous cell carcinoma remains the predominant type worldwide (Souza, 2002). The etiology of esophageal squamous cell carcinoma is multifactorial, but cigarette smoking and alcohol consumption are Article, publication date, and citation information can be found at

Prostaglandin E2 promotes cell proliferation via protein kinase C/extracellular signal regulated kinase pathway‐dependent induction of c‐Myc expression in human esophageal squamous cell carcinoma cells

“…We previously reported that PGE 2 significantly increased the phosphorylation of ERK from 10 to 30 min. 7 In the present study, we found that the mitogen-activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor U0126 at the concentration of 10 nmol/l completely abolished PGE 2 -induced c-Myc expression, suggesting that the protein stability of c-Myc was under the control of ERK pathway (Fig. 3c).…”

“…7 Equal amounts of protein (50 lg/lane) were resolved in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and transferred to Hybond C nitrocellulose membranes (GE Healthcare). The membrane was probed with primary antibodies overnight at 4°C and incubated for 1 hr with secondary peroxidase-conjugated antibody at room temperature.…”

“…The expression of EP2 receptor was downregulated using EP2 siRNA, which was employed in our previous study. 7 Cells at 40-60% confluence were transiently transfected with targeted specific siRNA (c-Myc or EP2) or control siRNA by using Lipofectamine 2000 reagent (Invitrogen) according to the manufacturer's instructions. The transfected cells were then serum-deprived for 24 hr before treatment.…”

“…7 For quantification of mRNA expression, realtime PCR was performed using the following primer pairs: c-Myc, 5…”

“…6 Moreover, PGE 2 can directly promote esophageal squamous cell carcinoma cell proliferation. 7 Epidemiological evidence also shows that regular or occasional use of aspirin or other nonsteroidal antiinflammatory drugs (NSAIDs), which inhibit COXdependent production of PGE 2 , is associated with a lower risk for esophageal squamous cell carcinoma. 8 The c-myc protooncogene was originally identified as the cellular homologue to the viral oncogene (v-myc) of the avian myelocytomatosis retrovirus.…”