title: Direct growth-inhibitory effects of prostaglandin E2 in pancreatic cancer cells in vitro through an EP4/PKA-mediated mechanism.
abstract: There is strong evidence linking inflammation and the development of pancreatic ductal adenocarcinoma. Cyclooxygenase-2 (COX-2) and COX-2-derived PGE2are overexpressed in human and murine pancreatic ductal adenocarcinoma. Several studies have demonstrated an important role of COX-2-derived PGE2in tumor-stroma interactions; however, the direct growth effects of prostaglandin E2(PGE2) on pancreatic ductal adenocarcinoma cells is less well defined. Our aim was to investigate the effects of PGE2on pancreatic ductal adenocarcinoma cell growth and to characterize the underlying mechanisms.
  
  
  
  Human pancreatic ductal adenocarcinoma cell lines, Panc-1 and MIA PaCa-2, were treated with PGE2in varying doses (0-10 μM). Effects on the phosphorylation of ERK1/2 were evaluated by Western blot. Colony formation was observed for cells treated with PGE2for 11 days. DNA synthesis was determined by (3H)-thymidine incorporation assay. Gene expression of E-type prostaglandin (EP)2/EP4 receptors and their correlation with survival in patients with pancreatic ductal adenocarcinoma were assessed using the RNA-Seq data set from The Cancer Genome Atlas Research Network.
  
  
  
  PGE2decreased the size and number of colonies in Panc-1 but not MIA PaCa-2 cells. In the Panc-1 cells, PGE2activated PKA/CREB and decreased phosphorylation of ERK1/2, which was reversed by an EP4 receptor antagonist, while an EP2 receptor antagonist had no effect. In contrast, in MIA PaCa-2 cells, PGE2had no effect on ERK1/2 phosphorylation. Treatment of both Panc-1 and MIA PaCa-2 cells with forskolin/IBMX decreased ERK1/2 phosphorylation. Finally, PGE2decreased DNA synthesis only in Panc-1 cells, which was reversed by an EP4 receptor antagonist. In human pancreatic ductal adenocarcinoma, high EP2 and low EP4 gene expression was correlated to worse median overall survival (15.6 vs 20.8 months, log-rank P = .017).
  
  
  
  Our study provides evidence that PGE2can inhibit directly pancreatic ductal adenocarcinoma cell growth through an EP4-mediated mechanism. Together with our gene expression and survival analysis, this observation suggests a protective role of EP4 receptors in human pancreatic ductal adenocarcinoma that expresses E-type prostaglandin receptors.
authors.affiliation: Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA; Klinik für Allgemein- und Viszeralchirurgie, Universitätsklinikum Freiburg, Freiburg, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Schmidt
authors.affiliation: Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: James
authors.initials: J
authors.lastname: Sinnett-Smith
authors.affiliation: Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Steven
authors.initials: S
authors.lastname: Young
authors.affiliation: Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Hui-Hua
authors.initials: HH
authors.lastname: Chang
authors.affiliation: Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: O Joe
authors.initials: OJ
authors.lastname: Hines
authors.affiliation: Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: David W
authors.initials: DW
authors.lastname: Dawson
authors.affiliation: Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Enrique
authors.initials: E
authors.lastname: Rozengurt
authors.affiliation: Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA. Electronic address: GEibl@mednet.ucla.edu.
authors.forename: Guido
authors.initials: G
authors.lastname: Eibl
mesh_terms: D000368:Aged; D015153:Blotting, Western; D021441:Carcinoma, Pancreatic Ductal / Q000473:pathology; D045744:Cell Line, Tumor / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000187:drug effects / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000166:cytology; D010190:Pancreatic Neoplasms / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D058306:Receptors, Prostaglandin E, EP1 Subtype / Q000235:genetics*; D058307:Receptors, Prostaglandin E, EP2 Subtype / Q000187:drug effects / Q000378:metabolism*; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000187:drug effects / Q000378:metabolism; D012680:Sensitivity and Specificity
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C545635:PTGER1 protein, human; D058306:Receptors, Prostaglandin E, EP1 Subtype; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; C015482:protein kinase modulator; D051546:Cyclooxygenase 2; D015232:Dinoprostone