Soluble EP2 neutralizes prostaglandin E2-induced cell signaling and inhibits osteolytic tumor growth.
Prostaglandin E2 (PGE2) plays a key role in osteolytic bone metastasis as well as roles in inflammation, cell growth, and tumor development. PGE2 exerts its effects by binding and activating E-prostanoid receptor (EP). In this study, we propose a new approach for blocking EP-mediated cell signaling using a soluble chimeric EP2 fragment. Mammalian expression vectors encoding several human EP2 cDNAs were introduced into 293 cells and the culture medium was tested for their function as a decoy receptor for PGE2. PGE2 binding assays revealed that culture medium containing the second extracellular region of EP2 (FuEP2/Ex2) had binding activity. FuEP2/Ex2 neutralized PGE2-induced cyclic AMP production, cyclic AMP-responsive element binding protein phosphorylation, and subsequent induction of cyclooxygenase-2, interleukin (IL)-1beta, and IL-6 mRNAs. In human osteoblasts, this culture medium neutralized the induction of receptor activator of nuclear factor-kappaB ligand mRNA. A stable transfectant expressing FuEP2/Ex2 was established from human prostate cancer PC-3 cells (PC3-FuEP2/Ex2). PC3-FuEP2/Ex2 cells grew at similar rates to vector control cells under normal culture conditions, although PGE2-induced growth stimulation was suppressed. Intraosseous injection of PC3-FuEP2/Ex2 cells into the tibia of athymic nude mice revealed that the degrees of tumor growth and osteolysis were decreased compared with control cell-injected mice, with decreased osteoclasts and increased apoptotic cells. Furthermore, the cyclooxygenase-2, IL-1beta, and IL-6 mRNA levels were reduced in the tumor lesions. These data suggest that FuEP2/Ex2 is useful for treating osteolytic bone metastasis and cancers that depend on EP signaling for their growth and development.
Takahashi
Tetsuyuki
T
Department of Molecular and Environmental Pathology, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15, Tokushima-shi, Tokushima, Japan.
Uehara
Hisanori
H
Bando
Yoshimi
Y
Izumi
Keisuke
K
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009369:Neoplasms / Q000473:pathology*; D010010:Osteoclasts / Q000187:drug effects / Q000473:pathology; D010014:Osteolysis / Q000201:enzymology / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D018078:Receptors, Prostaglandin E / Q000378:metabolism*; D058307:Receptors, Prostaglandin E, EP2 Subtype; D015398:Signal Transduction / Q000187:drug effects*; D012995:Solubility / Q000187:drug effects; D013977:Tibia / Q000473:pathology
D017077:Culture Media, Conditioned; D053583:Interleukin-1beta; D015850:Interleukin-6; C545644:PTGER2 protein, human; D010446:Peptide Fragments; C545645:Ptger2 protein, mouse; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D051546:Cyclooxygenase 2; D015232:Dinoprostone