title: Silymarin suppresses the PGE2 -induced cell migration through inhibition of EP2 activation; G protein-dependent PKA-CREB and G protein-independent Src-STAT3 signal pathways.
abstract: Silymarin has been known as a chemopreventive agent, and possesses multiple anti-cancer activities including induction of apoptosis, inhibition of proliferation and growth, and blockade of migration and invasion. However, whether silymarin could inhibit prostaglandin (PG) E2 -induced renal cell carcinoma (RCC) migration and what are the underlying mechanisms are not well elucidated. Here, we found that silymarin markedly inhibited PGE2 -stimulated migration. PGE2 induced G protein-dependent CREB phosphorylation via protein kinase A (PKA) signaling, and PKA inhibitor (H89) inhibited PGE2 -mediated migration. Silymarin reduced PGE2 -induced CREB phosphorylation and CRE-promoter activity. PGE2 also activated G protien-independent signaling pathways (Src and STAT3) and silymarin reduced PGE2 -induced phosphorylation of Src and STAT3. Inhibitor of Src (Saracatinib) markedly reduced PGE2 -mediated migration. We found that EP2, a PGE2 receptor, is involved in PGE2 -mediated cell migration. Down regulation of EP2 by EP2 siRNA and EP2 antagonist (AH6809) reduced PGE2 -inudced migration. In contrast, EP2 agonist (Butaprost) increased cell migration and silymarin effectively reduced butaprost-mediated cell migration. Moreover, PGE2 increased EP2 expression through activation of positive feedback mechanism, and PGE2 -induced EP2 expression, as well as basal EP2 levels, were reduced in silymarin-treated cells. Taken together, our study demonstrates that silymarin inhibited PGE2 -induced cell migration through inhibition of EP2 signaling pathways (G protein dependent PKA-CREB and G protein-independent Src-STAT3).
authors.affiliation: Department of Immunology, School of Medicine, Keimyung University, Daegu, South Korea.
authors.forename: Seon Min
authors.initials: SM
authors.lastname: Woo
authors.forename: Kyoung-Jin
authors.initials: KJ
authors.lastname: Min
authors.forename: In Gyeong
authors.initials: IG
authors.lastname: Chae
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Chun
authors.forename: Taeg Kyu
authors.initials: TK
authors.lastname: Kwon
mesh_terms: D000527:Alprostadil / Q000031:analogs & derivatives / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology*; D052117:Benzodioxoles / Q000494:pharmacology; D002292:Carcinoma, Renal Cell / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects* / Q000235:genetics; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015232:Dinoprostone / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015536:Down-Regulation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D019426:Integrases / Q000235:genetics; D007680:Kidney Neoplasms / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D011448:Prostaglandin Antagonists / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering; D058307:Receptors, Prostaglandin E, EP2 Subtype / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012838:Silymarin / Q000494:pharmacology*; D014945:Wound Healing; D044004:Xanthones / Q000494:pharmacology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000975:Antioxidants; D052117:Benzodioxoles; C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; C545644:PTGER2 protein, human; D011448:Prostaglandin Antagonists; D011799:Quinazolines; D034741:RNA, Small Interfering; D058307:Receptors, Prostaglandin E, EP2 Subtype; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D012838:Silymarin; D044004:Xanthones; C053876:6-isopropoxy-9-oxoxanthene-2-carboxylic acid; C515233:saracatinib; D019061:src-Family Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; C045073:Cre recombinase; D019426:Integrases; D019204:GTP-Binding Proteins; D000527:Alprostadil; C048491:butaprost; D015232:Dinoprostone
keywords: EP2; PGE2; migration; renal carcinoma; silymarin