title: Regulation of COX-2 mediated signaling by alpha3 type IV noncollagenous domain in tumor angiogenesis.
abstract: Human alpha3 chain, a noncollagenous domain of type IV collagen [alpha3(IV)NC1], inhibits angiogenesis and tumor growth. These biologic functions are partly attributed to the binding of alpha3(IV)NC1 to alphaVbeta3 and alpha3beta1 integrins. alpha3(IV)NC1 binds alphaVbeta3 integrin, leading to translation inhibition by inhibiting focal adhesion kinase/phosphatidylinositol 3-kinase/Akt/mTOR/4E-BP1 pathways. In the present study, we evaluated the role of alpha3beta1 and alphaVbeta3 integrins in tube formation and regulation of cyclooxygenase-2 (COX-2) on alpha3(IV)NC1 stimulation. We found that although both integrins were required for the inhibition of tube formation by alpha3(IV)NC1 in endothelial cells, only alpha3beta1 integrin was sufficient to regulate COX-2 in hypoxic endothelial cells. We show that binding of alpha3(IV)NC1 to alpha3beta1 integrin leads to inhibition of COX-2-mediated pro-angiogenic factors, vascular endothelial growth factor, and basic fibroblast growth factor by regulating IkappaBalpha/NFkappaB axis, and is independent of alphaVbeta3 integrin. Furthermore, beta3 integrin-null endothelial cells, when treated with alpha3(IV)NC1, inhibited hypoxia-mediated COX-2 expression, whereas COX-2 inhibition was not observed in alpha3 integrin-null endothelial cells, indicating that regulation of COX-2 by alpha3(IV)NC1 is mediated by integrin alpha3beta1. Our in vitro and in vivo findings demonstrate that alpha3beta1 integrin is critical for alpha3(IV)NC1-mediated inhibition of COX-2-dependent angiogenic signaling and inhibition of tumor progression.
authors.affiliation: Cell Signaling and Tumor Angiogenesis Laboratory, Department of Genetics, Boys Town National Research Hospital, Omaha, NE 68131, USA.
authors.forename: Chandra Shekhar
authors.initials: CS
authors.lastname: Boosani
authors.forename: Arjuna P
authors.initials: AP
authors.lastname: Mannam
authors.forename: Dominic
authors.initials: D
authors.lastname: Cosgrove
authors.forename: Rita
authors.initials: R
authors.lastname: Silva
authors.forename: Kairbaan M
authors.initials: KM
authors.lastname: Hodivala-Dilke
authors.forename: Venkateshwar G
authors.initials: VG
authors.lastname: Keshamouni
authors.forename: Akulapalli
authors.initials: A
authors.lastname: Sudhakar
mesh_terms: D020533:Angiogenesis Inhibitors / Q000235:genetics / Q000494:pharmacology; D000818:Animals; D002448:Cell Adhesion; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002478:Cells, Cultured; D024141:Collagen Type IV / Q000235:genetics / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000737:chemistry / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D039201:Integrin alpha3beta1 / Q000502:physiology*; D039302:Integrin alphaVbeta3 / Q000037:antagonists & inhibitors*; D008297:Male; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009369:Neoplasms; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000378:metabolism*; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism; D018243:Teratocarcinoma / Q000098:blood supply / Q000188:drug therapy / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D020533:Angiogenesis Inhibitors; D024141:Collagen Type IV; D052246:Cyclooxygenase 2 Inhibitors; D039201:Integrin alpha3beta1; D039302:Integrin alphaVbeta3; D016328:NF-kappa B; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D051546:Cyclooxygenase 2