title: Tumor angiogenesis promoted by ex vivo differentiated endothelial progenitor cells is effectively inhibited by an angiogenesis inhibitor, TK1-2.
abstract: Neovascularization plays a critical role in the growth and metastatic spread of tumors and involves recruitment of circulating endothelial progenitor cells (EPC) from bone marrow as well as sprouting of preexisting endothelial cells. In this study, we examined if EPCs could promote tumor angiogenesis and would be an effective cellular target for an angiogenesis inhibitor, the recombinant kringle domain of tissue-type plasminogen activator (TK1-2). When TK1-2 was applied in the ex vivo culture of EPCs isolated from human cord blood, TK1-2 inhibited adhesive differentiation of mononuclear EPCs into endothelial-like cells. In addition, it inhibited the migration of ex vivo cultivated EPCs and also inhibited their adhesion to fibronectin matrix or endothelial cell monolayer. When A549 cancer cells were coimplanted along with ex vivo cultivated EPCs s.c. in nude mice, the tumor growth was increased. However, the tumor growth and the vascular density of tumor tissues increased by coimplanted EPCs were decreased upon TK1-2 treatment. Accordingly, TK1-2 treatment reduced the remaining number of EPCs in tumor tissues and their incorporation into the host vascular channels. In addition, overall expression levels of vascular endothelial growth factor (VEGF) and von Willebrand factor in tumor tissues were decreased upon TK1-2 treatment. Interestingly, strong VEGF expression by implanted EPCs was decreased by TK1-2. Finally, we confirmed in vitro that TK1-2 inhibited VEGF secretion of EPCs. TK1-2 also inhibited endothelial cell proliferation and migration induced by the conditioned medium of EPCs. Therefore, we concluded that EPCs, as well as mature endothelial cells, could be an important target of TK1-2.
authors.affiliation: Cancer Research Institute, Department of Biomedical Science, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Ho-Kyun
authors.initials: HK
authors.lastname: Oh
authors.forename: Jung-Min
authors.initials: JM
authors.lastname: Ha
authors.forename: Eunju
authors.initials: E
authors.lastname: O
authors.forename: Byung Hun
authors.initials: BH
authors.lastname: Lee
authors.forename: Suk Keun
authors.initials: SK
authors.lastname: Lee
authors.forename: Byoung-Shik
authors.initials: BS
authors.lastname: Shim
authors.forename: Yong-Kil
authors.initials: YK
authors.lastname: Hong
authors.forename: Young Ae
authors.initials: YA
authors.lastname: Joe
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D048708:Cell Growth Processes / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects* / Q000473:pathology; D005312:Fetal Blood / Q000166:cytology; D006801:Humans; D018082:Kringles; D008175:Lung Neoplasms / Q000098:blood supply* / Q000188:drug therapy; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000473:pathology; D010446:Peptide Fragments / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D013234:Stem Cells / Q000187:drug effects* / Q000473:pathology; D010959:Tissue Plasminogen Activator / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D020533:Angiogenesis Inhibitors; D010446:Peptide Fragments; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator