title: Inhibition of tumor angiogenesis and melanoma growth by targeting vascular E-selectin.
abstract: OBJECTIVE
  Aggressive human melanomas express, C-X-C chemokine receptor 4 (CXCR4), the receptor for the chemokine, stromal cell-derived factor-1alpha (SDF-1α). The CXCR4-SDF-1α axis has been postulated to increase melanoma invasiveness. We discovered that SDF-1α specifically upregulates E-selectin on endothelial cells, thus tethering circulating endothelial progenitor cells (EPC) and facilitating homing. We investigated the hypothesis that small interfering ribonucleic acid (siRNA)-mediated E-selectin blockade inhibits melanoma angiogenesis and tumor growth.
  
  
  METHODS
  Human melanoma cells overexpressing SDF-1α were xenografted on severe combined immunodeficiency (SCID) mice. SDF-1α expression in cells was measured by enzyme-linked immunosorbent assay (ELISA). In vitro melanoma cell growth was examined by cell proliferation assay. In vivo vascular E-selectin knockdown was achieved by administration of high-volume E-selectin siRNA (100 pmol/180 μL/week × 3 times) and inhibition was validated by immunostaining (N = 6/group, E-Selectin siRNA vs control siRNA). Tumor angiogenesis was quantified (DiI-perfusion and LASER confocal microscopy). EPC homing to tumor vasculature was detected by immunostaining. Explanted in vivo tumor size and weight were measured.
  
  
  RESULTS
  Three melanoma cells tested expressed undetectable levels of SDF-1α. Additional enforced overexpression of SDF-1α (by Lenti-SDF-1α) increased melanoma cell growth both in vitro and in vivo, enhanced EPC homing to tumor tissue, and increased tumor angiogenesis. Knocking-down vascular E-selectin significantly inhibited SDF-1α-induced EPC homing, tumor angiogenesis, and decreased melanoma growth in vivo.
  
  
  CONCLUSIONS
  Downregulation of vascular E-selectin profoundly inhibits EPC homing, tumor angiogenesis, and tumor growth in human melanoma xenograft murine model, potentially by suppression of E-selectin-mediated EPC-endothelial cells interactions/homing. These findings identify E-selectin as a novel target for inhibition of melanoma angiogenesis and tumor growth.
authors.affiliation: Department of Surgery, Miller School of Medicine, University of Miami, Miami, FL 33101, USA.
authors.forename: Zhao-Jun
authors.initials: ZJ
authors.lastname: Liu
authors.forename: Runxia
authors.initials: R
authors.lastname: Tian
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Weijun
authors.initials: W
authors.lastname: An
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhuge
authors.forename: Alan S
authors.initials: AS
authors.lastname: Livingstone
authors.forename: Omaida C
authors.initials: OC
authors.lastname: Velazquez
mesh_terms: D000818:Animals; D054377:Chemokine CXCL12 / Q000187:drug effects* / Q000378:metabolism; D015536:Down-Regulation; D019040:E-Selectin / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008546:Melanoma, Experimental / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000627:therapeutic use*; D014183:Transplantation, Heterologous; D016896:Treatment Outcome; D015854:Up-Regulation
chemical_list: D054377:Chemokine CXCL12; D019040:E-Selectin; D034741:RNA, Small Interfering