title: Lymphocyte-facilitated tumour cell adhesion to endothelial cells: the role of high affinity leucocyte integrins.
abstract: OBJECTIVE
  Lymphocytes transiently express an active form of the beta_2 integrin LFA-1 (LFA-1Af) which has conformational changes in extracellular domains enabling higher affinity binding to the ligand ICAM-1. In this study, we investigated the role of lymphocytes bearing LFA-1Af as potential mediators of binding of ICAM-1-positive tumour cells to endothelium.
  
  
  METHODS
  LFA-1 expression on 51Cr-PBLs was modulated in order to express high affinity LFA-1Af and conjugates were formed with 35S-labelled COLO526. The binding of the conjugates to resting or IL-1beta-stimulated human umbilical vein endothelial cells (HUVECs) was then assessed via a modified radioactive HUVEC binding assay. In addition, the binding of PBL-COLO526 conjugates to HUVECs was demonstrated by confocal microscopy.
  
  
  RESULTS
  The binding of COLO526 to endothelial cells did not change significantly between unstimulated and stimulated HUVECs. In addition, pre-incubating the COLO526 with fresh PBLs did not significantly alter the binding of COLO526 to resting or activated HUVECs; whereas, in the presence of PBLs with LFA-1Af, the COLO526 conjugate binding dramatically increased from basal levels to 41% on resting HUVECs and 81% on stimulated HUVECs. COLO526-PBL(LFA-1Af) conjugate adhesion to stimulated HUVECs was inhibited by blocking antibody to LFA-1 (50%), VLA-4 (32%) or L-selectin (40%). Antibodies to the HUVEC adhesion molecules ICAM-1, VCAM-1 and E-selectin also inhibited COLO526-PBL(LFA-1Af) conjugate binding to activated HUVECs by 79, 60 and 73%, respectively.
  
  
  CONCLUSIONS
  PBLs bearing LFA-1Af can enhance COLO526 adhesion to both resting and activated HUVECs. Furthermore, blocking studies demonstrate that a range of pathways are involved in this phenomenon (LFA-1/ICAM-1, VLA4/VCAM-1, L-selectin/E-selectin). These studies have identified a novel alternative pathway for lymphocyte-facilitated tumour cell adhesion to endothelial cells.
authors.affiliation: Immunology Unit, Division of Laboratory Medicine, Austin and Repatriation Medical Centre, Melbourne, Victoria, Australia. pneeson@mail.med.upenn.edu
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Neeson
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Thurlow
authors.forename: Gary P
authors.initials: GP
authors.lastname: Jamieson
authors.forename: Chris
authors.initials: C
authors.lastname: Bradley
mesh_terms: D019138:Antibodies, Blocking / Q000494:pharmacology; D002296:Carcinosarcoma / Q000276:immunology / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D039041:Integrin alpha4beta1 / Q000276:immunology; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007375:Interleukin-1 / Q000494:pharmacology; D019041:L-Selectin / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000096:biosynthesis* / Q000276:immunology; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D018613:Microscopy, Confocal; D013462:Sulfur Radioisotopes; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms / Q000276:immunology / Q000378:metabolism*
chemical_list: D019138:Antibodies, Blocking; D039041:Integrin alpha4beta1; D007375:Interleukin-1; D016169:Lymphocyte Function-Associated Antigen-1; D013462:Sulfur Radioisotopes; D018799:Intercellular Adhesion Molecule-1; D019041:L-Selectin