title: Gap junction coupling is required for tumor cell migration through lymphatic endothelium.
abstract: OBJECTIVE
  The lymphatic vasculature is a well-established conduit for metastasis, but the mechanisms by which tumor cells interact with lymphatic endothelial cells (LECs) to facilitate escape remain poorly understood. Elevated levels of the lymphangiogenic peptide adrenomedullin are found in many tumors, and we previously characterized that its expression is necessary for lymphatic vessel growth within both tumors and sentinel lymph nodes and for distant metastasis.
  
  
  RESULTS
  This study used a tumor cell-LEC coculture system to identify a series of adrenomedullin-induced events that facilitated transendothelial migration of the tumor cells through a lymphatic monolayer. High levels of adrenomedullin expression enhanced adhesion of tumor cells to LECs, and further analysis revealed that adrenomedullin promoted gap junction coupling between LECs as evidenced by spread of Lucifer yellow dye. Adrenomedullin also enhanced heterocellular gap junction coupling as demonstrated by Calcein dye transfer from tumor cells into LECs. This connexin-mediated gap junction intercellular communication was necessary for tumor cells to undergo transendothelial migration because pharmacological blockade of this heterocellular communication prevented the ability of tumor cells to transmigrate through the lymphatic monolayer. In addition, treatment of LECs with adrenomedullin caused nuclear translocation of β-catenin, a component of endothelial cell junctions, causing an increase in transcription of the downstream target gene C-MYC. Importantly, blockade of gap junction intercellular communication prevented β-catenin nuclear translocation.
  
  
  CONCLUSIONS
  Our findings indicate that maintenance of cell-cell communication is necessary to facilitate a cascade of events that lead to tumor cell migration through the lymphatic endothelium.
authors: From the Department of Cell Biology and Physiology (N.O.K., K.M.C.) and Department of Genetics (K.M.C.), University of North Carolina at Chapel Hill.
authors: Natalie O
authors: NO
authors: Karpinich
authors: From the Department of Cell Biology and Physiology (N.O.K., K.M.C.) and Department of Genetics (K.M.C.), University of North Carolina at Chapel Hill. kathleen_caron@med.unc.edu.
authors: Kathleen M
authors: KM
authors: Caron
mesh_terms: D053607:Adrenomedullin / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002450:Cell Communication / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D004729:Endothelium, Lymphatic / Q000166:cytology* / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008207:Lymphatic Metastasis / Q000473:pathology / Q000503:physiopathology; D009360:Neoplastic Cells, Circulating / Q000187:drug effects / Q000473:pathology*; D014407:Tumor Cells, Cultured; D051176:beta Catenin / Q000187:drug effects / Q000378:metabolism
chemical_list: D051176:beta Catenin; D053607:Adrenomedullin
keywords: connexins; endothelial cells; gap junctions; neoplasm metastasis