Lymphatic endothelium-specific hyaluronan receptor LYVE-1 is expressed by stabilin-1+, F4/80+, CD11b+ macrophages in malignant tumours and wound healing tissue in vivo and in bone marrow cultures in vitro: implications for the assessment of lymphangiogenesis.
Lymphangiogenesis is a novel prognostic parameter for several cancers that is preferentially quantified by immunohistochemistry of the lymphatic endothelium-specific hyaluronan receptor LYVE-1. Recently, the specificity of LYVE-1 was challenged by serendipitous observations of LYVE-1 expression in rare tissue macrophages. As expression of the hyaluronan receptor-like molecule stabilin-1 is shared by sinusoidal endothelium and macrophages, a thorough analysis of LYVE-1 expression was performed using macrophage-specific markers in vivo and in vitro. In murine tumour models and excisional wound healing, LYVE-1 expression occurred in a subset of CD11b(+), F4/80(+) tissue macrophages that preferentially co-expressed stabilin-1. Upon comparison of single- and double-labelling immunofluorescence, it became apparent that LYVE-1(+) macrophages mimic sprouting and collapsed lymphatic vessels. In vitro, LYVE-1 expression was induced in 25-40% of murine bone marrow-derived macrophages upon exposure to B16F1 melanoma-conditioned medium and IL-4/dexamethasone. By FACS analysis, 11.5% of bone marrow-derived macrophages were LYVE-1(+), stabilin-1(+) double-positive, while 9.9% were LYVE-1(+), stabilin-1(-) and 33.5% were LYVE-1(-), stabilin-1(+). Northern and western analyses confirmed expression of LYVE-1 mRNA and protein in bone marrow-derived macrophages. In the light of the current debate about true endothelial trans-differentiation versus endothelial mimicry of monocytes/macrophages, LYVE-1(+), stabilin-1(+) non-continuous endothelial-like macrophages will require further developmental and functional analyses. In conclusion, the findings imply that LYVE-1 staining must be supplemented by double labelling with macrophage markers in order to differentiate clearly between LYVE-1(+) lymphatics and LYVE-1(+) tumour-infiltrating macrophages. This improved approach will help to clarify the prognostic significance of lymphangiogenesis in malignant tumours.
Department of Dermatology, Venerology, and Allergy, University Medical Centre Mannheim, Ruprecht-Karls University Heidelberg, Germany. kai.schledzewski@haut.ma.uni-heidelberg.de
K
K
Schledzewski
M
M
Falkowski
G
G
Moldenhauer
P
P
Metharom
J
J
Kzhyshkowska
R
R
Ganss
A
A
Demory
B
B
Falkowska-Hansen
H
H
Kurzen
S
S
Ugurel
G
G
Geginat
B
B
Arnold
S
S
Goerdt
D000818:Animals; D000943:Antigens, Differentiation / Q000032:analysis; D001854:Bone Marrow Cells / Q000378:metabolism; D039481:CD11b Antigen / Q000032:analysis; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004729:Endothelium, Lymphatic / Q000378:metabolism*; D005260:Female; D006023:Glycoproteins / Q000378:metabolism*; D042583:Lymphangiogenesis / Q000502:physiology*; D008264:Macrophages / Q000378:metabolism* / Q000502:physiology; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology / Q000556:secondary; D008562:Membrane Glycoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D009363:Neoplasm Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured; D033921:Vesicular Transport Proteins; D014945:Wound Healing / Q000502:physiology; D000098853:Podoplanin
D000943:Antigens, Differentiation; D039481:CD11b Antigen; D015816:Cell Adhesion Molecules, Neuronal; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009363:Neoplasm Proteins; D033921:Vesicular Transport Proteins; C490441:Pdpn protein, mouse; D000098853:Podoplanin; C119248:LYVE1 protein, human; C486732:Stab1 protein, mouse; C492273:LYVE1 protein, mouse; C036763:monocyte-macrophage differentiation antigen