PubMed · 15337387
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Ornella Flore. Kaposi's sarcoma.. https://doi.org/10.1016/s0140-6736(04)16952-3
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Advances in surgical treatment, including sentinel lymphadenectomy, permit the pathologic staging of regional lymph nodes most likely to contain metastasis by identifying afferent lymphatic channels, which specifically drain the primary tumor site. Recently, a new member of the angiogenic molecule in VEGF family, VEGF-D, has been identified that induces lymphangiogenesis via high-affinity binding to VEGFR-3. VEGF-D is predominantly expressed in lymphatic endothelium. We have previously developed a novel method for the isolation of anatomically-defined lymphatic endothelial cells (LECs) from human sentinel lymphatic channel during SLN biopsy. The effect of VEGF-D on the extracellular signal-regulated kinases (Erk)-1/2 and Akt signaling pathway was examined by Western blot analysis. VEGF-D (500 ng/ml) apparently upregulated phospho-p44/phospho-p42 activity in human isolated LECs by Western blot analysis, while phospho-Akt activity was not at all changed by VEGF-D exposure without the change of total p44/p42 and Akt expression. U0126 (20 microM), the MEK1/2 inhibitor, could completely block the VEGF-D induced phospholylation of Erk1/2 signaling pathway. These data demonstrate that VEGF-D induces p44/p42 in human LECs and suggests that this signaling pathway activation may be important in LEC biology and lymphoangiogenesis, which may lead to the progression of new strategies of cancer treatment.
The expression of platelet-endothelial cell adhesion molecule-1 (PECAM-1) on lymphatic and blood vessels of the human tongue was examined with fluorescence and transmission electron microscopy (TEM). The study used anti-desmoplakins antiserum for light microscopic identification of the lymphatic vessels, plus a pre-embedding immunogold electron microscopic technique for TEM observations. Before making TEM observations, cryostat serial sections were immunostained with anti-desmoplakins or anti-PECAM-1 and then embedded. Semithin sections from each cryostat section were photographed under a light microscope and compared in order to identify the lymphatic vessels expressing PECAM-1. In fluorescence microscopy, PECAM-1 expression on lymphatic vessels was weaker than that on blood vessels. TEM observations showed that PECAM-1 expression on the blood vessels was observed only on the luminal surface of the endothelium. In lymphatic vessels, PECAM-1 expression was found both on the luminal and abluminal surfaces of the endothelium. The density of the PECAM-1 reaction products was lower in lymphatic vessels than in blood vessels. The density of PECAM-1 reaction products on the luminal surface of lymphatic vessels was higher than on the abluminal surfaces. The results suggest that blood vessels are more active than lymphatic vessels in leukocyte migration. The expression of PECAM-1 on the abluminal surface of lymphatic endothelium may allow leukocytes to adhere to the endothelium and interact in their migration from tissue into lymphatic vessels.
In the human body there are about 800 lymph nodes, of which 300 are located in the head and neck area. The lymphatic system begins with initial finger-shaped lymphatic vessels consisting of valveless lymphatic capillaries and precollectors with valves. The precollectors become collectors and transport the lymph to the so-called lymph stems. These vessels lead into the right and left lymphatic duct and into the jugular trunk of the head and neck region. At the end they join into the blood circulation at the junction point of the jugular and subclavian veins. On the basis of the morphology of the initial lymphatics, these are probably the main port of entry of tumor cells. Investigations demonstrate the active invasion into the lymphatic system of melanoma cells. The preference of melanoma cells to adhere to the extracellular fibronectin of the endothelial cells may be a reason for the privileged invasion of the melanoma cells in the lymphatic system, because the extracellular matrix is not protected by a continuous basal lamina like blood vessels. Based on the directed movement of melanoma cells towards the fiber felt, there might be regulative mechanisms influencing the process of targeted adhesion.