Thrombin stimulates melanoma tumor-cell binding to endothelial cells and subendothelial matrix.
Thrombin has been shown to activate tumor-cell adhesion to platelets, fibronectin and von Willebrand factor 2- to 3-fold in vitro, and enhance metastasis 10- to 156-fold in vivo. We therefore elected to determine whether thrombin binds to tumor cells and whether thrombin-treated tumor cells enhance their adhesion to endothelial cells, the first barrier to tumor invasion and metastasis. Thrombin-treated human and hamster melanoma cells (SK-Mel-28 and HM-29) enhanced their adhesion to bovine aortic endothelial cells 2.1- to 2.3-fold, respectively. Similar results were obtained with bovine capillary endothelial cells. Thrombin activation of tumor cells was rapid, reaching its peak 15 min after thrombin activation; and transient, declining to baseline levels by 60 min. 125I-thrombin bound to both SK-Mel-28 and HM-29 cells in a saturation-dependent manner, was inhibitable by unlabelled thrombin, and could be 90% washed away with buffer following 30 min of incubation. Electron microscopy of tumor cells bound to fibronectin-coated millipore filters revealed adhesion of naive as well as thrombin-treated tumor cells to endothelial cells and subendothelial matrix between endothelial cells. Neither mode of adhesion was preferentially enhanced by thrombin-treated tumor cells. Both naive and thrombin-treated SK-Mel-28 cells had the adhesive ligand integrin receptors: alpha 3 beta l (fibronectin, laminin, collagen); alpha 5 beta l (fibronectin); alpha v beta x (vitronectin). Receptors for the beta 2 integrin family (LFA-I and Mac-I) were not found, nor were receptors of the beta 3 integrin family, GPIIIa. The receptor ligands fibronectin and vitronectin were present. None of the above receptors or ligands increased their density or appeared de novo after thrombin stimulation. Thus, 2 melanoma cell lines have thrombin receptors which, when occupied, lead to enhanced adhesion of tumor cells to endothelium and subendothelial matrix.
Klepfish
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Department of Medicine, New York University Medical Center, NY 10016.
Greco
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MA
Karpatkin
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D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002417:Cattle; D002448:Cell Adhesion / Q000187:drug effects; D006224:Cricetinae; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D008854:Microscopy, Electron; D013268:Stimulation, Chemical; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D013917:Thrombin