Asch A S, Tepler J, Silbiger S, Nachman R L
Department of Medicine, Cornell University Medical College, New York, New York 10021.
J Biol Chem. 1991 Jan 25;266(3):1740-5.
Tumor cell attachment to thrombospondin (TSP) in the extracellular matrix may be of critical importance in the processes of invasion and hematogenous dissemination. To determine the specific receptor systems that mediate the interaction of tumor cells with insoluble TSP, the attachment of HT1080 fibrosarcoma and C32 and G361 melanoma cells to TSP-coated discs was studied in the presence of heparin, Arg-Gly-Asp-Ser, or antibodies to glycoprotein (GP) IV (CD36, GPIIIb), a TSP receptor. HT1080 and C32 cell attachment to TSP was inhibited by the combination of heparin and a monoclonal (or polyclonal) antibody to GPIV but not by either alone. Heparin alone inhibited cell spreading. Neither control monoclonal antibodies nor the cell attachment peptide Arg-Gly-Asp-Ser inhibited tumor cell attachment to TSP, alone or in the presence of heparin. HT1080 cells attached equally as well to a 140-kDa proteolytic TSP fragment lacking the heparin-binding domain as to intact TSP. A monoclonal antibody to GPIV alone inhibited tumor cell attachment to the heparin-domainless 140-kDa TSP fragment. No attachment to the heparin-binding fragment was observed, but the addition of the heparin fragment to 140-kDa heparin-domainless TSP restored the heparin sensitivity of binding. G361 cells that lack GPIV attached well to TSP but were not inhibited by heparin or anti-GPIV alone or in combination. The combination of heparin and Arg-Gly-Asp-Ser inhibited G361 attachment to TSP. These studies suggest that tumor cells may utilize separate receptor systems in a cooperative manner to adhere to TSP. HT1080 fibrosarcoma and C32 melanoma cells utilize GPIV in concert with a heparin-modulated binding systems to attach and spread on TSP. G361 cells, which lack GPIV expression, attach and spread on TSP using an integrin system as well as a heparin-modulated system.
肿瘤细胞与细胞外基质中的血小板反应蛋白（TSP）的附着在侵袭和血行播散过程中可能至关重要。为了确定介导肿瘤细胞与不溶性TSP相互作用的特定受体系统，研究了在肝素、精氨酸-甘氨酸-天冬氨酸-丝氨酸（Arg-Gly-Asp-Ser）或针对TSP受体糖蛋白（GP）IV（CD36、GPIIIb）的抗体存在的情况下，HT1080纤维肉瘤细胞以及C32和G361黑色素瘤细胞与包被有TSP的圆盘的附着情况。肝素与抗GPIV的单克隆（或多克隆）抗体联合使用可抑制HT1080和C32细胞与TSP的附着，但单独使用其中任何一种均无此作用。单独使用肝素可抑制细胞铺展。无论是对照单克隆抗体还是细胞附着肽Arg-Gly-Asp-Ser，单独使用或与肝素联合使用时，均不能抑制肿瘤细胞与TSP的附着。HT1080细胞对缺乏肝素结合结构域的140 kDa蛋白水解TSP片段的附着与对完整TSP的附着一样好。单独使用抗GPIV单克隆抗体可抑制肿瘤细胞与无肝素结构域的140 kDa TSP片段的附着。未观察到与肝素结合片段的附着，但将肝素片段添加到无肝素结构域的140 kDa TSP中可恢复结合的肝素敏感性。缺乏GPIV的G361细胞能很好地附着于TSP，但单独或联合使用肝素或抗GPIV均不能对其产生抑制作用。肝素与Arg-Gly-Asp-Ser联合使用可抑制G361细胞与TSP的附着。这些研究表明，肿瘤细胞可能以协同方式利用不同的受体系统来附着于TSP。HT1080纤维肉瘤细胞和C32黑色素瘤细胞协同利用GPIV与肝素调节的结合系统来附着于TSP并在其上铺展。缺乏GPIV表达的G361细胞利用整合素系统以及肝素调节系统附着于TSP并在其上铺展。
