Lamszus K, Joseph A, Jin L, Yao Y, Chowdhury S, Fuchs A, Polverini P J, Goldberg I D, Rosen E M
Department of Radiation Oncology, Long Island Jewish Medical Center, New Hyde Park, New York 11040, USA.
Am J Pathol. 1996 Sep;149(3):805-19.
Scatter factor (SF) is an angiogenic growth factor that stimulates motility and invasion of carcinoma cells. SF is present in the extracellular matrix (ECM) of breast cancers, where it might act to promote tumor cell invasion and angiogenesis. To investigate how SF is incorporated into the ECM, we studied the binding of SF to various ECM components using a solid-phase binding assay based on the SF enzyme-linked immunosorbent assay. We found that SF binds to a variety of ECM molecules, with different binding capacities. The highest SF binding capacities were observed for thrombospondin-1 (TSP-1), fibronectin (Fn), and heparan sulfate proteoglycan, although SF did not bind to albumin. Mature two-chain SF and precursor single-chain SF bound approximately equally well to TSP-1 and Fn. Moreover, two SF alpha-chain peptides (NK1 and NK2) both bound to TSP-1 and Fn, suggesting that the whole SF molecule is not required for binding. Based on binding competition assays, TSP-1 exhibited higher affinity for SF than did nine other ECM molecules, including Fn and heparan sulfate proteoglycan. Although heparin in solution potently inhibited the binding of SF to TSP-1-coated surfaces, even very high concentrations of heparin could not elute SF already bound to TSP-1. SF binding was modulated by binding interactions among ECM molecules (TSP-1-Fn, TSP-1-collagen I, and Fn-collagen I), suggesting that the matrix capacity to bind SF depends upon its exact composition. SF bound in a dose-dependent fashion to ECMs secreted by three human breast carcinoma cell lines. Binding of SF to matrices from all three cell lines was significantly inhibited by preincubation of the matrices with antibodies against TSP-1, whereas antibodies against several other ECM components were less effective or ineffective in inhibiting SF binding. In addition, TSP-1 markedly inhibited chemotaxis of microvascular endothelial cells toward SF and SF-induced angiogenesis in the rat cornea neovascularization assay. Our findings suggest that 1) SF interacts with a variety of ECM components, 2) high affinity SF-TSP-1 interactions may mediate the binding of SF to the breast cancer matrix, and 3) the SF-TSP-1 interaction may contribute to modulation of angiogenesis. Possible implications of these findings for tumor angiogenesis are discussed.
散射因子（SF）是一种血管生成生长因子，可刺激癌细胞的运动和侵袭。SF存在于乳腺癌的细胞外基质（ECM）中，在那里它可能促进肿瘤细胞的侵袭和血管生成。为了研究SF如何整合到ECM中，我们使用基于SF酶联免疫吸附测定的固相结合测定法，研究了SF与各种ECM成分的结合。我们发现SF与多种ECM分子结合，具有不同的结合能力。血小板反应蛋白-1（TSP-1）、纤连蛋白（Fn）和硫酸乙酰肝素蛋白聚糖的SF结合能力最高，尽管SF不与白蛋白结合。成熟的双链SF和前体单链SF与TSP-1和Fn的结合能力大致相同。此外，两种SFα链肽（NK1和NK2）均与TSP-1和Fn结合，这表明结合并不需要完整的SF分子。基于结合竞争测定，TSP-1对SF的亲和力高于其他九种ECM分子，包括Fn和硫酸乙酰肝素蛋白聚糖。尽管溶液中的肝素能有效抑制SF与包被TSP-1的表面的结合，但即使是非常高浓度的肝素也无法洗脱已与TSP-1结合的SF。ECM分子之间的结合相互作用（TSP-1-Fn、TSP-1-胶原蛋白I和Fn-胶原蛋白I）调节了SF的结合，这表明基质结合SF的能力取决于其确切组成。SF以剂量依赖的方式与三种人乳腺癌细胞系分泌的ECM结合。用抗TSP-1抗体预先孵育基质可显著抑制SF与所有三种细胞系的基质的结合，而针对其他几种ECM成分的抗体在抑制SF结合方面效果较差或无效。此外，在大鼠角膜新生血管形成试验中，TSP-1显著抑制微血管内皮细胞对SF的趋化作用以及SF诱导的血管生成。我们的研究结果表明：1）SF与多种ECM成分相互作用；2）高亲和力的SF-TSP-1相互作用可能介导SF与乳腺癌基质的结合；3）SF-TSP-1相互作用可能有助于调节血管生成。本文讨论这些发现对肿瘤血管生成的可能影响。
