METASTASIS INHIBITION BY FIBRONECTIN-TUMOR INTERACTIONS

肿瘤转移是一个多步骤的过程，涉及多种 肿瘤与宿主因素的关系错综复杂。 最近在癌症研究方面的努力主要集中在 在识别有助于 转移行为，关于通过什么机制理解 肿瘤异质性是产生的，并且基于对宿主的理解 导致转移性疾病的因素。其基本原理是 在这些努力的背后，是对人的生物学的理解 肿瘤转移将催生新的策略，可能会证明 有助于改进治疗方案。纤维连接蛋白，一种主要的 组织和血浆中的非胶原细胞黏附糖蛋白，是 作为主持因素的关键候选人参与调解 实体组织肿瘤的转移。的表达方式 细胞表面的纤维连接蛋白在转化过程中发生变化。 此外，纤维连接蛋白已被证明能促进粘连。 和转移的肿瘤细胞在体外的迁移，它是 早期沉积在围绕新形成的基质中 转移灶。血浆纤维连接蛋白也参与了 同型/异型血栓栓子的形成 当肿瘤细胞进入循环系统时的聚集。 这些栓子中的纤维连接蛋白可以促进肿瘤生长和 促进细胞在血管系统外的迁移 渗出。细胞与纤维连接蛋白的黏附具有复合体 分子基础，由几类细胞表面介导 受体，包括细胞表面糖蛋白、糖脂和 细胞表面蛋白多糖。我们提出的证据表明 体外抑制小鼠实验性转移的实验研究 用纯化的蛋白水解物片段对肿瘤细胞进行预处理 与细胞表面相关的肝素结合的纤维连接蛋白 硫酸盐蛋白多糖(HSPGs)。孤立和部分 对这些蛋白多糖的表征表明， 至少有两个不同的细胞表面HSPG，其中一个可以是 通过外源性肝素从细胞表面提取，以及 第二类，需要胰酶处理才能提取。这些 两类热休克蛋白具有明显不同的侧链和 水动力性质，它们在不同的代谢 费率。两组HSPG都与纤维连接蛋白和层粘连蛋白结合 (基底膜的一种非胶原性糖蛋白)，因此两者 是潜在的细胞表面受体的候选者 细胞外基质黏附蛋白。这项研究建议 在这笔赠款中被设计来分离和表征这些 蛋白多糖，并产生针对热休克蛋白G的抗体 抑制这些分子与纤维连接蛋白的相互作用 还有层粘连蛋白。这些抗体将被用于研究生物 热休克蛋白G介导的肿瘤细胞与肿瘤细胞黏附的意义 细胞外基质。这些研究将包括对 这些抗体对肿瘤细胞黏附、运动、 和体外侵袭，他们还将接受测试，以确定是否有能力 抑制实验性体内转移。

Tumor metastasis is a multistep process that involves a variety of tumor and host factors which are related in a complex manner. Recent efforts in cancer research have largely been concentrated in the areas of identifying phenotypic traits which contribute to metastatic behavior, on understanding mechanisms by which tumor heterogeneity is generated, and on understanding host factors which contribute to metastatic disease. The rationale behind these efforts is that an understanding of the biology of tumor metastasis will spawn new strategies that might prove useful in improving therapeutic schemes. Fibronectin, a major noncollagenous cell adhesion glycoprotein of tissues and plasma, is a key candidate as a host factor which is involved in mediating the metastasis of solid tissue neoplasms. The expression of fibronectin on cell surfaces changes as a result of transformation. Furthermore, fibronectin has been shown to promote the adhesion and migration of metastatic tumor cells in vitro, and it is deposited early in the stroma which surrounds newly forming metastatic foci. Plasma fibronectin could also participate in thromboembolus formation during homotypic/heterotypic aggregation when tumor cells are in the circulatory system. Fibronectin within these emboli could promote tumor growth and facilitate the migration of cells out of the vasculature during extravasation. Cell adhesion to fibronectin has a complex molecular basis and is mediated by several classes of cell surface receptors, including cell surface glycoproteins, glycolipids, and cell surface proteoglycans. We present evidence that experimental metastasis can be inhibited in mice by ex vivo pretreatment of tumor cells with a purified proteolytic fragment of fibronectin which binds to cell surface associated heparan sulfate proteoglycans (HSPGs). Isolation and partial characterization of these proteoglycans demonstrates that there are at least two distinct cell surface HSPGs, one which can be extracted from the cell surface by exogenous heparin, and a second class which requires trypsinization for extraction. These two classes of HSPGs have distinctly different side chains and hydrodynamic properties, and they are metabolized at different rates. Both populations of HSPGs bind to fibronectin and laminin (a noncollagenous glycoprotein of basement membranes) thus both are candidates as potential cell surface receptors for extracellular matrix adhesion proteins. The studies proposed within this grant are designed to isolate and characterize these proteoglycans, and to generate antibodies against the HSPGs which inhibit the interaction of these molecules with fibronectin and laminin. These antibodies will be used to study the biological significance of HSPG mediated tumor cell adhesion to the extracellular matrix. These studies will include an examination of the effects of these antibodies on tumor cell adhesion, motility, and invasion in vitro, and they will also be tested for the ability to inhibit experimental metastasis in vivo.