METASTASIS INHIBITION BY FIBRONECTIN-TUMOR INTERACTIONS

肿瘤转移是一个多步骤的过程，涉及多种肿瘤细胞， 肿瘤和宿主因子以复杂的方式相关。 最近在癌症研究方面的努力主要集中在 在鉴定有助于 转移行为，了解机制， 肿瘤异质性的产生，并在了解宿主 导致转移性疾病的因素。 的理由 在这些努力的背后， 肿瘤转移将产生新的策略， 可用于改善治疗方案。 纤维连接蛋白，一种主要的 组织和血浆的非胶原细胞粘附糖蛋白， 一个关键的候选人作为一个主机因素，参与调解 实体组织肿瘤的转移。 的表达 细胞表面的纤连蛋白由于转化而改变。 此外，纤连蛋白已被证明可以促进粘附 和转移性肿瘤细胞在体外的迁移， 沉积在围绕着新形成的基质中 转移灶 血浆纤连蛋白也可能参与 同型/异型血栓形成 肿瘤细胞在循环系统中的聚集。 这些栓子中的纤维连接蛋白可以促进肿瘤生长， 促进细胞迁移出脉管系统， 外渗 细胞与纤连蛋白的粘附具有复杂的 分子基础，并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。 我们提供的证据表明 通过离体方法可以抑制小鼠的实验性转移 用纯化的蛋白水解片段预处理肿瘤细胞 与细胞表面相关的肝素结合的纤连蛋白 硫酸化蛋白聚糖（HSPG）。 隔离和部分隔离 这些蛋白聚糖的表征表明， 是至少两种不同的细胞表面HSPG，一种可以是 通过外源性肝素从细胞表面提取， 第二类，其需要胰蛋白酶消化以进行提取。 这些 两类HSPG具有明显不同的侧链， 水动力学特性，它们在不同的代谢条件下代谢， rates. 两种HSPG群体均与纤连蛋白和层粘连蛋白结合 （基底膜的非胶原糖蛋白）因此， 是潜在的细胞表面受体， 细胞外基质粘附蛋白。 建议的研究 在这个补助金内，旨在分离和表征这些 蛋白聚糖，并产生针对HSPG的抗体 其抑制这些分子与纤连蛋白的相互作用 和层粘连蛋白。 这些抗体将用于研究生物学 热休克蛋白G介导的肿瘤细胞粘附对肿瘤细胞增殖的影响 细胞外基质 这些研究将包括审查 这些抗体对肿瘤细胞粘附，运动， 和体外入侵，他们也将被测试的能力， 抑制体内实验性转移。

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.