Promotion Of Metastatic Processes By Laminin And Laminin

进行研究以确定肿瘤生长和转移的机制，并开发新的人类癌症动物模型。我们已经发现，基底膜提取物（Matrigel）当与人乳腺和前列腺肿瘤细胞（其在小鼠中不能很好地生长）预混合时促进肿瘤发生和生长。我们已经能够从小鼠体内生长的肿瘤中培养出新的高度分化的人类肿瘤细胞系，包括某些结肠和前列腺细胞系。层粘连蛋白是一种主要的基底膜成分，已被发现促进肿瘤细胞的恶性表型。层粘连蛋白粘附的黑素瘤和结肠癌细胞比非粘附细胞或亲本细胞更恶性。已经鉴定了多种具有生物活性的层粘连蛋白衍生的合成肽。来自α 5链的一种肽A5 G27通过以显性负性方式结合其受体来阻断乳腺癌生长和体内血管生成。我们现在已经开始进一步开发这种肽作为治疗药物（与肽化学家合作），并确定其信号通路。另一种肽，LQVQLSIR，增加各种肿瘤细胞类型（乳腺癌，黑色素瘤和卵巢癌）的转移，并与受体CD 44结合。这是迄今为止发现的促进肿瘤转移的层粘连蛋白上的唯一位点。该肽的受体已经被其他人证明在广泛的肿瘤细胞类型的转移中是重要的。我们还发现，CD 44在粘附选择该肽的黑色素瘤细胞中更高，并且当这些肽粘附选择的细胞注射到小鼠中时，在没有添加肽的情况下观察到更多的转移。使用抗体阵列技术，我们已经确定了由这种肽调控的基因。这些基因之一，纤连蛋白，在迄今为止测试的所有肿瘤细胞类型中被该肽上调。我们现在对这种肽如何促进肿瘤转移有了更好的了解。我们的目标是确定参与肿瘤生长和转移的分子机制。我们的方法是（1）选择和分离高度恶性细胞，（2）确定其细胞层粘连蛋白受体，（3）确定层粘连蛋白上促进或减少恶性表型的其他序列，（4）确定恶性肿瘤相关基因，（5）确定骨中负责前列腺癌和乳腺癌器官特异性转移的分子。我们研究了几种模型，包括B16 F10黑色素瘤细胞、乳腺、前列腺和唾液腺肿瘤细胞。 我们是第一个证明雌激素促进血管生成的人。我们现在已经开始确定雌激素促进血管生成和恶性肿瘤的机制。利用基因分析，我们已经确定了几个重要的基因在雌激素的功能。我们发现，雌激素上调乙酰肝素酶降解细胞外基质。因此，这种酶通过从基质中释放许多生长因子来增加生长因子活性。雌激素也会降低某种可溶性生长因子受体VEGFR-1的表达，VEGFR-1是一种“诱饵”。可溶性VEGFR-1的表达减少会增加可用的VEGF（血管内皮细胞生长因子）的量。生长因子VEGF通过直接作用于肿瘤细胞促进血管生成和肿瘤生长。因此，雌激素通过多种机制积极调节恶性肿瘤中的“血管生成开关”。

Studies are conducted to define the mechanisms involved in tumor growth and metastasis and to develop new animal models of human cancers. We have found that a basement membrane extract (Matrigel) when premixed with human breast and prostate tumor cells (which do not grow well in mice) promotes tumor incidence and growth. We have been able to culture new highly differentiated human tumor cell lines from the tumors grown in mice, including certain colon and prostate cell lines. Laminin, a major basement membrane component, has been found to promote the malignant phenotype of tumor cells. Laminin-adherent melanoma and colon cancer cells are more malignant than either the non-adherent cells or the parental cells. Various biologically active laminin-derived synthetic peptides have been identified. One peptide A5G27 from the alpha 5 chain blocks breast cancer growth and angiogenesis in vivo by binding in a dominant-negative manner to its receptor. We have now begun to further develop this peptide as a therapeutic (working with a peptide chemist) and to define its signaling pathways. Another peptide, LQVQLSIR, increases metastases in various tumor cell types (breast cancer, melanoma, and ovarian cancer) and binds to the receptor CD44. This is the only site on laminin found to date that promotes tumor metastasis. The receptor for this peptide has already been shown by others to be important in metastasis in a broad range of tumor cell types. We also find that CD44 is higher in melanoma cells that are adhesion-selected to this peptide, and when these peptide-adhesion-selected cells are injected into mice, more metastases are observed in the absence of added peptide. Using antibody array technology, we have identified genes regulated by this peptide. One of these genes, fibronectin, is upregulated by this peptide in all tumor cell types tested to date. We now have a better understanding of how this peptide promotes tumor metastasis. Our goal is to define the molecular mechanisms involved in tumor growth and metastases. Our approach is to (1) select for and isolate highly malignant cells, (2) define their cellular laminin receptors, (3) identify additional sequences on laminin which promote or reduce the malignant phenotype, (4) identify genes involved in malignancy, and (5) define molecules in bone responsible for prostate and breast cancer organ-specific metastases. We work with several models, including B16F10 melanoma cells, breast, prostate, and salivary gland tumor cells. We were the first to show that estrogen promotes angiogenesis. We now have begun to define the mechanisms by which estrogen promotes angiogenesis and malignancy. Using gene analysis, we have identified several genes important in the function of estrogen. We find that estrogen upregulates the enzyme heparanase which degrades the extracellular matrix. This enzyme thus increases growth factor activity by release of many growth factors from the matrix. Estrogen also down decreases the expression of a certain soluble growth factor receptor, VEGFR-1, that acts as a "decoy". Decreased expression of soluble VEGFR-1 increases the amount of VEGF (vascular endothelial cell growth factor)available. The growth factor, VEGF, promotes both angiogenesis and tumor growth by directly acting on the tumor cells. Thus, estrogen actively regulates the "angiogenic switch" in malignancy by multiple mechanisms.