NEUROTROPHIN RECEPTOR MEDIATED SUPPRESSION OF VEGF

在这一应用中，我们将发展我们的发现，神经营养素受体trk B的表达与甲状腺髓样癌(MTC)的肿瘤进展和血管生成因子VEGF的表达呈负相关。我们发现Trk B在正常C细胞、癌前增生性C细胞和微小的MTC中高表达，但在MTC的后期表达急剧减弱。在人MTC的细胞培养模型中，我们发现trk B的导入和表达导致裸鼠的致瘤性严重受损，并伴随着VEGF表达的显著减少。我们推测在MTC中trk B的表达通过对血管内皮生长因子的负调控来限制肿瘤的生长。提示血管内皮细胞生长因子可能是MTC的重要治疗靶点。此外，阐明trk B下调血管内皮生长因子的信号转导途径可能为控制其他癌症中血管内皮生长因子的产生提供新的靶点。这个应用程序将探索这些可能性。1.我们将直接检测血管内皮生长因子是否对裸鼠MTC细胞的肿瘤形成是必需的。因此，我们将在MTC细胞中引入反义血管内皮生长因子的构建，使其基础上表达高水平的血管内皮生长因子。我们还将在表达trk B基因的MTC细胞中结构性地表达VEGF；这些细胞基本表达低水平的VEGF，很少在裸鼠体内形成肿瘤。肿瘤致瘤性将通过皮下注射到裸鼠体内来监测。接下来，在一系列人类MTC肿瘤中，我们将询问血管内皮生长因子的表达是否与trk B的表达呈负相关。我们还将研究其他血管生成或生长相关基因是否也受到MTC细胞中trk B的调控。2.通过检测血管内皮生长因子转录、RNA稳定性和蛋白质翻译效率，探讨trk B调控血管内皮生长因子表达的机制。3.通过突变型trk B在MTC细胞中的表达，探讨哪些信号转导途径是调控血管内皮生长因子表达所必需的。

In this application, we will develop our finding that expression of the neurotrophin receptor trk B is inversely related to tumor progression and expression of the angiogenesis factor VEGF in medullary thyroid carcinoma (MTC). We have found that trk B is highly expressed in normal C-cells, precancerous hyperplastic C-cells, and microscopic MTC, but trk B expression is sharply diminished in later stages of MTC. in a cell culture model of human MTC, we have shown that introduction and expression of trk B results in severely impaired tumorigenicity in nude mice, accompanied by a marked reduction in VEGF expression. We hypothesize that trk B expression in MTC limits tumor growth by negative regulation of VEGF. This would suggest that VEGF may be an important therapeutic target in MTC. In addition, elucidation of the signal transduction pathways by which trk B downregulates VEGF may lead to new targets for control of VEGF production in other cancers. This application will explore these possibilities. 1. We will examine directly whether VEGF is necessary for tumorigenesis of MTC cells in nude mice. Thus, we will introduce antisense VEGF constructs into MTC cells, which basally express high levels of VEGF. We will also constitutively express VEGF in MTC cells in which we have expressed a trk B gene; these cells basally express low levels of VEGF and rarely form tumors in nude mice. Tumorigenicity will be monitored by subcutaneous injection into nude mice. Next, in a series of human MTC tumors, we will ask whether VEGF expression is inversely correlated with trk B expression. We will also examine whether other angiogenesis or growth related genes are also modulated by trk B in MTC cells. 2. We will investigate the mechanism of trk B control of VEGF expression, by examining VEGF transcription, RNA stability, and protein translation efficiency. 3. We will ask which signal transduction pathways are necessary fork B control of VEGF expression, by expression of mutant forms of trk B in MTC cells.