NEUROTROPHIN RECEPTOR MEDIATED SUPPRESSION OF VEGF

在本申请中，我们将发展我们的发现，即神经营养因子受体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。我们已经发现，trk B在正常C细胞、癌前增生C细胞和显微镜下的MTC中高度表达，但在MTC的晚期阶段，trk B表达急剧减少。在人MTC细胞培养模型中，我们已经表明trk B的引入和表达导致裸鼠中致瘤性严重受损，伴随着VEGF表达的显著降低。我们推测MTC中trk B的表达通过VEGF的负调节限制肿瘤生长。这表明VEGF可能是MTC的重要治疗靶点。此外，trk B下调VEGF的信号转导途径的阐明可能导致在其他癌症中控制VEGF产生的新靶点。本应用程序将探索这些可能性。1.我们将直接研究VEGF是否是MTC细胞在裸鼠中的肿瘤发生所必需的。因此，我们将反义VEGF构建体引入MTC细胞，其基本上表达高水平的VEGF。我们还将在MTC细胞中组成型表达VEGF，其中我们已经表达了trk B基因;这些细胞基本表达低水平的VEGF，并且很少在裸鼠中形成肿瘤。将通过皮下注射至裸鼠中监测致瘤性。接下来，在一系列人MTC肿瘤中，我们将研究VEGF表达是否与trk B表达负相关。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的调节。2.我们将通过检测VEGF转录、RNA稳定性和蛋白质翻译效率来研究trk B控制VEGF表达的机制。3.我们将通过在MTC细胞中表达突变形式的trk B来询问哪些信号转导途径是VEGF表达的B调控所必需的。

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.