NEUROTROPHIN RECEPTOR MEDIATED SUPPRESSION OF VEGF

在本应用中，我们将进一步发现神经营养因子受体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。我们发现trk B在正常c细胞、癌前增生性c细胞和显微MTC中高表达，但在MTC晚期，trk B的表达急剧下降。在人MTC细胞培养模型中，我们已经证明，trk B的引入和表达导致裸鼠的致瘤性严重受损，同时VEGF表达显著降低。我们假设trk B在MTC中的表达通过负调控VEGF来限制肿瘤的生长。这表明VEGF可能是MTC的重要治疗靶点。此外，阐明trk B下调VEGF的信号转导途径可能会为控制其他癌症中VEGF的产生提供新的靶点。本应用程序将探索这些可能性。1. 我们将直接研究VEGF在裸鼠MTC细胞的肿瘤发生中是否必要。因此，我们将反义VEGF构建体引入基本表达高水平VEGF的MTC细胞。我们还将在表达了trk B基因的MTC细胞中组成性地表达VEGF；这些细胞基本表达低水平的VEGF，在裸鼠中很少形成肿瘤。裸鼠皮下注射检测致瘤性。接下来，在一系列人类MTC肿瘤中，我们将探讨VEGF表达是否与trk B表达呈负相关。我们还将研究MTC细胞中的其他血管生成或生长相关基因是否也受到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叉B控制VEGF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.