REGULATION OF PAR 4 BY ONCOGENIC RAS

致癌 RAS 对 PAR 4 的调节

• 批准号: 6045418
• 负责人: Vivek M Rangnekar
• 金额: $ 23.71万
• 依托单位: UNIVERSITY OF KENTUCKY
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-01 至 2004-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6045418
• 关键词: 3T3 cells; AP1 protein; BCL2 gene /protein; apoptosis; athymic mouse; fos protein; mitogen activated protein kinase; neoplastic transformation; nuclear factor kappa beta; oncogenes; oncoproteins; prostate neoplasms; protein structure function; transcription factor; tumor suppressor proteins

Prostate apoptosis response-4 (Par-4) is a leucine zipper domain- containing protein that is required for stimulus-dependent apoptosis in both prostatic and non-prostatic cells. This widely expressed protein is not sufficient on its own to induce apoptosis, but can sensitize the cells to the action of apoptotic stimuli. We examined various tumors and corresponding normal tissues for Par-4 protein expression, and found that Par-4 levels are quantitatively decreased in renal cell carcinomas (RCCs) and pancreatic cancer but not in prostate cancer relative to the corresponding normal cells. This suggested that Par-4 down-regulation may play a role in the process of malignant transformation in certain cancers. Immortalized fibroblasts expressing the ras oncogene serve as an excellent model to study signaling pathways essential for transformation and tumorigenesis. Our preliminary studies in immortalized fibroblasts suggested that endogenous Par-4 protein expression is diminished by oncogenic Ras, and that restoration of Par-4 inhibits oncogenic Ras- inducible transformation without altering cell viability. These findings led to the hypothesis that down-regulation of Par-4 by oncogenic Ras is necessary for transformation because Par-4 may inhibit key oncogenic Ras-inducible pathway(s) that are required for transformation. Three specific aims proposed to test this hypothesis are: (1) To determine the molecular mechanism(s) by which oncogenic ras down-regulates Par-4; (2) To determine the molecular mechanism(s) by which replenishment of Par- 4 prevents the process of transformation; and (3) To identify the structural domains of Par-4 that regulate suppression of transformation. The signaling mechanisms invoked by oncogenic Ras and Par-4 will be elucidated in fibroblasts in vitro, and the findings will be extended to examine whether the structural domains of Par-4 that inhibit transformation, also prevent oncogenic ras-inducible tumor growth in fibroblast and epithelial cell backgrounds in vivo. The proposed studies will help dissect out the functional domains of Par-4 that regulate the anti- transformation and apoptosis-sensitization properties of the protein. Thus, these studies are expected to uncover the signaling pathways used by oncogenic Ras to overcome the mechanisms that interfere with transformation and identify novel mechanisms that are utilized by Par-4 to block cellular transformation or tumor growth. The findings may help future studies to explore the feasibility of using Par-4 over-expression for tumor growth control.

前列腺腺细胞凋亡反应-4(PAR-4)是一种含有亮氨酸拉链结构域的蛋白，在前列腺癌和非前列腺癌细胞的刺激依赖性凋亡中都是必需的。这种广泛表达的蛋白质本身不足以诱导细胞凋亡，但可以使细胞对凋亡刺激的作用敏感。我们检测了各种肿瘤和相应的正常组织中PAR-4蛋白的表达，发现相对于相应的正常细胞，PAR-4在肾细胞癌(RCC)和胰腺癌中的表达水平定量降低，而在前列腺癌中的表达水平没有变化。这提示PAR-4的下调可能在某些癌症的恶变过程中起作用。表达ras癌基因的永生化成纤维细胞是研究转化和肿瘤发生所必需的信号通路的极佳模型。我们在永生化成纤维细胞中的初步研究表明，致癌的RAS降低了内源性PAR-4蛋白的表达，而PAR-4的修复抑制了致癌的RAS诱导的转化，而不改变细胞的活力。这些发现导致了一种假设，即致癌RAS下调PAR-4是转化所必需的，因为PAR-4可能抑制转化所需的关键致癌RAS诱导途径(S)。检验这一假说的三个具体目标是：(1)确定致癌ras下调PAR-4的分子机制(S)；(2)确定补充PAR-4阻止转化过程的分子机制(S)；以及(3)确定调节转化抑制的PAR-4的结构域。致癌RAS和PAR-4激活的信号机制将在体外在成纤维细胞中阐明，这一发现将被扩展到检验PAR-4抑制转化的结构域是否也能在体内阻止成纤维细胞和上皮细胞背景下致癌ras诱导的肿瘤生长。所提出的研究将有助于剖析PAR-4的功能结构域，这些功能结构域调节该蛋白的抗转化和促凋亡特性。因此，这些研究有望揭示致癌RAS用来克服干扰转化的机制的信号通路，并确定PAR-4用来阻止细胞转化或肿瘤生长的新机制。这一发现可能有助于未来的研究探索利用PAR-4过表达来控制肿瘤生长的可行性。