Mechanisms on the Regulation of PTEN Expression by TGF-Beta

描述（由申请人提供）： PI的目标是阐明TGF-β对PTEN表达的调节作用的机制，这对于理解恶性胰腺肿瘤的发病机制至关重要。我们的初步数据表明，TGF-β通过SMAD依赖性和非依赖性途径在功能上影响PTEN的激活、稳定性和转录。我们的总体假设是TGF-β调节胰腺癌中PTEN的表达，这种调节将TGF-β从肿瘤抑制因子转化为肿瘤促进因子。我们的具体目标围绕这一假设，旨在确定TGF-β双重功能作用的机制。我们的第一个目标是研究K-RAS如何调节TGF-β诱导的SMAD依赖性PTEN表达，因为K-RAS在>90%的胰腺癌中被激活。初步数据表明，抑制致癌K-RAS可改善SMAD核转位并逆转TGF-β诱导的PTEN抑制。我们认为，这种PTEN上调是SMAD依赖性信号传导抑制肿瘤的关键。我们的第二个目的是研究TGF-β诱导的PTEN在翻译后水平的调节。根据我们的数据，TGF-β至少对胰腺癌中减少PTEN有两种作用-抑制PTEN转录和减少细胞质PTEN库。PI将确定酪蛋白激酶是否调节PTEN稳定性，以及PTEN的C-末端磷酸化是否会受到TGF-β诱导的酪蛋白激酶下调的影响。我们的第三个目标是研究TGF-β诱导的PTEN表达，这是SMAD独立的，特别是集中在NF-κ B作为介质。在我们的胰腺细胞模型中，TGF-β诱导的PTEN抑制发生在（a）SMAD 4缺失的细胞和（B）具有致癌K-RAS的细胞中，基本上完全抑制SMAD依赖性信号传导。我们从我们的数据推断，NF-κ B是一个很好的候选人，这种SMAD独立的途径。这些研究的策略将结合联合收割机药理学、分子和生物化学方法来表征胰腺癌中调节PTEN表达的途径。这些研究应该提供新的见解，精确的机制，调节TGF-β对PTEN表达的调节作用。这里提出的研究将探索对胰腺癌患者的基本理解和治疗，并作为Pi癌症研究发展的优秀指导项目。

DESCRIPTION (provided by applicant): The goal of the PI is to elucidate the mechanisms of the modulatory action of TGF-beta on PTEN expression that is critical to understand the pathogenesis of malignant pancreatic tumors. Our preliminary data show that TGF-beta functionally affects activation, stability, and transcription of PTEN via SMAD-dependent and - independent pathways. Our overall hypothesis is that TGF-beta modulates PTEN expression in pancreatic cancer, and this modulation converts TGF-beta from a tumor suppressor to a tumor promoter. Our Specific Aims center on this hypothesis, which are designed to determine the mechansims for the dual functional roles of TGF-beta. Our first aim studies how K-RAS modulates TGF-beta-induced, SMAD-dependent PTEN expression, as K-RAS is activated in >90% of pancreatic cancers. Preliminary data indicate that inhibition of oncogenic K-RAS improves SMAD nuclear translocation and reverses TGF-beta-induced PTEN suppression. We suggest that this PTEN upregulation is key to SMAD-dependent signaling being tumor suppressive. Our second aim studies TGF-beta-induced regulation of PTEN at post-translational levels. Based on our data, TGF-beta has at least two effects on reducing PTEN in pancreatic cancer - suppression of PTEN transcription and reduction of the cytoplasmic PTEN pool. The PI will determine if casein kinase regulates PTEN stability, and whether C-terminus phosphorylation of PTEN can be affected by TGF-beta- induced downregulation of casein kinase. Our third aim examines TGF-beta-induced PTEN expression that is SMAD-independent, and particularly focuses on NF-kB as the mediator. TGF-beta-induced PTEN suppression in our pancreatic cell models occurred in (a) SMAD4-null cells, and (b) with oncogenic K-RAS, essentially completely inhibiting SMAD-dependent signaling. We infer from our data that NF-kB is an excellent candidate for this SMAD-independent pathway. The strategy for these studies will combine pharmacological, molecular, and biochemical approaches to characterize pathways that regulate PTEN expression in pancreatic cancer. These studies should provide novel insights into the precise mechanisms that regulate the modulatory effect of the TGF-beta on PTEN expression. The research proposed here will explore basic understanding and treatment to patients with pancreatic cancer, and serve as an outstanding mentored project for the Pi's cancer research development.