AUTOCRINE TGF BETA AND CELL DEATH

项目描述（由申请人提供）：项目的总体理念是：TGF？受体再生介导生存素的抑制，从而促进与组蛋白去乙酰化酶抑制剂（HDACi）相关的抗肿瘤活性。人们认为，相对于目前可用的药物抑制的HDAC的范围，减少混杂会提高HDAC的疗效。因此，确定一个关键的HDAC(s)控制TGF？受体抑制对于制定适当的策略至关重要。我们的初步数据表明HDAC1是TGF？癌症中的受体抑制。TGF？受体表达及其肿瘤抑制基因（TSG）活性在结肠癌和乳腺癌细胞中经常发生。这与患者样本中这些受体在蛋白质和mRNA水平上的频繁丢失是一致的，其机制不太可能与TGF？信号组件。这些患者的受体表达缺失也与预后不良相关(3)。TGF？受体和信号被HDACi抑制剂逆转。在其他工作中，我们发现了一种新的内源性细胞死亡途径，其靶向抑制survivin的表达，是TGF？次数的活动。因此，我们将检验与HDAC活性抑制相关的肿瘤抑制与TGF？特异性目的：通过这种新的自分泌死亡途径激活TSG活性受体的表达，从而暗示HDAC1负责受体的转录抑制。在这个周期的项目中，我们发现TGF？受体转录依赖于几个Sp1位点的HDAC抑制。然而，这些位点在转录因子使用方面存在差异。因此，RII启动子的不同Sp1位点对HDAC抑制的不同反应机制的假设将在Aim II中得到验证。在异种移植物模型中，HDACi和特异性HDAC1抑制激活内在生存素介导的死亡途径的假设将在specific Aim III中得到验证。表征这种新的稳定的HDAC1敲低模型可能导致基于互补作用机制的合理组合方法的确定。具体目的是：1)确定HDAC 1抑制是否足以再生两种TGF？p21和survivin的受体和抑制。2) tgf ?的激活与沉默机制的确定3)确定hdac 1敲低是否足以在异种移植物中获得抗肿瘤活性。

DESCRIPTION (provided by applicant): The overall concept of the project is that TGF? receptor regeneration mediates the repression of survivin thereby contributing to the anti tumor activity associated with histone deacetylase inhibitors (HDACi). It is thought that HDACi efficacy would be improved by less promiscuity with respect to the range of HDAC's inhibited by currently available agents. Thus, identification of a key HDAC(s) controlling TGF? receptor repression would be of consequence for the development of appropriate strategies. Our preliminary data point to HDAC1 as a mediator of TGF? receptor repression in cancer. Transcriptional repression of TGF? receptor expression and hence its tumor suppressor gene (TSG) activity occurs frequently in colon and breast cancer cells. This is consistent with the frequent loss of these receptors at both the protein and mRNA levels in patient samples by mechanisms that are unlikely to be associated with mutations of TGF? signaling components. Loss of receptor expression is associated with poor prognosis in these patients as well (3). Loss of TGF? receptors as well as signaling was reversed by treatment with HDACi inhibitors. In other work we have found that a novel endogenous cell death pathway targeting repression of survivin expression is an important element of TGF? TSG activity. Consequently, we will test the hypothesis that tumor inhibition associated with inhibition of HDAC activity is linked to TGF? TSG activity through this novel autocrine death pathway in Specific Aim I. Stable expression of HDAC1 SiRNA regenerated deficient TGF? receptor expression thus implying that HDAC1 is responsible for transcriptional repression of the receptors. During this cycle of the project we found that reactivation of the TGF? receptor transcription was dependent upon the HDAC inhibition at several Sp1 sites. However, these sites differed with respect to transcription factor usage. Consequently, the hypothesis that different mechanisms of response to HDAC inhibition occurs at different Sp1 sites in the RII promoter will be tested in Aim II. The hypotheses that HDACi and specific HDAC1 inhibition activates an intrinsic survivin mediated death pathway in xenograft models will be tested in Specific Aim III. Characterization of this new stable HDAC1 knockdown model could lead to the identification of rational combination approaches based on complementary mechanisms of action. The Specific Aims are: 1) DETERMINE WHETHER HDAC 1 INHIBITION is SUFFICIENT FOR REGENERATION OF BOTH TGF? RECEPTORS AND REPRESSION OF P21 AND SURVIVIN. 2) DETERMINATION OF THE MECHANISMS OF ACTIVATION & SILENCING OF TGF? TRANSCRIPTION 3) DETERMINE WHETHER HDAC 1 KNOCKDOWN IS SUFFICIENT TO OBTAIN ANTI-TUMOR ACTIVITY IN XENOGRAFTS.