AUTOCRINE TGF BETA AND CELL DEATH

描述（由申请人提供）：该项目的总体概念是，TGF？受体再生介导存活素的抑制，从而有助于与组蛋白脱乙酰酶抑制剂（HDACi）相关的抗肿瘤活性。据认为，HDACi功效将通过相对于由目前可用的药剂抑制的HDAC的范围的较少混杂性来改善。因此，确定一个关键的HDAC（S）控制TGF？受体抑制对于适当策略的发展将是重要的。我们的初步数据点HDAC1作为TGF？癌症中的受体抑制。转化生长因子的转录抑制？受体表达和因此其肿瘤抑制基因（TSG）活性经常发生在结肠癌和乳腺癌细胞中。这是一致的，这些受体在蛋白质和mRNA水平的患者样本中的机制，是不太可能与突变的TGF？信号组件。受体表达缺失也与这些患者的不良预后相关（3）。失去TGF？通过用HDACi抑制剂处理逆转了受体以及信号传导。在其他工作中，我们已经发现，一种新的内源性细胞死亡途径，针对抑制生存素的表达是一个重要因素的TGF？TSG活动。因此，我们将测试与HDAC活性抑制相关的肿瘤抑制与TGF？特异性目的I中通过这种新的自分泌死亡途径的TSG活性。稳定表达HDAC1 siRNA再生缺陷型TGF？因此，HDAC 1负责受体的转录抑制。在该项目的这个周期中，我们发现，TGF？受体转录依赖于HDAC抑制在几个Sp1网站。然而，这些网站不同的转录因子的使用。因此，假设不同的机制，HDAC抑制反应发生在不同的Sp1位点的RII启动子将在目的II进行测试。HDACi和特异性HDAC1抑制激活异种移植模型中内源性存活素介导的死亡途径的假设将在特异性目的III中进行检验。这种新的稳定HDAC 1敲低模型的表征可能导致基于互补作用机制的合理组合方法的鉴定。具体目的是：1）确定HDAC 1抑制是否足以再生TGF？受体与P21和Survivin的抑制2)TGF？激活和沉默机制的确定过渡3）确定HDAC 1敲减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.