AUTOCRINE TGF BETA AND CELL DEATH

说明(申请人提供)：该项目的总体概念是，转化生长因子？受体再生介导Survivin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。人们认为，相对于目前可用的药物所抑制的HDAC的范围，较少的混杂将改善HDACi的疗效。因此，确定了控制转化生长因子的关键人物S？受体抑制将对开发适当的策略产生影响。我们的初步数据表明，HDAC1是一种转化生长因子？癌症中的受体抑制。转化生长因子的转录抑制？受体的表达及其肿瘤抑制基因(TSG)的活性经常发生在结肠癌和乳腺癌细胞中。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，其机制不太可能与转化生长因子？突变有关。信令组件。受体表达缺失也与这些患者的预后不良有关(3)。失去转化生长因子？用HDACi抑制剂处理后，受体和信号被逆转。在其他工作中，我们发现以抑制Survivin表达为靶点的新的内源性细胞死亡途径是转化生长因子？TSG活性。因此，我们将验证肿瘤抑制与HDAC活性抑制相关的假设与转化生长因子？TSG通过这一新的自分泌死亡途径具有特定的活性。I.稳定表达HDAC1 siRNA再生缺陷的转化生长因子？因此，受体的表达意味着HDAC1负责对受体的转录抑制。在这个项目的周期中，我们发现了重新激活的转化生长因子？受体的转录依赖于几个Sp1位点的HDAC抑制。然而，这些位点在转录因子的使用方面有所不同。因此，RII启动子上不同的Sp1位点对HDAC1的不同应答机制的假设将在Aim II中得到检验。HDACi和特定的HDAC1抑制在异种移植模型中激活内在Survivin介导的死亡途径的假设将在特定的Aim III中得到检验。这一新的稳定的HDAC1基因敲除模型的特征可能导致基于互补作用机制的合理组合方法的识别。其具体目的是：1)确定HDAC 1抑制是否足以促进两种转化生长因子的再生？受体与P21和Survivin的抑制。2)确定了转化生长因子的激活和沉默机制？转录3)确定HDAC 1基因敲除是否足以在异种移植瘤中获得抗肿瘤活性。

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.