The Development of STAT3 Inhibitors.

描述（由申请人提供）：STAT蛋白（信号转导和转录激活因子）介导多种细胞外信号。作为配体与受体结合的反应，这些蛋白质在位于c端附近的不变酪氨酸残基上被磷酸化。酪氨酸磷酸化后，STAT蛋白结合形成二聚体，其中一个单体的SH2结构域与另一个单体的pTyr结合，第二个单体的SH2结构域与第一个单体的pTyr结合。二聚体然后迁移到细胞核，结合特定的DNA启动子序列，并启动指定反应元件的转录。在正常细胞中，STATs介导来自生长因子受体和免疫刺激的信号。然而，在一些癌症类型中，STATs是组成性激活的。在本提案中，我们将重点关注Stat3，它已被证明在乳腺癌、结肠癌和脑癌中具有组成性激活。本提案的假设是，通过阻断Stat3的二聚化，我们可以消除该蛋白介导的促进增殖、阻止细胞凋亡的信号通路，从而抑制肿瘤细胞的生长。为了做到这一点，我们打算开发基于含磷酸酪氨酸的肽靶向Stat3 SH2结构域的肽模拟物。我们已经证明，从Stat3的pTyr 705衍生的磷酸肽能够抑制Stat3在细胞中的激活。在这项资助中，我们将开发Stat3二聚化抑制剂。Stat3 SH2结构域抑制肽氨基酸序列优化。2. 将约束的酪氨酸和其他构象约束放在最小的肽中，以锁定最佳结合相互作用的构象。3. 利用x射线晶体学和/或核磁共振确定我们与Stat3的SH2结构域结合的肽的结构，以用于改进我们的抑制剂。4. 检测我们的化合物作为二聚化和DNA结合抑制剂，并在生长抑制、软琼脂集落形成、细胞活力和凋亡的细胞基础试验中测试最有希望的化合物。

DESCRIPTION (provided by applicant): STAT proteins (signal transduction and activators of transcription) mediate a variety of extracellular signals. In response to ligand binding to receptor, these proteins become phosphorylated on an invariant tyrosine residue located near the C-terminus. Upon tyrosine phosphorylation, STAT proteins combine to form dimers, in which the SH2 domain of one monomer binds the pTyr of the second and the SH2 domain of the second monomer binds to the pTyr of the first. The dimer then migrates to the nucleus, binds to specific DNA promoter sequences and initiates transcription of designated response elements. In normal cells STATs mediate signaling from growth factor receptors and immune stimuli. However, in several cancer types, STATs are activated constitutively. In this proposal we will focus on Stat3, which has been shown to be constitutively activated in cancers of the breast, colon, and brain. The hypothesis of this proposal is that by blocking the dimerization of Stat3, we can eliminate the signaling mediated by this protein that promotes proliferation and prevents apoptosis and thereby inhibit the growth of tumor cells. To do this we intend to develop peptidomimetics based on phosphotyrosine containing peptides targeted to the Stat3 SH2 domain. We have demonstrated that a phosphopeptide derived from pTyr 705 of Stat3 is capable of inhibiting Stat3 activation in cells. In this grant we will develop inhibitors of Stat3 dimerization by 1. Optimizing amino acid sequences of Stat3 SH2 domain inhibitor peptides. 2. Put constrained tyrosines and other conformational constraints in smallest peptide to lock the conformation for optimal binding interactions. 3. Determine the structure of our peptides bound to the SH2 domain of Stat3 using X-ray crystallography and/or NMR to be used in refinement of our inhibitors. 4. Assay our compounds as inhibitors of dimerization and DNA binding, and test the most promising compounds in cell based assays of growth inhibition, soft agar colony formation, cell viability, and apoptosis.