Targeting STAT3 as a novel approach to cancer therapy

描述(由申请人提供)：这项拨款提案的总体目标是在设计小的合成分子的基础上发现新的抗癌药物，这些小分子可以抑制STAT3的二聚化和肿瘤中依赖STAT3生存的异常功能。压倒性的临床前证据表明，STAT3在促进癌症的几个特征方面发挥了关键作用，包括不受控制的细胞增殖、细胞凋亡逃避、血管生成和转移。此外，在临床上，在患者肿瘤中发现STAT3持续过度激活(酪氨酸磷酸化)，这与化疗耐药和预后不良有关。在含有异常激活的STAT3的肿瘤细胞中，以STAT3β为主的抑制STAT3功能，下调其表达或用STAT3激活抑制剂抑制其激活，可逆转恶性转化和/或诱导细胞凋亡。STAT3酪氨酸磷酸化和随后的二聚化是STAT3激活所必需的。这项资助所基于的假设是，STAT3二聚化选择性抑制剂将抑制STAT3的异常功能，抑制STAT3介导的抗凋亡和/或致癌蛋白的上调，并将抑制肿瘤生长和诱导细胞凋亡。为了验证这一假设，提出了以下具体目标：1)使用基于结构的虚拟HTS和分子建模，并进行实验性HTS来识别和设计有效和选择性的STAT3二聚抑制剂。2)确定特定目的1的先导化合物在整个细胞中有效和选择性地抑制STAT3二聚化、STAT3酪氨酸磷酸化、STAT3-DNA结合和STAT3依赖转录活性的能力；3)确定在特定目的2中确定的高选择性的STAT3二聚化抑制剂是否能够以STAT3依赖的方式有效和选择性地抑制人癌细胞中的STAT3依赖的致癌信号和抑制恶性转化；以及4)在高效和选择性的STAT3二聚化抑制剂的动物模型中评价其抗肿瘤活性、药效学、药代动力学和毒性。建议的研究将提供化学探针，使我们能够加强对STAT3在人类肿瘤发生中的重要性的理解，最终，这些研究将导致发现具有促凋亡和抗肿瘤活性的STAT3抑制剂，并将拓宽可以成功治疗的人类肿瘤的光谱。公共卫生相关性：这项拨款提案的总体目标是在设计致癌蛋白STAT3的抑制剂的基础上发现抗癌药物。压倒性的临床前和临床证据表明，STAT3在人类癌症中发挥着重要作用。例如，肿瘤中含有异常激活的STAT3的患者对癌症治疗具有抵抗力，寿命较短。在这项拨款提案中，我们将测试STAT3抑制剂将通过抑制STAT3的异常功能和通过诱导肿瘤细胞死亡来阻止STAT3致癌的假设。为了验证这一假设，我们将进行以下工作：1.我们将使用计算机建模和高通量筛选化学文库来鉴定STAT3的抑制剂。2.根据筛选结果设计更有效、更具选择性的STAT3抑制剂。3.确定STAT3抑制剂是否阻断STAT3在培养的人癌细胞中的致癌活性。4.用动物模型评价STAT3抑制剂的抗肿瘤活性和毒性。拟议中的研究最终将导致发现STAT3抑制剂，从而拓宽可成功治疗的人类肿瘤的范围。

DESCRIPTION (provided by applicant): The overall goal of this grant proposal is to discover novel anticancer drugs based on designing small synthetic molecules that inhibit STAT3 dimerization and aberrant function in tumors that depend on STAT3 for survival. Overwhelming pre-clinical evidence points to the pivotal involvement of STAT3 in promoting several hallmarks of cancer including uncontrolled cell proliferation, apoptosis evasion, angiogenesis, and metastasis. Furthermore, clinically, in patient tumors, STAT3 is found persistently hyper- activated (tyrosine phosphorylated) and this is associated with resistance to chemotherapy and poor prognosis. In tumor cells which harbor aberrantly activated STAT3, inhibiting STAT3 function with dominant negative STAT3 beta, knocking down its expression or inhibiting its activation by STAT3 activation inhibitors results in reversal of malignant transformation and/or induction of apoptosis. STAT3 tyrosine phosphorylation and subsequent dimerization are required for STAT3 activation. The hypothesis upon which this grant is based is that STAT3 dimerization selective inhibitors will suppress STAT3 aberrant function and inhibit STAT3-mediated up-regulation of anti-apoptotic and/or pro-oncogenic proteins, and will suppress tumor growth and induce apoptosis. To test this hypothesis the following specific aims are proposed: 1) To use structure-based Virtual HTS and molecular modeling and to perform experimental HTS to identify and design potent and selective STAT3 dimerization inhibitors. 2) To determine the ability of leads from Specific Aim 1 to potently and selectively inhibit STAT3 dimerization, STAT3 tyrosine phosphorylation, STAT3-DNA-binding and STAT3-dependent transcriptional activities in whole cells, 3) To determine if the highly selective STAT3 dimerization inhibitors identified in Specific Aim 2 are able to inhibit potently and selectively STAT3- dependent oncogenic signaling and suppress malignant transformation in a STAT3-dependent manner in human cancer cells, and 4) To evaluate the anti-tumor activity, pharmacodynamics, pharmacokinetics and toxicity in animal models of potent and selective STAT3 dimerization inhibitors. The studies proposed will provide chemical probes that will allow us to enhance our understanding of the importance of STAT3 in human oncogenesis, and ultimately, the studies will lead to the discovery of STAT3 inhibitors with pro-apoptotic and anti-tumor activities, and will broaden the spectrum of human tumors that can be successfully treated. PUBLIC HEALTH RELEVANCE: The overall goal of this grant proposal is to discover anticancer drugs based on designing inhibitors of the cancer-causing protein STAT3. Overwhelming pre-clinical and clinical evidence points to the important role that STAT3 plays in human cancer. For example, patients whose tumors contain aberrantly activated STAT3 are resistant to cancer therapy and live shorter lives. In this grant proposal we will test the hypothesis that STAT3 inhibitors will block STAT3 from causing cancer by inhibiting its aberrant function and by inducing tumor cell death. To test this hypothesis we will perform the following: 1. We will use computer modeling and high throughput screening of chemical libraries to identify inhibitors of STAT3. 2. To design more potent and selective inhibitors of STAT3 based on hits from our screening efforts. 3. To determine if STAT3 inhibitors block the cancer-causing activity of STAT3 in cultured human cancer cells. 4. To evaluate anti-tumor activity and toxicity of STAT3 inhibitors in animal models. The studies proposed will ultimately lead to the discovery of STAT3 inhibitors that will broaden the spectrum of human tumors that can be successfully treated.