Evaluating the anti-tumor effects of novel curcumin analogs in melanoma

描述（由申请人提供）：癌细胞中信号转导和转录激活因子-3（STAT 3）蛋白的组成性激活被认为促进细胞增殖和血管生成，抑制细胞凋亡，并驱动对侵袭和转移重要的基因。因此，STAT 3的抑制代表了大部分恶性肿瘤的癌症治疗的合理方法。一种有希望的STAT 3抑制先导化合物是天然产物姜黄素。姜黄素在许多模型中具有抗癌特性，并已显示出抑制多种细胞靶点，包括STAT 3。姜黄素的分子结构表明该分子以两种不同的互变异构形式存在：1）二酮形式（-酮）和2）酮-烯醇（-烯醇）形式。本课题组通过计算化学和构效关系的初步研究预测姜黄素的二酮互变异构体而非烯醇互变异构体可以抑制STAT 3的二聚化。因此，我们设计了锁定为二酮形式的新型姜黄素类似物，目的是增强STAT 3作为分子靶标的特异性。该提案中包含的初步数据表明，早期代类似物对STAT 3具有高度特异性，并在体外诱导有效的促凋亡作用。我们假设姜黄素的二酮互变异构体形式可以通过抑制STAT 3磷酸化和二聚化来操纵以产生对黑素瘤细胞的增强的促凋亡活性。为了验证这一假设，我们提出开发可溶的、代谢稳定的小分子姜黄素类似物，其特异性抑制STAT 3 SH 2磷酸化和二聚化（目的1）。随后将在体外评价所得STAT 3抑制性姜黄素类似物的促凋亡作用（目的2）。对于这些研究，黑色素瘤细胞将被用作模型，因为它代表了一种高度耐药性的肿瘤，其中STAT 3被认为起着主要作用。最后，我们将确定用姜黄素或其产生的类似物抑制STAT 3是否可以用于增强I型和II型干扰素对黑色素瘤细胞的直接抗肿瘤作用（目的3）。来自这些研究的数据将通过研究一种来自天然化合物的新型靶向药物，支持癌症治疗的补充方法的发展。目标3中提出的研究将扩展我们的重点，测试来源于姜黄素的STAT 3靶向抑制剂是否也可用于增强细胞因子（例如干扰素）常规黑色素瘤治疗的抗肿瘤作用。最终，从这些研究中获得的知识将指导未来的转化研究，为黑色素瘤和STAT 3发挥作用的任何其他癌症设计新的治疗策略。 公共卫生相关性：姜黄素是一种天然产物，来源于食用香料“姜黄”，已被证明可以杀死培养中的癌细胞。我们的研究小组进行的初步实验表明，姜黄素的化学结构可以进行修饰，使其对一种名为STAT 3的蛋白质更具特异性，这种蛋白质在癌细胞中高度活跃。我们建议进一步修改这种化学结构，以更有效地杀死黑素瘤皮肤癌细胞。我们还将确定这种改良的姜黄素衍生物是否可以增强标准药物（称为干扰素）杀死癌细胞的能力。

DESCRIPTION (provided by applicant): Constitutive activation of the signal transducer and activator of transcription-3 (STAT3) protein in cancer cells is thought to promote cell proliferation and angiogenesis, inhibit apoptosis, and drive genes important for invasion and metastasis. Therefore inhibition of STAT3 represents a rational approach to cancer therapy for a large proportion of malignancies. One promising lead compound for STAT3 inhibition is the natural product, curcumin. Curcumin has anti-cancer properties in numerous models and has been shown to inhibit a variety of cellular targets including STAT3. The molecular structure of curcumin indicates that the molecule exists in two distinct tautomeric forms: 1) a diketone form (-keto) and 2) an keto-enol (-enol) form. Computational chemistry and structure-activity-relationship preliminary studies conducted by our group have predicted that the diketo- tautomer but not the enol-tautomer of curcumin can inhibit STAT3 dimerization. Therefore, we have designed novel curcumin analogs locked into the diketo form with the goal of enhancing the specificity for STAT3 as a molecular target. Preliminary data contained within this proposal demonstrate that early generation analogs are highly specific for STAT3, and induce potent pro-apoptotic effects in vitro. We hypothesize that the diketo- tautomer form of curcumin can be manipulated to produce enhanced pro-apoptotic activity on melanoma cells by inhibiting STAT3 phosphorylation and dimerization. To test this hypothesis, we propose to develop soluble, metabolically stable, small molecule curcumin analogs that specifically inhibit STAT3 SH2 phosphorylation and dimerization (Aim 1). The pro-apoptotic effects of the resulting STAT3-inhibitory curcumin analogs will subsequently be evaluated in vitro (Aim 2). For these studies, melanoma cells will be used as a model as it represents a highly chemo-resistant tumor in which STAT3 is thought to play a major role. Finally, we will determine if STAT3 inhibition with curcumin or its resulting analogs can serve to augment the direct anti-tumor actions of Type I and Type II interferons on melanoma cells (Aim 3). The data derived from these studies will support the development of complementary approaches to cancer care by investigating a novel, targeted agent derived from a natural compound. The studies proposed in Aim 3 will extend our focus on testing whether STAT3-targeted inhibitors derived from curcumin could also be used to augment the anti-tumor effects of conventional melanoma therapy with cytokines (e.g. the interferons). Ultimately, knowledge gained from these studies will guide future translational research to devise novel therapeutic strategies for melanoma and any other cancer in which STAT3 plays a role. PUBLIC HEALTH RELEVANCE: Curcumin is a natural product derived from the dietary spice 'turmeric' that has been shown to kill cancer cells in culture. Preliminary experiments performed by our research group have shown that the chemical structure of curcumin can be modified to make it more specific for a protein named STAT3 that is highly active in cancer cells. We propose to further modify this chemical structure to more effectively kill melanoma skin cancer cells. We will also determine if this modified derivative of curcumin can enhance the ability of standard drugs (called interferons) to kill cancer cells.