Molecular Sensors for Imaging Histone Methylations in Living Animals

描述（由申请人提供）：“表观遗传学”是指由潜在DNA序列变化以外的机制引起的表型或基因表达的变化。异常的表观遗传控制机制现在被认为是包括癌症在内的不同疾病的病理生理的重要因素。诱导哺乳动物细胞表型变化的主要表观遗传机制是DNA甲基化、组蛋白甲基化和组蛋白乙酰化。最近许多靶向药物的开发工作都是针对这些表观遗传机制中的一种或多种进行修饰。在这方面，一些基于细胞培养的检测被用来分析不同的表观遗传过程，小分子药物调节这些表观遗传过程。然而，这些试验不能准确预测药物在活体体内的药代动力学和药效学行为。目前对此类药物的大力开发，以及对表观遗传学研究的兴趣不断增加，迫切需要开发新的更有意义的分子成像策略，以特异性地询问体内不同的表观遗传学机制。本提案的主要目标是开发新的体内成像策略来监测活体动物的细胞表观遗传过程，在成像不同癌症发展过程中发生的基本表观遗传变化时评估这些技术，并将这些成像平台应用于研究癌症中调节这些过程的治疗药物。具体来说，我们希望在体内成像和定量组蛋白甲基化，并应用这种新的分析工具来评估调节组蛋白甲基化的药物，这可能在癌症的分子治疗中有重要的应用。这将通过开发：1)光学生物发光（分裂-荧光素酶互补）和2)微pet（分裂-胸苷激酶互补）成像传感器来实现。使用不同表观遗传调节剂（组蛋白去乙酰化酶抑制剂与组蛋白甲基转移酶联合使用）的组合疗法目前被认为是治疗癌症和其他一些难治性细胞疾病的新方法。我们计划利用这笔拨款开发的传感器，有可能对细胞和活体动物中的分子事件进行成像。这些传感器将通过在活体动物中进行药物筛选和临床前评估，改善表观遗传调节剂在转化临床应用中的使用。异常组蛋白甲基化被认为是癌症发生的重要因素。综上所述，该提案将导致高灵敏度体内成像方法的发展，可用于进一步的表观遗传学研究，以及加速针对不同癌症和其他细胞疾病的药物的临床前评估。

DESCRIPTION (provided by applicant): "Epigenetics" refers to changes in phenotype or gene expression caused by mechanisms other than changes in the underlying DNA sequence. Abnormal epigenetic control mechanisms are now regarded as significant contributing factors to the pathophysiology of different diseases, including cancer. The main epigenetic mechanisms that induce phenotypic changes in mammalian cells are DNA methylation, histone methylation and histone acetylation. Many recent targeted drug development efforts have been directed towards the modification of one or more of these epigenetic mechanisms. In that regard, several cell culture based assays are being used to analyze different epigenetic processes, and small molecule drugs modulate these epigenetic processes. However these tests are not capable of predicting the exact behavior of drug pharmacokinetics and pharmacodynamics in living subjects. The current intense efforts to develop such drugs, as well as an ever increasing interest in epigenetics research, creates a paramount need to develop new more meaningful molecular imaging strategies that can specifically interrogate different epigenetic mechanisms in vivo. The main goal of this proposal is to develop novel in vivo imaging strategies to monitor cellular epigenetic processes in living animals, evaluating these techniques when imaging the basic epigenetic shifts occurring in the development of different cancers, and to apply these imaging platforms to study therapeutic drugs that modulate these processes in cancer. Specifically, we wish to image and quantitate histone methylation in vivo, and to apply this novel analytical tool to evaluate drugs that modulate histone methylation, which may have important applications in molecular therapeutics of cancer. This will be achieved by developing: 1) Optical bioluminescence (Split-Luciferase-complementation), and 2) microPET (Split-Thymidine kinase complementation) imaging sensors. Combinatorial therapies using different epigenetic modulators (inhibitors of histone deacetylases in combination with histone methyltransferases) is curently considered as a new approach for treating cancers and several other intractable cellular diseases. The sensors we are planning to develop by this grant, are having the potential to image molecular events in both cells and in live animals. These sensors will improve the use of epigenetic modulators in translational clinical applications by enabling drug screening and their pre-clinical evaluations in living animals. The aberrant histone methylation has been considered as an important player in the development of cancer. In summary, this proposal will lead to the development of highly sensitive in vivo imaging methods that can be used to further epigenetic research, as well as accelerating the pre-clinical evaluation of drugs targeting different cancers and other cellular diseases. PUBLIC HEALTH RELEVANCE: Currently, abnormal epigenetic mechanisms are regarded as significant contributing factors to the pathophysiology of different diseases, including cancer. Several cell-based assays are being used to identify and analyze drugs that target different epigenetic mechanisms. However most of these tests are not capable of predicting the exact behavior of drug pharmacokinetics and pharmacodynamics in living subjects. The ever- increasing interest in epigenetics research creates an immediate need to develop new more meaningful molecular imaging strategies that can specifically interrogate different epigenetic mechanisms in vivo. The main goal of this proposal is to develop novel in vivo imaging strategies to monitor cellular epigenetic processes in living animals. Specifically, we wish to image and quantitate histone methylation in vivo, and to apply this novel analytical tool to the evaluation of drugs that modulate epigenetic events, which may have important applications in molecular therapeutics of cancer.