Anti-Tumorigenic Potential of Novel Digitoxin Analogues

描述（由申请人提供）：洋地黄毒苷作为癌症治疗剂的潜力已被广泛研究;然而，狭窄的治疗指数和潜在的毒副作用已经排除了其在临床环境中作为抗癌剂的用途。本研究的长期目标是开发，使用组合合理的药物设计方法，洋地黄毒苷的新类似物，具有增强的抗肿瘤活性对肺癌相比，现有的强心苷，但具有较低的副作用。这项研究与NHLBI的使命直接相关。这些类似物将使用不同的从头钯催化碳水化合物合成方法生成，并使用体外、离体和计算机技术进行检测。此外，重要的细胞凋亡和血管生成介质，是至关重要的抗肿瘤作用的洋地黄毒素及其类似物在肺癌将划定。Aim I旨在 表征由已经鉴定的洋地黄毒苷的新型单糖类似物（MonoD）诱导的有效凋亡作用，鉴定其促凋亡作用的关键细胞内调节剂，并描绘介导MonoD和洋地黄毒苷对肺癌细胞作用的自由基的作用。初步数据清楚地表明，使用钯催化方法合成的MonoD在NCI的60种癌细胞系的面板上显示出比洋地黄毒苷高5倍以上的细胞毒性活性，并且对NSCLC细胞系特别有效。此外，数据显示MonoD的抗增殖作用可以通过调节Bcl 2和半胱天冬酶介导，这将在本文中进行评估。在目标II中，将研究MonoD和洋地黄毒苷的肿瘤血管生成抑制潜力、潜在的作用机制以及自由基的作用。 这得到了初步数据的支持，这些数据显示MonoD具有强大的抗血管生成潜力，并抑制了关键的血管生成介质Akt和HIF 1 β。这一目标将通过体外和离体技术实现，并将研究凋亡（Bcl 2）和血管生成（HIF 1 β，VEGF）途径之间的潜在串扰。为了进一步提高MonoD和洋地黄毒苷的疗效和特异性，并确定这些药物的新型结合底物，目的III中提出了合理的药物设计方法。与传统的SAR技术相反，同源建模和对接，将采用更快和更有效的计算机技术。此外，结合研究将用于鉴定MonoD和洋地黄毒苷的新型结合底物。在鉴定出洋地黄毒苷和MonoD的合适的潜在药物衍生物后，将使用固有灵活的从头方法来合成新的候选药物。将使用Aim I和Aim II中的技术验证这些药物的作用特异性，并通过测量增殖、迁移、侵袭和肿瘤转移来验证其抗肿瘤活性。这项研究不仅对了解强心苷在肺癌细胞中的作用模式很重要，而且还可以产生一类新的药物，这些药物可能靶向对肿瘤进展至关重要的多个新途径，因此可能被证明对各种癌症有效。

DESCRIPTION (provided by applicant): The potential of digitoxin as a cancer therapeutic has been extensively investigated; however a narrow therapeutic index and potential for toxic side effects have precluded its use in clinical settings as an anti-cancer agent. The long-term goal of this study is to develop, using a combinatorial rational drug-design approach, novel analogues of digitoxin that possess enhanced anti-tumor activity against lung cancer as compared to existing cardiac glycosides but with lower side effects. This study is directly relevant to the mission of the NHLBI. These analogues will be generated using a divergent de novo palladium-catalyzed carbohydrate synthesis methodology and tested using in vitro, ex vivo and in silico techniques. Further, important apoptotic and angiogenic mediators that are critical to the anti-tumor effect of digitoxin and its analogues in lung cancer will be delineated. Aim I is designed to characterize the potent apoptotic effect induced by an already identified novel monosaccharide analogue of digitoxin (MonoD), identify key intracellular regulators of its pro-apoptotic effect, ad delineate the role of free radicals that mediate MonoD and digitoxin action on lung cancer cells. Preliminary data clearly indicates that MonoD, synthesized using the palladium-catalyzed approach, demonstrates more than five-fold higher cytotoxic activity than digitoxin on NCI's panel of sixty cancer cell lines, and is particularly potent against NSCLC cell lines. Further, dat shows that the anti- proliferative effects of MonoD may be mediated by modulation of Bcl2 and caspases, which will be evaluated here. In Aim II, the tumor-angiostatic potential of MonoD and digitoxin, the underlying mechanisms of action, and the role of free radicals will be investigated. This is supported by preliminary data showing potent anti- angiogenic potential for MonoD, and inhibition of the key angiogenic mediators Akt and HIF1�. The objectives of this aim will be achieved using both in vitro and ex vivo techniques, and potential cross-talk between the apoptotic (Bcl2) and angiogenic (HIF1�, VEGF) pathways will be investigated. To further improve upon the efficacy and specificity of MonoD and digitoxin and identify novel biding substrates for these drugs, a rational drug-design approach is proposed in Aim III. As opposed to traditional SAR techniques, homology modeling and docking, in silico techniques that are quicker and more efficient will be employed. In addition, binding studies will be used to identify novel binding substrates for MonoD and digitoxin. Upon identification of suitable potential drug derivatives of digitoxin and MonoD, the inherently flexible de novo methodology will be used to synthesize the new candidate drugs. These drugs will be validated for specificity of action using techniques in Aim I and Aim II, and validated for anti-tumor activity by measuring proliferation, migration, invasion and tumor-metastasis. This study is important not only for the understanding of the mode of action of cardiac glycosides in lung cancer cells, but also to generate a new class of drugs that may target multiple novel pathways critical to tumor progression, and thus may prove to be effective across a variety of cancers.