Novel aureolic acid type antitumor agents

描述（由申请人提供）：金酸类抗癌药物，如米霉素（MTM）、色霉素（CMM）和杜哈霉素（DHM），是有效的抗癌和抗hiv药物，具有独特的作用方式。它们通过交联富含gc的DNA来抑制癌细胞的生长，从而关闭特异性蛋白（Sp）依赖于各种原癌基因的途径，包括c-myc和c-src，后者与这些药物中发现的独特的低钙活性有关。尤其是MTM，它已成为研究sp依赖性信号转导途径的常用生化工具，但由于其毒副作用，除了治疗其他化疗难以治疗的肿瘤高钙血症外，很少被用作抗癌药物。然而，2011年，NCI在筛选的5万种化合物中发现MTM是唯一一种抑制EWS-FLI1转录因子的先导物，EWS-FLI1转录因子是导致尤文氏肉瘤高度恶性表型的原因，这种肉瘤经常影响儿童，在过去的40年里无法治愈。此外，另一个NCI小组在2012年6月发现，MTM抑制香烟烟雾诱导的负责肺癌和食管癌耐药的ABCG2外流泵，并抑制与此类癌症的致瘤性和增殖相关的多种干细胞相关途径。几年前，MTM被确定为治疗神经系统疾病、关节炎和血液系统疾病的潜在先导药物。所有这些新的应用只需要非常小的、毒性较低的药物浓度，尽管在这些情况下的作用模式仍然不清楚，特别是影响EWS-FLI1转录因子的模式。MTM的生物合成在本研究项目之前的资助期内得到了深入的研究，随后进行的组合生物合成工作揭示了各种生物合成中间体和许多新的MTM类似物，从而可以推断出重要的结构-活性-关系。有两个区域特别令人感兴趣：首先，3侧链的修饰，首先在MTM SK和MTM SDK的优越类似物中得到了证明，与MTM本身相比，它具有更好的抗癌活性，治疗指数也大大提高。其次，d -洋地黄糖交换MTM三糖链e位的D-mycarose糖，产生了更优的类似物，毒副作用大大降低。这现在允许新的策略进一步集中在分子的这些区域，以进一步优化药物。在以往的生物合成研究中，生物合成是耐人寻味和有趣的关键

DESCRIPTION (provided by applicant): Aureolic acid-type anticancer agents, such as mithramycin (MTM), chromomycin (CMM) and durhamycin (DHM), are potent anticancer and anti-HIV drugs with a unique mode-of-action. They inhibit the growth of cancer cells by cross-linking GC-rich DNA thereby shutting down specificity-protein (Sp)-dependent pathways toward various proto-oncogenes including c-myc and c-src, the latter being associated with the unique hypocalcemic activity found for these drugs. Particularly, MTM is important, and has become a popular biochemical tool to study Sp-dependent signal transduction pathways, but -due to its toxic side effects- is rarely used as anticancer agent, except for the treatment of tumor hypercalcemia refractory to other chemotherapy. However, MTM was identified in 2011 by the NCI as the only lead from a screen of 50,000 compounds that inhibits the EWS-FLI1 transcription factor responsible for the highly malignant phenotype of Ewing sarcomas, which often affect children and were untreatable for the past 40 years. In addition, another NCI group found in June 2012 that MTM represses cigarette smoke induced ABCG2 efflux pumps responsible for the drug resistance of lung and esophageal cancers, and inhibited multiple stem-cell related pathways relevant for tumorigenicity and proliferation of such cancers. A few years ago MTM was identified as a potential lead drug against neurological diseases, arthritis, and for the treatment of hematologic disorders. All these new applications require only very small, less toxic concentrations of the drug, although the mode-of-action in these contexts remains obscure, particularly the mode affecting the EWS-FLI1 transcription factor. MTM's biosynthesis has been studied intensely during the previous funding periods of this research project, and consequently pursued combinatorial biosynthetic efforts revealed various biosynthetic intermediates and many new MTM-analogues, which allowed deducing important structure-activity-relationships. Two regions are of special interest: First, a modification of the 3-side chain, first exemplified in the superior analogues MTM SK and MTM SDK, led to much better anticancer activity profiles with a greatly improved therapeutic index compared to MTM itself. Second, exchange of the D-mycarose sugar in E-position of MTM's trisaccharide chain by D-digitoxose led to superior analogues with greatly reduced toxic side effects. This now allows for new strategies to further concentrate on these regions of the molecule for further drug optimization. During the previous biosynthetic studies biosynthetic intriguing and interesting key enzymes were discovered, which need to be further investigated, particularly the co-dependent enzymes MtmGIV/MtmC (bifunctional glycosyltransferase/methyltransferase-ketoreductase), MtmOIV/MtmW (C-C-bond cleaving oxygenase/ketoreductase), which play key roles for the 3-side chain and the trisaccharide chain formation. Furthermore, the PKS release remains unclear, and it is hypothesized that another co-dependent enzyme pair, namely oxygenase MtmOII and cyclase MtmX play an important role for this process. The goal here is to gain a deeper understanding of the biosynthetic roles, mechanisms and interactions of these key enzymes of the MTM pathway, to pave the way for the optimization and re-engineering of these enzymes that are crucial for novel, further improved MTM derivatives. It is planned to (a) further investigate unclear biosynthetic steps and mechanisms of the MTM and other aureolic acid pathways, (b) to further develop strategies for the selective generation of new, improved MTM analogues including selective 3-side chain and sugar exchange/glycorandomization strategies, (c) to analyze intriguing enzymes, particularly recently discovered co- dependent enzyme pairs. New resulting MTM analogues will be submitted to the NCI DTP (developmental therapeutics program) for further mechanistic investigations.