Current Medicinal Chemistry - Volume 15, Issue 25, 2008

Dual-specificity phosphatases (DSPs) are important, but poorly understood, cell signaling enzymes that remove phosphate groups from tyrosine and serine/threonine residues on their substrate. Deregulation of DSPs has been implicated in cancer, obesity, diabetes, inflammation, and Alzheimer's disease. Due to their biological and biomedical significance, DSPs have increasingly become the subject of drug discovery high-throughput screening (HTS) and focused compound library development efforts. Progress in identifying selective and potent DSP inhibitors has, however, been restricted by the lack of sufficient structural data on inhibitor-bound DSPs. The shallow, almost flat, substrate binding sites in DSPs have been a major factor in hampering the rational design and the experimental development of active site inhibitors. Recent experimental and virtual HTS studies, as well as advances in molecular modeling, provide new insights into the potential mechanisms for substrate recognition and binding by this important class of enzymes. We present herein an overview of the progress, along with a brief description of applications to two types of DSPs: Cdc25 and MAP kinase phosphatase (MKP) family members. In particular, we focus on combined computational and experimental efforts for designing Cdc25B and MKP-1 inhibitors and understanding their mechanisms of interactions with their target proteins. These studies emphasize the utility of developing computational models and methods that meet the two major challenges currently faced in structure-based in silico design of lead compounds: the conformational flexibility of the target protein and the entropic contribution to the selection and stabilization of particular bound conformers.

Metabolic disorders are amongst the most serious medical problems that are encountered in modern societies. To unravel the molecular mechanisms that underlie the metabolic adaptations to disturbed energy balance, wild and laboratory animal models are of primary importance. Previous studies have highlighted some aspects of the metabolic and endocrine variations that are triggered by marked energy reserve depletion/repletion. A brief overview of studies addressing the adaptive mechanisms to fasting/refeeding is presented here. This review also emphasises the necessity to not only consider gene or protein expression levels but to also take into account protein structures, to enable one to fully unravel the exact steps of intermediary metabolism and/or signal transduction pathways that are modulated by nutritional transitions. In this context, proteomic analysis, which uses high-performance tools for peptide/protein separation and mass spectrometry, has emerged as an indispensable tool to elucidate the complex molecular basis of various pathophysiological processes. Proteomics provides a global view of the protein dynamics in a given tissue of any organism. It provides hundreds of protein identifications and quantifications, as well as structure characterizations, from a single complex biological sample. Therefore, proteomic analysis is detailed here in terms of its analytical approaches, strategies, methods, instrumentation, and its limitations. The benefits of performing such analysis are discussed in the context of the fasting/refeeding paradigm and expected insights into the associated molecular mechanisms. Importantly, unravelling the adaptive responses to food deprivation may provide new therapeutic targets for the treatment and/or prevention of numerous pathophysiological conditions characterized by energy depletion

The urokinase-type plasminogen activator receptor (uPAR) and its structural homologue C4.4A are multidomain members of the Ly6/uPAR/α-neurotoxin protein domain family. Both are glycosylphosphatidylinositol-anchored membrane glycoproteins encoded by neighbouring genes located on chromosome 19q13 in the human genome. The structural relationship between the two proteins is, however, not reflected at the functional level. Whereas uPAR has a wellestablished role in regulating and focalizing uPA-mediated plasminogen activation to the surface of those cells expressing the receptor, the biological function of C4.4A remains elusive. Nonetheless, both uPAR and C4.4A have been implicated in human pathologies such as wound healing and cancer. A large body of experimental evidence thus demonstrates that high levels of uPAR in resected tumour tissue as well as in plasma are associated with poor prognosis in a number of human cancers including colon adenocarcinoma and pulmonary squamous cell carcinoma. Targeting uPAR in experimental animal models has also provided promising results regarding the interference with pathogenic plasminogen activation. In the case of C4.4A, very recent data have demonstrated that high protein expression in tumour cells of non-small cell pulmonary adenocarcinomas is associated with a particularly severe disease progression. This review will evaluate structuralfunctional and disease-related aspects of uPAR and C4.4A with a view to possible pharmacological targeting strategies for therapy and for non-invasive bioimaging.

Platinum complex-based chemotherapy is one of the major treatment options of many malignancies. Although severe side effects occur, and only a limited spectrum of tumors can be cured, Pt compounds are used in every second therapy scheme. Thus, many different drug design strategies have been employed for improving the properties of anticancer drugs including pH or redox activation in the tumor, variation of the metal center and therefore the redox and ligand exchange properties, the application of multinuclear metal complexes, the development of targeted approaches, etc. Application of carbohydrate-metal complexes is an example of a targeted approach exploiting the biochemical and metabolic functions of diverse sugars in living organisms for transport and accumulation. Natural carbohydrates and synthetic derivatives possess a manifold of donors endowing them with the ability to coordinate metal centers and providing some additional advantages over other ligands, e.g., biocompatibility, non-toxicity, enantiomeric purity, water solubility, and wellexplored chemistry. In recent years, several examples of carbohydrate compounds have been developed for diverse medicinal applications ranging from compounds with antibiotic, antiviral, or fungicidal activity and anticancer compounds. Herein, metal complexes with carbohydrate ligands are reviewed and the role of the carbohydrate carriers on the antineoplastic activity of these compounds, both in vitro and in vivo, is described.

Natural products have long been regarded as excellent sources for drug discovery given their structure diversity and wide variety of biological activities. Phenylethanoid glycosides are naturally occurring compounds of plant origin and are structurally characterized with a hydroxyphenylethyl moiety to which a glucopyranose is linked through a glycosidic bond. To date several hundred compounds of this type have been isolated from medicinal plants and further pharmacological studies in vitro or in vivo have shown that these compounds possess a broad array of biological activities including antibacterial, antitumor, antiviral, anti-inflammatory, neuro-protective, antioxidant, hepatoprotective, immunomodulatory, and tyrosinase inhibitory actions. Given their extensive activity profile, structure-activity relationships analyses of these compounds have been performed in a number of studies to reveal potential leads for future drug design. This article will summarize the major developments in phenylethanoid glycosides-based research in the past decade. The progresses made in phytochemistry and biological activity studies of these compounds will be reviewed. Particular attention will be given to the novel structures identified to date and the prominent therapeutic values associated with these molecules.

Having previously reported the synthesis and anticancer activities of cyclic 5-fluorouracil (5-FU) O,N-acetalic compounds, the decision was made to change 5-FU for uracil (U), with the prospect of finding an antiproliferative agent endowed with a new mechanism of action. The use of a reverse transcription-PCR-based assay decreased cyclin D1 mRNA, suggesting that this cyclic U O,N-acetalic compound exerts its regulatory action on cyclin D1 at the level of transcription. Following the ongoing Anticancer Drug Programme we planned the synthesis of compounds bearing a natural pyrimidine base and also, the oxygen atom at position 1 of the seven-membered cycle was replaced by its isosteric sulfur atom, and its oxidized states. Next, the pyrimidine base was substituted for the purine one, with the objective of increasing both the lipophilicity and the structural diversity of the target molecules. If the previously described compounds were not prodrugs, it would not be necessary to maintain the O,N-acetalic characteristic. Therefore, molecules were designed in which both structural entities (such as the benzoheterocyclic ring and the purine base) were linked by a heteroatom-C-C-N bond. A series of (RS)-9-(2,3-dihydro-1,4-benzoxathiin-3-ylmethyl)-9H-purine derivatives was obtained and the anticancer activity for the most active compounds was correlated with their capability to induce apoptosis. Finally, completing a SAR study, a series of (RS)-6-substituted-7- or 9-(1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-7H- or 9H-purines was prepared. The studies by microarray technology showed that the main molecular targets of some of these compounds are proapoptotic genes with protein kinase activity such as GP132, ERN1 or RAC1, which prevent the metastatic progression.

Fibrosis of the lung and other organ systems is an increasing cause of morbidity and mortality worldwide. Effective anti-fibrotic agents for such disorders are currently lacking. Injury to epithelium-lined tissues in mammals is typically associated with a mesenchymal response, including the activation of myofibroblasts. Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease that results from effacement of the normal alveolar architecture of the lung. Loss of lung capacity for gas-exchange and increased work of breathing eventually leads to respiratory failure and death. In cutaneous wound models, apoptosis of myofibroblasts are essential to scar-less wound healing. Recent studies indicate that acquisition of an apoptosis-resistant myofibroblast phenotype in the injured lung is associated with non-resolving and persistent fibrosis. The acquired resistance to apoptosis in myofibroblasts is mediated, at least in part, by the sustained activation of two critical pro-survival protein kinases, focal adhesion kinase (FAK) and protein kinase B (PKB/AKT). Therapeutic interventions that modulate the activity of these protein kinases with resultant alterations in the phenotype of myofibroblasts may prove to be effective anti-fibrotic therapeutic strategies. We discuss the potential roles for protein kinase inhibitors as novel drugs for fibrotic disorders. Progress in pre-clinical and clinical development of small molecule inhibitors targeting pro-survival protein kinases is reviewed.

Basic Helix-loop-Helix (bHLH) factors play a significant role in both development and disease. bHLH factors function as protein dimers where two bHLH factors compose an active transcriptional complex. In various species, the bHLH factor Twist has been shown to play critical roles in diverse developmental systems such as mesoderm formation, neurogenesis, myogenesis, and neural crest cell migration and differentiation. Pathologically, Twist1 is a master regulator of epithelial-to-mesenchymal transition (EMT) and is causative of the autosomal-dominant human disease Saethre Chotzen Syndrome (SCS). Given the wide spectrum of Twist1 expression in the developing embryo and the diverse roles it plays within these forming tissues, the question of how Twist1 fills some of these specific roles has been largely unanswered. Recent work has shown that Twist's biological function can be regulated by its partner choice within a given cell. Our work has identified a phosphoregulatory circuit where phosphorylation of key residues within the bHLH domain alters partner affinities for Twist1; and more recently, we show that the DNA binding affinity of the complexes that do form is affected in a cis-element dependent manner. Such perturbations are complex as they not only affect direct transcriptional programs of Twist1, but they indirectly affect the transcriptional outcomes of any bHLH factor that can dimerize with Twist1. Thus, the resulting lineage-restricted cell fate defects are a combination of loss-of-function and gain-offunction events. Relating the observed phenotypes of defective Twist function with this complex regulatory mechanism will add insight into our understanding of the critical functions of this complex transcription factor.