Current Medicinal Chemistry (v.16, #14)

Cancer Stem Cells: A New Paradigm for Understanding Tumor Growth and Progression and Drug Resistance by Rosaria Gangemi, Laura Paleari, Anna Orengo, Alfredo Cesario, Leonardo Chessa, Silvano Ferrini, Patrizia Russo (1688-1703).
Normal somatic stem cells (SC) are naturally resistant to chemotherapeutic agents due to their expression of various membrane transporter molecules (such as MDR-1), detoxifying enzymes and DNA repair proteins. In addition, they also have a slow rate of cell turnover and therefore escape from chemotherapeutic agents that target rapidly replicating cells. Cancer stem cells (CSC), being the mutated counterparts of normal SC, also have similar properties, which allow them to survive therapy. These surviving CSC then repopulate the tumor, causing relapse. The purpose of this review is to understand the most current research into the cellular and molecular biology of CSC. Topics that will be explored are the origin of CSC, the CSC niche, the regulation of self-renewal in normal and cancer SC, and CSC as therapeutic targets.

The Metastatic Process: Methodological Advances and Pharmacological Challenges by Antonio Mazzocca, Vinicio Carloni (1704-1717).
The metastatic spread of cancer is still the major barrier to the treatment of this disease. Understanding the molecular mechanisms underlying the metastatic process is of crucial importance to tune novel therapeutic strategies aimed at contrasting the dissemination of cancer. Metastasis is a sequential multistep process that ultimately leads to the cancer's outgrowth in a different organ from which it had originated. This clinically and experimentally involves the following steps: invasion of adjacent tissues, intravasation, transport of cancer cells through the circulatory system, arrest at a secondary site, extravasation and growth in a secondary organ. Additionally, tumor growth and metastasis depend on the ability of the tumor to induce its own blood supply through angiogenesis. Each of these steps can potentially be targeted by therapeutic agents, but the limited knowledge regarding the molecular events of metastasis makes most therapeutic strategies largely inefficient. However, important methodological advances have recently led to further insights into the biology of metastasis, thus raising the possibility of designing more appropriate pharmacological strategies to contrast the specific steps of the metastatic process. A variety of pharmacological approaches including inhibition of tumor invasion, angiogenesis, signal transduction pathways, and most recently the targeting of tumor stroma, are now under fervent development. Benefits and limits of these approaches, as well as, new therapeutic opportunities are herein discussed. Agents that limit any phase of the metastatic process may be therapeutically useful. Therefore, the future pharmacological challenge will be to combine drugs that target different aspects of this complex multistep process.

Role, Metabolism, Chemical Modifications and Applications of Hyaluronan by Nicola Volpi, Juergen Schiller, Robert Stern, Ladislav Soltes (1718-1745).
Hyaluronan (hyaluronic acid, HA) is a linear naturally occurring polysaccharide formed from repeating disaccharide units of N-acetyl-D-glucosamine and D-glucuronate. Despite its relatively simple structure, HA is an extraordinarily versatile glycosaminoglycan currently receiving attention across a wide front of research areas. It has a very high molar mass, usually in the order of millions of Daltons, and possesses interesting visco-elastic properties based on its polymeric and polyelectrolyte characteristics. HA is omnipresent in the human body and in other vertebrates, occurring in almost all biological fluids and tissues, although the highest amounts of HA are found in the extracellular matrix of soft connective tissues. HA is involved in several key processes, including cell signaling, wound repair and regeneration, morphogenesis, matrix organization and pathobiology. Clinically, it is used as a diagnostic marker for many disease states including cancer, rheumatoid arthritis, liver pathologies, and as an early marker for impending rejection following organ transplantation. It is also used for supplementation of impaired synovial fluid in arthritic patients, following cataract surgery, as a filler in cosmetic and soft tissue surgery, as a device in several surgical procedures, particularly as an antiadhesive following abdominal procedures, and also in tissue engineering. This review will provide an overview of the structure and physiological role of HA, as well as of its biomedical and industrial applications. Recent advances in biotechnological approaches for the preparation of HA-based materials, and as a component of tissue scaffolding for artificial organs will also be presented.

The 4-Quinolone-3-Carboxylic Acid Motif as a Multivalent Scaffold in Medicinal Chemistry by Claudia Mugnaini, Serena Pasquini, Federico Corelli (1746-1767).
Quinolones are among the most common frameworks present in the bioactive molecules and hence represent an attractive starting point for the design of combinatorial libraries. Since 1962 4-quinolone-3-carboxylic acid derivatives are clinically used as antibacterial agents worldwide. Currently, fluoroquinolones are approved by the WHO as second-line drugs to treat tuberculosis (TB), and their use in multidrug-resistant (MDR)-TB is increasing due to the fact that they have a broad and potent spectrum of activity and can be administered orally. In the last years, quinolones endowed with and#x201C;nonclassicaland#x201D; biological activities, such as antitumor, anti-HIV-1 integrase, cannabinoid receptor 2 agonist/antagonist activities, have been reported by our research group as well as by other researchers. This review focuses on the 4-quinolone-3- carboxylic acid motif as a privileged structure in medicinal chemistry for obtaining new compounds possessing antibacterial, antitumor, anti-HIV, and cannabinoid receptors modulating activities. Synthetic approaches, structure-activity relationships, mechanisms of action, and therapeutic potentials of these novel classes of pharmacologically active compounds are presented.

Structural Insight into PPARγ Ligands Binding by A. Farce, N. Renault, P. Chavatte (1768-1789).
Peroxisome Proliferator Activated Receptors (PPARs) are a family of three related nuclear receptors first cloned in 1990. Their involvement in glucidic and lipidic homeostasis quickly made them an attractive target for the treatment of metabolic syndrome, the most prevalent mortality factor in developed countries. They therefore attracted much synthetical efforts, more particularly PPARand#947;. Supported by a large number of crystallographic studies, data derived from these compounds lead to a fairly clear view of the agonist binding mode into the Ligand Binding Domain (LBD). Nearly all the compounds conform to a three-module structure, with a binder group involved in a series of hydrogen bonds in front of the ligand-dependent Activation Function (AF2), a linker mostly arranged around a phenoxyethyl and an effector end occupying the large cavity of the binding site. Following the marketing of the glitazones and the observation of the hepatotoxicity of troglitazone, variations in the binder led to the glitazars, and then pharmacomodulations have been undertaken on the two other modules, leading to a large family of highly related chemical structures. Some compounds, while still adhering to the three-module structure, diverge from the mainstream, such as the phthalates. Curiously, these plasticizers were known to elicit biological effects that led to the discovery of PPARs but were not actively studied as PPARs agonists. As the biological effects of PPARs became clearer, new compounds were also found to exert at least a part of their actions by the activation of PPARand#947;.

Progress of Biosensors Based on Cholinesterase Inhibition by Miroslav Pohanka, Kamil Musilek, Kamil Kuca (1790-1798).
Biosensors are available and applicable for detection and characterization of specific inhibitors of many enzymes. In this review, biosensors based on fixed acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) are presented. Inhibition of selected enzymes by various compounds, such as organophosphorus and carbamate pesticides, nerve agents (e.g. sarin or VX), and other natural toxins (e.g. aflatoxins), was employed to develop specific assays using biosensors only. Biosensor technology brings potential miniaturization and portability, when it is compared to standard methods. Construction of biosensors based on cholinesterases became a more important issue within the last decades. Novel approach with recombinant proteins, microelectrodes and immobilization protocol related to nanotechnologies opened new insight to the cholinesterase based biosensor construction and its perspective via routine assays. This review is focused on novel trends within such biosensors as a result of the known platform.

Carotid artery intima-media thickness measured by ultrasound has been shown to be correlated with the presence of cardiovascular disease and is now accepted and used as a surrogate marker for atherosclerotic disease, an important organ damage of hypercholesterolemia. In particular, statins reduce ischemic heart disease, improve endothelial function, reduce pro-inflammatory cytokines, reduce left ventricular hypertrophy and adverse remodeling, and slow/arrest atherosclerotic process. This last effect represents one of the most important targets of lipid-lowering drugs, in particular, carotid intima-media thickness, and an early-onset of atherosclerotic process. The acute anti-inflammatory effects of statins should further be explored as a potential mediator of change in intima-media thickness. Larger randomized controlled trials with selected patients and more detailed measurements of carotid intima-media thickness are needed to determine the clinical practice implications of these findings in participants who have asymptomatic evidence of atherosclerosis. The aim of this review is to explore the effectiveness of several used statins on carotid intima-media thickness regression.

It is believed that the production and accumulation of beta-amyloid (Aand#946;) peptide is a critical step to the pathogenesis of Alzheimer's disease (AD). BACE 1 (beta-site APP-cleaving enzyme 1 or and#946;-secretase), the key enzyme required for generating Aand#945; from the and#946;-amyloid precursor protein (APP), is regarded as an ideal target for AD therapeutic drug design. Due to low oral bioavailability, metabolic instability and poor ability to penetrate the central nervous system (CNS) of the existing peptidomimetic inhibitors, researchers have paid more attention to the development of nonpeptidomimetic inhibitors in recent years. A number of drug screening approaches and technologies have been used to identify novel nonpeptidomimetic BACE 1 inhibitors. This review mainly focuses on the recent developments in structure-based design and synthesis of the nonpeptidomimetic BACE 1 inhibitors.