Current Medicinal Chemistry - Volume 15, Issue 20, 2008

For many years, extracellular matrix (ECM) was considered to function as a tissue support and filler. However, we now know that ECM proteins control many cellular events through their interaction with cell-surface receptors and cytoplasmic signaling pathways. For example, they regulate cell proliferation, cell division, cell adhesion, cell migration, and apoptosis. We focus in this review on a laminin isoform, laminin-332 (formerly termed laminin-5), a major component of the basement membrane (BM) of skin and other epithelial tissues. It is composed of 3 subunits (α3, β3, and γ2) and interacts with at least two integrin receptors expressed by epithelial cells (α3β1 and α6β4 integrin). Mutations in either laminin-332 or integrin α6β4 result in junctional epidermolysis bullosa, a blistering skin disease, while targeting of laminin-332 by autoantibodies in cicatricial pemphigoid leads to dysadhesion of epithelial cells from their underlying connective tissue. Abnormal expression of laminin-332 and its integrin receptors is also a hallmark of certain tumor types and is believed to promote invasion of colon, breast and skin cancer cells. Moreover, there is emerging evidence that laminin-332 and its protease degradation products are not only found at the leading front of several tumors but also likely induce and/or promote tumor cell migration. Thus, in this review, we focus specifically on the role of laminin-332 and its integrin receptors in adhesion, proliferation, and migration/invasion of cancer cells. Finally, we discuss strategies for the development of laminin-332-based antagonists for the treatment of malignant tumors.

Atherosclerosis is an inflammatory disease. Monocyte-platelet interactions may play a key role in this process by various pathways. They “inflame” each other as well as adjacent cell types at the vascular wall by direct physical interactions, autocrine and paracrine activation processes. These processes promote monocyte recruitment (in)to the vascular wall - a key mechanism in atherogenesis. This article highlights the molecular basis and the inflammatory pathways initiated by platelet-monocyte interactions.

Human contains 49 ATP-binding cassette (ABC) transporter genes and the multidrug resistance associated proteins (MRP1/ABCC1, MRP2/ABCC2, MRP3/ABCC3, MRP4/ABCC4, MRP5/ABCC5, MRP6/ABCC6, MRP7/ABCC10, MRP8/ABCC11 and MRP9/ABCC12) belong to the ABCC family which contains 13 members. ABCC7 is cystic fibrosis transmembrane conductance regulator; ABCC8 and ABCC9 are the sulfonylurea receptors which constitute the ATPsensing subunits of a complex potassium channel. MRP10/ABCC13 is clearly a pseudo-gene which encodes a truncated protein that is highly expressed in fetal human liver with the highest similarity to MRP2/ABCC2 but without transporting activity. These transporters are localized to the apical and/or basolateral membrane of the hepatocytes, enterocytes, renal proximal tubule cells and endothelial cells of the blood-brain barrier. MRP/ABCC members transport a structurally diverse array of important endogenous substances and xenobiotics and their metabolites (in particular conjugates) with different substrate specificity and transport kinetics. The human MRP/ABCC transporters except MRP9/ABCC12 are all able to transport organic anions, such as drugs conjugated to glutathione, sulphate or glucuronate. In addition, selected MRP/ABCC members may transport a variety of endogenous compounds, such as leukotriene C4 (LTC4 by MRP1/ABCC1), bilirubin glucuronides (MRP2/ABCC2, and MRP3/ABCC3), prostaglandins E1 and E2 (MRP4/ABCC4), cGMP (MRP4/ABCC4, MRP5/ABCC5, and MRP8/ABCC11), and several glucuronosyl-, or sulfatidyl steroids. In vitro, the MRP/ABCC transporters can collectively confer resistance to natural product anticancer drugs and their conjugated metabolites, platinum compounds, folate antimetabolites, nucleoside and nucleotide analogs, arsenical and antimonial oxyanions, peptide-based agents, and in concert with alterations in phase II conjugating or biosynthetic enzymes, classical alkylating agents, alkylating agents. Several MRP/ABCC members (MRPs 1-3) are associated with tumor resistance which is often caused by an increased efflux and decreased intracellular accumulation of natural product anticancer drugs and other anticancer agents. Drug targeting of these transporters to overcome MRP/ABCC-mediated multidrug resistance may play a role in cancer chemotherapy. Most MRP/ABCC transporters are subject to inhibition by a variety of compounds. Based on currently available preclinical and limited clinical data, it can be expected that modulation of MRP members may represent a useful approach in the management of anticancer and antimicrobial drug resistance and possibly of inflammatory diseases and other diseases. A better understanding of their substrates and inhibitors has important implications in development of drugs for treatment of cancer and inflammation.

Computational chemistry software for lead discovery has become well established in pharmaceutical industry and has found its way to the desktop computers of medicinal chemists for different purposes, providing insight on the mode of action and binding properties, and creating new ideas for lead structure refinement. In this review we investigate the performance and reliability of recent state-of-the-art data modeling techniques, as well as ligand-based and structurebased modeling approaches for 3D virtual screening. We discuss and summarize recently published success stories and lately developed techniques. Parallel screening is one of these emerging approaches allowing for efficient activity in silico profiling of several compounds against different targets or anti-targets simultaneously. This is of special interest to medicinal chemists, as the approach allows revealing unknown binding modes (‘target-fishing’) as well as integrated ADME profiling or - more generally - the prediction of off-target effects.

Renal failure, both acute and chronic, represents an important health problem by its social, sanitary and economic aspects. Mitogen-activated protein kinases (MAPK) are a family of mediators involved in the transduction of extracellular stimuli to intracellular responses. The best studied members of this family are extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2), Jun NH2-terminal kinase (JNK), p38 kinase and extracellular signal regulated kinases 5 (ERK5) also known as big MAP Kinase 1 (BMK1). MAPKs plays a role in regulating renal function and all these pathways have been demonstrated to be activated in many “in vivo” and cellular models or renal failure. As MAP kinases are key regulators in the control of cell proliferation and cell death, many more or less specific inhibitors of these pathways are being developed for the treatment of tumors. The purpose of this review is to examine the data available on the role of MAPKs activation in “in vivo” models of renal failure, as well as in different renal cell types (especially in mesangial cells, podocytes, tubular epithelial cells and fibroblasts) subjected to stress or damage. We have also reviewed the effect of MAPKs inhibition on renal damage, both “in vivo” and “in vitro”. Data collected allow to suggest that therapy of chronic and acute renal disease with MAPKs inhibitors is a promising therapeutic area, although much more basic and clinical studies are necessary before this kind of therapy can be used in the everyday clinic.

It is now recognized that necrosis is not the only mechanism responsible for chemically-induced cell death. It is believed that apoptosis could be the major form of cell death induced by toxicants and that necrosis is associated only with circumstances of gross cell injury. The liver is a key target organ for drug toxicity and an important effort in drugdiscovery deals with the identification of molecules with hepatotoxic potential. The importance of apoptosis in toxicology has been underestimated given the difficulty of identifying apoptotic cells in in vitro models when apoptosis normally degenerates to secondary necrosis. Nowadays, the central role played by apoptosis in the toxicity of many xenobiotics and P450-generated metabolites is recognized. The detection of drug-induced apoptosis constitutes one of the highest priorities of the pharmaceutical industry. Different markers aimed at identifying apoptotic compounds irrespectively of the pathway of how cell apoptosis was initiated have been proposed. The aim of the present paper is to review the utility of some available in vitro strategies for studying drug-induced liver apoptosis. The evaluation of apoptotic or anti-apoptotic effects of chemicals in hepatocytes is illustrated by several examples including model apoptotic compounds, pharmaceutical drugs which have been shown to induce apoptosis as an adverse effect; and drugs preventing apoptosis. By combining appropriated markers, apoptosis can be detected in hepatocytes long before cell necrosis, at sub-cytotoxic concentrations of the drugs. The possibility of using small amounts of cells cultured in multiwell formats and automation has notably contributed to develop reproducible, reliable, sensitive, easy-to-handle and rapid multiparametric assays that are ideally amenable to high throughput screening (HTS).