Current Medicinal Chemistry - Volume 17, Issue 8, 2010

Various human tumors preferentially metastasize by lymphatic route and lymphovascular invasion predicts lymph node metastasis. In this review article, we will summarize recent literature data concerning lymphangiogenesis, focusing on tumor lymphangiogenesis. In detail, we try to answer some important questions related to: a) The specificity of lymphatic endothelial cell markers; b) The differential characteristics of lymphatic vessels in tumors; c) The interplay between different lymphangiogenic factors; d) The role of pre-existing and newly-formed lymphatic vessels in tumors and their proliferative potential; e) The role of lymphatic vessels in tumor metastases; e) The prognostic significance of lymphatic microvascular density in tumors; f) The inhibition of lymphangiogenesis in tumors.

Hepatocellular carcinoma and cholangiocarcinoma are the two most important primary malignancies of the liver. These are among the tumours with the lowest response to pharmacological treatment based on currently available drugs. This is due either to the existence of refractoriness of the initial tumour or to the ability of cancer cells to develop chemoresistance during treatment. Liver cancers share some of the mechanisms responsible for drug refractoriness with other types of tumours, such as a reduction in drug uptake; enhanced drug export; intracellular inactivation of the active agent; alteration of the molecular target; an increase in the activity of the target route to be inhibited, or the appearance or stimulation of alternative routes; enhanced repair of drug-induced modifications in the target molecules, and the activation/ inhibition of intracellular signalling pathways, all of which lead to a negative balance between the apoptosis/survival of tumour cells. The aim of the present article is to review how these mechanisms of chemoresistance affect the different families of drugs that are being or have been used to treat hepatocellular carcinoma and cholangiocarcinoma. A better understanding of the molecular bases of drug refractoriness is needed in order to develop novel drugs or pharmacological strategies aimed at overcoming resistance to anticancer agents.

The gp120 molecule of HIV-1 is a glycoprotein that is part of the outer layer of the virus. It presents itself as viral membrane spikes consisting of 3 molecules of gp120 linked together and anchored to the membrane by gp41 protein. Gp120 is essential for viral infection as it facilitates HIV entry into the host cell and this is its best-known and most researched role in HIV infection. However, it is becoming increasingly evident that gp120 might also be facilitating viral persistence and continuing HIV infection by influencing the T cell immune response to the virus. Several mechanisms might be involved in this process of which gp120 binding to the CD4 receptor of T cells is the best known and most important interaction as it facilitates viral entry into the CD4+ cells and their depletion, a hallmark of the HIV infection. Gp120 is shed from the viral membrane and accumulates in lymphoid tissues in significant amounts. Here, it can induce apoptosis and severely alter the immune response to the virus by dampening the antiviral CTL response thus impeding the clearance of HIV. The effects of gp120 and how it interacts and influences T cell immune response to the virus is an important topic and this review aims to summarize what has been published so far in hopes of providing guidance for future work in this area.

The life cycle of HIV-1 requires extensive assistance from the host cell proteins and pathways. TSG101 is one of the cellular proteins involved in the budding process of HIV-1, and plays an important role in the cellular vacuolar protein sorting (Vps) pathway. Its main function being recognizing ubiquitinated cargo, TSG101 also proved to be essential for the budding process of HIV-1 virions. In this process, TSG101 is recruited from internal site of the infected cell to the budding site to aid in the release of the HIV-1 virus particles. Depletion of TSG101 from virus-producing cells can lead to a budding defect. Therefore, TSG101 is a potentially new attractive target for therapeutic intervention in AIDS. This review describes the structure and function of TSG101 and latest progress in the discovery of TSG101-directed HIV-1 inhibitors.

Human induced pluripotent stem (iPS) cells hold great promise for therapy of a number of degenerative diseases such as ischemic heart failure, Parkinson's disease, Alzheimer's disease, diabetes mellitus, sickle cell anemia and Huntington disease. They also have the potential to accelerate drug discovery in 3 ways. The first involves the delineation of chemical components for efficient reprogramming of patient's blood cells or cells from biopsies, obviating the need for cellular delivery of reprogramming exogenous transgenes, thereby converting hope into reality for patients suffering from degenerative diseases. Patients worldwide stand to benefit from the clinical applicability of iPS cell-based cell replacement therapy for a number of degenerative diseases. The second is the potential for discovering novel drugs in a high throughput manner using patient-specific iPS cell-derived somatic cells possessing the etiology of the specific disease. The third is their suitability for toxicological testing of drugs and environmental factors. This review focuses on these potential applications of iPS cells with special emphasis on recent updates of iPS cell research contributing to the accelerated drug discovery.

Cells contain a multitude of different chemical reaction paths running simultaneously and quite independently next to each other. This amazing feat is enabled by molecular recognition, the ability of biomolecules to form stable and specific complexes with each other and with their substrates. A better understanding of this process, i.e. of the kinetics, structures and thermodynamic properties of biomolecule binding, would be invaluable in the study of biological systems. In addition, as the mode of action of many pharmaceuticals is based upon their inhibition or activation of biomolecule targets, predictive models of small molecule receptor binding are very helpful tools in rational drug design. Since the goal here is normally to design a new compound with a high inhibition strength, one of the most important thermodynamic properties is the binding free energy ΔG0. The prediction of binding constants has always been one of the major goals in the field of computational chemistry, because the ability to reliably assess a hypothetical compound's binding properties without having to synthesize it first would save a tremendous amount of work. The different approaches to this question range from fast and simple empirical descriptor methods to elaborate simulation protocols aimed at putting the computation of free energies onto a solid foundation of statistical thermodynamics. While the later methods are still not suited for the screenings of thousands of compounds that are routinely performed in computational drug design studies, they are increasingly put to use for the detailed study of protein ligand interactions. This review will focus on molecular mechanics force field based free energy calculations and their application to the study of protein ligand interactions. After a brief overview of other popular methods for the calculation of free energies, we will describe recent advances in methodology and a variety of exemplary studies of molecular dynamics simulation based free energy calculations.

P-glycoprotein (P-gp) is an ATP-driven transmembrane transporter capable of effluxing a wide variety of structurally diverse and functionally unrelated hydrophobic compounds out of the cell. Multidrug resistance (MDR), often associated with the over-expression of P-gp, has been implicated as a major obstacle to effective chemotherapy for cancer, parasitic diseases, AIDS, and other diseases. Drug efflux mediated by P-gp is also involved in decreasing the oral bioavailability of drugs by limiting intestinal absorption. Our appreciation of the structural and functional aspects of P-gp has definitely improved in recent years, benefiting from the deciphering of the structure of some bacterial transporters that paved the way for construction of homology models for more complex transporters. Here, we will review the recent advances in the studies of the structure and functional characteristics of P-gp with the hopes of facilitating rational drug design in developing novel potent MDR modulators.