Combinatorial Chemistry & High Throughput Screening - Volume 15, Issue 3, 2012

Omics is an emerging area that aims to understand molecules as networks using mathematical, statistical and computing methods to solve biological problems involving nucleotides, amino acid sequences and other related information. It encompasses huge amounts of data relevant to genomics, transcriptomics, proteomics, metabolomics, interactomics, cytomics and bioinformatics. Using omics-based platforms, unprecedented potential has been endowed on researchers to screen cells at the gene, transcript, protein, metabolite and interaction network level in the search for novel drug targets. More importantly, it enables us to elucidate the primary mechanism-of-action of certain drugs, further understand their side effects in unanticipated off-target interaction, validate existing drug candidates and find seminal potential therapeutic applications for an established drug, thus facilitating the translation from bench to bedside. In this volume, we have invited a number of scientists who are at the forefront in the development and application of high throughput omics-based technologies for the characterization of novel drug targets to share their expert knowledge in this series of reviews. These topics range from explicit preamble of the serological analysis of recombinant cDNA expression libraries (SEREX) technology to several of the most widely applied and emerging technologies available for novel druggable target screening. In addition, the metabolomic signatures of certain diseases that would become potential targets for therapy have also been explicitly elucidated. Although it may be difficult to encompass all available approaches and/or instrumentation in a single issue, these articles have included the most widely utilized approaches in the current drug target screening environment. We hope that our readers will find the articles featured in this volume (part 1 - issue 3 and part 2 - issue 4) useful and informative for their own drug target screening projects.

Advances in novel tumor-associated antigen (TAA) screening strategy have accelerated the identification and characterization of biomarkers and potential target molecules for tumor subtyping, diagnosis and therapeutics, which may facilitate early detection and diagnosis of the diseases individually and enhance treatment approaches for cancer. Over the past decades, a plethora of non-invasive methodologies dedicated to identify novel target molecules have been primarily focusing on the discovery of human tumor antigens recognized by the autologous antibody repertoire or cytotoxic T lymphocytes, among which serological analysis of recombinant cDNA expression libraries (SEREX) technology is chronologically first established and is of outstanding sensitivity and antigen coverage. This approach involves immunoscreening cDNA libraries extracted from fresh tumor tissues with sera from cancer patients to identify gene products recognized by IgG antibody. SEREX-defined clones can be directly sequenced and their expression profiles can be readily determined, allowing for immediate structural definition of the antigenic target and subsequent identification of TAAs and their cognate autoantibodies. This review is not only devoted to outline the SEREX technology and its advantages, drawbacks and recent modifications currently available for discovering provocative tumor antigens, but also to translate these SEREX-defined peptides into valuable cancer-specific signatures that would aid in the development of diagnostics, prognostics and therapeutics for cancer patients.

DNA hypermethylation of CpG islands plays an important role in gene regulation during cancer development. Many techniques have been developed to detect global DNA methylation in cancer cells compared to normal tissues. This knowledge helps us to better understand cancer progression and also aids in the development of new biomarker for early cancer detection. New prognostic tools for monitoring drug efficacy during cancer treatment can also be developed. In this review, we will examine the different techniques that have been used to study DNA methylation, as well as the emerging high resolution, high throughput techniques for identification of methylated regions to defining cancer related genes in the cancer methylome.

The mass spectrometry (MS)-based quantitative proteomics is powerful to discover disease biomarkers that can provide diagnostic, prognostic and therapeutic targets, and it also can address important problems in clinical and translational medical research. The current status of MS-based quantification strategy and technical advances of several main quantitative assays (two-dimensional (2-D) gel-based methods, stable isotope labeling with amino acids in cell culture (SILAC), isotope-coded affinity tag (ICAT), the isobaric tags for relative and absolute quantification (iTRAQ),18O labeling, absolute quantitation and label-free quantitation) have been summarized and reviewed. At present, except 2-D gel-based methods, several stable isotope labeling quantitative techniques, including SILAC, ICAT and iTRAQ, etc, have been widely applied in identification of differential expression of proteins, post-translational modifications and protein-protein interactions in order to look for novel candidate cancer biomarkers from different physiological states of cells, body fluids or tissue samples. Also, the advantages and challenges of different quantitative proteomic approaches are discussed in identification and validation of candidate targets.

G protein-coupled receptors (GPCRs) which constitute one of the largest and most versatile families of cell surface receptors are involved in a wide spectrum of physiological functions, such as, neuronal transmission, chemotaxis, pacemaker activity and embryonic development. Therefore, in the past a few years GPCR families have become very important targets in pharmaceutical design. However, according to the human genome project, there are approximately 1000 genes encoding GPCRs, only about 200 of GPCRs have known ligands and functions. Searching for ligands of the unknown GPCRs and better modulators of known GPCRs are currently attracting lots of interest. High throughput screening (HTS), which is commonly defined as an automatic process of testing potential drug candidates efficiently, is widely used in drug discovery. In this review, the use of high throughput screening (HTS) in studying GPCRs and the choice of screening technology in different G-protein signaling pathways were summarized.

Aging and its related diseases are severe issues in modern society. Many efforts have been made to understand the mechanisms of aging and to find the ways to prevent age-related diseases. Identifying the compounds targeting agingrelated signals is a challenging work because there are so many proteins and signals involved. Recently, alone with the progresses in high throughput screening (HTS) technology, increasing numbers of small molecules targeting aging-related pathologic processes have been identified. In this review, we introduce the basic workflow, classification and assay strategies of HTS technology, and sort out known small molecules identified via HTS technology by their roles in aging related diseases, such as neural degenerative diseases, diabetes and tumors. Given the fact that application of HTS on aging research is still at an early stage, we also summarize the cellular mechanisms about aging process, paralleled with the compounds which can modulate the functions of proteins important for aging signals. Finally, we briefly discuss some advanced HTS technologies for their potent applications on the discovery of anti-aging compounds. The main purpose of this review is to provide updated and useful information to those who are interested in pharmacology and HTS technology, but not familiar with aging biology, or vice versa.

Lipid rafts are sphingolipid- and cholesterol-enriched membrane microdomains, which are involved in entry, assembly and budding of various types of viruses. Identification of rafts associated proteins modified by virus infection could therefore provide novel insights into the mechanisms of virus infection as well as the development of new biomarkers for diagnosis and drug development. Proteomic approaches, such as LC-ESI-MS/MS, two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), two-dimensional difference gel electrophoresis (2D-DIGE), isotopecoded affinity tags (ICAT), Proteolytic18O Labeling, isotope Tags for Relative and Absolute Quantification (iTRAQ), Stable Isotope Labeling with Amino acids in Cell culture (SILAC) and Multidimensional Protein Identification Technology (MudPIT), provide the large scale and unbiased platform to determine the dynamic profiles of the lipid rafts proteome. In this review, we summarized the research advance regarding modern proteomics analysis of host lipid rafts alterations in response to diverse virus infection.

The repertoire of small-molecular-weight substances present in cells, tissue and body fluids are known as the metabolites. The global analysis of metabolites, such as by high-resolution 1H nuclear magnetic resonance spectroscopy and mass spectrometry, is integral to the rapidly expanding field of metabolomics, which is making progress in various diseases. In the area of cancer and metabolic phenotype, the integrated analysis of metabolites may provide a powerful platform for detecting changes related to cancer diagnosis and discovering novel biomarkers. In this review, metabolomics including the technologies in metabolomics research and extracting information from metabolomics datasets are described. Then we discuss the challenges and opportunities in metabolomics for finding metabolic processes in cancer and discovering novel cancer biomarkers. Finally, we assess the clinical applicability of metabolomics.

Tumorigenesis may be affected by various cellular components in the tumor cells and/or by tumor microenvironmental factors. Cytokines, including chemokines (chemotactic cytokines) are polypeptides or small soluble proteins generated by leukocytes and non-leukocytes, including cancer cells and stromal cells, for example, fibroblasts, mesenchymal stem cells (MSCs) and epithelial cells. Cytokines exert their functions on the cells that secrete them, on nearby cells, or on distant cells. Chemokines have expanded beyond their initial roles in impinging on every aspect of the immune system and leukocyte biology. They display multifunctional effects for regulating angiogenesis, tumor cell proliferation and apoptosis, mediating tumor cell metastasis in an organ-specific manner. This review will focus on the structural and functional aspects of chemokines as well as the roles that cytokines and their receptors play in angiogenesis, tumor invasion and metastasis, and discuss their potential value as important therapeutic targets for intervention in cancer.