A Melanophore-Based Screening Assay for Erythropoietin Receptors

Semi-solid tumor model in Xenopus laevis/gilli cloned tadpoles for intravital study of neovascularization, immune cells and melanophore infiltration

Tumors have the ability to grow as a self-sustaining entity within the body. This autonomy is in part accomplished by the tumor cells ability to induce the formation of new blood vessels (angiogenesis) and by controlling cell trafficking inside the tumor mass. These abilities greatly reduce the efficacy of many cancer therapies and pose challenges for the development of more effective cancer treatments. Hence, there is a need for animal models suitable for direct microscopy observation of blood vessel formation and cell trafficking, especially during early stages of tumor establishment. Here, we have developed a reliable and cost effective tumor model system in tadpoles of the amphibian Xenopus laevis. Tadpoles are ideally suited for direct microscopy observation because of their small size and transparency. Using the thymic lymphoid tumor line 15/0 derived from, and transplantable into, the X. laevis/gilli isogenic clone LG-15, we have adapted a system that consists in transplanting 15/0 tumor cells embedded into rat collagen under the dorsal skin of LG-15 tadpole recipients. This system recapitulates many facets of mammalian tumorigenesis and permits real time visualization of the active formation of the tumor microenvironment induced by 15/0 tumor cells including neovascularization, collagen rearrangements as well as infiltration of immune cells and melanophores.

High-Throughput Lead Finding and Optimisation for GPCR Targets

Driven by past successes and the detailed knowledge of signalling cascades and physiological processes, G-protein-coupled receptors are taking a prominent place in the portfolios of many pharmaceutical companies. To successfully address this target class, scientists need not only a good understanding of the specific receptor under investigation, but also the right tools from assay technology, reagent production to a hit-to-lead process that acknowledges the importance of parameters beyond potency and embraces the gain in knowledge of the last decade. This manuscripts attempts to summarise some of the changes and progress made across the pharmaceutical industry to design an efficient and effective strategy for finding and optimising small molecules modulating the activity of GPCRs.

Going to the well no more: lawn format assays for ultra-high-throughput screening

Screening in a 'well-less' or lawn format provides a means to screen large compound collections against many targets in a fast, versatile and cost effective manner. The development of generic lawn format assays to screen various gene families against large compound collections should facilitate the identification of hits and tools to use in drug discovery and chemogenomic endeavours. Lawn format holds particular promise for screening GPCRs and selected enzyme families with potential use in other gene families.

Discovery of cytokine mimics using cell-based systems

The successful cloning and subsequent clinical application of recombinant cytokines and/or growth factors has generated a number of important therapeutics. In contrast to the G-protein-coupled receptors, identification of small-molecule agonists of the cytokine and/or growth factor receptor family has proved difficult. The first small peptides and non-peptidic small-molecule agonists for several receptors have recently been reported. The initial identification and/or crucial characterization of these molecules as true mimics was dependent on the use of cell-based functional assays. This article will review recent cell-based assay technologies that are suitable for HTS and that are being applied to the discovery of novel cytokine and growth factor mimics.

High-throughput screening: new technology for the 21st century

New technologies in high-throughput screening have significantly increased throughput and reduced assay volumes. Key advances over the past few years include new fluorescence methods, detection platforms and liquid-handling technologies. Screening 100,000 samples per day in miniaturized assay volumes will soon become routine. Furthermore, new technologies are now being applied to information-rich cell-based assays, and this is beginning to remove one of the key bottlenecks downstream from primary screening.

High-throughput and ultra-high-throughput screening: solution- and cell-based approaches

The trend towards assay miniaturization for high-throughput and ultra-high-throughput screening continues to spur development of homogeneous, fluorescence-based assays in higher density, smaller volume microplate formats. Recently, first-generation microfluidic devices have been designed for performing continuous-flow biochemical and cell-based assays. These devices provide orders-of-magnitude reduction in reagent consumption, and offer the potential for implementing high-throughput screening in formats that integrate up-front compound handling with unique assay functionality.