A Quantitative Cell-Based High-Content Screening Assay for the Epidermal Growth Factor Receptor-Specific Activation of Mitogen-Activated Protein Kinase

Anti-cancer agents in Saudi Arabian herbals revealed by automated high-content imaging

Natural products have been used for medical applications since ancient times. Commonly, natural products are structurally complex chemical compounds that efficiently interact with their biological targets, making them useful drug candidates in cancer therapy. Here, we used cell-based phenotypic profiling and image-based high-content screening to study the mode of action and potential cellular targets of plants historically used in Saudi Arabia’s traditional medicine. We compared the cytological profiles of fractions taken from Juniperus phoenicea (Arar), Anastatica hierochuntica (Kaff Maryam), and Citrullus colocynthis (Hanzal) with a set of reference compounds with established modes of action. Cluster analyses of the cytological profiles of the tested compounds suggested that these plants contain possible topoisomerase inhibitors that could be effective in cancer treatment. Using histone H2AX phosphorylation as a marker for DNA damage, we discovered that some of the compounds induced double-strand DNA breaks. Furthermore, chemical analysis of the active fraction isolated from Juniperus phoenicea revealed possible anti-cancer compounds. Our results demonstrate the usefulness of cell-based phenotypic screening of natural products to reveal their biological activities.

Quantitative Cell-Based High-Content Screening for Vasopressin Receptor Agonists Using Transfluor®Technology

The authors demonstrate the use of a simple, universal G-protein-coupled receptor (GPCR) assay to screen for agonists for a specific GPCR. Cells stably expressing a green fluorescent protein (GFP)-labeled β-arrestin fusion protein and the vasopressin V2 receptor (V2R) were used in a high-content screening (HCS) assay to screen a small peptide library for V2R agonists. Cells were treated with the peptides at a final concentration of 500 nM for 30min. Agonist stimulation causes V2R internalization into endosomes. GFP-β-arrestin remains associated with the V2R in endosomes, resulting in a fluorescent pattern of intracellular spots. Assay plates were automatically imaged and quantitatively analyzed using an HCS imaging platformand a fast turnkey image analysis application optimized for detection of receptor activation and intracellular spots. Hits were further evaluated to determine their potency. The combination of unique biology, automated high-content analysis, and a powerful means of validating hits results in better leads.

Development and Evaluation of a Fluorescent Antibody-Drug Conjugate for Molecular Imaging and Targeted Therapy of Pancreatic Cancer

Antibodies are widely available and cost-effective research tools in life science, and antibody conjugates are now extensively used for targeted therapy, immunohistochemical staining, or in vivo diagnostic imaging of cancer. Significant advances in site-specific antibody labeling technologies have enabled the production of highly characterized and homogenous conjugates for biomedical purposes, and some recent studies have utilized site-specific labeling to synthesize bifunctional antibody conjugates with both imaging and drug delivery properties. While these advances are important for the clinical safety and efficacy of such biologics, these techniques can also be difficult, expensive, and time-consuming. Furthermore, antibody-drug conjugates (ADCs) used for tumor treatment generally remain distinct from conjugates used for diagnosis. Thus, there exists a need to develop simple dual-labeling methods for efficient therapeutic and diagnostic evaluation of antibody conjugates in pre-clinical model systems. Here, we present a rapid and simple method utilizing commercially available reagents for synthesizing a dual-labeled fluorescent ADC. Further, we demonstrate the fluorescent ADC’s utility for simultaneous targeted therapy and molecular imaging of cancer both in vitro and in vivo. Employing non-site-specific, amine-reactive chemistry, our novel biopharmaceutical theranostic is a monoclonal antibody specific for a carcinoembryonic antigen (CEA) biomarker conjugated to both paclitaxel and a near-infrared (NIR), polyethylene glycol modified (PEGylated) fluorophore (DyLight™ 680-4xPEG). Using in vitro systems, we demonstrate that this fluorescent ADC selectively binds a CEA-positive pancreatic cancer cell line (BxPC-3) in immunofluorescent staining and flow cytometry, exhibits efficient internalization kinetics, and is cytotoxic. Model studies using a xenograft of BxPC-3 cells in athymic mice also show the fluorescent ADC’s efficacy in detecting tumors in vivo and inhibiting tumor growth more effectively than equimolar amounts of unconjugated drug. Overall, our results demonstrate that non-selective, amine-targeting chemistry is an effective dual-labeling method for synthesizing and evaluating a bifunctional fluorescent antibody-drug conjugate, allowing concurrent detection, monitoring and treatment of cancer.

The development of high-content screening (HCS) technology and its importance to drug discovery

INTRODUCTION

High-content screening (HCS) was introduced about twenty years ago as a promising analytical approach to facilitate some critical aspects of drug discovery. Its application has spread progressively within the pharmaceutical industry and academia to the point that it today represents a fundamental tool in supporting drug discovery and development.

AREAS COVERED

Here, the authors review some of significant progress in the HCS field in terms of biological models and assay readouts. They highlight the importance of high-content screening in drug discovery, as testified by its numerous applications in a variety of therapeutic areas: oncology, infective diseases, cardiovascular and neurodegenerative diseases. They also dissect the role of HCS technology in different phases of the drug discovery pipeline: target identification, primary compound screening, secondary assays, mechanism of action studies and in vitro toxicology.

EXPERT OPINION

Recent advances in cellular assay technologies, such as the introduction of three-dimensional (3D) cultures, induced pluripotent stem cells (iPSCs) and genome editing technologies (e.g., CRISPR/Cas9), have tremendously expanded the potential of high-content assays to contribute to the drug discovery process. Increasingly predictive cellular models and readouts, together with the development of more sophisticated and affordable HCS readers, will further consolidate the role of HCS technology in drug discovery.

A High-Content Assay to Screen for Modulators of EGFR Function

Cell-based assays have the potential and advantage to identify cell-permeable modulators of kinase function, and hence provide an alternative to the conventional enzymatic activity-driven discovery approaches that rely on purified recombinant kinase catalytic domains. Here, we describe a domain-based high-content biosensor approach to study endogenous EGFR activity whereby EGF-induced receptor activation, subsequent trafficking, and internalization are imaged and quantified using time-dependent granule formation in cells. This method can readily be used to search for EGFR modulators in both chemical and RNAi screening; with potential applicability to other receptor tyrosine kinases.

Multiplexed high content screening assays create a systems cell biology approach to drug discovery

High content screening (HCS) has emerged as an important platform technology for early drug discovery from target identification through in vitro ADME/Tox. The focus is now on implementing multiplexed assays, developing and using advanced reagents and developing and harnessing more sophisticated informatics tools. Multiplexed HCS assays have the potential to dramatically improve the early drug discovery process by creating systems cell biology profiles on the activities of compounds. It is predicted that multiplexed HCS assays will accelerate the overall workflow and produce deeper functional knowledge, thereby permitting better decisions on what compounds to pursue.:

Lipoprotein-based nanoparticles rescue the memory loss of mice with Alzheimer's disease by accelerating the clearance of amyloid-beta

Amyloid-beta (Aβ) accumulation in the brain is believed to play a central role in Alzheimer's disease (AD) pathogenesis, and the common late-onset form of AD is characterized by an overall impairment in Aβ clearance. Therefore, development of nanomedicine that can facilitate Aβ clearance represents a promising strategy for AD intervention. However, previous work of this kind was concentrated at the molecular level, and the disease-modifying effectiveness of such nanomedicine has not been investigated in clinically relevant biological systems. Here, we hypothesized that a biologically inspired nanostructure, apolipoprotein E3-reconstituted high density lipoprotein (ApoE3-rHDL), which presents high binding affinity to Aβ, might serve as a novel nanomedicine for disease modification in AD by accelerating Aβ clearance. Surface plasmon resonance, transmission electron microscopy, and co-immunoprecipitation analysis showed that ApoE3-rHDL demonstrated high binding affinity to both Aβ monomer and oligomer. It also accelerated the microglial, astroglial, and liver cell degradation of Aβ by facilitating the lysosomal transport. One hour after intravenous administration, about 0.4% ID/g of ApoE3-rHDL gained access to the brain. Four-week daily treatment with ApoE3-rHDL decreased Aβ deposition, attenuated microgliosis, ameliorated neurologic changes, and rescued memory deficits in an AD animal model. The findings here provided the direct evidence of a biomimetic nanostructure crossing the blood-brain barrier, capturing Aβ and facilitating its degradation by glial cells, indicating that ApoE3-rHDL might serve as a novel nanomedicine for disease modification in AD by accelerating Aβ clearance, which also justified the concept that nanostructures with Aβ-binding affinity might provide a novel nanoplatform for AD therapy.

A systems approach for analysis of high content screening assay data with topic modeling

Background

High Content Screening (HCS) has become an important tool for toxicity assessment, partly due to its advantage of handling multiple measurements simultaneously. This approach has provided insight and contributed to the understanding of systems biology at cellular level. To fully realize this potential, the simultaneously measured multiple endpoints from a live cell should be considered in a probabilistic relationship to assess the cell's condition to response stress from a treatment, which poses a great challenge to extract hidden knowledge and relationships from these measurements.

Method

In this work, we applied a text mining method of Latent Dirichlet Allocation (LDA) to analyze cellular endpoints from in vitro HCS assays and related to the findings to in vivo histopathological observations. We measured multiple HCS assay endpoints for 122 drugs. Since LDA requires the data to be represented in document-term format, we first converted the continuous value of the measurements to the word frequency that can processed by the text mining tool. For each of the drugs, we generated a document for each of the 4 time points. Thus, we ended with 488 documents (drug-hour) each having different values for the 10 endpoints which are treated as words. We extracted three topics using LDA and examined these to identify diagnostic topics for 45 common drugs located in vivo experiments from the Japanese Toxicogenomics Project (TGP) observing their necrosis findings at 6 and 24 hours after treatment.

Results

We found that assay endpoints assigned to particular topics were in concordance with the histopathology observed. Drugs showing necrosis at 6 hour were linked to severe damage events such as Steatosis, DNA Fragmentation, Mitochondrial Potential, and Lysosome Mass. DNA Damage and Apoptosis were associated with drugs causing necrosis at 24 hours, suggesting an interplay of the two pathways in these drugs. Drugs with no sign of necrosis we related to the Cell Loss and Nuclear Size assays, which is suggestive of hepatocyte regeneration.

Conclusions

The evidence from this study suggests that topic modeling with LDA can enable us to interpret relationships of endpoints of in vitro assays along with an in vivo histological finding, necrosis. Effectiveness of this approach may add substantially to our understanding of systems biology.

Domain-based biosensor assay to screen for epidermal growth factor receptor modulators in live cells

Traditional drug discovery efforts have resulted in the approval of a handful of receptor tyrosine kinase (RTK) inhibitors; however, their discovery relied solely on screening recombinant kinases, often with poor cellular activity outcome. The ability to screen RTKs in their natural environment is sought as an alternative approach. We have adapted a novel strategy utilizing a green fluorescent protein-labeled SRC homology 2 domain-based biosensor as a surrogate reporter of endogenous epidermal growth factor receptor (EGFR) activity in A549 cells. Upon activation of the receptor, EGFR function in live cells is measured by the number of green granules that form. Here we describe assay miniaturization and demonstrate specificity for EGFR through its chemical inhibition and RNAi-dependent knockdown resulting in complete abrogation of granule formation. Gefitinib and PD 153035 were identified as hits in a pilot screen. This approach allows for the identification of novel EGFR modulators in high-throughput formats for screening chemical and RNAi libraries.

Statistical issues in subpopulation analysis of high content imaging data

High content imaging (HCI) is an increasingly important method for elucidating changes in cellular biology. The combination of validated immuno-fluorescent assays, availability of automated microscopy, and advances in image analysis software has led to increased exploitation of this technology in a variety of settings ranging from cellular signaling pathways to drug discovery. Recent advances in HCI have made the collection of multi-parametric datasets from high-throughput screening routine, but analysis of these data remains a challenge. The few existing analytical tools used to analyze HCI data, usually provided by HCI platform vendors, require extensive operator interaction and, more importantly, lack statistical power. This results in serious under-utilization of the information available from this powerful technology. As HCI applications become increasingly complex, measurements to estimate the composition of the cell population and thus the underlying data structure also becomes more complicated, and the analysis to facilitate the understanding of the biological system will rely heavily on analytical expertise that requires advanced statistical training. The aim of this article is to review the major statistical issues in HCI data analysis, with a focus on quantitative analysis of cell subpopulations.

The JNK pathway amplifies and drives subcellular changes in tau phosphorylation

Neurofibrillary tangles composed of hyperphosphorylated tau are a major hallmark of Alzheimer's Disease. This phosphorylated tau may be a root cause of the disorder and therefore understanding its regulation is important for therapeutic intervention. To model this pathology, Okadaic acid (OA) has been used in primary cultured hippocampal neurons to investigate effects on tau, and the role of the JNK pathway in tau phosphorylation. The use of high content screening has allowed us to quantitatively assess the profound spatiotemporal profile of these proteins, finding dramatic and inhibitable changes. Furthermore, in vitro phosphorylation experiments show that the JNK3 isoform, which is predominantly expressed in the brain, can strongly autophosphorylate itself. This has profound implications on the importance of JNK3 in the CNS and its ability to sustain signaling both towards tau and other apoptotic targets. Together these data provide novel insights into the JNK pathway and a high resolution perspective on how this pathway influences tau phosphorylation and dynamics in neurons.

The use of Cellomics to study enterocyte cytoskeletal proteins in coeliac disease patients

Coeliac disease is characterised by inflammation of small intestinal mucosa accompanied by abnormal villous architecture. It is now accepted that some patients with positive coeliac serology tests may have minor mucosal lesions that may not be apparent on routine histopathological analysis. The aim of the study was to perform detailed examination of enterocyte morphology and cytoskeletal structures using a high content analysis technology. Duodenal biopsies from 14 untreated and 10 treated coeliac patients and from 20 non-coeliac controls were examined. Tissue sections from six patients (study group subjects) before and after the development of gluten-sensitive enteropathy were also investigated. Immunohistochemical studies were performed on paraffin-embedded sections using an anti-α-tubulin antibody. Significant differences in enterocyte morphology and intracellular cytoskeletal structures were demonstrated in patients with proven coeliac disease and in the study group subjects. These changes were present in study group biopsies before evidence of enteropathy, as assessed by routine microscopy. This is the first study to demonstrate detailed characteristics of enterocyte morphology in coeliac patients using a high content analysis approach. The use of this technology allows a quantitative analysis of enterocyte intracellular structures from routine biopsy material and permits detection of subtle changes that precede the characteristic histological lesion.

Pro-apoptotic and microtubule-disassembly effects of ardisiacrispin (A+B), triterpenoid saponins from Ardisia crenata on human hepatoma Bel-7402 cells

Ardisiacrispin (A+B) is a mixture of ardisiacrispins A and B, derived from Ardisia crenata with a fixed proportion (2:1). The present study was conducted to investigate its anticancer activity on human cancer cells and its underlying mechanism of action. The (IC50)s of ardisiacrispin (A+B) on proliferation of several human cancer cell lines were in the range of 0.9-6.5 microg/ml by sulphorhodamine B-based colorimetric assay, in which Bel-7402 was the most sensitive cell line. Moreover, ardisiacrispin (A+B) induced dose-dependent apoptosis in Bel-7402 cells at doses of 1-10 microg/ml by flow cytometry, and resulted in the changes of the mitochondrial membrane depolarization, membrane permeability enhancement, and nuclear condensation in a dose-dependent manner through high-content screening analysis. Furthermore, ardisiacrispin (A+B) could disassemble microtubule in Bel-7402 cells; the fluorescence intensity of microtubules decreased at the concentration of 5-20 microg/ml. These findings suggest that ardisiacrispin (A+B) could inhibit the proliferation of Bel-7402 cells by inducing apoptosis and disassembling microtubule.

Induction of apoptosis accompanying with G(1) phase arrest and microtubule disassembly in human hepatoma cells by jaspolide B, a new isomalabaricane-type triterpene

Jaspolide B is a novel isomalabaricane-type triterpene isolated from sponge Jaspis sp. We investigated its effects on human hepatoma cells in this study. After 48 h of incubation, jaspolide B inhibited the growth of Bel-7402 and HepG2 cells with IC(50) values of 29.1 and 29.5 μM, respectively. Incubation with 0.5 μM of jaspolide B caused time-dependent induction of apoptosis in up to 66.8% of Bel-7402 cells for 48 h, and the induction of apoptosis was confirmed by the enhancement of mitochondrial masses and cell membrane permeability, and nuclear condensation in Bel-7402 and HepG2 cells. Moreover, jaspolide B arrested cell cycle progression at G(1) phase of human hepatoma cells in a dose- and time-dependent manner. In addition, treatment of the compound caused dose-dependent disassembly of microtubule cytoskeleton in Bel-7402 cells at indicated concentrations, and this effect being similar but weaker than that of colchicine, a well-known microtubule-disassembly agent. We conclude that the anti-cancer effect of jaspolide B relates to the apoptosis induction, cell cycle arrest and microtubule disassembly, and these multiple mechanisms of jaspolide B, especially the induction of apoptosis, open interesting perspectives for further exploration of the isomalabaricane-type terpenes and compounds of marine sponge origin as potential anticancer agents.

High-content imaging analysis of the knockdown effects of validated siRNAs and antisense oligonucleotides

High-content imaging (HCI) provides researchers with a powerful tool for understanding cellular processes. Although phenotypic analysis generated through HCI is a potent technique to determine the overall cellular effects of a given treatment, it frequently produces complex data sets requiring extensive interpretation. The authors developed statistical analyses to decrease the time spent to determine the outcome of each HCI assay and to better understand complex phenotypic changes. To test these tools, the authors performed a comparison experiment between 2 types of oligonucleotide-mediated gene silencing (OMGS), antisense oligonucleotides (ASOs), and short, double-stranded RNAs (siRNAs). Although similar in chemical structure, these 2 methods differ in cellular mechanism of action and off-target effects. Using a library of 50 validated ASOs and siRNAs to the same targets, the authors characterized the differential effects of these 2 technologies using a HeLa cell G2-M cell cycle assay. Although knockdown of a variety of targets by ASOs or siRNAs affected the cell cycle profile, few of those targets were affected by both ASOs and siRNAs. Distribution analysis of population changes induced through target knockdown led to the identification of targets that, when inhibited, could affect the G2-M transition in the cell cycle in a statistically significant manner. The distinctly different mechanisms of action of these 2 forms of gene silencing may help define the use of these treatments in both clinical and research environments.

Quantitative characterization of mitosis-blocked tetraploid cells using high content analysis

A range of cellular evidence supporting a G1 tetraploidy checkpoint was obtained from different assay methods including flow cytometry, immunoblotting, and microscopy. Cancer research would benefit if these cellular properties could instead be measured by a single, quantitative, automated assay method, such as high content analysis (HCA). Thus, nocodazole-treated cells were fluorescently labeled for different cell cycle-associated properties, including DNA content, retinoblastoma (Rb) and histone H3 phosphorylation, p53 and p21(WAF1) expression, nuclear and cell sizes, and cell morphology, and automatically imaged, analyzed, and correlated using HCA. HCA verified that nocodazole-induced mitosis block resulted in tetraploid cells. Rb and histone H3 were maximally hyperphosphorylated by 24 h of nocodazole treatment, accompanied by cell and nuclear size decreases and cellular rounding. Cells remained tetraploid and mononucleated with longer treatments, but other targets reverted to G1 levels, including Rb and histone H3 dephosphorylation accompanied by cellular respreading. This was accompanied by increased p53 and p21(WAF1) expression levels. The range of effects accompanying nocodazole-induced block of mitosis and the resulting tetraploid cells' reversal to a pseudo-G1 state can be quantitatively measured by HCA in an automated manner, recommending this assay method for the large-scale biology challenges of modern cancer drug discovery.

Multiplex analysis of inflammatory signaling pathways using a high-content imaging system

This chapter describes a robust high-content cellular screening assay to simultaneously analyze the spatiotemporal activation of three different kinase-associated signaling pathways involving NF-kappaB, JNK, and p38, all of which are closely implicated in proliferative and proinflammatory responses. Signal transduction is dependent on the translocation of NF-kappaB p65 and phosphorylated c-Jun and p38 from the cytosol to the nucleus, and fluorescent immunolabeling was used to monitor changes in their cellular distribution. Cellular screening, data acquisition, and data interpretation were conducted on the ArrayScan HCS Reader (Cellomics Inc., Pittsburgh, PA). Assay adaptation to various cellular systems is feasible when sufficient separation of the nuclear and cytosolic compartment can be achieved and if cell adhesion properties permit proper attachment to the culture plates. Substitution of NF-kappaB p65 and phosphorylated forms of c-Jun and p38 as targets to analyze other translocating components is possible and is limited primarily by antibody specificity and the risk of fluorescent bleed-through between emission channels. Because assay validity is particularly confounded by inadequate spectral separation of the detection dyes in multicolor labeling assays, means of eliminating or counterbalancing staining artifacts are illustrated. Also, protocol parameter settings important for imaging and image processing are described, including object identification, image exposure settings, separation of cytosolic and nuclear regions, number of cells sufficient for analysis, and the use of gating thresholds critical for cell sorting and subpopulation analysis. This assay is a useful tool to investigate the interplay between signaling pathways and the mode of action, potency, and selectivity of compound inhibition of specific target molecules in a cellular context.

High-content screening moves to the front of the line

High-content screening (HCS) has been used in late-stage drug discovery for a decade. In the past few years, technological advances have expanded the role of HCS into the early stages of drug discovery, including high-throughput screening and hit-to-lead studies. More recently, computational advances in image analysis and technological advancements in general cell biology have extended the utility of HCS into target validation and basic biological studies, including RNAi screening. The use of HCS in target validation is expanding the work that can be done at this stage, especially the range of targets that can be characterized, and putting it into a more biological context.

Cellular imaging in drug discovery

Traditional screening paradigms often focus on single targets. To facilitate drug discovery in the more complex physiological environment of a cell or organism, powerful cellular imaging systems have been developed. The emergence of these detection technologies allows the quantitative analysis of cellular events and visualization of relevant cellular phenotypes. Cellular imaging facilitates the integration of complex biology into the screening process, and addresses both high-content and high-throughput needs. This review describes how cellular imaging technologies contribute to the drug discovery process.

The Use of High-Content Screening for the Discovery and Characterization of Compounds That Modulate Mitotic Index and Cell Cycle Progression by Differing Mechanisms of Action

The advent of high-content screening has expanded the ability of researchers to identify and quantify compound effects on a number of cellular events in a manner that allows for the rapid screening of chemical libraries. We have validated an approach for characterizing inhibitors of Aurora kinase family members using high-content screening by determining compound effects on the levels of the mitotic marker phospho-histone H3 (Ser10). Analysis of the data from these experiments led us to the discovery of a series of related compounds that increased the level of cells staining positive for the mitotic marker, indicating a block of cell cycle progression at M-phase. We then reconfigured the Aurora kinase inhibition assay and validated a high-content approach to identify compounds that block progression through M-phase. We were able to take advantage of the flexibility within the high-content screening platform to measure DNA content, activation of apoptosis, and effects on beta-tubulin staining patterns, all of which directly led to the identification of the cellular target of this new class of compounds.

Inflammatory Pathway Analysis Using a High Content Screening Platform

High content cellular screening assays are useful tools to investigate the interplay between signaling pathways and offer valuable platforms to determine the mode of action, potency, and selectivity of potential drug candidates in a biological setting. We describe a cell-based multiplex fluorescent imaging assay that permits concurrent detection and quantification of the distribution of nuclear factor kappaB (NFkappaB) p65/RelA and phosphorylated forms of p38 and c-Jun between the cytosol and nucleus. Cellular screening, data acquisition, and data interpretation were conducted on the ArrayScan HCS Reader (Cellomics Inc., Pittsburgh, PA). A significant window between untreated and interleukin-1alpha (IL-1alpha) stimulated HeLa cells for all three targets was achieved with low variability. Staining specificity was confirmed with blocking peptides and pharmacological inhibition of p38, c-Jun-N-terminal kinase (JNK), and inhibitory kappaB kinase 2, and channel bleed-through was eliminated or counterbalanced by the use of fixed exposure times together with careful reporter channel selection. The JNK inhibitor SP600125 was used as a demonstration compound because in addition to inhibiting nuclear accumulation of phosphorylated c-Jun it reduced nuclear translocation of phosphorylated p38 and NFkappaB p65/RelA in a dose-dependent manner, indicating a lack of SP600125 selectivity. This was supported by RNA interference where co-transfection of small interfering RNA targeting both JNK1 and JNK2, to limit signaling redundancy, significantly inhibited IL-1alpha-stimulated translocation of phosphorylated c-Jun without altering phosphorylated p38 and NFkappaB p65/RelA redistribution. This image analysis application is a valuable and information-rich screening tool to investigate compound selectivity and/or cross-talk between key signaling pathways involved in the inflammatory response.

Cell microarrays and RNA interference chip away at gene function

The recent development of cell microarrays offers the potential to accelerate high-throughput functional genetic studies. The widespread use of RNA interference (RNAi) has prompted several groups to fabricate RNAi cell microarrays that make possible discrete, in-parallel transfection with thousands of RNAi reagents on a microarray slide. Though still a budding technology, RNAi cell microarrays promise to increase the efficiency, economy and ease of genome-wide RNAi screens in metazoan cells.