featuring the Echo Acoustic Technology
TITLES and AUTHORS
Many compounds with potentially reactive chemical motifs and poor physicochemical properties are published as selective modulators of biomolecules without sufficient validation and then propagated in the scientific literature as useful chemical probes. Several histone acetyltransferase (HAT) inhibitors with these liabilities are now routinely used to probe epigenetic pathways. We profile the most commonly used HAT inhibitors and confirm that the majority of them are nonselective interference compounds. Most (15 out of 23, 65%) of the inhibitors are flagged by ALARM NMR, an industry-developed counter-screen for promiscuous compounds. Biochemical counter-screens confirm that most of these compounds are either thiol-reactive or aggregators. Selectivity panels show many of these compounds modulate unrelated targets in vitro, while several also demonstrate nonspecific effects in cell assays. These data demonstrate the usefulness of performing counter-screens for bioassay promiscuity and assay interference, and raise caution about the utility of many widely used, but insufficiently validated, compounds employed in chemical biology.
Many cancer drugs are effective in only a small percentage of patients. This raises a somewhat profound question: how do we know that a certain drug will work well for some patients? If a potential drug cures 3 percent of patients, the data may never be found in the population at large. Likewise, adverse effects on a different – but still small – percentage of the total population, may be lost.
Pharmacological and functional genomic screens play an essential role in the discovery and characterization of therapeutic targets and associated pharmacological inhibitors. Although these screens affect thousands of gene products, the typical readout is based on low complexity rather than genome-wide assays. To address this limitation, we introduce pooled library amplification for transcriptome expression (PLATE-Seq), a low-cost, genome-wide mRNA profiling methodology specifically designed to complement high-throughput screening assays. Introduction of sample-specific barcodes during reverse transcription supports pooled library construction and low-depth sequencing that is 10- to 20-fold less expensive than conventional RNA-Seq. The use of network-based algorithms to infer protein activity from PLATE-Seq data results in comparable reproducibility to 30 M read sequencing. Indeed, PLATE-Seq reproducibility compares favorably to other large-scale perturbational profiling studies such as the connectivity map and library of integrated network-based cellular signatures.
If this is the biology laboratory of the future, it doesn’t look so different from today’s. Scientists in white lab coats walk by with boxes of frozen tubes. The chemicals on the shelves—bottles of pure alcohol, bins of sugar, protein, and salts—are standard issue for growing microbes and manipulating their genes. You don’t even notice the robots until you hear them: They sound like crickets singing to each other amid the low roar of fans.
Liquid handling plays an integral part inthe Biotechnology industry, since a major part of daily lab operations for testing, research, or production relies on the efficient transfer of samples and reagents to designated containers. Traditional liquid handling approaches that use pipettes often cannot achieve required levels of miniaturization, precision, and accuracy, and introduce chances of contamination.
Christopher Voigt is a professor of biological engineering at the Massachusetts Institute of Technology, where his lab focuses on synthetic biology. Two major areas of interest for him are developing a genetic programming language for cells and applying synthetic biology to biotechnology challenges. Ultimately, Voigt aims to design whole genomes for applications from agriculture to medicine. DDW chatted with Voigt to learn more about the impact this field will have on pharmaceutical workflows and drug pipelines.
There are people who will die of cancer this week even though there are drugs that could help them.
At the same time, hundreds of patients will undergo cancer chemotherapy that, while debilitating and expensive, will not cure them of their disease. While cancer is a formidable foe, there is a way to improve patient care and prognosis immediately.
Researchers in Finland, Sweden and Spain have modified ex-vivo testing of cancer cells with significant results. Their approach is far more “personalized” than traditional precision medicine. Their results are striking. They provide a missing link between genomics-based mutation determination and clinical efficacy. Precision medicine (also referred to as “personalized medicine” or PM) appears to many patients, doctors and researchers to be a golden highway from disease identification to cure. The idea of interrogating the genome of a particular cancer to determine its Achilles heel is intuitively satisfying and understandable. There are, however, significant problems. First, PM is neither personalized nor precise. PM strives to identify the appropriate biomarker (usually a DNA mutation but proteins, peptides and metabolites can stand as biomarkers as well) to categorize the patient as a member of a specific group of patients. The patient is treated with a drug that has shown positive results on previous members of the group. In other words, personalized medicine is actually population-based medicine.
A handful of academic groups in Europe and the US are using high-throughput (HT) ex vivo screening to test the sensitivity of individual patient tumors to hundreds of combinations of cancer drugs - a strategy that in earlier iterations failed to predict response to therapy. HT screening is used routinely in drug discovery. Thanks to advances in nanoliter-scale sample handling and computational biology, evidence is slowly building the potential of HT approaches to identify novel combination therapies, first in leukemia and hopefully for treating other cancers.
The high throughput direct measurement of substrate-to-product conversion by label-free detection has been considered the “Holy Grail” of drug discovery screening. Mass spectrometry as a detection system has the potential to be part of the ultimate screening solution. However, MS with existing sample introduction modes, despite being widely used in drug discovery typically cannot meet the throughput requirements of HTS. We propose a unique, innovative solution to the problem of throughput by using acoustic droplet ejection (ADE) to transfer femtoliter samples from microliter assays rapidly, precisely and accurately directly into a mass spectrometer. Acoustic technology has been widely used to support compound management activities within the pharmaceutical industry. The speed, accuracy, precision and robustness of acoustic dispensers have been proven. In principle, the integration of an acoustic source with a MS detector would result in a system capable of delivering ~4000 data points per hour into a high sensitivity label-free detector. It would enable sampling from 1536-well plates and reduce the total required assay volume to <5µL. The rapidity of sampling would enable real-time kinetic studies to capture multiple data points within the first minute of initiating a reaction. Together Labcyte Inc, Waters Corp and AstraZeneca have built a prototype acoustic source linked to a mass spectrometer. Droplets in the range of 50-200fL are acoustically ejected directly into the MS through a charge field. The ion beam is detected in the single quad MS where the typical signal has a very sharp attack profile and instant stop when the acoustic spray is turned on and off. This process produces a square wave signal which is simple to integrate for quantitative assays, and generates reliable and reproducible spectra. The system works in both positive and negative ion modes. The process is capable of producing singly or multiply charged species. The ability to load samples into a MS detector at such a high rate from much reduced assay volumes has significant potential not only within drug discovery but other areas of industry. Dynamic fluid analysis, the ability of the acoustic injector to adjust automatically to varying viscosities and surface tensions of the sample, allows the generation of droplets from a wide range of fluids including blood, plasma, cell culture medium, acid digests, and chemical syntheses. In principle, the simplicity of the acoustic source enables it to be fitted to any type of MS detector with an atmospheric pressure interface (single quad, triple quad, ToF), extending the range of applications into the “omics” field.
Epigenetics continues to emerge as an important target class for drug discovery and cancer research. As programs scale to evaluate many new targets related to epigenetic expression, new tools and techniques are required to enable efficient and reproducible highthroughput epigenetic screening. Echo liquid handlers can transfer compounds, samples, and reagents in sub-microliter volumes to high density assay formats using only acoustic energy - no contact or tips required. This eliminates tip costs and reduces the risk of reagent carryover. The PHERAstar FS multi-mode plate reader, with the highest sensitivity and lowest read time of assays in high density plate formats, is a perfect complement to enable an unparalleled solution for cost-effective, high-throughput epigenetic screening. Using the HTRF EPIgeneous™ Methyltransferase kit from Cisbio, we developed a miniaturized methyltransferase assay that can be easily adapted to automation and increased throughput, while maintaining high data quality. HTRF assays are typically performed at volumes of about 20 µL in a 384-well low volume plate. However, with the nanoliter dispense increments of the Echo liquid handler, assay volumes can be reduced significantly while maintaining data quality. In this study we were able to reduce a methyltransferase assay to a 2 µL final volume with excellent results.
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