The National Cancer Institute and Cannabis and Cannabinoids Research.

The landscape of both recreational and medicinal cannabis use has changed dramatically over the past decade; however, research examining the risks and benefits of cannabis and cannabinoid use has lagged significantly behind the increased media promotion and their use by the general public and cancer patients. The National Cancer Institute (NCI) has supported cannabis-related research projects and funding opportunity announcements. In addition, NCI organized a virtual symposium on December 15-18, 2020, to discuss recent research findings on the use of cannabis and cannabinoids in relationship to cancer risk, prevention, and care. Specifically, the symposium sought to highlight the state of the science regarding cannabis, including the chemical constituents of cannabis (eg, cannabinoids), and cancer research involving cannabis, including cancer epidemiology, use in cancer patients, cancer biology and prevention, and preclinical and clinical cancer symptom and treatment side effect management with cannabis and cannabinoids as therapeutics. The symposium identified promising areas of future study, current barriers to conducting the research, and strategies to overcome those barriers. The series of papers in this special edition provide a summary of the symposium sessions as well as a synopsis of opportunities and challenges related to conducting research in this area.

Evaluation of the GENE-UP®Salmonella Method for the Detection of Salmonella Species in a Broad Range of Foods and Select Environmental Surfaces: Collaborative Study, First Action 2020.02.

BACKGROUND: The GENE-UP®Salmonella assay (Performance Tested MethodSM [PTM] 121802) is a PCR detection method that utilizes fluorescence resonance energy transfer (FRET) hybridization probes for the rapid detection of Salmonella species in foods and on environmental surfaces. OBJECTIVE: The purpose of this validation was to evaluate the method's interlaboratory performance for submission to AOAC INTERNATIONAL for adoption as First Action Official Method of AnalysisSM. METHOD: The GENE-UP method was evaluated in a multi-laboratory study using unpaired test portions for one food matrix, raw ground beef (80% lean). The candidate method was compared to the US Department of Agriculture (USDA), Food Safety Inspection Service, Microbiology Laboratory Guidebook (MLG) 4.10 reference method. An alternative confirmation procedure, using ASAP™ and CHROMID®Salmonella chromogenic agars, was included in the validation study. Fifteen collaborators from 14 laboratories participated. Three levels of contamination were evaluated: a non-inoculated control level (0 CFU/test portion), a low contamination level (∼0.7 CFU/test portion), and a high contamination level (∼2 CFU/test portion). Data were analyzed using the probability of detection (POD) statistical model. RESULTS: The dLPODC values with 95% confidence interval for the GENE-UP Salmonella method, with either alternative or traditional confirmation, were: 0.00 (-0.03, 0.03), -0.02 (-0.15, 0.12), and 0.02 (-0.03, 0.09) for the non-inoculated, low, and high contamination levels respectively. CONCLUSIONS: The dLPODC results demonstrate no difference in performance between the candidate method and reference method for the matrix evaluated. HIGHLIGHTS: The GENE-UP Salmonella method, with ASAP and CHROMID Salmonella, provides industry with a simplified, rapid, and accurate workflow for the detection of Salmonella in a broad range of foods and select environmental surfaces.

Identification of small molecule modulators of gene transcription with anticancer activity.

Epigenetic regulation of gene expression is essential in many biological processes, and its deregulation contributes to pathology including tumor formation. We used an image-based cell assay that measures the induction of a silenced GFP-estrogen receptor reporter to identify novel classes of small molecules involved in the regulation of gene expression. Using this Locus Derepression assay, we queried 283,122 compounds by quantitative high-throughput screening evaluating compounds at multiple concentrations. After confirmation and independent validation, the Locus Derepression assay identified 19 small molecules as new actives that induce the GFP message over 2-fold. Viability assays demonstrated that 17 of these actives have anti-proliferative activity, and two of them show selectivity for cancer versus patient-matched normal cells and cause unique changes in gene expression patterns in cancer cells by altering histone marks. Hence, these compounds represent chemical tools for understanding the molecular mechanisms of epigenetic control of transcription and for modulating cell growth pathways.

Evaluation of VIDAS UP Listeria assay (LPT) for the detection of Listeria in a variety of foods and environmental surfaces: First Action 2013.10.

The VIDAS UP Listeria (LPT) is an automated rapid screening enzyme phage-ligand based assay for the detection of Listeria species in human food products and environmental samples. The VIDAS LPT method was compared in a multi-laboratory collaborative study to AOAC Official Method 993.12 Listeria monocytogenes in Milk and Dairy Products reference method following current AOAC guidelines. A total of 14 laboratories participated, representing government and industry, throughout the United States. One matrix, queso fresco (soft Mexican cheese), was analyzed using two different test portion sizes, 25 and 125 g. Samples representing each test portion size were artificially contaminated with Listeria species at three levels, an uninoculated control level [0 colony-forming units (CFU)/test portion], a low-inoculum level (0.2-2 CFU/test portion), and a high-inoculum level (2-5 CFU/test portion). For this evaluation, 1800 unpaired replicate test portions were analyzed by either the VIDAS LPT or AOAC 993.12. Each inoculation level was analyzed using the Probability of Detection (POD) statistical model. For the low-level inoculated test portions, difference in collaborator POD (dLPOD) values of 0.01, (-0.10, 0.13), with 95% confidence intervals, were obtained for both 25 and 125 g test portions. The range of the confidence intervals for dLPOD values for both the 25 and 125 g test portions contains the point 0.0 indicating no statistically significant difference in the number of positive samples detected between the VIDAS LPT and the AOAC methods. In addition to Oxford agar, VIDAS LPT test portions were confirmed using Agar Listeria Ottavani and Agosti (ALOA), a proprietary chromogenic agar for the identification and differentiation of L. monocytogenes and Listeria species. No differences were observed between the two selective agars. The VIDAS LPT method, with the optional ALOA agar confirmation method, was adopted as Official First Action status for the detection of Listeria species in a variety of foods and environmental samples.

Evaluation of VIDAS Listeria monocytogenes Xpress (LMX) for the detection of Listeria monocytogenes in a variety of foods: First Action 2013.11.

The VIDAS Listeria monocytogenes Xpress (LMX) is an automated rapid screening enzyme immunoassay for the detection of Listeria monocytogenes in food products. The VIDAS LMX method was compared in a multi-laboratory collaborative study to AOAC Official Method 993.12 Listeria monocytogenes in Milk and Dairy Products reference method following current AOAC guidelines. A total of 14 laboratories participated, representing government and industry, throughout the United States. One matrix, queso fresco (soft Mexican cheese), was analyzed using two different test portion sizes, 25 and 125 g. Samples representing each portion size were artificially contaminated with L. monocytogenes at three levels: an uninoculated control level [0 colony forming units (CFU)/test portion], a low inoculum level (0.2-2 CFU/test portion), and a high inoculum level (2-5 CFU/test portion). For this evaluation, 1800 unpaired replicate test portions were analyzed by either the VIDAS LMX or AOAC 993.12. Each level was analyzed using the Probability of Detection (POD) statistical model. For the low-level inoculated test portions, difference in collaborator POD (dLPOD) values of 0.04, (-0.08, 0.15) and 0.01, (-0.10, 0.13), with 95% confidence intervals, were obtained, respectively, for 25 and 125 g test portions. The range of the confidence intervals for dLPOD values for both the 25 and 125 g test portions contain the point 0.0 indicating no statistically significant difference in the number of positive samples detected between the VIDAS LMX and the AOAC method. In addition to Oxford Agar (OXA), VIDAS LMX test portions were confirmed using Agar Listeria Ottavani and Agosti (ALOA), a proprietary chromogenic agar for the identification and differentiation of L. monocytogenes and Listeria species. No differences were observed between the two selective agars. The VIDAS LMX method, with the optional ALOA agar confirmation method, was adopted as Official First Action status for the detection of L. monocytogenes in a variety of foods.

Identification of Potent and Selective Diphenylpropanamide RORγ Inhibitors.

Retinoic acid-related orphan receptor RORγt plays a pivotal role in the differentiation of TH17 cells. Antagonizing RORγt transcriptional activity is a potential means to treat TH17-related autoimmune diseases. Herein, we describe the identification of a series of diphenylpropanamides as novel and selective RORγ antagonists. Diphenylpropanamide 4n inhibited transcriptional activity of RORγt, but not RORα, in cells. In addition, it suppressed human TH17 cell differentiation at sub-micromolar concentrations.

Evaluation of VIDAS UP Salmonella (SPT) assay for the detection of Salmonella in a variety of foods and environmental samples: collaborative study.

The VIDAS UP Salmonella (SPT) uses recombinant phage proteins to detect Salmonella species in human and animal food products and production environmental samples after 18-26 h of enrichment. The VIDAS SPT assay is performed with the automated VIDAS or mini-VIDAS instruments. The VIDAS SPT method was compared in a multilaboratory collaborative study to the U.S. Department of Agriculture/Food Safety and Inspection Service-Microbiology Laboratory Guidebook (USDA/FSIS-MLG) 4.05 (2011) Isolation and Identification of Salmonella from Meat, Poultry, Pasteurized Egg and Catfish Products reference method following the current AOAC guidelines. A total of 15 laboratories representing government, academia, and industry throughout the United States participated. One matrix, raw ground beef, was analyzed using two different test portion sizes, 25 and 375 g. Each test portion was artificially contaminated with Salmonella at three inoculation levels, an uninoculated control level (0 CFU/test portion), a low inoculum level (0.2-2 CFUltest portion), and a high inoculum level (2-5 CFU/test portion). In this study, 1656 unpaired replicate samples were analyzed. Of those unpaired replicates, 476 were presumptive positive by the VIDAS method, with 475 confirmed positive by the traditional confirmation procedures and 476 confirmed positive by an alternative confirmation procedure. There were 411 confirmed positive replicates by the USDA/FSIS-MLG reference method. Statistical analysis was conducted according to the probability of detection (POD). For the low-level 375 g test portions, the following dLPOD values, with 95% confidence intervals, were obtained: 0.01 (-0.12, +0.15) for samples confirmed following the traditional confirmation; 0.02 (-0.18, +0.2) for samples confirmed following traditional confirmation on IBISA and ASAP; and 0.03 (-0.18, +0.24) for samples confirmed following the alternative confirmation on IBISA and ASAP. For the low-level 25 g test portions, the following dLPOD values, with 95% confidence intervals, were obtained: 0.41, (0.32, +0.49) for samples confirmed following the traditional confirmation, the traditional confirmation on IBISA and ASAP, and the alternative confirmation on IBISA and ASAP. With 0.0 within the confidence intervals for the 375 g test portions, there was no statistically significant difference in the number of positive samples detected by the VIDAS SPT method and the USDA/FSIS-MLG method at the 0.05 level. For the 25 g test portions, a statistically significant difference was observed between the VIDAS SPT method and the reference method for the low inoculum level, where the VIDAS SPT method recovered a higher number of positive results than the reference method. It is recommended that the VIDAS SPT method with the optional ASAP and IBISA agar confirmation method be adopted for Official First Action status for the detection of Salmonella in a variety of foods and environmental samples.

A class of tricyclic compounds blocking malaria parasite oocyst development and transmission.

Malaria is a deadly infectious disease in many tropical and subtropical countries. Previous efforts to eradicate malaria have failed, largely due to the emergence of drug-resistant parasites, insecticide-resistant mosquitoes and, in particular, the lack of drugs or vaccines to block parasite transmission. ATP-binding cassette (ABC) transporters are known to play a role in drug transport, metabolism, and resistance in many organisms, including malaria parasites. To investigate whether a Plasmodium falciparum ABC transporter (Pf14_0244 or PfABCG2) modulates parasite susceptibility to chemical compounds or plays a role in drug resistance, we disrupted the gene encoding PfABCG2, screened the recombinant and the wild-type 3D7 parasites against a library containing 2,816 drugs approved for human or animal use, and identified an antihistamine (ketotifen) that became less active against the PfABCG2-disrupted parasite in culture. In addition to some activity against asexual stages and gametocytes, ketotifen was highly potent in blocking oocyst development of P. falciparum and the rodent parasite Plasmodium yoelii in mosquitoes. Tests of structurally related tricyclic compounds identified additional compounds with similar activities in inhibiting transmission. Additionally, ketotifen appeared to have some activity against relapse of Plasmodium cynomolgi infection in rhesus monkeys. Further clinical evaluation of ketotifen and related compounds, including synthetic new derivatives, in blocking malaria transmission may provide new weapons for the current effort of malaria eradication.

Evaluation of the VITEK 2 gram positive (GP) microbial identification test card: collaborative study.

A collaborative study was conducted to evaluate the performance of the VITEK 2 Gram Positive (GP) identification card for use with the VITEK 2 automated microbial identification system. The GP test card is used in the identification of selected Gram positive organisms, including Listeria and Staphylococcus species. The VITEK 2 GP card is based on 43 biochemical tests measuring carbon source utilization, inhibition and resistance, and enzymatic activities. A total of 20 laboratories representing government, industry, and private testing laboratories throughout the United States participated. In this study, 720 Gram-positive inclusivity isolates were analyzed by the GP Identification method. Of the 720 well-characterized isolates, 714 were identified correctly, zero were misidentified, zero were unidentified, and six were not characterized as a Gram-positive organism by the VITEK 2 GP method. Additionally, 120 strains exclusive of Gram-positive organisms were screened by Gram stain. A total of 106 isolates were correctly excluded. Fourteen organisms were incorrectly characterized by Gram stain procedures, thus resulting in improper analysis and misidentification by VITEK GP. The VITEK 2 GP identification method is an acceptable automated method for the rapid identification of selected Gram-positive bacteria.

High-throughput screening for genes that prevent excess DNA replication in human cells and for molecules that inhibit them.

High-throughput screening (HTS) provides a rapid and comprehensive approach to identifying compounds that target specific biological processes as well as genes that are essential to those processes. Here we describe a HTS assay for small molecules that induce either DNA re-replication or endoreduplication (i.e. excess DNA replication) selectively in cells derived from human cancers. Such molecules will be useful not only to investigate cell division and differentiation, but they may provide a novel approach to cancer chemotherapy. Since induction of DNA re-replication results in apoptosis, compounds that selectively induce DNA re-replication in cancer cells without doing so in normal cells could kill cancers in vivo without preventing normal cell proliferation. Furthermore, the same HTS assay can be adapted to screen siRNA molecules to identify genes whose products restrict genome duplication to once per cell division. Some of these genes might regulate the formation of terminally differentiated polyploid cells during normal human development, whereas others will prevent DNA re-replication during each cell division. Based on previous studies, we anticipate that one or more of the latter genes will prove to be essential for proliferation of cancer cells but not for normal cells, since many cancer cells are deficient in mechanisms that maintain genome stability.

Chemical genomic profiling for antimalarial therapies, response signatures, and molecular targets.

Malaria remains a devastating disease largely because of widespread drug resistance. New drugs and a better understanding of the mechanisms of drug action and resistance are essential for fulfilling the promise of eradicating malaria. Using high-throughput chemical screening and genome-wide association analysis, we identified 32 highly active compounds and genetic loci associated with differential chemical phenotypes (DCPs), defined as greater than or equal to fivefold differences in half-maximum inhibitor concentration (IC(50)) between parasite lines. Chromosomal loci associated with 49 DCPs were confirmed by linkage analysis and tests of genetically modified parasites, including three genes that were linked to 96% of the DCPs. Drugs whose responses mapped to wild-type or mutant pfcrt alleles were tested in combination in vitro and in vivo, which yielded promising new leads for antimalarial treatments.

A quantitative high-throughput screen identifies novel inhibitors of the interaction of thyroid receptor beta with a peptide of steroid receptor coactivator 2.

The thyroid hormone receptors (TR) are members of the nuclear hormone receptor (NHR) superfamily that regulate development, growth, and metabolism. Upon ligand binding, TR releases bound corepressors and recruits coactivators to modulate target gene expression. Steroid receptor coactivator 2 (SRC2) is an important coregulator that interacts with TRß to activate gene transcription. To identify novel inhibitors of the TRß and SRC2 interaction, the authors performed a quantitative high-throughput screen (qHTS) of a TRß-SRC2 fluorescence polarization assay against more than 290 000 small molecules. The qHTS assayed compounds at 6 concentrations up to 92 µM to generate titration-response curves and determine the potency and efficacy of all compounds. The qHTS data set enabled the characterization of actives for structure-activity relationships as well as for potential artifacts such as fluorescence interference. Selected qHTS actives were tested in the screening assay using fluoroprobes labeled with Texas Red or fluorescein. The retest identified 19 series and 4 singletons as active in both assays with 40% or greater efficacy, free of compound interference, and not toxic to mammalian cells. Selected compounds were tested as independent samples, and a methylsulfonylnitrobenzoate series inhibited the TRß-SRC2 interaction with 5 µM IC(50). This series represents a new class of thyroid hormone receptor-coactivator modulators.

Discovery of new antimalarial chemotypes through chemical methodology and library development.

In an effort to expand the stereochemical and structural complexity of chemical libraries used in drug discovery, the Center for Chemical Methodology and Library Development at Boston University has established an infrastructure to translate methodologies accessing diverse chemotypes into arrayed libraries for biological evaluation. In a collaborative effort, the NIH Chemical Genomics Center determined IC(50)'s for Plasmodium falciparum viability for each of 2,070 members of the CMLD-BU compound collection using quantitative high-throughput screening across five parasite lines of distinct geographic origin. Three compound classes displaying either differential or comprehensive antimalarial activity across the lines were identified, and the nascent structure activity relationships (SAR) from this experiment used to initiate optimization of these chemotypes for further development.

Evaluation of VIDAS Listeria species Xpress (LSX) immunoassay method for the detection of Listeria species in foods: collaborative study.

In a multilaboratory study, the effectiveness of an alternative method for rapid screening of Listeria species compared to traditional reference methods was demonstrated in a variety of food products. A collaborative study was conducted to compare the VIDAS Listeria species Xpress (LSX) method and the standard cultural methods for the detection of Listeria species in foods. Six food types were tested: vanilla ice cream, cheddar cheese, raw ground beef, frozen green beans, deli turkey, and cooked shrimp. Each food, inoculated with a different Listeria strain at two levels and uninoculated test portions, was analyzed by each method. A total of 15 laboratories representing government and industry participated. In this study 1134 tests were analyzed in the statistical analysis. There were 490 positives by the VIDAS LSX method using the sample boiling step, 483 positives by the VIDAS LSX method using the Heat and Go system, and 439 positives by the standard culture methods. Overall, the Chi-square result for the VIDAS LSX method with boiling for all foods was 7.25, indicating a significant statistical difference between the VIDAS method and the standard methods at the 5% confidence. For the VIDAS LSX method with the Heat and Go system, the Chi-square result for all foods was 5.37, indicating a significant statistical difference between the VIDAS LSX assay with the Heat and Go system and the standard methods at the 5% level of significance. In both cases, the VIDAS method was more sensitive than the standard methods. The LSX method detects Listeria species in foods with negative or presumptive positive results in a minimum of 30 h compared to at least 5 days for the cultural methods. Based on the results of this collaborative study, it is recommended that the VIDAS LSX method be adopted as an AOAC Official Method for the detection of Listeria species in dairy products, vegetables, seafood, raw meats and poultry, and processed meats and poultry.

Methylsulfonylnitrobenzoates, a new class of irreversible inhibitors of the interaction of the thyroid hormone receptor and its obligate coactivators that functionally antagonizes thyroid hormone.

Thyroid hormone receptors (TRs) are members of the nuclear hormone receptor (NR) superfamily and regulate development, growth, and metabolism. Upon binding thyroid hormone, TR undergoes a conformational change that allows the release of corepressors and the recruitment of coactivators, which in turn regulate target gene transcription. Although a number of TR antagonists have been developed, most are analogs of the endogenous hormone that inhibit ligand binding. In a screen for inhibitors that block the association of TRß with steroid receptor coactivator 2 (SRC2), we identified a novel methylsulfonylnitrobenzoate (MSNB)-containing series that blocks this interaction at micromolar concentrations. Here we have studied a series of MSNB analogs and characterized their structure activity relationships. MSNB members do not displace thyroid hormone T3 but instead act by direct displacement of SRC2. MSNB series members are selective for the TR over the androgen, vitamin D, and PPARγ NR members, and they antagonize thyroid hormone-activated transcription action in cells. The methylsulfonylnitro group is essential for TRß antagonism. Side-chain alkylamine substituents showed better inhibitory activity than arylamine substituents. Mass spectrum analysis suggested that MSNB inhibitors bind irreversibly to Cys-298 within the AF-2 cleft of TRß to disrupt SRC2 association.

An image-based, high-throughput screening assay for molecules that induce excess DNA replication in human cancer cells.

Previous studies have shown DNA re-replication can be induced in cells derived from human cancers under conditions in which it is not possible for cells derived from normal tissues. Because DNA re-replication induces cell death, this strategy could be applied to the discovery of potential anticancer therapeutics. Therefore, an imaging assay amenable to high-throughput screening was developed that measures DNA replication in excess of four genomic equivalents in the nuclei of intact cells and indexes cell proliferation. This assay was validated by screening a library of 1,280 bioactive molecules on both normal and tumor-derived cells where it proved more sensitive than current methods for detecting excess DNA replication. This screen identified known inducers of excess DNA replication, such as inhibitors of microtubule dynamics, and novel compounds that induced excess DNA replication in both normal and cancer cells. In addition, two compounds were identified that induced excess DNA replication selectively in cancer cells and one that induced endocycles selectively in cancer cells. Thus, this assay provides a new approach to the discovery of compounds useful for investigating the regulation of genome duplication and for the treatment of cancer.

Evaluation of VIDAS Salmonella (SLM) easy Salmonella method for the detection of Salmonella in a variety of foods: collaborative study.

The VIDAS Salmonella (SLM) Easy Salmonella method is a specific enzyme-linked fluorescent immunoassay performed in the automated VIDAS instrument. The VIDAS Easy Salmonella method is a simple 2-step enrichment procedure, using pre-enrichment followed by selective enrichment in a newly formulated broth, SX2 broth. This new method was compared in a multilaboratory collaborative study to the U.S. Food and Drug Administration's Bacteriological Analytical Manual, Chapter 5 method for five food matrixes (liquid egg, vanilla ice cream, spinach, raw shrimp, and peanut butter) and the U.S. Department of Agriculture's Microbiology Laboratory Guidebook 4.04 method for deli turkey. Each food type was artificially contaminated with Salmonella at three inoculation levels. A total of 15 laboratories representing government, academia, and industry, throughout the United States, participated. In this study, 1583 samples were analyzed, of which 792 were paired replicates and 791 were unpaired replicates. Of the 792 paired replicates, 285 were positive by both the VIDAS and reference methods. Of the 791 unpaired replicates, 341 were positive by the VIDAS method and 325 were positive by the cultural reference method. A Chi-square analysis of each of the six food types was performed at the three inoculation levels tested. For all foods evaluated, the VIDAS Easy SLM method demonstrated results comparable to those of the reference methods for the detection of Salmonella.

The pilot phase of the NIH Chemical Genomics Center.

The NIH Chemical Genomics Center (NCGC) was the inaugural center of the Molecular Libraries and Screening Center Network (MLSCN). Along with the nine other research centers of the MLSCN, the NCGC was established with a primary goal of bringing industrial technology and experience to empower the scientific community with small molecule compounds for use in their research. We intend this review to serve as 1) an introduction to the NCGC standard operating procedures, 2) an overview of several of the lessons learned during the pilot phase and 3) a review of several of the innovative discoveries reported during the pilot phase of the MLSCN.

Genetic mapping of targets mediating differential chemical phenotypes in Plasmodium falciparum.

Studies of gene function and molecular mechanisms in Plasmodium falciparum are hampered by difficulties in characterizing and measuring phenotypic differences between individual parasites. We screened seven parasite lines for differences in responses to 1,279 bioactive chemicals. Hundreds of compounds were active in inhibiting parasite growth; 607 differential chemical phenotypes, defined as pairwise IC(50) differences of fivefold or more between parasite lines, were cataloged. We mapped major determinants for three differential chemical phenotypes between the parents of a genetic cross, and we identified target genes by fine mapping and testing the responses of parasites in which candidate genes were genetically replaced with mutant alleles. Differential sensitivity to dihydroergotamine methanesulfonate (1), a serotonin receptor antagonist, was mapped to a gene encoding the homolog of human P-glycoprotein (PfPgh-1). This study identifies new leads for antimalarial drugs and demonstrates the utility of a high-throughput chemical genomic strategy for studying malaria traits.

A quantitative high-throughput screen for modulators of IL-6 signaling: a model for interrogating biological networks using chemical libraries.

Small molecule modulators are critical for dissecting and understanding signaling pathways at the molecular level. Interleukin 6 (IL-6) is a cytokine that signals via the JAK-STAT pathway and is implicated in cancer and inflammation. To identify modulators of this pathway, we screened a chemical collection against an IL-6 responsive cell line stably expressing a beta-lactamase reporter gene fused to a sis-inducible element (SIE-bla cells). This assay was optimized for a 1536-well microplate format and screened against 11 693 small molecules using quantitative high-throughput screening (qHTS), a method that assays a chemical library at multiple concentrations to generate titration-response profiles for each compound. The qHTS recovered 564 actives with well-fit curves that clustered into 32 distinct chemical series of 13 activators and 19 inhibitors. A retrospective analysis of the qHTS data indicated that single concentration data at 1.5 and 7.7 microM scored 35 and 71% of qHTS actives, respectively, as inactive and were therefore false negatives. Following counter screens to identify fluorescent and non-selective series, we found four activator and one inhibitor series that modulated SIE-bla cells but did not show similar activity in reporter gene assays induced by EGF and hypoxia. Small molecules within these series will make useful tool compounds to investigate IL-6 signaling mediated by JAK-STAT activation.