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GSE18858
Mus musculus
242 Downloadable Samples
Affymetrix Mouse Genome 430 2.0 Array (mouse4302)
Description
Two-year rodent bioassays play a central role in evaluating both the carcinogenic potential of a chemical and generating quantitative information on the dose-response behavior for chemical risk assessments. The bioassays involved are expensive and time-consuming, requiring nearly lifetime exposures (two years) in mice and rats and costing $2 to $4 million per chemical. Since there are approximately 80,000 chemicals registered for commercial use in the United States and 2,000 more are added each year, applying animal bioassays to all chemicals of concern is clearly impossible. To efficiently and economically identify carcinogens prior to widespread use and human exposure, alternatives to the two-year rodent bioassay must be developed. In this study, animals were exposed for 13 weeks to 10 chemicals that were positive for liver tumors in the two-year rodent bioassay, 14 chemicals that were negative for liver tumors, and two chemicals that produced an equivocal response. Matched vehicle control groups were run concurrently with each chemical treatment. Gene expression analysis was performed on the livers of the animals to assess the potential for identifying gene expression biomarkers and signaling pathways that can predict tumor formation in a two-year bioassay following a 13 week exposure.
Publication Title
Application of transcriptional benchmark dose values in quantitative cancer and noncancer risk assessment.
Sample Metadata Fields
Sex, Age, Subject
View Samples- Mus musculus
- 235 Downloadable Samples
- Affymetrix Mouse Genome 430 2.0 Array (mouse4302)
Description
Isoniazid induced varying degrees of hepatic steatosis in an inbred strain Mouse Diversity Panel (MDP) study. RNA was isolated from all animals for analysis of gene expression changes in the liver. The objective of this study was to identify gene expression changes that drive isoniazid-induced steatosis.
Publication Title
A systems biology approach utilizing a mouse diversity panel identifies genetic differences influencing isoniazid-induced microvesicular steatosis.
Sample Metadata Fields
Sex, Specimen part, Treatment
View Samples- Mus musculus
- 191 Downloadable Samples
- Affymetrix Mouse Genome 430 2.0 Array (mouse4302)
Description
The process for evaluating chemical safety is inefficient, costly, and animal intensive. There is growing consensus that the current process of safety testing needs to be significantly altered to improve efficiency and reduce the number of untested chemicals. In this study, the use of short-term gene expression profiles was evaluated for predicting the increased incidence of mouse lung tumors. Animals were exposed to a total of 26 diverse chemicals with matched vehicle controls over a period of three years. Upon completion, significant batch-related effects were observed. Adjustment for batch effects significantly improved the ability to predict increased lung tumor incidence. For the best statistical model, the estimated predictive accuracy under honest five-fold cross-validation was 79.3% with a sensitivity and specificity of 71.4 and 86.3%, respectively. A learning curve analysis demonstrated that gains in model performance reached a plateau at 25 chemicals, indicating that the size of the current data set was sufficient to provide a robust classifier. The classification results showed a small subset of chemicals contributed disproportionately to the misclassification rate. For these chemicals, the misclassification was more closely associated with genotoxicity status than efficacy in the original bioassay. Statistical models were also used to predict dose-response increases in tumor incidence for methylene chloride and naphthalene. The average posterior probabilities for the top models matched the results from the bioassay for methylene chloride. For naphthalene, the average posterior probabilities for the top models over-predicted the tumor response, but the variability in predictions were significantly higher. The study provides both a set of gene expression biomarkers for predicting chemically-induced mouse lung tumors as well as a broad assessment of important experimental and analysis criteria for developing microarray-based predictors of safety-related endpoints.
Publication Title
Use of short-term transcriptional profiles to assess the long-term cancer-related safety of environmental and industrial chemicals.
Sample Metadata Fields
Sex, Age, Specimen part, Disease, Subject
View Samples- Homo sapiens
- 144 Downloadable Samples
- Affymetrix HT HG-U133+ PM Array Plate (hthgu133pluspm)
Description
As part of a larger effort to provide proof-of-concept in vitro only risk assessments, we have developed a suite of high throughput assays for key readouts in the p53 DNA damage response toxicity pathway: DSB DNA damage (p-H2AX), permanent chromosomal damage (micronuclei; MN), p53 activation, p53 transcriptional activity, and cell fate (cell cycle arrest, apoptosis,MN). Dose-response studies were performed with these protein and cell fate assays, together with whole genome transcriptomics, for three prototype chemicals: etoposide (ETP), quercetin (QUE) and methyl methanesulfonate (MMS). Data were collected in a human cell line expressing wild-type p53 (HT1080) and results were confirmed in a second p53 competent cell line (HCT 116). At chemical concentrations causing similar increases in p53 protein expression, p53-mediated protein expression and cellular processes showed substantial chemical-specific differences. These chemical-specific differences in the p53 transcriptional response appear to be determined by augmentation of the p53 response by co-regulators. More importantly, dose-response data for each of the chemicals indicates that the p53 transcriptional response does not prevent MN induction at low concentrations. In fact, the no observed effect levels (NOELs) and benchmark doses (BMDs) for MN induction were less than or equal to those for p53-mediated gene transcription regardless of the test chemical, indicating that p53s post-translational responses may be more important than transcriptional activation in the response to low dose DNA damage. This effort demonstrates the process of defining key assays required for a pathway-based, in vitro-only risk assessment, using the p53-mediated DNA damage response pathway as a prototype.
Publication Title
Profiling dose-dependent activation of p53-mediated signaling pathways by chemicals with distinct mechanisms of DNA damage.
Sample Metadata Fields
Specimen part, Cell line
View Samples- Homo sapiens
- 118 Downloadable Samples
- Affymetrix HT HG-U133+ PM Array Plate (hthgu133pluspm)
Description
Nuclear receptor activation in liver leads to coordinated alteration of the expression of multiple gene products with attendant phenotypic changes of hepatocytes. Peroxisome proliferators including endogenous fatty acids, environmental chemicals, and drugs induce a multi-enzyme metabolic response that affects lipid and fatty acid processing. We studied the signaling network for the peroxisome proliferator-associated receptor alpha (PPAR) in primary human hepatocytes using the selective PPAR ligand, GW7647. We measured gene expression over multiple concentrations and times and conducted ChIP-seq studies at 2 and 24 hours to assess genomic binding of PPAR. Over all treatments there were 192 genes differentially expressed. Of these only 51% showed evidence of PPAR binding either directly at PPAR response elements or via alternative mechanisms. Almost half of regulated genes had no PPAR binding. We then developed two novel bioinformatics methods to visualize the dose-dependent activation of both the transcription factor circuitry for PPAR and the downstream metabolic network in relation to functional annotation categories. Available databases identified several key transcription factors involved with the non-genomic targets after GW7647 treatment, including SP1, STAT1, ETS1, ER, and HNF4. The linkage from PPAR binding through gene expression likely requires intermediate protein kinases to activate these transcription factors. We found enrichment of functional annotation categories for organic acid metabolism and cell lipid metabolism among the differentially expressed genes. Lipid transport processes showed enrichment at the highest concentration of GW7647 (10M). While our strategy for mapping transcriptional networks is evolving, these approaches are necessary in moving from toxicogenomic methods that derive signatures of activity to methods that establish pathway structure, showing the coordination of the activated nuclear receptor with other signaling pathways.
Publication Title
A map of the PPARĪ± transcription regulatory network for primary human hepatocytes.
Sample Metadata Fields
Age, Subject
View Samples- Homo sapiens
- 100 Downloadable Samples
- Affymetrix HT HG-U133+ PM Array Plate (hthgu133pluspm)
Description
Several genotoxic chemicals have been reported to produce threshold-shaped dose-response curves for mutation and genotoxicity assays, both in vivo and in vitro. These data challenge the current default practice for risk assessment of genotoxic chemicals, which assumes a linear dose-response below the lowest tested dose. Due to the inherent challenges in data collection and analysis, statistical methods cannot determine whether a biological threshold exists with sufficient confidence to overturn this assumption of linearity. Indeed, to truly define the shape of the dose-response curves, we must look to the underlying biology and develop targeted experiments to identify and measure the key processes governing cellular response at low doses. This chapter describes a series of studies aimed at defining the transcriptional responses to DNA damage in an effort to identify the key processes regulating low-dose DNA damage response.
Publication Title
No associated publication
Sample Metadata Fields
Specimen part, Cell line
View Samples- Rattus norvegicus
- 98 Downloadable Samples
- Affymetrix Rat Genome 230 2.0 Array (rat2302)
Description
Formaldehyde, an important industrial chemical, is used for multiple commercial purposes throughout the industrialized world. This simple, one carbon aldehyde is a natural metabolite formed in cells throughput the body. However, it is also a rodent nasal carcinogen, when inhaled by rats every day for two-years at irritant concentrations. High tumor incidences occur at concentration of 10 ppm and above; no tumors are observed at concentrations below 6.0 ppm. The US Environmental Protection Agency (US EPA) is now (2007) conducting a risk assessment to try to evaluate possible cancer risks for much lower levels of human exposure. Sensitive methods are needed to evaluate tissue responses below those concentrations that are clearly irritant or carcinogenic. This microarray study was undertaken to evaluate the mode of action for nasal responses to inhaled formaldehyde in Fisher 344 rats over a range of exposure concentrations. The range of concentrations used spanned those at which virtually no tissue responses were observed (0.7 ppm) to those that represent the highest concentration in the cancer studies (15 ppm) that produced nasal tumors in half the exposed group of rats. The study identified doses at which there were no statistically significant changes in gene expression; intermediate doses with changes in a small number of genes not easily grouped by function; and then concentrations where changes were consistent with irritation and cell stress responses.
Publication Title
A method to integrate benchmark dose estimates with genomic data to assess the functional effects of chemical exposure.
Sample Metadata Fields
Sex, Subject
View Samples- Homo sapiens
- 91 Downloadable Samples
- Affymetrix HT HG-U133+ PM Array Plate (hthgu133pluspm)
Description
GGF2 is a recombinant human neuregulin-1 in development for chronic heart failure. Phase 1 clinical trials of GGF2 were put on hold when transient elevations in serum aminotransferases and total bilirubin were observed in 2 of 43 subjects receiving GGF2. However, aminotransferase elevations were modest and not typical of liver injury sufficient to result in elevated serum bilirubin. Several translational approaches were used to understand the liver response associated with GGF2.
Publication Title
Transient Changes in Hepatic Physiology That Alter Bilirubin and Bile Acid Transport May Explain Elevations in Liver Chemistries Observed in Clinical Trials of GGF2 (Cimaglermin Alfa).
Sample Metadata Fields
Treatment
View Samples- Rattus norvegicus
- 72 Downloadable Samples
- Affymetrix Rat Genome 230 2.0 Array (rat2302)
Description
Formaldehyde (FA), an endogenous cellular aldehyde, is a rat nasal carcinogen. In this study, concentration- and exposure-duration transitions in FA mode of action (MOA) were examined with pharmacokinetic (PK) modeling for tissue formaldehyde acetal (FAcetal) and glutathione (GSH) and with histopathology and gene expression studies for tissue responses in nasal epithelium from rats exposed to 0, 0.7, 2, 6, 10 or 15 ppm FA 6 hr/day for 1, 4 or 13 weeks. The study had two goals. The first goal was to develop a basic PK model to estimate various forms of tissue formaldehyde and tissue glutathione (GSH). The second goal was to compare histopathology and gene expression changes in nasal tissues caused by inhalation of FA with changes in tissue FAcetal and free GSH calculated from the PK model. Patterns of gene expression varied with concentration and with duration. At 0.7 and 2 ppm, sensitive response genes (SRGs) - associated with cellular stress, thiol transport/reduction, inflammation, and cell proliferation - were similarly upregulated at all exposure durations. At 6 ppm and greater, gene expression changes showed enrichment of pathways involved in cell cycle, DNA repair, and apoptosis processes. ERBB, EGFR, WNT, TGF-, Hedgehog, and Notch signaling were also enriched in differentially expressed genes. Benchmark doses (BMDs) for genes in significantly enriched pathways were lower at 13 weeks than at 1 or 4-week. The transcriptional and histological changes corresponded to PK model-predicted changes in free GSH at 0.7 and 2 ppm and in FAcetal at 6 ppm. DNA-replication stress, enhanced proliferation, metaplasia, and stem cell-niche activation appear to be associated with FA carcinogenesis at 6 ppm and above. Dose dependencies in MOA, the presence of high physiological FAcetal, and non-linear FAcetal/GSH tissue kinetics indicate that FA concentrations below 150 ppb (and probably any concentrations below irritant levels, i.e., ~ 1 ppm) would not increase cancer risks of inhaled FA in the nose or any other tissue. Closer examination of dose response relationships for endogenous compound toxicity could help guide biologically relevant approaches for chemical risk assessment.
Publication Title
Formaldehyde: integrating dosimetry, cytotoxicity, and genomics to understand dose-dependent transitions for an endogenous compound.
Sample Metadata Fields
Sex, Age, Specimen part, Subject, Time
View Samples- Mus musculus
- 70 Downloadable Samples
- Affymetrix Mouse Genome 430 2.0 Array (mouse4302)
Description
The primary goal of toxicology and safety testing is to identify agents that have the potential to cause adverse effects in humans. Unfortunately, many of these tests have not changed significantly in the past 30 years and most are inefficient, costly, and rely heavily on the use of animals. The rodent cancer bioassay is one of these safety tests and was originally established as a screen to identify potential carcinogens that would be further analyzed in human epidemiological studies. Today, the rodent cancer bioassay has evolved into the primary means to determine the carcinogenic potential of a chemical and generate quantitative information on dose-response behavior in chemical risk assessments. Due to the resource-intensive nature of these studies, each bioassay costs $2 to $4 million and takes over three years to complete. Over the past 30 years, only 1,468 chemicals have been tested in a rodent cancer bioassay. By comparison, approximately 9,000 chemicals are used by industry in quantities greater than 10,000 lbs and nearly 90,000 chemicals have been inventoried by the U.S. Environmental Protection Agency as part of the Toxic Substances Control Act. Given the disparity between the number of chemicals tested in a rodent cancer bioassay and the number of chemicals used by industry, a more efficient and economical system of identifying chemical carcinogens needs to be developed.
Publication Title
Application of genomic biomarkers to predict increased lung tumor incidence in 2-year rodent cancer bioassays.
Sample Metadata Fields
Sex, Age, Subject
View Samples