Unknown,Transcriptomics,Genomics,Proteomics

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In vitro carcinogenicity testing with Balb/c 3T3 Cells treated with various chemical carcinogens

ABSTRACT: Background: Information on the carcinogenic potential of chemicals is only availably for High Production Volume products. There is however, a pressing need for alternative methods allowing for the chronic toxicity of substances, including carcinogenicity, to be detected earlier and more reliably. Here we applied advanced genomics to a cellular transformation assay to identify gene signatures useful for the prediction of risk for carcinogenicity. Methods: Genome wide gene expression analysis and qRT-PCR were applied to untransformed and transformed Balb/c 3T3 cells that exposed to 2, 4-diaminotoluene (DAT), benzo(a)pyrene (BaP), 2-Acetylaminoflourene (AAF) and 3-methycholanthrene (MCA) for 24h and 120h, at different concentrations, respectively. Furthermore, various bioinformatics tools were used to identify gene signatures predicting for the carcinogenic risk. Results: Bioinformatics analysis revealed distinct datasets for the individual chemicals tested while the number of significantly regulated genes increased with ascending treatment concentration of the cell cultures. Filtering of the data revealed a common gene signature that comprised of 13 genes whose regulation in cancer tissue has already been established. Strikingly, this gene signature was already identified prior to cell transformation therefore confirming the predictive power of this gene signature in identifying carcinogenic risks of chemicals. Comparison of fold changes determined by microarray analysis and qRT-PCR were in good agreement. Conclusion: Our data describes selective and commonly regulated carcinogenic pathways observed in an easy to use in vitro carcinogenicity assay. Here we defined a set of genes which can serve as a simply assay to predict the risk for carcinogenicity by use of an alternative in vitro testing strategy. Balb/c 3T3 cells were seeded at 200 cells in each 60 x 15 mm culture dish with 4 ml M10F, using six culture dishes for every treatment. When cells reached a confluence of 60-65%, the culture medium was removed and replaced with fresh medium containing all tested chemicals at a specific concentration and two time points (24 and 120h). First we treated the cells both 24h and 120h with concentrations reported in the literature (0.5ÂµM BaP, 50ÂµM DAT, 25ÂµM AAF and 2ÂµM MCA). In a second approach IC20 concentrations were investigated for each chemical at both time points. The concentrations determined for IC20 ranged from 1.5 ÂµM BaP to 700 ÂµM DAT for 24h of treatment, and from 0.1 ÂµM BaP or MCA to 10ÂµM AAF for 120h of treatment. Balb/c 3T3 cells treated with 0.75% DMSO alone were kept as controls. Each experiment was run in triplicate.

ORGANISM(S): Mus musculus

SUBMITTER: Jens Linge

PROVIDER: E-GEOD-22180 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Toxicogenomics applied to in vitro carcinogenicity testing with Balb/c 3T3 cells revealed a gene signature predictive of chemical carcinogens.

Rohrbeck Astrid A Salinas Gabriela G Maaser Kerstin K Linge Jens J Salovaara Susan S Corvi Raffaella R Borlak Juergen J

Toxicological sciences : an official journal of the Society of Toxicology 20100816 1

Information on the carcinogenic potential of chemicals is primarily available for High Production Volume (HPV) products. Because of the limited knowledge gain from routine cancer bioassays and the fact that HPV chemicals are tested only, there is the need for more cost-effective and informative testing strategies. Here we report the application of advanced genomics to a cellular transformation assay to identify toxicity pathways and gene signatures predictive for carcinogenicity. Specifically, g ...[more]

PMID: 20713471

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Project description:Animals have developed extensive mechanisms of response to xenobiotic chemical attacks. Although recent genome surveys have suggested a broad conservation of the chemical defensome across metazoans, global gene expression responses to xenobiotics are not known in most invertebrates. Here, using high density tiling arrays with over 2 million probes, we explored genome-wide gene expression in the tunicate Oikopleura dioica in response to two model xenobiotic chemicals – the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) the pharmaceutical compound Clofibrate (Clo). The genotoxic compound BaP induced xenobiotic biotransformation and oxidative stress responsive genes, as in vertebrates. Notable exceptions were genes of the aryl hydrocarbon receptor (AhR) signaling pathway. Clo also affected the expression of many biotransformation genes and markedly repressed genes involved in energy metabolism and muscle contraction pathways. Oikopleura appears to have basic defensome toolkit consisting of phase I, phase II and phase III biotransformation genes. Exposure of about 130 four-days-old animals in 1L seawater in glass beakers. Pooled animals used, no replicates. DMSO Treatments: -Clofibrate (Clo) (Sigma-Aldrich, St. Louis, MO): 1 µM and 5 µM. -Benzo[a]pyrene (BaP (Sigma-Aldrich): 0.2 µM and 1 µM - Controls received 1 ml Dimethyl sulfoxide (DMSO). -The animals kept at room temperature and harvested after 10 hrs and frozen. -Total RNA was isolated from the pooled animals using the RNeasy Mini Kit according to manufacturer’s protocols (QIAGEN, Hilden, Germany). - 5 µg total RNA was converted to dscDNA using SuperScript Double-Stranded cDNA Synthesis Kit (Invitrogen, Carlsbad, CA), and dscDNA samples were submitted for microarray analysis. BaP and Clo treated samples were labeled using Cy3-coupled random nonamers and DMSO controls were labeled using Cy5-coupled random nonamers. Total 4 hybridizations for the 8 samples (single hybridization for each treatment and DMSO control pair), no replicates.

Project description:The polycyclic aromatic hydrocarbon (PAH), benzo[a]pyrene (BaP), was compared to dibenzo[def,p]chrysene (DBC) and combinations of three environmental PAH mixtures (coal tar, diesel particulate and cigarette smoke condensate) using a two stage, FVB/N mouse skin tumor model. DBC (4 nmol) was most potent, reaching 100% tumor incidence with a shorter latency to tumor formation, less than 20 weeks of 12-O-tetradecanoylphorbol-13-acetate (TPA) promotion compared to all other treatments. Multiplicity was 4 times greater than BaP (400 nmol). Both PAHs produced primarily papillomas followed by squamous cell carcinoma and carcinoma in situ. Diesel particulate extract (1 mg SRM 1650b; mix 1 ) did not differ from toluene controls and failed to elicit a carcinogenic response. Addition of coal tar extract (1 mg SRM 1597a; mix 2) produced a response similar to BaP. Further addition of 2 mg of cigarette smoke condensate (mix 3) did not alter the response of mix 2. PAH-DNA adducts measured in epidermis 12 h post initiation and analyzed by 32P post- labeling, did not correlate with tumor incidence. PAH dependent alteration in transcriptome of skin 12 h post initiation was assessed by microarray. Principal component analysis (sum of all treatments) of the 922 significantly altered genes (p<0.05), showed DBC and BaP to cluster distinct from PAH mixtures and each other. BaP and mixtures up-regulated phase 1 and 2 metabolizing enzymes while DBC did not. The carcinogenicity with DBC and two of the mixtures was much greater than would be predicted based on published Relative Potency Factors (RPFs). Gene expression was measured in mouse skin 12 hours after initiation with PAH carcinogens. The following initiation treatments were applied to mice (N=4 or 5 per biological replicates treatment); toluene vehicle control (200 M-NM-<l), BaP 400 nmol (100 M-NM-<g), DBC 4 nmol (1.2 M-NM-<g), or to mixtures of environmental PAH mixtures containing diesel particulate extract, coal tar extract, or cigarette smoke condensate.

Dataset Information

In vitro carcinogenicity testing with Balb/c 3T3 Cells treated with various chemical carcinogens

Publications

Toxicogenomics applied to in vitro carcinogenicity testing with Balb/c 3T3 cells revealed a gene signature predictive of chemical carcinogens.

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