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Characterization of gene expression changes associated with MNNG, arsenic, or metal mixture treatment in human
Dong-Soon Bae1, William H Hanneman, Raymond S H Yang
1Center for Environmental Toxicology and Technology, Colorado State University, Fort Collins, USA. .
Abstract:
The identification of molecular markers related to critical biological processes during carcinogenesis may aid in the evaluation of carcinogenic potentials of chemicals and chemical mixtures. Work from our laboratory demonstrated that a single treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) enhanced spontaneous malignant transformation of the human keratinocyte cell line RHEK-1. In contrast, chronic low-level exposure of cells to arsenic alone or in a mixture containing arsenic, cadmium, chromium, and lead inhibited malignant conversion. To identify changes in gene expression that influence these different outcomes, cDNA microarray technology was used. Analysis of multiple human arrays in MNNG-transformed RHEK-1 cells, designated OM3, and those treated with arsenic or the arsenic-containing metal mixture showed unique patterns of gene expression. Genes that were overexpressed in OM3 included oncogenes, cell cycle regulators, and those involved in signal transduction, whereas genes for DNA repair enzymes and inhibitors of transformation and metastasis were suppressed. In arsenic-treated cells, multiple DNA repair proteins were overexpressed. Mixture-treated cells showed increased expression of a variety of genes including metallothioneins and integrin 4. These cells showed decreased expression of oncogenes, DNA repair proteins, and genes involved in the mitogen-activated protein kinase pathway. For comparison we are currently analyzing gene expression changes in RHEK-1 cells transformed by other means. The goal of these studies is to identify common batteries of genes affected by chemical modulators of the carcinogenic process. Mechanistic studies may allow us to correlate alterations in their expression with sequential stages in the carcinogenic process and may aid in the risk assessment of other xenobiotics.
Insights
Chemicals like N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) can enhance cancer development, while others like arsenic may inhibit it. Gene expression analysis reveals distinct molecular changes associated with these different carcinogenic potentials.
Area of Science:
- Toxicology
- Molecular Biology
- Carcinogenesis Research
Background:
- Chemicals and their mixtures can modulate carcinogenic processes.
- Understanding gene expression changes is crucial for evaluating chemical carcinogenicity.
- Human keratinocyte cell line RHEK-1 is a model for studying malignant transformation.
Purpose of the Study:
- To identify molecular markers associated with chemical-induced carcinogenesis.
- To compare gene expression patterns resulting from different chemical exposures.
- To aid in the risk assessment of xenobiotics.
Main Methods:
- Utilized cDNA microarray technology to analyze gene expression.
- Exposed RHEK-1 cells to N-methyl-N itro-N-nitrosoguanidine (MNNG), arsenic, and a metal mixture.
- Analyzed gene expression profiles in transformed and exposed cells.
Main Results:
- MNNG treatment enhanced malignant transformation, altering expression of oncogenes and DNA repair genes.
- Arsenic and metal mixture exposure inhibited malignant conversion, with distinct gene expression changes.
- Overexpressed genes in MNNG-treated cells included oncogenes; suppressed genes included DNA repair enzymes.
- Arsenic-exposed cells showed overexpression of DNA repair proteins.
- Mixture-exposed cells exhibited increased metallothioneins and integrin 4, with decreased oncogenes and MAPK pathway genes.
Conclusions:
- Different chemical exposures induce unique gene expression signatures.
- Identifying common gene expression patterns can help assess carcinogenic potential.
- Mechanistic studies correlating gene expression with carcinogenesis stages are needed for risk assessment.