A Tox21 Approach to Altered Epigenetic Landscapes: Assessing Epigenetic Toxicity Pathways Leading to Altered Gene Expression and Oncogenic Transformation In Vitro.

An emerging vision for toxicity testing in the 21st century foresees in vitro assays assuming the leading role in testing for chemical hazards, including testing for carcinogenicity. Toxicity will be determined by monitoring key steps in functionally validated molecular pathways, using tests designed to reveal chemically-induced perturbations that lead to adverse phenotypic endpoints in cultured human cells. Risk assessments would subsequently be derived from the causal in vitro endpoints and concentration vs.

Novel design and controls for focused DNA microarrays: applications in quality assurance/control and normalization for the Health Canada ToxArray.

Background: Microarray normalizations typically apply methods that assume absence of global transcript shifts, or absence of changes in internal control features such as housekeeping genes. These normalization approaches are not appropriate for focused arrays with small sets of genes where a large portion may be expected to change. Furthermore, many microarrays lack control features that can be used for quality assurance (QA).

Tandemly repeated DNA sequence instabilities induced by two promoters of morphological transformation in vitro: a short-term response to non-mutagenic agents in C3H/10T1/2 cells.

The ability of tumour promoters to alter DNA stability within regions that contain tandemly repeated sequences (TRSs), was studied in a cell culture model of multi-stage carcinogenesis. Non-cytotoxic concentrations of TPA (12-O-tetradecanoyl-phorbol-13-acetate) and xanthine oxidase with xanthine substrate, sufficient to promote morphological transformation in C3H/10T1/2 cultures, were tested for their effects on mutation frequencies in TRSs by a DNA fingerprinting approach. Specifically, restriction digests of genomic DNA samples from randomly selected, non-transformed clones, isolated from cultures after several days exposure to promoters, were visualized by Southern hybridizations with the multi-locus pentamer repeat sequence probe, Ms6-Hm (Pc-1).

Mitogen-regulated protein/proliferin mRNA induction following single applications of tumor promoters to murine skin.

Mitogen-regulated protein/proliferin (mrp/plf) gene family transcripts rise in abundance as a response to diverse chemical and physical agents that promote morphological transformation in the murine C3H/10T1/2 cultured cell model of multi-step carcinogenesis. To determine if proliferin genes respond to tumor promoters in vivo, RNA was extracted from the whole skin of SENCAR mice after single applications of 2 or 20 microg 12-O-tetradecanoylphorbol-13-acetate (TPA); 3.2 or 32 nmole), 20 or 40 mg benzoyl peroxide (BPO; 83, 165 micromole), or acetone vehicle alone (2.

Combined effects of tumor promoters and serum on proliferin mRNA induction: a biomarker sensitive to saccharin, 2,3,7,8-TCDD, and other compounds at minimal concentrations promoting C3H/10T1/2 cell transformation.

Increases in proliferin (PLF) gene family mRNA abundance and promotional effects in cell transformation assays are paired responses that follow exposures to diverse chemical and physical agents in the C3H/10T1/2 in vitro model of multi-stage carcinogenesis. This study measured PLF mRNA abundance changes over 1 to 3 d in response to several types of promoters that were previously unassessed for this effect. Saccharin is a known promoter of cell transformation in C3H/10T1/2 cell cultures, but unlike 12-O-tetradecanoylphorbol 13-acetate (TPA) or mezerein, PLF mRNA abundance increases were inconsistently detected following simple addition of saccharin to the culture medium.

Air pollution induces heritable DNA mutations.

Hundreds of thousands of people worldwide live or work in close proximity to steel mills. Integrated steel production generates chemical pollution containing compounds that can induce genetic damage (1, 2). Previous investigations of herring gulls in the Great Lakes demonstrated elevated DNA mutation rates near steel mills (3, 4) but could not determine the importance of airborne or aquatic routes of contaminant exposure, or eliminate possible confounding factors such as nutritional status and disease burden.