Comparative genomic hybridization analysis of N-methyl-N'-nitrosoguanidine-induced rat gastrointestinal tumors discloses a cytogenetic fingerprint

Comparative genomic hybridization (CGH) in genotoxicology

In the past two decades comparative genomic hybridization (CGH) and array CGH have become crucial and indispensable tools in clinical diagnostics. Initially developed for the genome-wide screening of chromosomal imbalances in tumor cells, CGH as well as array CGH have also been employed in genotoxicology and most recently in toxicogenomics. The latter methodology allows a multi-endpoint analysis of how genes and proteins react to toxic agents revealing molecular mechanisms of toxicology. This chapter provides a background on the use of CGH and array CGH in the context of genotoxicology as well as a protocol for conventional CGH to understand the basic principles of CGH. Array CGH is still cost intensive and requires suitable analytical algorithms but might become the dominating assay in the future when more companies provide a large variety of different commercial DNA arrays/chips leading to lower costs for array CGH equipment as well as consumables such as DNA chips. As the amount of data generated with microarrays exponentially grows, the demand for powerful adaptive algorithms for analysis, competent databases, as well as a sound regulatory framework will also increase. Nevertheless, chromosomal and array CGH are being demonstrated to be effective tools for investigating copy number changes/variations in the whole genome, DNA expression patterns, as well as loss of heterozygosity after a genotoxic impact. This will lead to new insights into affected genes and the underlying structures of regulatory and signaling pathways in genotoxicology and could conclusively identify yet unknown harmful toxicants.

Cytotoxic effects of the main active components from three Chinese herbal medicines on N-methyl-N-nitro-N-nitrosoguanidine transformed GES-1 cells

AIM: To investigate the cytotoxic effects of Panax Notogengsing Saponin (PNS), Astragalin Saponin (AS) and Baicalin (Ba), the main active components from 3 Chinese herbal medicines, on an immortalized human gastric epithelial cell line GES-1 and the N-methyl-N-nitro-N- nitrosoguanidine (MNNG) transformed GES-1 cells (MC cells).

METHODS: GES-1 cells were transformed by 2×10^-5 mol/L MNNG. The transformed cells were named as MC cells. MC cells were treated with the 3 medicines alone or in different combinations. Cell viability was detected by MTT assay and soft agar colony formation assay, while apoptosis/necrosis were determined by electron microscopy, fluoroscopy and flow cytometry with annexin V staining.

RESULTS: PNS, AS and Ba inhibited the growth of GES-1 and MC cells in a dose and time-dependent manner. The colony formation efficiency in soft agar of MC cells was also decreased after treated with PNS, AS, Ba alone or in combination (P<0.05 or P<0.01vs control group). The 3 medicines induced apoptosis and/or necrosis of MC cells time-dependently. These effects were greatly enhanced when two or three of these medicines were used together (P<0.05 or P<0.01 vs 3 medicines used alone). The most potent combination was PNS+AS+Ba, followed by PNS+AS, AS+Ba and PNS+Ba, in a decreasing order.

CONCLUSION: PNS, AS and Ba can inhibit cell growth and induce cell death on MC cells. The cell death is partially caused by cell apoptosis. These effects can be enhanced to different extent by different combinations of these drugs.