DNA amplification in genetic toxicology.

Chemical compounds can cause amplification of specific DNA sequences. DNA amplification may result in an enhanced production of gene products which help cells to cope with the chemicals. This may lead to a resistance of the cells toward the agent. Additionally, initiation of transformation or progression of transformed cells to tumorigenicity may also involve DNA amplification. Therefore, it is of interest to study the potential of chemicals to induce DNA amplification. This report focuses on the investigation of a variety of chemicals in 2 systems with which the amplification of viral DNA is measured within cells in culture. One model system comprises the measurement of SV40 DNA content in an SV40-transformed Chinese hamster cell line following chemical treatment. Antitumor agents as well as genotoxic and non-genotoxic compounds were studied in this system as a first step to determine the DNA amplification-inducing potential of a variety of differently acting chemical compounds. Also, a novel assay based on adeno-associated virus infection of cells is described. This system may offer the possibility of studying DNA amplification in a variety of different target cells. For the future, the need is stressed to develop and analyze versatile systems to study amplification of specific target genes in untransformed cells and in tumor cells.