The application of comparative genomic hybridization and fluorescence in situ hybridization to the characterization of genotoxicity screening tester strains AHH-1 and MCL-5

AHH-1 TK+/- is a human B cell-derived lymphoblastoid cell line that constit utively expresses a high level of the cytochrome CYP1A1, The MCL-5 cell lin e was developed by transfection of AHH-1 with cDNAs encoding the human cyto chrome P450s, CYP1A2, CYP2A6, CYP2E1, CYP3A4 and microsomal epoxide hydrola se carried in plasmids, The metabolic components of these cell lines make t hem a useful screening tool for use in mutagenicity studies. Although AHH-1 and MCL-5 are closely related, the two cell lines show differences which c annot be attributed to transfection, In the present study both cell lines w ere investigated for chromosome stability by comparative genomic hybridizat ion (CGH) and fluorescence in situ hybridization (FISH) using whole chromos ome probes and telomeric probes. Amplification in chromosomes 4q, 3q and 9p was observed in both cell lines. To compare the cell lines directly, AHH-1 and MCL-5 DNAs were co-hybridized on the same metaphases using a modified CGH technique. The only difference observed between AHH-1 and MCL-5 was the degree of amplification involving the subtelomeric region of chromosome 4; the additional telomeric region (4q) was translocated onto chromosome 11 a nd/or chromosome X, FISH was use to show the presence of isochromosomes 3q and 9p in both cell lines with a chromosome number of 48 or higher. These d ata demonstrate that CGH and FISH with chromosome-specific probes are able to resolve complex karyotypes and to highlight subchromosomal regions invol ved in rearrangements and potential chromosome fragile sites. Analyses such as those described here may be of considerable value in the determination of the stability of a variety of the cell lines used in the mutagenicity te sting of chemicals.