Consistent chromosome abnormalities associated with mouse bladder epithelial cell lines transformed in vitro

Nine epithelial tumor cell lines that were derived from inbred C57BL/lcrf-a(t) adult male mouse bladder and were transformed in vitro were cytogenetically analyzed. Most cell lines were near-diploid and showed only minor karyotypic deviations from normal. Tetraploid cell lines showed duplication of chromosome markers, which suggested that they arose originally as near-diploid cell lines with minor karyotypic changes. Chromosome abnormalities were consistent among different cell lines and involved chromosomes #6, #3, and #15. The Y-chromosome was frequently missing. Identical chromosome abnormalities were present in cell lines that arose in control, dimethyl sulfoxide-treated, or 7,12-dimethylbenz[a]anthracene-treated cultures. the most frequent abnormality was the presence of three copies (trisomy) of chromosome 6. Few structural chromosome abnormalities were detected, although a marker chromosome derived from chromosome #3 was present in several cell lines. Two cell lines had excesses of chromosome #15. These results suggest that excesses of individual chromosomes or parts of chromosomes, particularly chromosome 6, may be important in the expression of the malignant phenotype in mouse bladder epithelium.