Differential induction of numerical chromosome changes by sodium butyrate in two transformed cell lines

Transformed cell lines generally exhibit similar response to a given chemical. However, when two transformed cell lines, the Chinese hamster (CHO 9) and mouse (L929) were treated with sodium butyrate (SB) to investigate its effect on chromosome distribution, the two lines behaved differently from each other. At concentrations as low as 10−7 M, the CHO 9 cells exhibited polyploidy as well as errors of numerical distributions resulting in aneuploidy. The majority of aneuploid cells were in quasitetraploid range indicating an association between the induction of polyploidy and aneuploidy. Upon staining with spindle antibody, the CHO cells exhibited a disarray of spindle microtubules as well as an abnormal cytoskeleton. In many instances the metaphase chromosomes were found to have a distorted spindle or lack an associated spindle altogether. The L929 cells, however, turned out to be far less sensitive to SB: a 100-fold increase in concentration of sodium butyrate (10−5 M) did not result in production of polyploid cells. However, when the extent of aneuploidy induction was measured by using a marker chromosome, both loss and gain of the chromosome was noticed. The effect of SB on the spindle was much more modest than it was the case with CHO cells as only minor disarray in cytoskeleton or spindle morphology was observed. The L929 cells, however, showed some effect on microtubule orientation as well as an effect on the segmentation of midbody. The application of SB resulted in less intense and more diffuse phosphorylation; the chromosomes had a punctate appearance of the label compared with the solid appearance on untreated cells. This was ture for both species. In mouse, the centromeric heterochromatin, which generally is intensely labeled, appeared to be labeled only as intensely as euchromatin. The data show that different transformed cell lines do not respond similarly to SB.