The effect of dexamethasone on the karyotype of A9HT cells

In the majority of glucocorticoid-resistant receptor containing variants of A9HT cells, the numbers of dot chromosomes was found to be significantly higher than in the parent cells. The higher number of dot chromosomes, however, did not always correlate with the resistance of L cells to dexamethasone. The formation of dot chromosomes was not the consequence of dexamethasone-induced chromosome breaks. Dot-chromosome formation could not be induced by dexamethasone in human diploid cells. It seems likely that dexamethasone can select for A9HT cells with higher number of dot chromosomes.