Decreased acquisition of glucocorticoid resistance in tetraploid human lymphoid cells

Resistance to dexamethasone (1 microM) was measured in glucocorticoid-sensitive diploid and tetraploid clones of the human leukaemic cell line CCRF-CEM (clone C7) during continuous culture and after X-ray or chemical mutagenesis. In continuous culture resistant diploid cells accumulated at a rate of about one cell per 10(5) divisions, while the rate for tetraploid cells was less than one per 10(7) divisions. Chemical and X-ray mutagenesis caused a marked increase in the number of resistant diploid cells but had very little effect on tetraploid cells. These results are consistent with a mutational basis for the acquisition of the glucocorticoid-resistant phenotype in human lymphoid cells.