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Friend leukemia cells grown in the presence of dimethyl sulfoxide show enhanced erythroid differentiation and hemoglobin synthesis. The effects of dimethyl sulfoxide stimulation are inhibited by BrdU. To determine the effect of BrdU on the amount of globin mRNA present in cells treated and not treated with dimethyl sulfoxide, molecular hybridization between total cell RNA and [ 3 H]DNA complementary to mouse globin mRNA was used. Cells treated with BrdU and dimethyl sulfoxide had 70% less globin mRNA than cells treated with dimethyl sulfoxide alone. The size and base sequence of the residual globin mRNA in the cultures treated with BrdU and dimethyl sulfoxide were unaltered. Cells treated with BrdU alone contained slightly more globin mRNA than did the untreated controls, suggesting that BrdU may have a dual effect in transcription of messenger RNA.

Cells of a cloned line of murine virus-induced erythroleukemia were stimulated to differentiate along the erythroid pathway by dimethyl sulfoxide at concentrations that did not inhibit growth. A rise in the number of benzidine-positive normoblasts was accompanied by increased synthesis of heme and hemoglobin and a decrease in the malignancy of the cells. This action of dimethyl sulfoxide, which was reversible, may represent the derepression of leukemic cells to permit their maturation.