The level of c-myc transcript in differentiation-defective mouse erythroleukemia cells

We isolated several mouse erythroleukemia (MEL) cell lines, deficient in in vitro erythroid differentiation, and examined the change in level of c-myc mRNA after exposing the cells to dimethyl sulfoxide (DMSO). The results showed all the mutant MEL cells to exhibit a similar change in c-myc mRNA level to that in parental (DS19) cells with regard to both an initial decline and a subsequent increase to the pretreatment level. The c-myc mRNA level did not, however, decline again thereafter, as observed in the parental cells, but remained at the pretreatment level, even on prolonged culture in the presence of DMSO. Essentially the same results were obtained for the parental cells in the presence of DMSO and either 12-O-tetradecanoylphorbol 13-acetate (TPA) or dexamethasone, specific inhibitors of MEL cell differentiation. These results suggest that the crucial stage in MEL cell differentiation, regarding c-myc mRNA level, is the late stage, when the MEL cells become committed to differentiation.