| Abstract: | Treatment of Friend leukemia cells with BrdU, the thymidine analog which interferes with DMSO induced differentiation in these cells as well as the expression of differentiated character in many other cell systems, is capable of inducing erythroid differentiation. Globin mRNA, as assayed by hybridization to globin cDNA, increases 2.5- to 30-fold after appropriate treatment with BrdU. This effect was observed with several different subclones of three independent Friend tumor cell lines. After BrdU treatment, globin mRNA content may reach up to 10-20% of the levels in DMSO induced cultures. The induction of erythroid differentiation is also apparent when accumulated heme content or the appearance of benzidine positive cells is monitored. One Friend cell line (745) we examined was not induced by BrdU although it incorporated an amount of BrdU into its DNA comparable to that incorporated by the other cell lines. In addition, BrdU did interfere with DMSO induction in this cell line. These results suggest that two different mechanisms may be operative in regulating erythroid differentiation in Friend leukemia cells. While BrdU interferes with the mechanism activated by DMSO treatment, this analog could independently activate an alternative mechanism. |
