Mitosis may be an obligatory route to terminal differentiation in the Friend erythroleukemia cell

In previous studies, it was shown that treatment of Friend erythroleukemia (FEL) cells with dimethylsulfoxide (DMSO) and the poly(ADP-ribose) polymerase inhibitor 3-aminobenzamide (3AB) blocked the differentiation pathway just prior to commitment. These studies show that the exposure of DMSO(+3AB)-induced cells to the mitotic inhibitors colcemid or nocodazole resulted in commitment to terminal differentiation. Expression of differentiated phenotype required further incubation without the mitotic inhibitors. Microscopic examination indicated that the number of cells blocked in mitosis and those that differentiated were approximately equivalent. These observations suggest that commitment had occurred during mitosis and that expression of the differentiated state occurred after completion of mitosis. Since commitment was not inhibited by blocking DNA replication by aphidicolin or cytokinesis by cytochalasin B, mitosis may be the only phase of the cell cycle required for commitment.