Induction of erythroid differentiation by 5-fluorouracil in K562 leukemia cells.

K562 cell line, established from a patient in the blast crisis of chronic myeloid leukemia, expresses high levels of c-myc and bcr/abl gene products. Exposure of K562 cells to 5-fluorouracil (5-FU) resulted in a marked benzidine-positive erythroid differentiation with concomitant reduction in cell proliferation. No change in c-myc mRNA or protein levels occurred during 96 h of drug treatment. In contrast, a biphasic change of p210bcr/abl and the abl-associated kinase activities was observed upon treatment with 5-FU. The change in p210bcr/abl expression may be mediated at the translational level, since the steady-state level and the enzymatic activity of p210bcr/abl are reduced, whereas bcr/abl mRNA levels are unaltered. The results are consistent with the existence of pleiotropic differentiation pathways in K562 cells.