ABSTRACT
To determine the mechanism of the growth inhibition associated with the induction of erythroid differentiation in K562 cells by hemin, we used two K562 subclones with different hemoglobin (Hb)-producing activity. Hemin strongly inhibited the growth of K562-L, which had a low Hb-producing activity, but not that of K562-H, which had a high Hb-producing activity. When the cell growth of K562-L was inhibited by hemin, the S phase of the cell cycle decreased and the G2/M phase increased. In contrast, hemin had no effect on the cell cycle of K562-H. Without hemin treatment, the alpha-globin mRNA level was related to the degree of Hb production in K562-L and -H but the gamma-globin mRNA level was not. With hemin treatment, there was no increase in the alpha-globin mRNA level in K562-L but there was an increase in K562-H. The difference in alpha-globin mRNA levels correlated with the Hb production in K562-L and -H induced by hemin. The levels of c-myc and c-myb mRNAs in K562-L decreased when cell growth was strongly inhibited by hemin. These findings indicate that the growth inhibition of K562 cells by hemin is due to a suppression of the progression from the G0/G1 phase to the S phase and a delay in the G2/M phase, caused by the inhibition of c-myc and c-myb transcription. It is also affected by the Hb production, reflected in alpha-globin transcription.
Subject(s)
Hemin/pharmacology , Hemoglobins/biosynthesis , Leukemia, Experimental/metabolism , Blotting, Northern , Cell Cycle/drug effects , Gene Expression/drug effects , Genes, myc/drug effects , Globins/biosynthesis , Humans , Oncogenes/drug effects , RNA, Messenger/biosynthesis , Tumor Cells, CulturedABSTRACT
Two subclones (K562-L and -H) were previously isolated from K562 human leukemic cells according to hemoglobin production: K562-L was expressed in less than 5% and K562-H in more than 90% of dianisidine positive cells. 12-O-Tetradecanoylphorbol-13- acetate (TPA) suppressed the expression of the erythrocytic (glycophorin A) and myelocytic (CD11b) antigens in K562-L, but increased the expression of these antigens in K562-H. TPA increased the megakaryocytic (CD61) antigens in both cells. These findings suggest that there are distinct TPA responsible factors in K562-L and -H on the expression of the erythrocytic and myelocytic antigens.
Subject(s)
Antigens, Surface/analysis , Glycophorins/analysis , Leukemia, Erythroblastic, Acute/immunology , Macrophage-1 Antigen/analysis , Tetradecanoylphorbol Acetate/pharmacology , Humans , Tumor Cells, CulturedABSTRACT
Two clones of the K562 human leukemic cell line were isolated according to hemoglobin (Hb) expression. One clone was expressed less than 5% (K562-L) and the other more than 90% (K562-H). The two clones did not exhibit any difference in cell growth or cell cycle. However, the Hb expression of K562-H cells was reduced by succinylacetone (S.A.). The above results suggested that the difference in the Hb production of K562-L and K562-H cells depended on the heme synthetic activity. On the other hand, glycophorin A was expressed to a greater extent on K562-L cells than on K562-H cells. These findings suggested that heme synthesis and the expression of glycophorin A on K562 cells were not always related. The CD11b and the CD61 were also expressed to a greater extent on K562-L cells than on K562-H cells, but the CD34 was not expressed on these cells.
