FIGURE 3.

Adhesion-dependent acceleration of hemin-stimulated erythroid differentiation of K562 cells. A, cell suspension with or without hemin (50 μm) were seeded into a 96-well plate coated with FN (5 μg/ml) and cultured in the presence of TNIIIA2 (0–75 μg/ml), TNIIIA2scr (75 μg/ml), or Mn²⁺ (0.5 mm). B, erythroid differentiation was stimulated by hemin (50 μm) (open triangles with a dotted line) or by hemin plus TNIIIA2 (75 μg/ml) (open circles with a solid line) in the presence of FNIII14 at the indicated concentrations. C, effects of antagonists for VLA-5 (RGD peptide) and VLA-4 (CS-1 peptide) on the acceleration of hemin-stimulated erythroid differentiation in response to TNIIIA2. Erythroid differentiation was stimulated with hemin (50 μm) in the presence of TNIIIA2 (75 μg/ml) with or without the RGD peptide (100 and 200 μg/ml) or the CS-1 peptide (100 and 200 μg/ml). After culture for 3 days, hemoglobinized cells were stained with o-dianisidine as described under “Experimental Procedures.” Data represent the mean ± S.E. of triplicate determinations. One of three individual experiments is shown. *, p < 0.05 compared with control.