Impaired SDF-1–induced PKB and ERK1/2 activation in MDS CD34⁺ cells. (A) Isolated CD34⁺ cells from 9 MDS patients and 9 healthy controls were stimulated with 100 ng/mL SDF-1 for the indicated times. Western blotting was performed using antibodies against phosphorylated PKB (p-PKB, top panels) or phosphorylated ERK1/2 (p-ERK1/2, middle panels). To correct for loading differences the blots were reprobed with antibodies against ERK1/2 (bottom panels). 3 representative examples of PKB activation and 2 examples of ERK1/2 phosphorylation are shown. For quantification of phosphorylated PKB (B) and ERK1/2 (C), densitometry values were divided by the densitometry values of total ERK1/2 protein present in the same samples. Means of 9 independent experiments are shown. Significant differences are indicated with *(P < .05).