(A) STAT5 activation in MDS patients cells after incubation with Epo. Equivalent amounts of cells were obtained and extracted after 15 minutes of incubation without factor (lanes 1, 4, 7, 10, 13, 16), with IL-3 (lanes 2, 5, 8, 11, 14, 17), or with Epo (lanes 3, 6, 9, 12, 15, 18). Marrow cells used were obtained from patient 8 (lanes 1 through 3), patient 13 (lanes 4 through 6), patient 2 (lanes 7 through 9), patient 1 (lanes 10 through 12), patient 19 (lanes 13 through 15), patient 7 (lanes 16 through 18); patient numbers correlate to case numbers in Table 1. Nuclear extracts were incubated with the β-casein probe. Arrow indicates position of STAT5 complex. (B) Activation of STAT5 in MDS at different time points. Cells from two patients with MDS (patient 13, lanes 1 through 7; and patient 8, lanes 8 through 14) were obtained and extracted after no stimulation (lanes 1 and 8), or after incubation with Epo for 5 (lanes 2 and 9), 15 (lanes 3 and 10), 30 (lanes 4 and 11), 60 (lanes 5 and 12), or 180 minutes (lanes 6 and 13), or after incubation for 15 minutes with IL-3 (lanes 7 and 14). The probe used is the β-casein probe, and the film was relatively overexposed. Arrow indicates position of STAT5 complex.