P210/STAT5A–/– CML mice have prolonged survival due to slower CML disease kinetics. (A) The survival of mice with the pure CML-like disease resulting from the transplantation of P210/STAT5A–/– or P210/STAT5A+/+ BM cells was analyzed by Kaplan-Meier survival curve. The median survival of P210/STAT5A–/– CML animals was 44 days, compared with 21 days for P210/STAT5A+/+ CML animals (P < .001, log-rank test). (B) Serial peripheral WBC counts from mice dying of the pure CML-like illness. Note that P210/STAT5A–/–-reconstituted CML animals (no. 608 and no. 611) had WBC counts of 76 × 109/L (76 000/μL) and 28 × 109/L (28 000/μL), respectively, on day 25 after BM reconstitution, comprised mostly of maturing granulocytic lineage cells, intermixed with some B lymphoblasts (left panels, single arrows). Relatively little change was noted in serial WBC counts until days 45 and 52, when the P210/STAT5A–/– mice died from the CML-like disease with WBC counts of 135 × 109/L (135 000/μL) and 146 × 109/L (146 000/μL), respectively, composed entirely of granulocytes, including relatively immature myeloid cells (right panels, double arrows). For comparison, P210/STAT5A+/+-reconstituted CML mice (no. 605 and no. 607) had WBC counts of 40 × 109/L (40 000/μL) and 38.5 × 109/L (38 500/μL), respectively, on day 17, and died 4 days later from CML with WBC counts of 190 × 109/L (190 000/μL) and 345 × 109/L (345 000/μL). (C) Peripheral blood cytospins from nonleukemic STAT5A-null and STAT5A wild-type (WT) mice are shown for comparison, composed of lymphocytes and mature granulocytes (average 80% and 20%, and 79% and 21%, respectively). A 10-μm size bar is shown at bottom left of each photomicrograph.
