Reduction in Stat5 gene dosage attenuates BCR-ABL1–induced CML-like MPN. Kaplan-Meier survival curve for recipients of Stat5a/b^fl/+ (n = 2) or Stat5a/b^fl/− (n = 4) BM transduced with p210MIGFP retrovirus, and recipients of Stat5a/b^fl/+ (n = 8) or Stat5a/b^fl/− (n = 11) BM transduced with p210MIGFPCre retrovirus is shown. The symbols indicate individual recipient mice, with the disease phenotype of each designated by the shading: black, CML-like MPN; white, B-ALL; black and white, mixed CML/B-ALL; gray, histiocytic sarcoma (HS). Relative to the p210MIGFP→Stat5a/b^fl/+ cohort, the survival of the p210MIGFP→Stat5a/b^fl/− and p210MIGFPCre→Stat5a/b^fl/+cohorts was significantly prolonged (P = .017 and P = .0009, respectively, by Mantel-Cox test). Relative to the p210MIGFPCre→Stat5a/b^fl/+ cohort, the survival of the p210MIGFPCre→Stat5a/b^fl/− cohort was also significantly prolonged (P = .008).