Differences in STAT5 signaling and MF-specific STAT3 signaling in CD34⁻ cells from patients with MPN. (A) Representative histogram profiles of phospho-ERK (top row) and phospho-STAT5 (middle row) staining in a control and a PV patient (left and center panels, respectively). Phospho-STAT3 staining (bottom row) is shown for an MF patient and a control. The bar graph on the right shows increased STAT5 signaling in MPN patients, which reached statistical significance in PV and MF patients compared with controls. There was also a statistical significant difference in STAT5 signaling between PV and ET patients. Statistically significant STAT3 signaling compared with controls and PV occurred only with MF patients. (B) A signaling heat-map table is shown for all control and MPN CD34⁻ samples analyzed. The patient numbers correspond to those in Figure 2B plus additional patients for whom CD34⁻ cells were available for analysis. Where the patient is JAK2 V617F positive, we have also documented the allele burden of the CD34⁻/GPA⁺/CD71⁺ compartment.