SET-2 cells were plated in MethoCult H4435 (STEMCELL Technologies) after 48 hours of drug treatment, followed by washout in low FCS media and low-dose cytokines (24 hours) and scored for colony-forming unit blast at 10 days. Primary CD34+ stem/progenitor cells from peripheral blood samples from patients with JAK2V617F mutant positive myelofibrosis were purified by flow cytometry using anti–CD34-APC (clone 8G12), anti-human CD45RA Brilliant Violet 605, anti-CD90 fluorescein isothiocyanate, anti-human CD123-phycoerythrin (PE), and anti-human CD38 PE-Cy7 and plated in MethoCult H4435 at 1000 CD34+ per plate after ruxolitinib treatment and washout.