Samples from patients with chronic phase CML (n = 5) were enriched for CD34+ and cultured for 24h in serum-free medium (SFM) supplemented with growth factor cocktail comprising 100 ng/mL Flt3-ligand, 100 ng/mL stem cell factor, and 20 ng/mL each of interleukin (IL)-3, IL-6 and granulocyte-colony stimulating factor (G-CSF). This evidence concerns the gene CSF3 and chronic myelogenous leukemia, BCR-ABL1 positive.