In patients with myelofibrosis, abnormal immature megakaryocytes in the bone marrow display reduced GATA1 protein expression and secrete a range of pro-inflammatory cytokines (such as IL-1ß, TGF-ß) and growth factors (including b-FGF, PDGF, and VEGF). This evidence concerns the gene GATA1 and myelofibrosis.