TGFB1 and myelofibrosis: Further support for a key role of inflammation in MPN progression is that the development of fibrosis in myelofibrosis has been reported in some studies to correlate more strongly with the levels of certain cytokines including IL‐8 and TGF‐β than malignant clone burden (e.g. JAK2V617F variant allele frequency).24, 25