Therefore, CXCL12 may also be involved in protecting the leukemic stem cells and contributing to myelofibrosis progression [22], though CXCR4 is downregulated in the malignant progenitors, which may explain extramedullary clonal hematopoiesis in myelofibrosis [41]. Here, CXCR4 is linked to myelofibrosis.