PF4 and chronic myelogenous leukemia, BCR-ABL1 positive: It has been shown that malignant MKs produce TGF-β, which supports leukemogenic capacity of CML cells (Tanabe et al., 2020), and also, MK-derived expression of TGF-β and CXCL4 is known to maintain HSC quiescence (Bruns et al., 2014; Zhao et al., 2014).