PF4 and acute promyelocytic leukemia: We found that: first, the ability of immature neutrophils to release ETs was impaired, while mature neutrophils trended to produce ETs in APL; second, ATRA+ATO induction enhanced ETosis of mature neutrophils; third, PF4 derived from PLTs stimulated ETs formation, and ETs activated PLTs to secrete active substances, forming a positive feedback loop; finally, ETs trigger endothelial retraction and gap formation, leading to RBCs leakage.