Promyelocytic extracellular chromatin exacerbates coagulation and fibrinolysis in acute promyelocytic leukemia

• Published in: Blood 2017-03, Vol.129 (13), p.1855-1864
• Main Authors: Cao, Muhua, Li, Tao, He, Zhangxiu, Wang, Lixiu, Yang, Xiaoyan, Kou, Yan, Zou, Lili, Dong, Xue, Novakovic, Valerie A., Bi, Yayan, Kou, Junjie, Yu, Bo, Fang, Shaohong, Wang, Jinghua, Zhou, Jin, Shi, Jialan
• Format: Article
• Language: English
• Subjects: Blood Coagulation; Cells, Cultured; Chromatin - pathology; Chromatin - physiology; Chromatin - ultrastructure; Endothelial Cells; Fibrin - metabolism; Fibrinolysis; Granulocyte Precursor Cells - pathology; Humans; Leukemia, Promyelocytic, Acute - blood; Leukemia, Promyelocytic, Acute - complications; Thrombosis and Hemostasis; Tretinoin - pharmacology; Tumor Cells, Cultured
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2016-09-739334

Despite routine treatment of unselected acute promyelocytic leukemia (APL) with all-trans-retinoic acid (ATRA), early death because of hemorrhage remains unacceptably common, and the mechanism underlying this complication remains elusive. We have recently demonstrated that APL cells undergo a novel cell death program, termed ETosis, which involves release of extracellular chromatin. However, the role of promyelocytic extracellular chromatin in APL-associated coagulation remains unclear. Our objectives were to identify the novel role of ATRA-promoted extracellular chromatin in inducing a hypercoagulable and hyperfibrinolytic state in APL and to evaluate its interaction with fibrin and endothelial cells (ECs). Results from a series of coagulation assays have shown that promyelocytic extracellular chromatin increases thrombin and plasmin generation, causes a shortening of plasma clotting time of APL cells, and increases fibrin formation. DNase I but not anti-tissue factor antibody could inhibit these effects. Immunofluorescence staining showed that promyelocytic extracellular chromatin and phosphatidylserine on APL cells provide platforms for fibrin deposition and render clots more resistant to fibrinolysis. Additionally, coincubation assays revealed that promyelocytic extracellular chromatin is cytotoxic to ECs, converting them to a procoagulant phenotype. This cytotoxity was blocked by DNase I by 20% or activated protein C by 31%. Our current results thus delineate the pathogenic role of promyelocytic extracellular chromatin in APL coagulopathy. Furthermore, the remaining coagulation disturbance in high-risk APL patients after ATRA administration may be treatable by intrinsic pathway inhibition via accelerating extracellular chromatin degradation. •ATRA promotes ETosis leading to procoagulant promyelocytic extracellular chromatin.•Extracellular chromatin fosters excess thrombin production and fibrin deposition, increases plasmin, and causes endothelium damage.