Malherbe Jacques A J, Fuller Kathryn A, Mirzai Bob, Kavanagh Simon, So Chi-Chiu, Ip Ho-Wan, Guo Belinda B, Forsyth Cecily, Howman Rebecca, Erber Wendy N
School of Pathology and Laboratory Medicine, University of Western Australia, Crawley, Western Australia, Australia.
School of Pathology and Laboratory Medicine, University of Western Australia, Crawley, Western Australia, Australia PathWest Laboratory Medicine, Nedlands, Western Australia, Australia.
J Clin Pathol. 2016 Apr 8;69(11):1017-24. doi: 10.1136/jclinpath-2016-203625.
Megakaryocyte expansion in myeloproliferative neoplasms (MPNs) is due to uncontrolled proliferation accompanied by dysregulation of proapoptotic and antiapoptotic mechanisms. Here we have investigated the intrinsic and extrinsic apoptotic pathways of megakaryocytes in human MPNs to further define the mechanisms involved.
The megakaryocytic expression of proapoptotic caspase-8, caspase-9, Diablo, p53 and antiapoptotic survivin proteins was investigated in bone marrow specimens of the MPNs (n=145) and controls (n=15) using immunohistochemistry. The megakaryocyte percentage positivity was assessed by light microscopy and correlated with the MPN entity, JAK2/CALR mutation status and platelet count.
The proportion of megakaryocytes in the MPNs expressing caspase-8, caspase-9, Diablo, survivin and p53 was significantly greater than controls. A greater proportion of myeloproliferative megakaryocytes expressed survivin relative to its reciprocal inhibitor, Diablo. Differences were seen between myelofibrosis, polycythaemia vera and essential thrombocythaemia for caspase-9 and p53. CALR-mutated cases had greater megakaryocyte p53 positivity compared to those with the JAK2 mutation. Proapoptotic caspase-9 expression showed a positive correlation with platelet count, which was most marked in myelofibrosis and CALR-mutated cases.
Disruptions targeting the intrinsic apoptotic cascade promote megakaryocyte hyperplasia and thrombocytosis in the MPNs. There is progressive dysfunction of apoptosis as evidenced by the marked reduction in proapoptotic caspase-9 and accumulation of p53 in myelofibrosis. The dysfunction of caspase-9, which is necessary for proplatelet formation, may be the mechanism for the excess thrombocytosis associated with CALR mutations. Survivin seems to be the key protein mediating the megakaryocyte survival signature in the MPNs and is a potential therapeutic target.
骨髓增殖性肿瘤（MPN）中巨核细胞扩增是由于不受控制的增殖以及促凋亡和抗凋亡机制失调所致。在此，我们研究了人类MPN中巨核细胞的内在和外在凋亡途径，以进一步明确其中涉及的机制。
采用免疫组织化学方法，在MPN患者（n = 145）和对照组（n = 15）的骨髓标本中，研究促凋亡蛋白半胱天冬酶 - 8、半胱天冬酶 - 9、暗黑破坏神蛋白（Diablo）、p53以及抗凋亡蛋白生存素（survivin）在巨核细胞中的表达。通过光学显微镜评估巨核细胞阳性百分比，并将其与MPN类型、JAK2/CALR突变状态和血小板计数相关联。
MPN中表达半胱天冬酶 - 8、半胱天冬酶 - 9、暗黑破坏神蛋白、生存素和p53的巨核细胞比例显著高于对照组。相对于其相互抑制剂暗黑破坏神蛋白，增殖性巨核细胞中表达生存素的比例更高。在骨髓纤维化、真性红细胞增多症和原发性血小板增多症之间，半胱天冬酶 - 9和p53存在差异。与JAK2突变患者相比，CALR突变患者的巨核细胞p53阳性率更高。促凋亡蛋白半胱天冬酶 - 9的表达与血小板计数呈正相关，在骨髓纤维化和CALR突变病例中最为明显。
针对内在凋亡级联反应的破坏促进了MPN中巨核细胞增生和血小板增多。骨髓纤维化中促凋亡蛋白半胱天冬酶 - 9显著减少和p53积累表明凋亡存在进行性功能障碍。对于前血小板形成所必需的半胱天冬酶 - 9功能障碍，可能是与CALR突变相关的血小板增多症的机制。生存素似乎是介导MPN中巨核细胞存活特征性的关键蛋白，是一个潜在的治疗靶点。
