Silva M, Richard C, Benito A, Sanz C, Olalla I, Fernández-Luna J L
Servicio de Immunologia, Hospital Universitario Marqués de Valdecilla, Santander, Spain.
N Engl J Med. 1998 Feb 26;338(9):564-71. doi: 10.1056/NEJM199802263380902.
Deregulating the expression of Bcl-xL, an inhibitor of apoptosis, in an erythropoietin-dependent erythroblast cell line averts apoptosis induced by the withdrawal of erythropoietin. Since in polycythemia vera an abnormal clone of erythroid progenitors is independent of erythropoietin, we investigated whether the endogenous expression of Bcl-xL was deregulated in these cells.
Erythroid colonies from patients with polycythemia vera and normal subjects were cultured in the presence and absence of erythropoietin and assessed by immunocytochemical and flow-cytometric analysis with anti-Bcl-x antibodies that recognize the two species of Bcl-x (Bcl-xL and Bcl-xS). Reverse-transcriptase-polymerase-chain-reaction analysis was used to determine which one of the two species was responsible for anti-Bcl-x staining. Bone marrow mononuclear cells from 8 healthy bone marrow donors, 14 patients with polycythemia vera, 19 patients with other myeloproliferative syndromes, and 12 patients with secondary erythrocytosis were analyzed by flow cytometry with antibodies against Bcl-x and glycophorin A, an erythroid marker.
Erythroid cells from patients with polycythemia vera survived in vitro without erythropoietin, and this finding correlated with the expression of Bcl-x protein (Bcl-xL messenger RNA was the main species of Bcl-x found), even in mature erythroblasts that normally do not express Bcl-x. The mean (+/-SD) percentage of cells positive for both glycophorin A and Bcl-x in the 14 patients with polycythemia vera (21.8+/-3.6 percent) was significantly higher than that in 8 normal donors (6.62+/-1.58 percent), 12 patients with secondary erythrocytosis (6.87+/-1.95 percent), 9 patients with essential thrombocythemia (3.81+/-0.97 percent), and 10 patients with chronic myeloid leukemia (2.7+/-0.41 percent).
Deregulated expression of Bcl-x may contribute to the erythropoietin-independent survival of erythroid-lineage cells in polycythemia vera and thereby contribute to the pathogenesis of this disease.
在一种依赖促红细胞生成素的成红细胞系中，解除凋亡抑制因子Bcl-xL的表达调控可避免因撤除促红细胞生成素而诱导的凋亡。由于真性红细胞增多症中异常的红系祖细胞克隆不依赖促红细胞生成素，我们研究了这些细胞中Bcl-xL的内源性表达是否失调。
将真性红细胞增多症患者和正常受试者的红系集落分别在有和没有促红细胞生成素的情况下进行培养，并用识别两种Bcl-x（Bcl-xL和Bcl-xS）的抗Bcl-x抗体通过免疫细胞化学和流式细胞术分析进行评估。采用逆转录-聚合酶链反应分析来确定两种Bcl-x中的哪一种导致了抗Bcl-x染色。用抗Bcl-x抗体和红系标志物血型糖蛋白A，通过流式细胞术分析了8名健康骨髓供者、14名真性红细胞增多症患者、19名其他骨髓增殖性综合征患者和12名继发性红细胞增多症患者的骨髓单个核细胞。
真性红细胞增多症患者的红系细胞在无促红细胞生成素的情况下能在体外存活，这一发现与Bcl-x蛋白的表达相关（Bcl-xL信使核糖核酸是所发现的主要Bcl-x种类），即使在通常不表达Bcl-x的成熟成红细胞中也是如此。14例真性红细胞增多症患者中血型糖蛋白A和Bcl-x均呈阳性的细胞的平均（±标准差）百分比（21.8±3.6%）显著高于8名正常供者（6.62±1.58%）、12例继发性红细胞增多症患者（6.87±1.95%）、9例原发性血小板增多症患者（3.81±0.97%）和10例慢性髓性白血病患者（2.7±0.41%）。
Bcl-x的表达失调可能有助于真性红细胞增多症中红系细胞不依赖促红细胞生成素的存活，从而促成该病的发病机制。
