Privitera E, Schirò R, Longoni D, Ronchi A, Rambaldi A, Bernasconi S, Ottolenghi S, Masera G, Biondi A
Department of Genetica e di Biologia dei Microganismi, Università di Milano, Italy.
Blood. 1995 Jul 1;86(1):323-8.
Juvenile chronic myelocytic leukemia (JCML) is a rare disorder of early childhood. Characteristic of JCML are the progressive appearance of high levels of fetal hemoglobin (HbF), reflecting a true reversion to a fetal type of erythropoiesis, and the presence of colony-forming cells able to grow in vitro spontaneously in the absence of growth factors. To better understand the relationship between the erythroid abnormalities and the leukemic process, we analyzed the expression pattern of specific genes related to erythroid differentiation--GATA-1, EPOR, alpha-globin, beta-globin, and gamma-globin genes--in JCML peripheral blood (PB) cells and in vitro-derived colonies. Northern blot analysis of PB cells from five JCML patients indicated levels of GATA-1 transcripts much higher than those usually found in other types of leukemic cells, and S1 nuclease protection assay detected significantly increased expression of gamma-globin mRNA. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of single granulocyte-macrophage colony-forming unit (CFU-GM) colonies, obtained in vitro in the absence of added growth factors from four JCML patients, detected GATA-1, EPOR, and globin (alpha and gamma) transcripts in most of the colonies tested, in contrast with control CFU-GM from normal bone marrow, which were positive only for GATA-1. Single JCML colonies were tested for the presence of two different transcripts; whereas alpha- and gamma-globin genes appeared mostly coexpressed, beta-globin mRNA was detected only in a minority of the gamma-globin-positive colonies, indicating that the leukemic pattern of hemoglobin synthesis is mainly fetal. In addition, the leukemic cells occurring during blast crisis of one of our patients displayed the typical features of a stem cell leukemia (CD34+, CD19-, CD2-, myeloperoxidase-). In this sorted CD34+ population, we detected the presence of a marker chromosome, der(12)t(3;12), previously identified in bone marrow cells at diagnosis and an expression pattern superimposable to that of the JCML colonies, consistently displaying a high gamma-globin:beta-globin mRNA ratio. The expression of erythroid markers within populations of leukemic cells, both in vivo and in vitro, supports the hypothesis that abnormal JCML erythroid cells may originate from the same mutated progenitor that sustains the growth of the leukemic cells.
青少年慢性粒细胞白血病（JCML）是一种儿童早期的罕见疾病。JCML的特征是逐渐出现高水平的胎儿血红蛋白（HbF），这反映了真正向胎儿型红细胞生成的逆转，以及存在能够在无生长因子的情况下于体外自发生长的集落形成细胞。为了更好地理解红系异常与白血病进程之间的关系，我们分析了与红系分化相关的特定基因——GATA-1、EPOR、α-珠蛋白、β-珠蛋白和γ-珠蛋白基因——在JCML外周血（PB）细胞和体外衍生集落中的表达模式。对5例JCML患者的PB细胞进行的Northern印迹分析表明，GATA-1转录本水平远高于其他类型白血病细胞中通常所见的水平，S1核酸酶保护试验检测到γ-珠蛋白mRNA表达显著增加。对4例JCML患者在无添加生长因子的情况下体外获得的单个粒-巨噬细胞集落形成单位（CFU-GM）集落进行逆转录-聚合酶链反应（RT-PCR）分析，在大多数测试的集落中检测到了GATA-1、EPOR和珠蛋白（α和γ）转录本，而来自正常骨髓的对照CFU-GM仅对GATA-1呈阳性。对单个JCML集落检测两种不同转录本的存在；虽然α-珠蛋白和γ-珠蛋白基因大多共表达，但β-珠蛋白mRNA仅在少数γ-珠蛋白阳性集落中检测到，表明血红蛋白合成的白血病模式主要是胎儿型。此外，我们其中一位患者在急变期出现的白血病细胞表现出干细胞白血病的典型特征（CD34+、CD19-、CD2-、髓过氧化物酶-）。在这个分选的CD34+群体中，我们检测到一条标记染色体der(12)t(3;12)的存在，该染色体先前在诊断时的骨髓细胞中已被鉴定，其表达模式与JCML集落的表达模式重叠，始终显示出高γ-珠蛋白:β-珠蛋白mRNA比值。白血病细胞群体中红系标志物的体内和体外表达支持了这样一种假说，即异常的JCML红系细胞可能起源于维持白血病细胞生长的同一突变祖细胞。
