Early E, Moore M A, Kakizuka A, Nason-Burchenal K, Martin P, Evans R M, Dmitrovsky E
Department of Medicine, Laboratory of Molecular Medicine, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Proc Natl Acad Sci U S A. 1996 Jul 23;93(15):7900-4. doi: 10.1073/pnas.93.15.7900.
The translocation found in acute promyelocytic leukemia rearranges the promyelocytic leukemia gene (PML) on chromosome 15 with the retinoic acid receptor alpha (RARalpha) on chromosome 17. This yields a fusion transcript, PML/RARalpha, a transcription factor with reported dominant negative functions in the absence of hormone. Clinical remissions induced with all-trans retinoic acid (RA) treatment in acute promyelocytic leukemia are linked to PML/RARalpha expression in leukemic cells. To evaluate the PML/RARalpha role in myelopoiesis, transgenic mice expressing PML/RARalpha were engineered. A full-length PML/RARalpha cDNA driven by the CD11b promoter was expressed in transgenic mice. Expression was confirmed in the bone marrow with a reverse transcription PCR assay. Basal total white blood cell and granulocyte counts did not appreciably differ between PML/RARalpha transgenic and control mice. Cell sorter analysis of CD11b+ bone marrow cells revealed similar CD11b+ populations in transgenic and control mice. However, in vitro clonal growth assays performed on peripheral blood from transgenic versus control mice revealed a marked reduction of myeloid progenitors, especially in those responding to granulocyte/ macrophage colony-stimulating factor. Granulocyte/macrophage colony-stimulating factor and kit ligand cotreatment did not overcome this inhibition. Impaired myelopoiesis in vivo was shown by stressing these mice with sublethal irradiation. Following irradiation, PML/RARalpha transgenic mice, as compared with controls, more rapidly depressed peripheral white blood cell and granulocyte counts. As expected, nearly all control mice (94.4%) survived irradiation, yet this irradiation was lethal to 45.8% of PML/RARalpha transgenic mice. Lethality was associated with more severe leukopenia in transgenic versus control mice. Retinoic acid treatment of irradiated PML/RARalpha mice enhanced granulocyte recovery. These data suggest that abnormal myelopoiesis due to PML/RARalpha expression is an early event in oncogenic transformation.
急性早幼粒细胞白血病中发现的易位使15号染色体上的早幼粒细胞白血病基因（PML）与17号染色体上的维甲酸受体α（RARα）发生重排。这产生了一种融合转录本PML/RARα，它是一种转录因子，在没有激素的情况下具有报道的显性负性功能。急性早幼粒细胞白血病中全反式维甲酸（RA）治疗诱导的临床缓解与白血病细胞中PML/RARα的表达有关。为了评估PML/RARα在骨髓生成中的作用，构建了表达PML/RARα的转基因小鼠。由CD11b启动子驱动的全长PML/RARα cDNA在转基因小鼠中表达。通过逆转录PCR分析在骨髓中证实了表达。PML/RARα转基因小鼠和对照小鼠的基础全白细胞和粒细胞计数没有明显差异。对CD11b +骨髓细胞的细胞分选分析显示转基因小鼠和对照小鼠中的CD11b +群体相似。然而，对转基因小鼠与对照小鼠外周血进行的体外克隆生长试验显示髓系祖细胞明显减少，尤其是对粒细胞/巨噬细胞集落刺激因子有反应的祖细胞。粒细胞/巨噬细胞集落刺激因子和kit配体联合治疗不能克服这种抑制作用。通过对这些小鼠进行亚致死剂量照射来显示体内骨髓生成受损。照射后，与对照相比，PML/RARα转基因小鼠外周白细胞和粒细胞计数下降更快。正如预期的那样，几乎所有对照小鼠（94.4％）在照射后存活，但这种照射对45.8％的PML/RARα转基因小鼠是致命的。致死性与转基因小鼠比对照小鼠更严重的白细胞减少有关。对照射后的PML/RARα小鼠进行维甲酸治疗可增强粒细胞恢复。这些数据表明，由于PML/RARα表达导致的异常骨髓生成是致癌转化中的早期事件。
