Mechanism(s) of Leukemogenesis in Genetically-Altered Mouse Models

白血病的发病率正在增加，特别是在儿童中，并且无处不在的暴露于环境致白血病原的贡献是未知的。由于突变的ras癌基因是人类骨髓增生异常综合征和急性髓性白血病中最常见的异常，我们选择使用z-珠蛋白促进的v-Ha-ras Tg.AC转基因系来研究暴露于苯（BZ）后诱导致癌ras在诱导白血病中的作用。在这里，我们描述了形态学和免疫表型分析以及脾集落测定数据，以证明反复皮肤接触Tg.AC小鼠BZ，但不是非转基因亲本株FVB/N，诱导骨髓性白血病。严重贫血和明显嗜中性粒细胞增多伴左移，骨髓中分化为粒细胞的祖细胞数量明显增加，骨髓细胞浸润造血组织，是BZ诱导疾病的特征。造血细胞的转化通过向同基因的、辐射的FVB/N受体的移植实验来证实。在未经治疗的Tg.AC中没有症状，如在非转基因亲本株中一样，表明v-Ha-ras转基因信息在BZ诱导的髓性白血病的发展中的作用。我们提出，BZ诱导的转基因发生在骨髓（BM）祖细胞直接向粒细胞谱系。通过原位杂交（ISH）、逆转录聚合酶链反应（RT-PCR）和免疫组织化学染色，我们证实了只有白血病受者脾脏和白血病供者脾脏和肝脏表达可诱导的ras转基因信息，并伴随着造血母细胞的有丝分裂活性。与对照相反，BZ处理的Tg.AC BM细胞均不表达转基因信息，这可能是由于BZ代谢物对祖细胞的毒性。然而，用表达转基因信息的正常Tg.AC BM细胞注射的受体小鼠没有发生白血病，这表明细胞转化需要其他突变。最后，核糖核酸酶保护分析（RPA）表明，BZ处理的BM中细胞因子的改变可以促进转化细胞的存活。我们假设，在祖细胞中v-Ha-ras的激活和BM中细胞因子的改变的组合允许转化细胞的克隆获得新的突变和髓性白血病从MPD发展。- 苯，癌，白血病，转基因，杂合性丢失，p53，抑癌基因，ras，原癌基因

Leukemia incidence is increasing, especially in children, and the contribution of ubiquitous exposure to environmental leukemogens is unknown. Since mutated ras oncogene is the most frequent abnormality reported in myelodysplastic syndromes and acute myeloid leukemias in humans, we chose to use the z-globin promoted v-Ha-ras Tg.AC transgenic line to investigate the role of an inducible oncogenic ras in the induction of leukemia after exposure to benzene (BZ). Here we describe the morphological and immunophenotypic analysis as well as a spleen colony assay data, to demonstrate that repeated dermal exposure of Tg.AC mice to BZ, but not the nontransgenic parent strain FVB/N, induced a myelogenous leukemia. Profound anemia and marked neutrophilia with presence of a left shift, marked increase in the number of progenitors that differentiated to granulocytes in bone marrow, and infiltration of hematopoietic tissues by myeloid cells characterized the BZ-induced disease. Transformation of a hematopoietic cell was confirmed by transplantation experiments to isogenic, irradiated FVB/N recipients. The absence of symptoms in untreated Tg.AC, as in nontransgenic parent strain, indicated a role for the v-Ha-ras transgene message in the development of BZ-induced myelogenous leukemia. We propose that BZ-induction of the transgene occurred in a bone marrow (BM) progenitor directed toward the granulocytic lineage. By in situ hybridization (ISH) analysis, reverse transcription polymerase chain reaction (RT-PCR) assay and immunohistochemistry staining, here we demonstrated that only leukemic recipient spleen and leukemic donor spleen and liver expressed the inducible ras transgene message concomitant to mitotic activity of hematopoietic blasts. Contrary to control, none of the BZ-treated Tg.AC BM cells expressed the transgene message, possibly due to BZ metabolite toxicity for progenitors. However, recipient mice injected with normal Tg.AC BM cells that express the transgene message did not develop leukemia, suggesting that cell transformation required other mutation(s). Finally, a ribonuclease protection analysis (RPA) demonstrated that the alteration of cytokines in BZ-treated BM could promote the survival of a transformed cell. We hypothesize that the combination of v-Ha-ras activation in a progenitor and the alteration of the cytokines in BM were permissive for a clone of transformed cell to acquire new mutation(s) and the myelogenous leukemia to develop from MPD. - benzene, cancer, leukemia, transgenic, loss of heterozygosity, p53, tumor suppressor gene, ras, protooncogene