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，而无处不在的暴露于环境中的白血病原的贡献尚不清楚。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系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转基因系来研究可诱导的致癌ras在苯(BZ)暴露后诱发白血病中的作用。在这里，我们描述了形态学和免疫表型分析以及脾集落分析数据，以证明Tg.AC小鼠反复皮肤暴露于BZ，而不是非转基因亲本株FVB/N，诱发了髓系白血病。严重的贫血和明显的中性粒细胞左移，骨髓中分化为粒细胞的祖细胞数量显著增加，髓系细胞渗入造血组织是BZ诱发疾病的特征。通过将造血细胞移植到同基因的辐射FVB/N受体身上，证实了造血细胞的转化。未经治疗的Tg.AC没有症状，与非转基因亲本株一样，表明v-Ha-ras转基因信息在BZ诱导的髓系白血病的发展中发挥了作用。我们认为BZ对转基因的诱导发生在针对粒系的骨髓(BM)祖细胞中。通过原位杂交(ISH)、逆转录聚合酶链式反应(RT-PCR)和免疫组织化学染色，我们证实只有白血病受体脾和白血病供体脾和肝表达伴随有丝分裂活性的诱导型ras转基因信息。与对照相反，BZ处理的Tg.AC BM细胞中没有表达转基因信息，可能是由于BZ代谢物对祖细胞的毒性。然而，注射了表达转基因信息的正常Tg.AC BM细胞的受体小鼠没有出现白血病，这表明细胞转化需要其他突变(S)。最后，核糖核酸酶保护分析(RPA)表明，BZ处理的BM中细胞因子的变化可以促进转化细胞的存活。我们推测，祖细胞中v-Ha-ras的激活和骨髓中细胞因子的改变相结合，允许转化细胞的克隆获得新的突变(S)，并允许髓系白血病从MPD发展成髓系白血病。-苯，癌症，白血病，转基因，杂合性缺失，p53，肿瘤抑制基因，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