Chan Iris T, Kutok Jeffery L, Williams Ifor R, Cohen Sarah, Kelly Lauren, Shigematsu Hirokazu, Johnson Leisa, Akashi Koichi, Tuveson David A, Jacks Tyler, Gilliland D Gary
Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
J Clin Invest. 2004 Feb;113(4):528-38. doi: 10.1172/JCI20476.
Oncogenic ras alleles are among the most common mutations found in patients with acute myeloid leukemia (AML). Previously, the role of oncogenic ras in cancer was assessed in model systems overexpressing oncogenic ras from heterologous promoters. However, there is increasing evidence that subtle differences in gene dosage and regulation of gene expression from endogenous promoters play critical roles in cancer pathogenesis. We characterized the role of oncogenic K-ras expressed from its endogenous promoter in the hematopoietic system using a conditional allele and IFN-inducible, Cre-mediated recombination. Mice developed a completely penetrant myeloproliferative syndrome characterized by leukocytosis with normal maturation of myeloid lineage cells; myeloid hyperplasia in bone marrow; and extramedullary hematopoiesis in the spleen and liver. Flow cytometry confirmed the myeloproliferative phenotype. Genotypic and Western blot analysis demonstrated Cre-mediated excision and expression, respectively, of the oncogenic K-ras allele. Bone marrow cells formed growth factor-independent colonies in methylcellulose cultures, but the myeloproliferative disease was not transplantable into secondary recipients. Thus, oncogenic K-ras induces a myeloproliferative disorder but not AML, indicating that additional mutations are required for AML development. This model system will be useful for assessing the contribution of cooperating mutations in AML and testing ras inhibitors in vivo.
致癌性Ras等位基因是急性髓系白血病（AML）患者中最常见的突变之一。以前，致癌性Ras在癌症中的作用是在从异源启动子过表达致癌性Ras的模型系统中评估的。然而，越来越多的证据表明，来自内源性启动子的基因剂量和基因表达调控的细微差异在癌症发病机制中起关键作用。我们使用条件性等位基因和IFN诱导的Cre介导的重组，表征了从其内源性启动子表达的致癌性K-Ras在造血系统中的作用。小鼠发展出一种完全显性的骨髓增殖综合征，其特征为白细胞增多且髓系谱系细胞成熟正常；骨髓中髓系增生；以及脾脏和肝脏中的髓外造血。流式细胞术证实了骨髓增殖表型。基因分型和蛋白质印迹分析分别证明了致癌性K-Ras等位基因的Cre介导的切除和表达。骨髓细胞在甲基纤维素培养物中形成不依赖生长因子的集落，但骨髓增殖性疾病不能移植到二级受体中。因此，致癌性K-Ras诱导骨髓增殖性疾病而非AML，这表明AML的发展需要额外的突变。该模型系统将有助于评估AML中协同突变的作用，并在体内测试Ras抑制剂。
