Endogenous Oncogenic Nras Mutation Initiates Hematopoietic Malighnancies in a Dose- and cell Type-Dependent Manner
Both monoallelic and biallelic oncogenic NRAS mutations are identified in human leukemias, suggesting a dose-dependent role of oncogenic NRAS in leukemogenesis. Here, we use a hypomorphic oncogenic Nras allele and a normal oncogenic Nras allele (Nras G12D(hypo) and Nras G12D, respectively) to create a gene dose gradient ranging from 25% to 200% of endogenous Nras G12D/+. Mice expressing Nras G12D(hypo)/G12D(hypo) develop normally and are tumor-free, whereas early embryonic expression of Nras G12D/+ is lethal. Somatic expression of Nras G12D/G12D but not Nras G12D/+ leads to hyperactivation of ERK, excessive proliferation of myeloid progenitors, and consequently an acute myeloproliferative disease. Using a bone marrow transplant model, we previously showed that ∼ 95% of animals receiving Nras G12D/+ bone marrow cells develop chronic myelomonocytic leukemia (CMML), while ∼ 8% of recipients develop acute T-cell lymphoblastic leukemia/lymphoma [TALL] (TALL-het). Here we demonstrate that 100% of recipients transplanted with Nras G12D/G12D bone marrow cells develop TALL (TALL-homo). Although both TALL-het and -homo tumors acquire Notch1 mutations and are sensitive to a γ-secretase inhibitor, endogenous Nras G12D/+ signaling promotes TALL through distinct genetic mechanism(s) from Nras G12D/G12D. Our data indicate that the tumor transformation potential of endogenous oncogenic Nras is both dose- and cell type-dependent
Wang J., Liu Y., Li Z., Wang Z., Tan LX., Ryu MJ., Meline B., Du J., Young KH., Ranheim E., Chang Q., Zhang J. Endogenous oncogenic Nras mutation initiates hematopoietic malignancies in a dose- and cell type-dependent manner. Blood (2011) 118(2):368-79.
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