Selection for Evi1 activation in myelomonocytic leukemia induced by hyperactive signaling through wild-type NRas

• Published in: Oncogene Vol. 32; no. 25; pp. 3028 - 3038
• Main Authors: Wolf, S, Rudolph, C, Morgan, M, Büsche, G, Salguero, G, Stripecke, R, Schlegelberger, B, Baum, C, Modlich, U
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20.06.2013; Nature Publishing Group
• Subjects: 631/67/395; 631/67/68; 631/80/86; 692/699/67/1990/283; Acute myeloid leukemia; AKT protein; Animal models; Animals; Apoptosis; Bcl-2 protein; Bone marrow; Bone Marrow Transplantation; Cell activation; Cell Biology; Cell Line, Tumor; Cell Proliferation; Cellular signal transduction; DNA-Binding Proteins - metabolism; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases - metabolism; Gene expression; Gene mutations; Genes, ras; Genetic aspects; Histiocytosis; Human Genetics; Humans; Internal Medicine; Leukemia; Leukemia, Myelomonocytic, Acute - genetics; Leukemia, Myelomonocytic, Acute - metabolism; Leukemogenesis; MDS1 and EVI1 Complex Locus Protein; Medicine; Medicine & Public Health; Mice; Mice, Inbred C57BL; Mutation; Myelocytic leukemia; Myelomonocytic leukemia; Nonlymphoid leukemia; Oncology; original-article; Pathogenesis; Physiological aspects; Proteins; Proto-Oncogene Proteins c-akt - metabolism; Proto-Oncogene Proteins c-bcl-2 - metabolism; Proto-Oncogenes; ras Proteins - genetics; ras Proteins - metabolism; Risk factors; Signal Transduction; Stat5 protein; STAT5 Transcription Factor - metabolism; Transcription Factors - metabolism; Germany; Evi1; NRas; murine BMT model; malignant histiocytosis; retroviral vector; myelomonocytic leukemia
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2012.329

Activation of NRas signaling is frequently found in human myeloid leukemia and can be induced by activating mutations as well as by mutations in receptors or signaling molecules upstream of NRas. To study NRas-induced leukemogenesis, we retrovirally overexpressed wild-type NRas in a murine bone marrow transplantation (BMT) model in C57BL/6J mice. Overexpression of wild-type NRas caused myelomonocytic leukemias ∼3 months after BMT in the majority of mice. A subset of mice (30%) developed malignant histiocytosis similar to mice that received mutationally activated NRas(G12D)-expressing bone marrow. Aberrant Ras signaling was demonstrated in cells expressing mutationally active or wild-type NRas, as increased activation of Erk and Akt was observed in both models. However, more NRas(G12D) were found to be in the activated, GTP-bound state in comparison with wild-type NRas. Consistent with observations reported for primary human myelomonocytic leukemia cells, Stat5 activation was also detected in murine leukemic cells. Furthermore, clonal evolution was detected in NRas wild-type-induced leukemias, including expansion of clones containing activating vector insertions in known oncogenes, such as Evi1 and Prdm16 . In vitro cooperation of NRas and Evi1 improved long-term expansion of primary murine bone marrow cells. Evi1-positive cells upregulated Bcl-2 and may, therefore, provide anti-apoptotic signals that collaborate with the NRas-induced proliferative effects. As activation of Evi1 has been shown to coincide with NRAS mutations in human acute myeloid leukemia, our murine model recapitulates crucial events in human leukemogenesis.