Mutant N-ras induces myeloproliferative disorders and apoptosis in bone marrow repopulated mice.
Mutations that activate the N-ras oncogene are among the most frequently detected genetic alterations in human acute myeloid leukemias (AMLs), Philadelphia chromosome-negative myeloproliferative disorders (MPDs), and myelodysplastic syndromes (MDSs). However, because N-ras has not been shown to induce these disorders in an in vivo model, the role of N-ras in the evolution of myeloid leukemia is unclear. To investigate the potential of N-ras to induce myeloid leukemia, lethally irradiated mice were reconstituted with bone marrow (BM) cells infected with a retroviral vector carrying activated N-ras. Approximately 60% of these mice developed hematopoietic disorders, including severe MPDs resembling human chronic myelogenous leukemia (CML) or AML with differentiation (French-American-British [FAB] classification M2). Other reconstituted mice succumbed to hematopoietic defects that were pathologically similar to human MDSs. The latter disorders appeared to be due to a myeloid impairment that was demonstrated by enumeration of day-12 colony-forming units-spleen (CFU-S) and by in vitro colony assays. A high level of apoptosis associated with thymic atrophy and peripheral blood (PB) lymphopenia was also evident in N-ras reconstituted mice. Our results are consistent with a model in which antiproliferative effects are a primary consequence of N-ras mutations and secondary transforming events are necessary for the development of myeloid leukemia. This is the first report of an in vivo model for N-ras induced MPD and leukemia. (+info)
Patients with thrombocytosis have normal or slightly elevated thrombopoietin levels.
BACKGROUND AND OBJECTIVE: The distinction between clonal and reactive thrombocytoses is a frequent problem and implies different therapeutic options. As thrombopoietin (TPO) is the main regulator of megakaryocytopoiesis and thrombopoiesis, we measured TPO levels in patients with thrombocytosis in an attempt to understand the regulation and potential utility of distinguishing thrombocytoses. DESIGN AND METHODS: Serum TPO levels, platelet counts, mean platelet volume, hemoglobin, erythrocyte sedimentation rate and age were evaluated in 25 patients with clonal thrombocytosis (15 with essential thrombocythemia, 6 with polycythemia vera and 4 with chronic myeloid leukemia) and in 50 patients with reactive thrombocytosis distributed in three groups: 1) patients in post-surgical states; 2) patients with solid tumors; and 3) patients with inflammatory diseases. RESULTS: TPO levels were slightly increased in patients with clonal (135+/-50 pg/mL) and reactive (147+/-58 pg/mL) thrombocytosis compared with controls (121+/-58 pg/mL). Analyzing the different groups, patients with essential thrombocythemia had the lowest TPO levels (120+/-28 pg/mL) and patients with solid tumors the highest levels (162+/-59 pg/mL). Patients with clonal thrombocytosis were older, had higher platelet counts, mean platelet volume and hemoglobin, and lower erythrocyte sedimentation rate than patients with reactive thrombocytosis. INTERPRETATION AND CONCLUSIONS: Minor differences were observed in TPO levels between patients with primary and secondary thrombocytoses. Erythrocyte sedimentation rate, but not TPO levels, may be a useful tool for discriminating both types of thrombocytoses. (+info)
Trisomy 21 associated transient neonatal myeloproliferation in the absence of Down's syndrome.
Although usually associated with Down's syndrome, transient neonatal myeloproliferation (TMD) can occur in the absence of a constitutional trisomy 21. This report describes two such cases, both of whom had a trisomy 21 restricted to clonal cells. Unlike in previous such reported cases, spontaneous morphological, cytogenetic, and molecular remission in both cases was followed by re-emergence, in one case, of an evolved clone with a more malignant phenotype which required pharmacological intervention. Awareness that trisomy 21 bearing leukaemia in the neonatal period can be transient even in the absence of Down's syndrome is important to prevent unnecessary treatment. Equally, such cases require indefinite follow up as a proportion may have a recurrence which may require treatment. (+info)
Characterization of FIM-FGFR1, the fusion product of the myeloproliferative disorder-associated t(8;13) translocation.
The t(8;13) translocation found in a rare type of stem cell myeloproliferative disorder generates a constitutively activated tyrosine kinase containing N-terminal sequence encoded by the FIM gene linked to the FGFR1 kinase domain. Here we have further characterized FIM and FIM-FGFR1 proteins. Firstly, we have studied their respective subcellular localization. We show that FIM has nuclear and nucleolar localization, whereas FIM-FGFR1 is mainly cytoplasmic. Within the nucleolus, FIM colocalizes with the upstream binding factor in interphasic cells, indicating that FIM may be involved in the regulation of rRNA transcription. We demonstrate that the targetting of FIM to the nucleus depends upon its C-terminal region, which is absent in the cytoplasmic FIM-FGFR1 protein. Secondly, we demonstrate that FIM-FGFR1 has constitutive dimerization capability mediated by the FIM N-terminal sequences. Finally, we show that FIM-FGFR1 promotes survival of pro-B Ba/F3 cells after interleukin-3 withdrawal, whereas ligand-activated FGFR1 induced not only cell survival but also interleukin-3 independence. Taken together, these results indicate that FIM-FGFR1 is activated by dimerization as a cytoplasmic kinase and suggest that FIM-FGFR1 partially signals through the FGFR1 pathways. (+info)
Bcr-Abl with an SH3 deletion retains the ability To induce a myeloproliferative disease in mice, yet c-Abl activated by an SH3 deletion induces only lymphoid malignancy.
The bcr-abl oncogene plays a critical role in the pathogenesis of chronic myelogenous leukemia (CML). The fusion of Bcr sequences to Abl constitutively activates the Abl protein tyrosine kinase. We have recently shown that expression of Bcr-Abl in bone marrow cells by retroviral transduction efficiently induces in mice a myeloproliferative disease resembling human CML and that Abl kinase activity is essential for Bcr-Abl to induce a CML-like myeloproliferative disease. However, it is not known if activation of the Abl kinase alone is sufficient to induce a myeloproliferative disease. In this study, we examined the role of the Abl SH3 domain of Bcr-Abl in induction of myeloproliferative disease and tested whether c-Abl activated by SH3 deletion can induce a CML-like disease. We found that Bcr-Abl with an Abl SH3 deletion still induced a CML-like disease in mice. In contrast, c-Abl activated by SH3 deletion induced only lymphoid malignancies in mice and did not stimulate the growth of myeloid colonies from 5-fluorouracil-treated bone marrow cells in vitro. These results indicate that Bcr sequences in Bcr-Abl play additional roles in inducing myeloproliferative disease beyond simply activating the Abl kinase domain and that functions of the Abl SH3 domain are either not required or redundant in Bcr-Abl-induced myeloproliferative disease. The results also suggest that the type of hematological neoplasm induced by an abl oncogene is influenced not only by what type of hematopoietic cells the oncogene is targeted into but also by the intrinsic oncogenic properties of the particular abl oncogene. In addition, we found that DeltaSH3 c-Abl induced less activation of Akt and STAT5 than did Bcr-Abl, suggesting that activation of these pathways plays a critical role in inducing a CML-like disease. (+info)
De novo appearance of the ph-1 chromosome in a previously monosomic bone marrow (45,XX,-6): conversion of a myeloproliferative disorder to acute myelogenous leukemia.
Bone marrow examination of a patient with a myeloproliferative disorder revealed monosomy for chromosome No. 6 (45,XX,-6). Two months later, during blastic crisis, reinvestigation of the bone marrow showed the presence of the Ph-1 chromosome in the previously aneuploid cell line (45,XX,-6,-22,+Ph-1). This case differs from those previously published in that the Ph-1 chromosome appeared de novo during the development of frank acute myelogenous leukemia. (+info)
Patients' psychosocial concerns following stem cell transplantation.
Information regarding the nature, frequency, correlates and temporal trajectory of concerns of stem cell transplantation (SCT) recipients is critical to the development of interventions to enhance quality of life (QOL) in these individuals. This study examined psychosocial concerns in 110 SCT (87% autologous) recipients drawn from two SCT centers. Participants were a mean of 46 years of age and 17 months post-SCT (range 3-62 months). Information regarding current and past SCT-related concerns, performance status, and demographic characteristics was collected by telephone interview or questionnaire. Recipients reported a wide variety of psychosocial concerns following SCT. Recipients who were younger, female and evidenced a poorer performance status reported a larger number of post-SCT concerns. Examination of the temporal trajectory of concerns suggests that some concerns are salient throughout the course of post-SCT recovery (eg disease recurrence, energy level, 'returning to normal'), some are salient early in the course of recovery (eg quality of medical care, overprotectiveness by others), and others emerge later in the course of recovery (eg feeling tense or anxious, sexual life, sleep, relationship with spouse/partner, ability to be affectionate). Implications for the development of interventions to enhance post-SCT QOL are identified. (+info)
Forty-three operative procedures were performed on a population of 250 patients with myeloproliferative disorders, including polycythemia vera, myeloid metaplasia (MM) and chronic myelogenous leukemia (CML). The overall operative mortality was approximately 7% and the incidence of excessive bleeding which could be related to coagulopathy was 5%. Twenty-one patients with MM or CML underwent splenectomy for palliation of symptoms related to the enlarged spleen or hematologic problems. Eighty-four percent of the latter group were improved. Adverse hematologic effects which could be attributed to splenectomy in these patients were confined to two patients who developed marked thrombocytosis. Among the 23 patients with MM, 9 had portal hypertension. Three underwent portacaval shunt and one a splenorenal shunt for bleeding varices. One of the patients died of hepatic necrosis. Estimated hepatic blood flow determinations (EHBF) in 4 patients with portal hypertension demonstrated a marked absolute increase and an increase in the ratio of EHBF/Cardiac Index. Absence of any evidence of intrahepatic or extrahepatic obstruction in these patients and the demonstration that splenectomy relieved portal hypertension defined at surgery in 4 patients, suggests that augmented adhepatic flow contributes to portal hypertension in some cases. The review leads to the conclusions that: 1) Operative procedures in prepared patients with myeloproliferative disorders are not associated with prohibitive mortality and morbidity rates. 2) Splenectomy is indicated for patients with increasing transfusion requirements and symptomatic splenomegaly or hypersplenism and should be performed early in the course of disease. 3) When associated portal hypertension and bleeding varices are present, hemodynamic studies should be carried out to define if splenectomy alone, or a portal systemic decompressive procedure is indicated. (+info)