参考文献

Mice transgenic for antisense Notch and normal mice treated with inhibitors of the Notch-activating enzyme gamma-secretase showed reduced damage to brain cells and improved functional outcome in a model of focal ischemic stroke. Notch endangers neurons by modulating pathways that increase their vulnerability to apoptosis,and by activating microglial cells and stimulating the infiltration of proinflammatory leukocytes. These findings suggest that Notch signaling may be a therapeutic target for treatment of stroke and related neurodegenerative conditions. View Publication

Most patients with acute promyelocytic leukemia (APL) express PML-RAR alpha,the fusion product of t(15;17)(q22;q11.2). Transgenic mice expressing PML-RAR alpha develop APL with long latency,low penetrance,and acquired cytogenetic abnormalities. Based on observations that 4% to 10% of APL patients harbor oncogenic ras mutations,we coexpressed oncogenic K-ras from its endogenous promoter with PML-RAR alpha to generate a short-latency,highly penetrant mouse model of APL. The APL disease was characterized by splenomegaly,leukocytosis,extramedullary hematopoiesis (EMH) in spleen and liver with an increased proportion of immature myeloperoxidase-expressing myeloid forms; transplantability to secondary recipients; and lack of cytogenetic abnormalities. Bone marrow cells showed enhanced self-renewal in vitro. This model establishes a role for oncogenic ras in leukemia pathogenesis and thus validates the oncogenic RAS signaling pathway as a potential target for therapeutic inhibition in leukemia patients. This mouse model should be useful for investigating signaling pathways that promote self-renewal in APL and for testing the in vivo efficacy of RAS signaling pathway inhibitors in conjunction with other targeted therapies such as ATRA (all trans retinoic acid) and arsenic trioxide. View Publication

Mechanisms of lethality of the three-substituted indolinone and putatively selective cyclin-dependent kinase (CDK)2 inhibitor 3-[1-(3H-imidazol-4-yl)-meth-(Z)-ylidene]-5-methoxy-1,3-dihydro-indol-2-one (SU9516) were examined in human leukemia cells. Exposure of U937 and other leukemia cells to SU9516 concentrations textgreater or =5 microM rapidly (i.e.,within 4 h) induced cytochrome c release,Bax mitochondrial translocation,and apoptosis in association with pronounced down-regulation of the antiapoptotic protein Mcl-1. These effects were associated with inhibition of phosphorylation of the carboxyl-terminal domain (CTD) of RNA polymerase (Pol) II on serine 2 but not serine 5. Reverse transcription-polymerase chain reaction analysis revealed pronounced down-regulation of Mcl-1 mRNA levels in SU9516-treated cells. Similar results were obtained in Jurkat and HL-60 leukemia cells. Furthermore,cotreatment with the proteasome inhibitor N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal (MG132) blocked SU9516-mediated Mcl-1 down-regulation,implicating proteasomal degradation in diminished expression of this protein. Ectopic expression of Mcl-1 largely blocked SU9516-induced cytochrome c release,Bax translocation,and apoptosis,whereas knockdown of Mcl-1 by small interfering RNA potentiated SU9516 lethality,confirming the functional contribution of Mcl-1 down-regulation to SU9516-induced cell death. It is noteworthy that SU9516 treatment resulted in a marked increase in reactive oxygen species production,which was diminished,along with cell death,by the free radical scavenger N-acetylcysteine (NAC). We were surprised to find that NAC blocked SU9516-mediated inhibition of RNA Pol II CTD phosphorylation on serine 2,reductions in Mcl-1 mRNA levels,and Mcl-1 down-regulation. Together,these findings suggest that SU9516 kills leukemic cells through inhibition of RNA Pol II CTD phosphorylation in association with oxidative damage and down-regulation of Mcl-1 at the transcriptional level,culminating in mitochondrial injury and cell death. View Publication

IL-17A is a T cell-derived proinflammatory cytokine required for microbial host defense. In vivo expression profoundly stimulates granulopoiesis. At baseline,the hemopoietic system of IL-17R knockout mice (IL-17Ra(-/-)) is,with the exception of increased splenic progenitor numbers,indistinguishable from normal control mice. However,when challenged with gamma irradiation,hemopoietic toxicity is significantly more pronounced in IL-17Ra(-/-) animals,with the gamma irradiation-associated LD(50) being reduced by 150 rad. In spleen-derived T cells,gamma irradiation induces significant murine IL-17A expression in vivo but not in vitro. After sublethal radiation injury (500 rad),the infusion of purified CD4(+) T cells enhances hemopoietic recovery. This recovery is significantly impaired in IL-17Ra(-/-) animals or after in vivo blockade of IL-17Ra in normal mice,resulting in a reduction of hemopoietic precursors by 50% and of neutrophils by 43%. Following sublethal radiation-induced myelosuppression,in vivo overexpression of murine IL-17A in normal mice substantially enhanced granulopoietic restoration in mice with a 4-fold increase in neutrophils and splenic precursors on day 8 (CFU-granulocyte-macrophage/granulocyte-erythrocyte-megakaryocyte-monocyte,CFU-high proliferative potential),as well as 2- and 3-fold increases of bone marrow precursors,respectively. This establishes IL-17A as a hemopoietic response cytokine to radiation injury in mice and an inducible mechanism that is required for recovery of granulopoiesis after radiation injury. View Publication

The t(16:16) and inv(16) are associated with FAB M4Eo myeloid leukemias and result in fusion of the CBFB gene to the MYH11 gene (encoding smooth muscle myosin heavy chain [SMMHC]). Knockout of CBFbeta causes embryonic lethality due to lack of definitive hematopoiesis. Although knock-in of CBFB-MYH11 is not sufficient to cause disease,expression increases the incidence of leukemia when combined with cooperating events. Although mouse models are valuable tools in the study of leukemogenesis,little is known about the contribution of CBFbeta-SMMHC to human hematopoietic stem and progenitor cell self-renewal. We introduced the CBFbeta-MYH11 cDNA into human CD34+ cells via retroviral transduction. Transduced cells displayed an initial repression of progenitor activity but eventually dominated the culture,resulting in the proliferation of clonal populations for up to 7 months. Long-term cultures displayed a myelomonocytic morphology while retaining multilineage progenitor activity and engraftment in NOD/SCID-B2M-/- mice. Progenitor cells from long-term cultures showed altered expression of genes defining inv(16) identified in microarray studies of human patient samples. This system will be useful in examining the effects of CBFbeta-SMMHC on gene expression in the human preleukemic cell,in characterizing the effect of this oncogene on human stem cell biology,and in defining its contribution to the development of leukemia. View Publication

A JAK2(V617F) mutation is frequently found in several BCR/ABL-negative myeloproliferative disorders. To address the contribution of this mutant to the pathogenesis of these different myeloproliferative disorders,we used an adoptive transfer of marrow cells transduced with a retrovirus expressing JAK2(V617F) in recipient irradiated mice. Hosts were analyzed during the 6 months after transplantation. For a period of 3 months,mice developed polycythemia,macrocytosis and usually peripheral blood granulocytosis. Transient thrombocytosis was only observed in a low-expresser group. All mice displayed trilineage hyperplasia in marrow and spleen along with an amplification of myeloid and erythroid progenitor cells and a formation of endogenous erythroid colonies. After 3 to 4 months,polycythemia regressed,abnormally shaped red blood cells and platelets were seen in circulation,and a deposition of reticulin fibers was observed in marrow and spleen. Development of fibrosis was associated with anemia,thrombocytopenia,high neutrophilia,and massive splenomegaly. These features mimic human polycythemia vera and its evolution toward myelofibrosis. This work demonstrates that JAK2(V617F) is sufficient for polycythemia and fibrosis development and offers an in vivo model to assess novel therapeutic approaches for JAK2(V617F)-positive pathologies. Questions remain regarding the exact contribution of JAK2(V617F) in other myeloproliferative disorders. View Publication

Chronic phase-to-blast crisis transition in chronic myelogenous leukemia (CML) is associated with differentiation arrest and down-regulation of C/EBPalpha,a transcription factor essential for granulocyte differentiation. Patients with CML in blast crisis (CML-BC) became rapidly resistant to therapy with the breakpoint cluster region-Abelson murine leukemia (BCR/ABL) kinase inhibitor imatinib (STI571) because of mutations in the kinase domain that interfere with drug binding. We show here that the restoration of C/EBPalpha activity in STI571-sensitive or -resistant 32D-BCR/ABL cells induced granulocyte differentiation,inhibited proliferation in vitro and in mice,and suppressed leukemogenesis. Moreover,activation of C/EBPalpha eradicated leukemia in 4 of 10 and in 6 of 7 mice injected with STI571-sensitive or -resistant 32D-BCR/ABL cells,respectively. Differentiation induction and proliferation inhibition were required for optimal suppression of leukemogenesis,as indicated by the effects of p42 C/EBPalpha,which were more potent than those of K298E C/EBPalpha,a mutant defective in DNA binding and transcription activation that failed to induce granulocyte differentiation. Activation of C/EBPalpha in blast cells from 4 patients with CML-BC,including one resistant to STI571 and BMS-354825 and carrying the T315I Abl kinase domain mutation,also induced granulocyte differentiation. Thus,these data indicate that C/EBPalpha has potent antileukemia effects even in cells resistant to ATP-binding competitive tyrosine kinase inhibitors,and they portend the development of anti-leukemia therapies that rely on C/EBPalpha activation. View Publication

Targeted cancer therapies exploit the continued dependence of cancer cells on oncogenic mutations. Such agents can have remarkable activity against some cancers,although antitumor responses are often heterogeneous,and resistance remains a clinical problem. To gain insight into factors that influence the action of a prototypical targeted drug,we studied the action of imatinib (STI-571,Gleevec) against murine cells and leukemias expressing BCR-ABL,an imatinib target and the initiating oncogene for human chronic myelogenous leukemia (CML). We show that the tumor suppressor p53 is selectively activated by imatinib in BCR-ABL-expressing cells as a result of BCR-ABL kinase inhibition. Inactivation of p53,which can accompany disease progression in human CML,impedes the response to imatinib in vitro and in vivo without preventing BCR-ABL kinase inhibition. Concordantly,p53 mutations are associated with progression to imatinib resistance in some human CMLs. Our results identify p53 as a determinant of the response to oncogene inhibition and suggest one way in which resistance to targeted therapy can emerge during the course of tumor evolution. View Publication

The pathogenesis of malarial anemia is multifactorial,and the mechanisms responsible for its high mortality are poorly understood. Studies indicate that host mediators produced during malaria infection may suppress erythroid progenitor development (Miller,K.L.,J.C. Schooley,K.L. Smith,B. Kullgren,L.J. Mahlmann,and P.H. Silverman. 1989. Exp. Hematol. 17:379-385; Yap,G.S.,and M.M. Stevenson. 1991. Ann. NY Acad. Sci. 628:279-281). We describe an intrinsic role for macrophage migration inhibitory factor (MIF) in the development of the anemic complications and bone marrow suppression that are associated with malaria infection. At concentrations found in the circulation of malaria-infected patients,MIF suppressed erythropoietin-dependent erythroid colony formation. MIF synergized with tumor necrosis factor and gamma interferon,which are known antagonists of hematopoiesis,even when these cytokines were present in subinhibitory concentrations. MIF inhibited erythroid differentiation and hemoglobin production,and it antagonized the pattern of mitogen-activated protein kinase phosphorylation that normally occurs during erythroid progenitor differentiation. Infection of MIF knockout mice with Plasmodium chabaudi resulted in less severe anemia,improved erythroid progenitor development,and increased survival compared with wild-type controls. We also found that human mononuclear cells carrying highly expressed MIF alleles produced more MIF when stimulated with the malarial product hemozoin compared with cells carrying low expression MIF alleles. These data suggest that polymorphisms at the MIF locus may influence the levels of MIF produced in the innate response to malaria infection and the likelihood of anemic complications. View Publication

Erythropoiesis,the essential process of hematopoietic stem cell development into erythrocytes,is controlled by lineage-specific transcription factors that determine cell fate and differentiation and by the hormone erythropoietin that stimulates cell survival and proliferation. Here we identify the Sry-related high-mobility-group (HMG) box transcription factor Sox6 as an important enhancer of definitive erythropoiesis. Sox6 is highly expressed in proerythroblasts and erythroblasts in the fetal liver,neonatal spleen,and bone marrow. Mouse fetuses and pups lacking Sox6 develop erythroid cells slowly and feature misshapen,short-lived erythrocytes. They compensate for anemia by elevating the serum level of erythropoietin and progressively enlarging their erythropoietic tissues. Erythroid-specific inactivation of Sox6 causes the same phenotype,demonstrating cell-autonomous roles for Sox6 in erythroid cells. Sox6 potentiates the ability of erythropoietin signaling to promote proerythroblast survival and has an effect additive to that of erythropoietin in stimulating proerythroblast and erythroblast proliferation. Sox6 also critically facilitates erythroblast and reticulocyte maturation,including hemoglobinization,cell condensation,and enucleation,and ensures erythrocyte cytoskeleton long-term stability. It does not control adult globin and erythrocyte cytoskeleton genes but acts by stabilizing filamentous actin (F-actin) levels. Sox6 thus enhances erythroid cell development at multiple levels and thereby ensures adequate production and quality of red blood cells. View Publication

BACKGROUND Hematopoietic stem cells (HSC) have traditionally been frozen using the cryoprotectant DMSO in dextran-40,saline or albumin. However,the process of freezing and thawing results in loss of HSC numbers and/or function. METHODS This study investigated the use of CryoStor for the freezing of HSC from cord blood (CB). CB donations (n = 30) were collected under an Institutional Ethics Committee-approved protocol,volume reduced and frozen using three different methods of cryoprotection. Aliquots were frozen with either 10% DMSO in dextran-40,10% DMSO in CryoStor or 5% DMSO in CryoStor. Prior to freezing samples were separated for nucleated cell (NC) and CD34+ counts and assessment of CD34+ viability. Aliquots were frozen and kept in vapor phase nitrogen for a minimum of 72 h. Vials were rapidly thawed at 37 degrees C and tested for NC and CD34+ counts and CD34+ viability and colony-forming unit (CFU) assay. RESULTS Cells frozen with CryoStor in 10% DMSO had significantly improved NC (P < 0.001),CD34+ recovery,viable CD34+ (P < 0.001) and CFU numbers (P < 0.001) compared with dextran in 10% DMSO. CryoStor in 5% DMSO resulted in significantly improved NC (P < 0.001) and CFU (P < 0.001). DISCUSSION These results suggest that improved HSC recovery,viability and functionality can be obtained using CryoStor with 10% DMSO and that similar if not better numbers can be obtained with 5% DMSO compared with dextran-40 with 10% DMSO. View Publication

Apoptosis is a key pathogenic mechanism in sepsis that induces extensive death of lymphocytes and dendritic cells,thereby contributing to the immunosuppression that characterizes the septic disorder. Numerous animal studies indicate that prevention of apoptosis in sepsis improves survival and may represent a potential therapy for this highly lethal disorder. Recently,novel cell-penetrating peptide constructs such as HIV-1 TAT basic domain and related peptides have been developed to deliver bioactive cargoes and peptides into cells. In the present study,we investigated the effects of sepsis-induced apoptosis in Bcl-x(L) transgenic mice and in wild-type mice treated with an antiapoptotic TAT-Bcl-x(L) fusion protein and TAT-BH4 peptide. Lymphocytes from Bcl-x(L) transgenic mice were resistant to sepsis-induced apoptosis,and these mice had a approximately 3-fold improvement in survival. TAT-Bcl-x(L) and TAT-BH4 prevented Escherichia coli-induced human lymphocyte apoptosis ex vivo and markedly decreased lymphocyte apoptosis in an in vivo mouse model of sepsis. In conclusion,TAT-conjugated antiapoptotic Bcl-2-like peptides may offer a novel therapy to prevent apoptosis in sepsis and improve survival. View Publication