技术资料

Hematologic stem cell rescue after high-dose cytotoxic therapy is extensively used for the treatment of many hematopoietic and solid cancers. Gene marking studies suggest that occult tumor cells within the autograft may contribute to clinical relapse. To date purging of autografts contaminated with cancer cells has been unsuccessful. The selective oncolytic property of reovirus against myriad malignant histologies in in vitro,in vivo,and ex vivo systems has been previously demonstrated. In the present study we have shown that reovirus can successfully purge cancer cells within autografts. Human monocytic and myeloma cell lines as well as enriched ex vivo lymphoma,myeloma,and Waldenström macroglobulinemia patient tumor specimens were used in an experimental purging model. Viability of the cell lines or purified ex vivo tumor cells of diffuse large B-cell lymphoma,chronic lymphocytic leukemia,Waldenström macroglobulinemia,and small lymphocytic lymphoma was significantly reduced after reovirus treatment. Further,[35S]-methionine labeling and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of cellular proteins demonstrated reovirus protein synthesis and disruption of host cell protein synthesis as early as 24 hours. Admixtures of apheresis product with the abovementioned tumor cells and cell lines treated with reovirus showed complete purging of disease. In contrast,reovirus purging of enriched ex vivo multiple myeloma,Burkitt lymphoma,and follicular lymphoma was incomplete. The oncolytic action of reovirus did not affect CD34+ stem cells or their long-term colony-forming assays even after granulocyte colony-stimulating factor (G-CSF) stimulation. Our results indicate the ex vivo use of an unattenuated oncolytic virus as an attractive purging strategy for autologous stem cell transplantations. View Publication

The c-Myb gene encodes a transcription factor required for proliferation and survival of normal myeloid progenitors and leukemic blast cells. Targeting of c-Myb by antisense oligodeoxynucleotides has suggested that myeloid leukemia blasts (including chronic myelogenous leukemia [CML]-blast crisis cells) rely on c-Myb expression more than normal progenitors,but a genetic approach to assess the requirement of c-Myb by p210(BCR/ABL)-transformed hematopoietic progenitors has not been taken. We show here that loss of a c-Myb allele had modest effects (20%-28% decrease) on colony formation of nontransduced progenitors,while the effect on p210(BCR/ABL)-expressing Lin(-) Sca-1(+) and Lin(-) Sca-1(+)Kit(+) cells was more pronounced (50%-80% decrease). Using a model of CML-blast crisis,mice (n = 14) injected with p210(BCR/ABL)-transduced p53(-/-)c-Myb(w/w) marrow cells developed leukemia rapidly and had a median survival of 26 days,while only 67% of mice (n = 12) injected with p210(BCR/ABL)-transduced p53(-/-)c-Myb(w/d) marrow cells died of leukemia with a median survival of 96 days. p210(BCR/ABL)-transduced c-Myb(w/w) and c-Myb(w/d) marrow progenitors expressed similar levels of the c-Myb-regulated genes c-Myc and cyclin B1,while those of Bcl-2 were reduced. However,ectopic Bcl-2 expression did not enhance colony formation of p210(BCR/ABL)-transduced c-Myb(w/d) Lin(-)Sca-1(+)Kit(+) cells. Together,these studies support the requirement of c-Myb for p210(BCR/ABL)-dependent leukemogenesis. View Publication

Current induction schemes directing hematopoietic differentiation of human embryonic stem cells (hESCs) are not well defined to mimic the sequential stages of hematopoietic development in vivo. Here,we report a 3-stage method to direct differentiation of hESCs toward hematopoietic progenitors in chemically defined mediums. In the first 2 stages,we efficiently generated T-positive primitive streak/mesendoderm cells and kinase domain receptor-positive (KDR(+)) platelet-derived growth factor receptor α-negative (PDGFRα(-)) hemato-vascular precursors sequentially. In the third stage,we found that cells in a spontaneous differentiation condition mainly formed erythroid colonies. Addition of all-trans retinoic acid (RA) greatly enhanced generation of hematopoietic progenitors in this stage while suppressing erythroid development. The RA-treated cells highly expressed definitive hematopoietic genes,formed large numbers of multilineage and myeloid colonies,and gave rise to greater than 45% CD45(+) hematopoietic cells. When hematopoietic progenitors were selected with CD34 and C-Kit,greater than 95% CD45(+) hematopoietic cells could be generated. In addition,we found that endogenous RA signaling at the second stage was required for vascular endothelial growth factor/basic fibroblast growth factor-induced hemato-vascular specification,whereas exogenously applied RA efficiently induced KDR(-)PDGFRα(+) paraxial mesoderm cells. Our study suggests that RA signaling plays diverse roles in human mesoderm and hematopoietic development. View Publication

The kinase inhibitor imatinib mesylate targeting the oncoprotein Bcr-Abl has revolutionized the treatment of chronic myeloid leukemia (CML). However,even though imatinib successfully controls the leukemia in chronic phase,it seems not to be able to cure the disease,potentially necessitating lifelong treatment with the inhibitor under constant risk of relapse. On a molecular level,the cause of disease persistence is not well understood. Initial studies implied that innate features of primitive progenitor cancer stem cells may be responsible for the phenomenon. Here,we describe an assay using retroviral insertional mutagenesis (RIM) to identify genes contributing to disease persistence in vivo. We transplanted mice with bone marrow cells retrovirally infected with the Bcr-Abl oncogene and subsequently treated the animals with imatinib to select for leukemic cells in which the proviral integration had affected genes modulating the imatinib response. Southern blot analysis demonstrated clonal outgrowth of cells carrying similar integration sites. Candidate genes located near the proviral insertion sites were identified,among them the transcription factor RUNX3. Proviral integration near the RUNX3 promoter induced RUNX3 expression,and Bcr-Abl-positive cell lines with stable or inducible expression of RUNX1 or RUNX3 were protected from imatinib-induced apoptosis. Furthermore,imatinib treatment selected for RUNX1-expressing cells in vitro and in vivo after infection of primary bone marrow cells with Bcr-Abl and RUNX1. Our results demonstrate the utility of RIM for probing molecular modulators of targeted therapies and suggest a role for members of the RUNX transcription factor family in disease persistence in CML patients. View Publication

Mutations in the RUNX1 gene are found at high frequencies in minimally differentiated acute myelogenous leukemia. In addition to null mutations,many of the mutations generate Runx1 DNA-binding (RDB) mutants. To determine if these mutants antagonize wild-type protein activity,cDNAs were transduced into murine bone marrow or human cord blood cells using retroviral vectors. Significantly,the RDB mutants did not act in a transdominant fashion in vivo to disrupt Runx1 activity in either T-cell or platelet development,which are highly sensitive to Runx1 dosage. However,RDB mutant expression impaired expansion and differentiation of the erythroid compartment in which Runx1 expression is normally down-regulated,showing that a RDB-independent function is incompatible with erythroid differentiation. Significantly,both bone marrow progenitors expressing RDB mutants or deficient for Runx1 showed increased replating efficiencies in vitro,accompanied by the accumulation of myeloblasts and dysplastic progenitors,but the effect was more pronounced in RDB cultures. Disruption of the interface that binds CBFbeta,an important cofactor of Runx1,did not impair RDB mutant replating activity,arguing against inactivation of Runx1 function by CBFbeta sequestration. We propose that RDB mutants antagonize Runx1 function in early progenitors by disrupting a critical balance between DNA-binding-independent and DNA-binding-dependent signaling. View Publication

Multiple myeloma is characterized by increased osteoclast activity that results in bone destruction and lytic lesions. With the prolonged overall patient survival achieved by new treatment modalities,additional drugs are required to inhibit bone destruction. We focused on a novel and more potent structural analog of the nonsteroidal anti-inflammatory drug etodolac,known as SDX-308,and its effects on osteoclastogenesis and multiple myeloma cells. SDX-101 is another structural analog of etodolac that is already used in clinical trials for the treatment of B-cell chronic lymphocytic leukemia (B-CLL). Compared with SDX-101,a 10-fold lower concentration of SDX-308 induced potent (60%-80%) inhibition of osteoclast formation,and a 10- to 100-fold lower concentration inhibited multiple myeloma cell proliferation. Bone resorption was completely inhibited by SDX-308,as determined in dentin-based bone resorption assays. SDX-308 decreased constitutive and RANKL-stimulated NF-kappaB activation and osteoclast formation in an osteoclast cellular model,RAW 264.7. SDX-308 effectively suppressed TNF-alpha-induced IKK-gamma and IkappaB-alpha phosphorylation and degradation and subsequent NF-kappaB activation in human multiple myeloma cells. These results indicate that SDX-308 effectively inhibits multiple myeloma cell proliferation and osteoclast activity,potentially by controlling NF-kappaB activation signaling. We propose that SDX-308 is a promising therapeutic candidate to inhibit multiple myeloma growth and osteoclast activity and that it should receive attention for further study. View Publication

BACKGROUND AND OBJECTIVES: Chemokines are soluble mediators involved in angiogenesis,cellular growth control and immunomodulation. In the present study we investigated the effects of various chemokines on proliferation of acute myelogenous leukemia (AML) cells and constitutive chemokine release by primary AML cells. DESIGN AND METHODS: Native human AML cells derived from 68 consecutive patients were cultured in vitro. We investigated AML cell proliferation (3H-thymidine incorporation,colony formation),chemokine receptor expression,constitutive chemokine release and chemotaxis of normal peripheral blood mononuclear cells. RESULTS: Exogenous chemokines usually did not have any effect on AML blast proliferation in the absence of hematopoietic growth factors,but when investigating growth factor-dependent (interleukin 3 + granulocyte-macrophage colony-stimulating factor + stem cell factor) proliferation in suspension cultures the following patient subsets were identified: (i) patients whose cells showed chemokine-induced growth enhancement (8 patients); (ii) divergent effects on proliferation (15 patients); and (iii) no effect (most patients). These patient subsets did not differ in chemokine receptor expression,but,compared to CD34- AML cells,CD34+ cells showed higher expression of several receptors. Chemokines also increased the proliferation of clonogenic AML cells from the first subset of patients. Furthermore,a broad constitutive chemokine release profile was detected for most patients,and the following chemokine clusters could be identified: CCL2-4/CXCL1/8,CCL5/CXCL9-11 (possibly also CCL23) and CCL13/17/22/24/CXCL5 (possibly also CXCL6). Only the CCL2-4/CXCL1/8 cluster showed significant correlations between corresponding mRNA levels and NFkB levels/activation. The chemotaxis of normal immunocompetent cells for patients without constitutive chemokine release was observed to be decreased. INTERPRETATION AND CONCLUSIONS: Differences in chemokine responsiveness as well as chemokine release contribute to patient heterogeneity in AML. Patients with AML can be classified into distinct subsets according to their chemokine responsiveness and chemokine release profile. View Publication

Multiple myeloma is a highly radiosensitive skeletal malignancy,but bone-seeking radionuclides have not yet found their place in disease management. We previously reported that the proteasome inhibitor PS-341 selectively sensitizes myeloma cells to the lethal effects of ionizing radiation. To extend these observations to an in vivo model,we combined PS-341 with the bone-seeking radionuclide 153-Sm-EDTMP. In vitro clonogenic assays demonstrated synergistic killing of myeloma cells exposed to both PS-341 and 153-Sm-EDTMP. Using the orthotopic,syngeneic 5TGM1 myeloma model,the median survivals of mice treated with saline,2 doses of PS-341 (0.5 mg/kg),or a single nonmyeloablative dose of 153-Sm-EDTMP (22.5 MBq) were 21,22,and 28 days,respectively. In contrast,mice treated with combination therapy comprising 2 doses of PS-341 (0.5 mg/kg),1 day prior to and 1 day following 153-Sm-EDTMP (22.5 MBq) showed a significantly prolonged median survival of 49 days (P textless .001). In addition to prolonged survival,this treatment combination yielded reduced clonogenicity of bone marrow-resident 5TGM1 cells,reduced serum myeloma-associated paraprotein levels,and better preservation of bone mineral density. Myelosuppression,determined by peripheral blood cell counts and clonogenicity assays of hematopoietic progenitors,did not differ between animals treated with 153-Sm-EDTMP alone versus those treated with the combination of PS-341 plus 153-Sm-EDTMP. PS-341 is a potent,selective in vivo radiosensitizer that may substantially affect the efficacy of skeletal-targeted radiotherapy in multiple myeloma. View Publication

The t(12;21)(p13;q22) translocation is the most common chromosomal abnormality yet identified in any pediatric leukemia and gives rise to the TEL-AML1 fusion product. To investigate the effects of TEL-AML1 on hematopoiesis,fetal liver hematopoietic progenitor cells (HPCs) were transduced with retroviral vectors expressing this fusion protein. We show that TEL-AML1 dramatically alters differentiation of HPCs in vitro,preferentially promoting B-lymphocyte development,enhancing self-renewal of B-cell precursors,and leading to the establishment of long-term growth factor-dependent pre-B-cell lines. However,it had no effect on myeloid development in vitro. Further experiments were performed to determine whether TEL-AML1 also demonstrates lineage-specific activity in vivo. TEL-AML1-expressing HPCs displayed a competitive advantage in reconstituting both B-cell and myeloid lineages in vivo but had no effect on reconstitution of the T-cell lineage. Despite promoting these alterations in hematopoiesis,TEL-AML1 did not induce leukemia in transplanted mice. Our study provides a unique insight into the role of TEL-AML1 in leukemia predisposition and a potential model to study the mechanism of leukemogenesis associated with this fusion. View Publication

The role of autophagy,a lysosomal degradation pathway which prevents cellular damage,in the maintenance of adult mouse hematopoietic stem cells (HSCs) remains unknown. Although normal HSCs sustain life-long hematopoiesis,malignant transformation of HSCs leads to leukemia. Therefore,mechanisms protecting HSCs from cellular damage are essential to prevent hematopoietic malignancies. In this study,we crippled autophagy in HSCs by conditionally deleting the essential autophagy gene Atg7 in the hematopoietic system. This resulted in the loss of normal HSC functions,a severe myeloproliferation,and death of the mice within weeks. The hematopoietic stem and progenitor cell compartment displayed an accumulation of mitochondria and reactive oxygen species,as well as increased proliferation and DNA damage. HSCs within the Lin(-)Sca-1(+)c-Kit(+) (LSK) compartment were significantly reduced. Although the overall LSK compartment was expanded,Atg7-deficient LSK cells failed to reconstitute the hematopoietic system of lethally irradiated mice. Consistent with loss of HSC functions,the production of both lymphoid and myeloid progenitors was impaired in the absence of Atg7. Collectively,these data show that Atg7 is an essential regulator of adult HSC maintenance. View Publication