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SHP2,a cytoplasmic protein-tyrosine phosphatase encoded by the PTPN11 gene,plays a critical role in developmental hematopoiesis in the mouse,and gain-of-function mutations of SHP2 are associated with hematopoietic malignancies. However,the role of SHP2 in adult hematopoiesis has not been addressed in previous studies. In addition,the role of SHP2 in human hematopoiesis has not been described. These questions are of considerable importance given the interest in development of SHP2 inhibitors for cancer treatment. We used shRNA-mediated inhibition of SHP2 expression to investigate the function of SHP2 in growth factor (GF) signaling in normal human CD34(+) cells. SHP2 knockdown resulted in markedly reduced proliferation and survival of cells cultured with GF,and reduced colony-forming cell growth. Cells expressing gain-of-function SHP2 mutations demonstrated increased dependency on SHP2 expression for survival compared with cells expressing wild-type SHP2. SHP2 knockdown was associated with significantly reduced myeloid and erythroid differentiation with retention of CD34(+) progenitors with enhanced proliferative capacity. Inhibition of SHP2 expression initially enhanced and later inhibited STAT5 phosphorylation and reduced expression of the antiapoptotic genes MCL1 and BCLXL. These results indicate an important role for SHP2 in STAT5 activation and GF-mediated proliferation,survival,and differentiation of human progenitor cells. View Publication

Redirecting Ag specificity by transfer of TCR genes into PBLs is an attractive method to generate large numbers of cytotoxic T cells for immunotherapy of cancer and viral diseases. However,transferred TCR chains can pair with endogenous TCR chains,resulting in the formation of mispaired TCR dimers and decreased or unspecific reactivity. TCR gene transfer into hematopoietic stem cells (HSCs) is an alternative to create T cells with desired Ag specificity,because in this case expression of endogenous TCR chains is then less likely owing to allelic exclusion. We generated TCR-transduced T cells from peripheral T cells using the lymphocytic choriomeningitis virus-specific P14 TCR. After transfer of the P14 TCR genes into HSCs and subsequent reconstitution of irradiated mice,TCR-engineered HSC-derived T cells were produced. We then compared the Ag-specific T cell populations with P14 TCR-transgenic T cells for their therapeutic efficiency in three in vivo models. In this study,we demonstrate that TCR-transduced T cells and TCR-engineered HSC-derived T cells are comparable in controlling lymphocytic choriomeningitis virus infection in mice and suppress growth of B16 tumor cells expressing the cognate Ag in a comparable manner. View Publication

Erythropoietin (Epo) is a cytokine that binds and activates an Epo receptor (EpoR) expressed on the surface of erythroid progenitor cells to promote erythropoiesis. While early studies suggested EpoR transcripts were expressed exclusively in the erythroid compartment,low-level EpoR transcripts were detected in nonhematopoietic tissues and tumor cell lines using sensitive RT-PCR methods. However due to the widespread use of nonspecific anti-EpoR antibodies there are conflicting data on EpoR protein expression. In tumor cell lines and normal human tissues examined with a specific and sensitive monoclonal antibody to human EpoR (A82),little/no EpoR protein was detected and it was not functional. In contrast,EpoR protein was reportedly detectable in a breast tumor cell line (MCF-7) and breast cancer tissues with an anti-EpoR polyclonal antibody (M-20),and functional responses to rHuEpo were reported with MCF-7 cells. In another study,a functional response was reported with the lung tumor cell line (NCI-H838) at physiological levels of rHuEpo. However,the specificity of M-20 is in question and the absence of appropriate negative controls raise questions about possible false-positive effects. Here we show that with A82,no EpoR protein was detectable in normal human and matching cancer tissues from breast,lung,colon,ovary and skin with little/no EpoR in MCF-7 and most other breast and lung tumor cell lines. We show further that M-20 provides false positive staining with tissues and it binds to a non-EpoR protein that migrates at the same size as EpoR with MCF-7 lysates. EpoR protein was detectable with NCI-H838 cells,but no rHuEpo-induced phosphorylation of AKT,STAT3,pS6RP or STAT5 was observed suggesting the EpoR was not functional. Taken together these results raise questions about the hypothesis that most tumors express high levels of functional EpoR protein. View Publication

BACKGROUND Mortality rates for leukemia are high despite considerable improvements in treatment. Since polyphenols exert pro-apoptotic effects in solid tumors,our study investigated the effects of polyphenols in haematological malignancies. The effect of eight polyphenols (quercetin,chrysin,apigenin,emodin,aloe-emodin,rhein,cis-stilbene and trans-stilbene) were studied on cell proliferation,cell cycle and apoptosis in four lymphoid and four myeloid leukemic cells lines,together with normal haematopoietic control cells. METHODS Cellular proliferation was measured by CellTiter-Glo(®) luminescent assay; and cell cycle arrest was assessed using flow cytometry of propidium iodide stained cells. Apoptosis was investigated by caspase-3 activity assay using flow cytometry and apoptotic morphology was confirmed by Hoescht 33342 staining. RESULTS Emodin,quercetin,and cis-stilbene were the most effective polyphenols at decreasing cell viability (IC50 values of 5-22 μM,8-33 μM,and 25-85 μM respectively) and inducing apoptosis (AP50 values (the concentration which 50% of cells undergo apoptosis) of 2-27 μM,19-50 μM,and 8-50 μM respectively). Generally,lymphoid cell lines were more sensitive to polyphenol treatment compared to myeloid cell lines,however the most resistant myeloid (KG-1a and K562) cell lines were still found to respond to emodin and quercetin treatment at low micromolar levels. Non-tumor cells were less sensitive to all polyphenols compared to the leukemia cells. CONCLUSIONS These findings suggest that polyphenols have anti-tumor activity against leukemia cells with differential effects. Importantly,the differential sensitivity of emodin,quercetin,and cis-stilbene between leukemia and normal cells suggests that polyphenols are potential therapeutic agents for leukemia. View Publication

Aldehyde dehydrogenase (ALDH) activity is a widely used marker for human hematopoietic stem cells (HSCs),yet its relevance and role in murine HSCs remain unclear. We found that murine marrow cells with a high level of ALDH activity as measured by Aldefluor staining (ALDH(br) cells) do not contain known HSCs or progenitors. In contrast,highly enriched murine HSCs defined by the CD48(-)EPCR(+) and other phenotypes contain two subpopulations,one that stains dimly with Aldefluor (ALDH(dim)) and one that stains at intermediate levels (ALDH(int)). The CD48(-)EPCR(+)ALDH(dim) cells are virtually all in G(0) and yield high levels of engraftment via both intravenous and intrabone routes. In contrast the CD48(-)EPCR(+)ALDH(int) cells are virtually all in G(1),have little intravenous engraftment potential,and yet can engraft long-term after intrabone transplantation. These data demonstrate that Aldefluor staining of unfractionated murine marrow does not identify known HSCs or progenitors. However,varying levels of Aldefluor staining when combined with CD48 and EPCR detection can identify novel populations in murine marrow including a highly enriched population of resting HSCs and a previously unknown HSC population in G(1) with an intravenous engraftment defect. View Publication

BACKGROUND: Anaemia and microcytosis are common post kidney transplantation. The aim of this study was to evaluate the potential role of mammalian target of rapamycin (mTOR) inhibition in the development of anaemia and microcytosis in healthy animals and in human erythroid cultures in vitro. METHODS: Rats with normal kidney function were treated with sirolimus (n = 7) or vehicle (n = 8) for 15 weeks. Hemograms were determined thereafter. In the sirolimus withdrawal part of the study,rats received sirolimus (SRL) for 67 days (n = 4) 1 mg/kg three times per week or for 30 days (n = 4) and were observed until Day 120. Hemograms were performed regularly. Peripheral blood mononuclear cells from healthy controls (HC; n = 8),kidney transplant patients with sirolimus treatment with (SRL + MC; n = 8) or without microcytosis (SRL - MC; n = 8) were isolated and cultured in the absence or presence of SRL (5 ng/mL). RESULTS: SRL-treated animals had a reduced mean corpuscular volume (MCV) and elevated erythrocyte count compared with control animals after 15 weeks of treatment. This effect was evident as early as 4 weeks (MCV: 61.5 ± 1.8 versus 57 ± 1.7 fL; P = 0.0156; Red blood count 7.4 ± 0.3 × 10(9)/L versus 8.6 ± 0.5 × 10(9)/L; P = 0.0156) and was reversible 90 days after SRL withdrawal. SRL in the culture medium of erythroid cultures led to fewer colonies in cultures from HC as well as from kidney transplant patients (without SRL: 34.2 ± 11.4 versus with SRL: 27.5 ± 9.9 BFU-E-derived colonies P = 0.03),regardless if the cultures were derived from recipients with normocytic or with microcytic erythrocytes. The presence of tacrolimus in the culture medium had no influence on the number and size of colonies. CONCLUSION: mTOR inhibition induces microcytosis and polyglobulia,but not anaemia in healthy rats. This might be caused by growth inhibition of erythroid precursor cells. View Publication

CREB-binding protein (CREBBP) is important for the cell-autonomous regulation of hematopoiesis,including the stem cell compartment. In the present study,we show that CREBBP plays an equally pivotal role in microenvironment-mediated regulation of hematopoiesis. We found that the BM microenvironment of Crebbp(+/-) mice was unable to properly maintain the immature stem cell and progenitor cell pools. Instead,it stimulates myeloid differentiation,which progresses into a myeloproliferation phenotype. Alterations in the BM microenvironment resulting from haploinsufficiency of Crebbp included a marked decrease in trabecular bone that was predominantly caused by increased osteoclastogenesis. Although CFU-fibroblast (CFU-F) and total osteoblast numbers were decreased,the bone formation rate was similar to that found in wild-type mice. At the molecular level,we found that the known hematopoietic modulators matrix metallopeptidase-9 (MMP9) and kit ligand (KITL) were decreased with heterozygous levels of Crebbp. Lastly,potentially important regulatory proteins,endothelial cell adhesion molecule 1 (ESAM1) and cadherin 5 (CDH5),were increased on Crebbp(+/-) endothelial cells. Our findings reveal that a full dose of Crebbp is essential in the BM microenvironment to maintain proper hematopoiesis and to prevent excessive myeloproliferation. View Publication

4-Hydroxy-5-methoxy-2,3-dihydro-1H-[1,3]benzodioxolo[5,6-c]pyrrolo[1,2-f]-phenanthridium chloride (NK314) is a benzo[c] phenanthridine alkaloid that inhibits topoisomerase IIα,leading to the generation of DNA double-strand breaks (DSBs) and activating the G(2) checkpoint pathway. The purpose of the present studies was to investigate the DNA intercalating properties of NK314,to evaluate the DNA repair mechanisms activated in cells that may lead to resistance to NK314,and to develop mechanism-based combination strategies to maximize the antitumor effect of the compound. A DNA unwinding assay indicated that NK314 intercalates in DNA,a property that likely cooperates with its ability to trap topoisomerase IIα in its cleavage complex form. The consequence of this is the formation of DNA DSBs,as demonstrated by pulsed-field gel electrophoresis and H2AX phosphorylation. Clonogenic assays demonstrated a significant sensitization in NK314-treated cells deficient in DNA-dependent protein kinase (DNA-PK) catalytic subunit,Ku80,ataxia telangiectasia mutated (ATM),BRCA2,or XRCC3 compared with wild-type cells,indicating that both nonhomologous end-joining and homologous recombination DNA repair pathways contribute to cell survival. Furthermore,both the DNA-PK inhibitor 8-(4-dibenzothienyl)-2-(4-morpholinyl)-4H-1-benzopyran-4-one (NU7441) and the ATM inhibitor 2-(4-morpholinyl)-6-(1-thianthrenyl)-4H-pyran-4-one (KU55933) significantly sensitized cells to NK314. We conclude that DNA-PK and ATM contribute to cell survival in response to NK314 and could be potential targets for abrogating resistance and maximizing the antitumor effect of NK314. View Publication

Recent evidence suggests that enhanced aldehyde dehydrogenase (ALDH) activity is a hallmark of cancer stem cells (CSC) measurable by the aldefluor assay. ALDH1A1,one of 19 ALDH isoforms expressed in humans,was generally believed to be responsible for the ALDH activity of CSCs. More recently,experiments with murine hematopoietic stem cells,murine progenitor pancreatic cells,and human breast CSCs indicate that other ALDH isoforms,particularly ALDH1A3,significantly contribute to aldefluor positivity,which may be tissue and cancer specific. Therefore,potential prognostic application involving the use of CSC prevalence in tumor tissue to predict patient outcome requires the identification and quantification of specific ALDH isoforms. Herein we review the suggested roles of ALDH in CSC biology and the immunohistological studies testing the potential application of ALDH isoforms as novel cancer prognostic indicators. View Publication

Even though myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis,the molecular alterations that lead to marrow failure have not been well elucidated. We have previously shown that the myelosuppressive TGF-β pathway is constitutively activated in MDS progenitors. Because there is conflicting data about upregulation of extracellular TGF-β levels in MDS,we wanted to determine the molecular basis of TGF-β pathway overactivation and consequent hematopoietic suppression in this disease. We observed that SMAD7,a negative regulator of TGF-β receptor I (TBRI) kinase,is markedly decreased in a large meta-analysis of gene expression studies from MDS marrow-derived CD34(+) cells. SMAD7 protein was also found to be significantly decreased in MDS marrow progenitors when examined immunohistochemically in a bone marrow tissue microarray. Reduced expression of SMAD7 in hematopoietic cells led to increased TGF-β-mediated gene transcription and enhanced sensitivity to TGF-β-mediated suppressive effects. The increased TGF-β signaling due to SMAD7 reduction could be effectively inhibited by a novel clinically relevant TBRI (ALK5 kinase) inhibitor,LY-2157299. LY-2157299 could inhibit TGF-β-mediated SMAD2 activation and hematopoietic suppression in primary hematopoietic stem cells. Furthermore,in vivo administration of LY-2157299 ameliorated anemia in a TGF-β overexpressing transgenic mouse model of bone marrow failure. Most importantly,treatment with LY-2157199 stimulated hematopoiesis from primary MDS bone marrow specimens. These studies demonstrate that reduction in SMAD7 is a novel molecular alteration in MDS that leads to ineffective hematopoiesis by activating of TGF-β signaling in hematopoietic cells. These studies also illustrate the therapeutic potential of TBRI inhibitors in MDS. View Publication

Chemotherapy is the most common way to treat malignancies,but myelosuppression,one of its common side-effects,is a formidable problem. The present study described the protective role of dammarane sapogenins (DS),an active fraction from oriental ginseng,on myelosuppression induced by cyclophosphamide (CP) in mice. DS was orally administered at different dosages (37.5,75,and 150 mg/kg) for 10 d after CP administration (200 mg/kg intraperitoneally). The results showed that DS increased the number of white blood cells (WBC) on day 3 and day 7 (P textless 0.05),such that WBC levels were increased by 105.7 ± 29.5% at 75 mg/kg of DS on day 3 (P textless 0.05,compared with the CP group). Similar results were observed in red blood cells and platelets in DS-treated groups. The colony-forming assay demonstrated that the depressed numbers of CFU-GM (colony-forming unit-granulocyte and macrophage),CFU-E (colony-forming unit-erythroid),BFU-E (burst-forming unit-erythroid),CFU-Meg (colony-forming unit-megakaryocyte) and CFU-GEMM (colony-forming unit-granulocyte,-erythrocyte,-monocyte and -megakaryocyte) induced by CP were significantly reversed after DS treatment. Moreover,the ameliorative effect of DS on myelosuppression was also observed in the femur by hematoxylin/eosin staining. In DS-treated groups,ConA-induced splenocyte proliferation was enhanced significantly at all the doses (37.5,75,150 mg/kg) on day 3 at the rate of 50.3 ± 8.0%,77.6 ± 8.5% and 44.5 ± 8.4%,respectively,while lipopolysaccharide-induced proliferation was increased mainly on day 7 (P textless 0.01),with an increased rate of 39.8 ± 5.6%,34.9 ± 6.6% and 38.3 ± 7.3%,respectively. The thymus index was also markedly increased by 70.4% and 36.6% at 75 mg/kg on days 3 and 7,respectively,as compared with the CP group. In summary,DS has a protective function against CP-induced myelosuppression. Its mechanism might be related to stimulating hematopoiesis recovery,as well as enhancing the immunological function. View Publication

The stem-cell pool is considered to be maintained by a balance between symmetric and asymmetric division of stem cells. The cell polarity model proposes that the facultative use of symmetric and asymmetric cell division is orchestrated by a polarity complex consisting of partitioning-defective proteins Par3 and Par6,and atypical protein kinase C (aPKCζ and aPKCλ),which regulates planar symmetry of dividing stem cells with respect to the signaling microenvironment. However,the role of the polarity complex is unexplored in mammalian adult stem-cell functions. Here we report that,in contrast to accepted paradigms,polarization and activity of adult hematopoietic stem cell (HSC) do not depend on either aPKCζ or aPKCλ or both in vivo. Mice,having constitutive and hematopoietic-specific (Vav1-Cre) deletion of aPKCζ and aPKCλ,respectively,have normal hematopoiesis,including normal HSC self-renewal,engraftment,differentiation,and interaction with the bone marrow microenvironment. Furthermore,inducible complete deletion of aPKCλ (Mx1-Cre) in aPKCζ(-/-) HSC does not affect HSC polarization,self-renewal,engraftment,or lineage repopulation. In addition,aPKCζ- and aPKCλ-deficient HSCs elicited a normal pattern of hematopoietic recovery secondary to myeloablative stress. Taken together,the expression of aPKCζ,aPKCλ,or both are dispensable for primitive and adult HSC fate determination in steady-state and stress hematopoiesis,contrary to the hypothesis of a unique,evolutionary conserved aPKCζ/λ-directed cell polarity signaling mechanism in mammalian HSC fate determination. View Publication