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Hematopoietic stem cells (HSCs) have the capacity to self-renew and continuously differentiate into all blood cell lineages throughout life. At each branching point during differentiation,interactions with the environment are key in the generation of daughter cells with distinct fates. Here,we examined the role of the cell adhesion molecule JAM-C,a protein known to mediate cellular polarity during spermatogenesis,in hematopoiesis. We show that murine JAM-C is highly expressed on HSCs in the bone marrow (BM). Expression correlates with self-renewal,the highest being on long-term repopulating HSCs,and decreases with differentiation,which is maintained longest among myeloid committed progenitors. Inclusion of JAM-C as a sole marker on lineage-negative BM cells yields HSC enrichments and long-term multilineage reconstitution when transferred to lethally irradiated mice. Analysis of Jam-C-deficient mice showed that two-thirds die within 48 hours after birth. In the surviving animals,loss of Jam-C leads to an increase in myeloid progenitors and granulocytes in the BM. Stem cells and myeloid cells from fetal liver are normal in number and homing to the BM. These results provide evidence that JAM-C defines HSCs in the BM and that JAM-C plays a role in controlling myeloid progenitor generation in the BM. View Publication

The aim of the current study is to determine whether butein (3,4,2',4'-tetrahydroxychalcone) exhibits antiproliferative effects against tumor cells through suppression of the signal transducer and activator of transcription 3 (STAT3) activation pathway. We investigated the effects of butein on constitutive and inducible STAT3 activation,role of tyrosine kinases and phosphatases in STAT3 activation,STAT3-regulated gene products,and growth modulation of tumor cells. We found that this chalcone inhibited both constitutive and interleukin-6-inducible STAT3 activation in multiple myeloma (MM) cells. The suppression was mediated through the inhibition of activation of the upstream kinases c-Src,Janus-like kinase (JAK) 1,and JAK2. Vanadate treatment reversed the butein-induced down-regulation of STAT3 activation,suggesting the involvement of a tyrosine phosphatase. Indeed,we found that butein induced the expression of the tyrosine phosphatase SHP-1 and deletion of SHP-1 gene by small interfering RNA abolished the ability of butein to inhibit STAT3 activation,suggesting the critical role of SHP-1 in the action of this chalcone. Butein down-regulated the expression of STAT3-regulated gene products such as Bcl-xL,Bcl-2,cyclin D1,and Mcl-1,and this led to the suppression of proliferation and induction of apoptosis. Consistent with these results,overexpression of constitutive active STAT3 significantly reduced the butein-induced apoptosis. Moreover,we found that butein significantly potentiated the apoptotic effects of thalidomide and Velcade in MM cells. Overall,these results suggest that butein is a novel blocker of STAT3 activation and thus may have potential in suppression of tumor cell proliferation and reversal of chemoresistance in MM cells. View Publication

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Using endothelial cells for therapeutic angiogenesis/vasculogenesis of ischemia diseases has led to exploring human embryonic stem cells (hESCs) as a potentially unlimited source for endothelial progenitor cells. With their capacity for self-renewal and pluripotency,hESCs and their derived endothelial cells (hESC-ECs) may be more advantageous than other endothelial cells obtained from diseased populations. However,hESC-ECs' poor differentiation efficiency and poorly characterized in vivo function after transplantation present significant challenges for their future clinical application. This review will focus on the differentiation pathways of hESCs and their therapeutic potential for vascular diseases,as well as the monitoring of transplanted cells' fate via molecular imaging. Finally,cell enhancement strategies to improve the engraftment efficiency of hESC-ECs will be discussed. View Publication

Toll-like receptors (TLRs) play important roles in innate immunity. Several TLR family members have recently been shown to be expressed by neurons and glial cells in the adult brain,and may mediate responses of these cells to injury and infection. To address the possibility that TLRs play a functional role in development of the nervous system,we analyzed the expression of TLRs during different stages of mouse brain development and assessed the role of TLRs in cell proliferation. TLR3 protein is present in brain cells in early embryonic stages of development,and in cultured neural stem/progenitor cells (NPC). NPC from TLR3-deficient embryos formed greater numbers of neurospheres compared with neurospheres from wild-type embryos. Numbers of proliferating cells,as assessed by phospho histone H3 and proliferating cell nuclear antigen labeling,were also increased in the developing cortex of TLR3-deficient mice compared with wild-type mice in vivo. Treatment of cultured embryonic cortical neurospheres with a TLR3 ligand (polyIC) significantly reduced proliferating (BrdU-labeled) cells and neurosphere formation in wild type but not TLR3(-/-)-derived NPCs. Our findings reveal a novel role for TLR3 in the negative regulation of NPC proliferation in the developing brain. View Publication

Current sources of mesenchymal cells,including bone marrow,fat and muscle,all require invasive procurement procedures,and provide relatively low frequencies of progenitors. Here,we describe the non-invasive isolation,and characterization,of a rich source of mesenchymal progenitor cells,which we call human umbilical cord perivascular cells (HUCPVCs). HUCPVCs show a similar immunological phenotype to bone marrow-derived mesenchymal stromal cells (BM-MSCs),since they are non-alloreactive,exhibit immunosuppression,and significantly reduce lymphocyte activation,in vitro. They present a non-hematopoietic myofibroblastic mesenchymal phenotype (CD45-,CD34-,CD105+,CD73+,CD90+,CD44+,CD106+,3G5+,CD146+); with a 1:300 frequency at harvest,a short-doubling time,and a clonogenic frequency of textgreater1:3 in culture. Furthermore,in addition to robust quinti-potential differentiation capacity in vitro,HUCPVCs have been shown to contribute to both musculo-skeletal and dermal wound healing in vivo. View Publication

All-trans-retinoic acid (ATRA) and its associated analogues are important mediators of cell differentiation and function during the development of the nervous system. It is well known that ATRA can induce the differentiation of neural tissues from human pluripotent stem cells. However,it is not always appreciated that ATRA is highly susceptible to isomerisation when in solution,which can influence the effective concentration of ATRA and subsequently its biological activity. To address this source of variability,synthetic retinoid analogues have been designed and synthesised that retain stability during use and maintain biological function in comparison to ATRA. It is also shown that subtle modifications to the structure of the synthetic retinoid compound impacts significantly on biological activity,as when exposed to cultured human pluripotent stem cells,synthetic retinoid 4-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-ylethynyl)benzoic acid,4a (para-isomer),induces neural differentiation similarly to ATRA. In contrast,stem cells exposed to synthetic retinoid 3-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-ylethynyl)benzoic acid,4b (meta-isomer),produce very few neurons and large numbers of epithelial-like cells. This type of structure-activity-relationship information for such synthetic retinoid compounds will further the ability to design more targeted systems capable of mediating robust and reproducible tissue differentiation. View Publication

Two types of acquired loss of heterozygosity are possible in cancer: deletions and copy-neutral uniparental disomy (UPD). Conventionally,copy number losses are identified using metaphase cytogenetics,whereas detection of UPD is accomplished by microsatellite and copy number analysis and as such,is not often used clinically. Recently,introduction of single nucleotide polymorphism (SNP) microarrays has allowed for the systematic and sensitive detection of UPD in hematologic malignancies and other cancers. In this study,we have applied 250K SNP array technology to detect previously cryptic chromosomal changes,particularly UPD,in a cohort of 301 patients with myelodysplastic syndromes (MDS),overlap MDS/myeloproliferative disorders (MPD),MPD,and acute myeloid leukemia. We show that UPD is a common chromosomal defect in myeloid malignancies,particularly in chronic myelomonocytic leukemia (CMML; 48%) and MDS/MPD-unclassifiable (38%). Furthermore,we show that mapping minimally overlapping segmental UPD regions can help target the search for both known and unknown pathogenic mutations,including newly identified missense mutations in the proto-oncogene c-Cbl in 7 of 12 patients with UPD11q. Acquired mutations of c-Cbl E3 ubiquitin ligase may explain the pathogenesis of a clonal process in a subset of MDS/MPD,including CMML. View Publication

The recent identification of cancer stem cells (CSCs) in multiple human cancers provides a new inroad to understanding tumorigenesis at the cellular level. CSCs are defined by their characteristics of self-renewal,multipotentiality,and tumor initiation upon transplantation. By testing for these defining characteristics,we provide evidence for the existence of CSCs in a transgenic mouse model of glioma,S100beta-verbB;Trp53. In this glioma model,CSCs are enriched in the side population (SP) cells. These SP cells have enhanced tumor-initiating capacity,self-renewal,and multipotentiality compared with non-SP cells from the same tumors. Furthermore,gene expression analysis comparing fluorescence-activated cell sorting-sorted cancer SP cells to non-SP cancer cells and normal neural SP cells identified 45 candidate genes that are differentially expressed in glioma stem cells. We validated the expression of two genes from this list (S100a4 and S100a6) in primary mouse gliomas and human glioma samples. Analyses of xenografted human glioblastoma multiforme cell lines and primary human glioma tissues show that S100A4 and S100A6 are expressed in a small subset of cancer cells and that their abundance is positively correlated to tumor grade. In conclusion,this study shows that CSCs exist in a mouse glioma model,suggesting that this model can be used to study the molecular and cellular characteristics of CSCs in vivo and to further test the CSC hypothesis. View Publication

BACKGROUND Valproic acid (VPA),a commonly used mood stabilizer that promotes neuronal differentiation,regulates multiple signaling pathways involving extracellular signal-regulated kinase (ERK) and glycogen synthase kinase3beta (GSK3beta). However,the mechanism by which VPA promotes differentiation is not understood. RESULTS We report here that 1 mM VPA simultaneously induces differentiation and reduces proliferation of basic fibroblast growth factor (bFGF)-treated embryonic day 14 (E14) rat cerebral cortex neural progenitor cells (NPCs). The effects of VPA on the regulation of differentiation and inhibition of proliferation occur via the ERK-p21Cip/WAF1 pathway. These effects,however,are not mediated by the pathway involving the epidermal growth factor receptor (EGFR) but via the pathway which stabilizes Ras through beta-catenin signaling. Stimulation of differentiation and inhibition of proliferation in NPCs by VPA occur independently and the beta-catenin-Ras-ERK-p21Cip/WAF1 pathway is involved in both processes. The independent regulation of differentiation and proliferation in NPCs by VPA was also demonstrated in vivo in the cerebral cortex of developing rat embryos. CONCLUSION We propose that this mechanism of VPA action may contribute to an explanation of its anti-tumor and neuroprotective effects,as well as elucidate its role in the independent regulation of differentiation and inhibition of proliferation in the cerebral cortex of developing rat embryos. View Publication

Throughout its history,chronic myeloid leukemia (CML) has set precedents for cancer research and therapy. These range from the identification of the first specific chromosomal abnormality associated with cancer to the development of imatinib as a specific,targeted therapy for the disease. The successful development of imatinib as a therapeutic agent for CML can be attributed directly to decades of scientific discoveries. These discoveries determined that the BCR-ABL tyrosine kinase is the critical pathogenetic event in CML and an ideal target for therapy. This was confirmed in clinical trials of imatinib,with imatinib significantly improving the long-term survival of patients with CML. Continuing in this tradition of scientific discoveries leading to improved therapies,the understanding of resistance to imatinib has rapidly led to strategies to circumvent resistance. Continued studies of hematologic malignancies will allow this paradigm of targeting molecular pathogenetic events to be applied to many additional hematologic cancers. View Publication

Neurotrophins (NTs) and their receptors play a key role in neurogenesis and survival. The TRK (tropomyosin-related kinase) receptor protein tyrosine kinases (TRKA,TRKB,TRKC) are high-affinity NT receptors that are expressed in a variety of human tissues. Their role in normal and malignant hematopoiesis is poorly understood. In a prospective study involving 94 adult patients we demonstrate for the first time cell-surface expression of the 3 TRKs and constitutive activation in blasts from patients with de novo or secondary acute leukemia. At least one TRK was expressed in 55% of the analyzed cases. We establish a clear correlation between the TRK expression pattern and FAB classification. Although only few point mutations were found in TRK sequences by reverse-transcriptase-polymerase chain reaction (RT-PCR),we observed coexpression of BDNF (ligand for TRKB) in more than 50% of TRKB(+) cases (16/30). Activation of TRKA or TRKB by NGF and BDNF,respectively,efficiently rescued murine myeloid cells from irradiation-induced apoptosis. Coexpression of TRKB/BDNF or TRKA/NGF in murine hematopoietic cells induced leukemia. Moreover,activation of TRKs was important for survival of both human and murine leukemic cells. Our findings suggest that TRKs play an important role in leukemogenesis and may serve as a new drug target. View Publication