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BACKGROUND The development of novel influenza vaccines inducing a broad immune response is an important objective. The aim of this study was to evaluate live vaccines which induce both strong humoral and cell-mediated immune responses against the novel human pandemic H1N1 influenza virus,and to show protection in a lethal animal challenge model. METHODOLOGY/PRINCIPAL FINDINGS For this purpose,the hemagglutinin (HA) and neuraminidase (NA) genes of the influenza A/California/07/2009 (H1N1) strain (CA/07) were inserted into the replication-deficient modified vaccinia Ankara (MVA) virus--a safe poxviral live vector--resulting in MVA-H1-Ca and MVA-N1-Ca vectors. These live vaccines,together with an inactivated whole virus vaccine,were assessed in a lung infection model using immune competent Balb/c mice,and in a lethal challenge model using severe combined immunodeficient (SCID) mice after passive serum transfer from immunized mice. Balb/c mice vaccinated with the MVA-H1-Ca virus or the inactivated vaccine were fully protected from lung infection after challenge with the influenza H1N1 wild-type strain,while the neuraminidase virus MVA-N1-Ca induced only partial protection. The live vaccines were already protective after a single dose and induced substantial amounts of neutralizing antibodies and of interferon-gamma-secreting (IFN-gamma) CD4- and CD8 T-cells in lungs and spleens. In the lungs,a rapid increase of HA-specific CD4- and CD8 T cells was observed in vaccinated mice shortly after challenge with influenza swine flu virus,which probably contributes to the strong inhibition of pulmonary viral replication observed. In addition,passive transfer of antisera raised in MVA-H1-Ca vaccinated immune-competent mice protected SCID mice from lethal challenge with the CA/07 wild-type virus. CONCLUSIONS/SIGNIFICANCE The non-replicating MVA-based H1N1 live vaccines induce a broad protective immune response and are promising vaccine candidates for pandemic influenza. View Publication

It has recently been shown that nucleosome distribution,histone modifications and RNA polymerase II (Pol II) occupancy show preferential association with exons (exon-intron marking")� View Publication

In mammals DNA methylation occurs at position 5 of cytosine in a CpG context and regulates gene expression. It plays an important role in diseases and inhibitors of DNA methyltransferases (DNMTs)--the enzymes responsible for DNA methylation--are used in clinics for cancer therapy. The most potent inhibitors are 5-azacytidine and 5-azadeoxycytidine. Zebularine (1-(beta-D-ribofuranosyl)-2(1H)- pyrimidinone) is another cytidine analog described as a potent inhibitor that acts by forming a covalent complex with DNMT when incorporated into DNA. Here we bring additional experiments to explain its mechanism of action. First,we observe an increase in the DNA binding when zebularine is incorporated into the DNA,compared to deoxycytidine and 5-fluorodeoxycytidine,together with a strong decrease in the dissociation rate. Second,we show by denaturing gel analysis that the intermediate covalent complex between the enzyme and the DNA is reversible,differing thus from 5-fluorodeoxycytidine. Third,no methylation reaction occurs when zebularine is present in the DNA. We confirm that zebularine exerts its demethylation activity by stabilizing the binding of DNMTs to DNA,hindering the methylation and decreasing the dissociation,thereby trapping the enzyme and preventing turnover even at other sites. View Publication

Tumor angiogenesis is essential for malignant growth and metastasis. Bone marrow (BM)-derived endothelial progenitor cells (EPC) contribute to angiogenesis-mediated tumor growth. EPC ablation can reduce tumor growth; however,the lack of a marker that can track EPCs from the BM to tumor neovasculature has impeded progress in understanding the molecular mechanisms underlying EPC biology. Here,we report the use of transgenic mouse and lentiviral models to monitor the BM-derived compartment of the tumor stroma; this approach exploits the selectivity of the transcription factor inhibitor of DNA binding 1 (Id1) for EPCs to track EPCs in the BM,blood,and tumor stroma,as well as mature EPCs. Acute ablation of BM-derived EPCs using Id1-directed delivery of a suicide gene reduced circulating EPCs and yielded significant defects in angiogenesis-mediated tumor growth. Additionally,use of the Id1 proximal promoter to express microRNA-30-based short hairpin RNA inhibited the expression of critical EPC-intrinsic factors,confirming that signaling through vascular endothelial growth factor receptor 2 is required for EPC-mediated tumor biology. By exploiting the selectivity of Id1 gene expression in EPCs,our results establish a strategy to track and target EPCs in vivo,clarifying the significant role that EPCs play in BM-mediated tumor angiogenesis. View Publication

CRKL (CRK-like) is an adapter protein predominantly phosphorylated in cells that express the tyrosine kinase p210(BCR-ABL),the fusion product of a (9;22) chromosomal translocation causative for chronic myeloid leukemia. It has been unclear,however,whether CRKL plays a functional role in p210(BCR-ABL) transformation. Here,we show that CRKL is required for p210(BCR-ABL) to support interleukin-3-independent growth of myeloid progenitor cells and long-term outgrowth of B-lymphoid cells from fetal liver-derived hematopoietic progenitor cells. Furthermore,a synthetic phosphotyrosyl peptide that binds to the CRKL SH2 domain with high affinity blocks association of endogenous CRKL with the p210(BCR-ABL) complex and reduces c-MYC levels in K562 human leukemic cells as well as in mouse hematopoietic cells transformed by p210(BCR-ABL) or the imatinib-resistant mutant T315I. These results indicate that the function of CRKL as an adapter protein is essential for p210(BCR-ABL)-induced transformation. View Publication

The recent technique of transducing key transcription factors into unipotent cells (fibroblasts) to generate pluripotent stem cells (induced pluripotent stem cells [iPSCs]) has significantly changed the stem cell field. These cells have great promise for many clinical applications,including that of regenerative medicine. Our findings show that iPSCs can be derived from human adipose-derived stromal cells (hASCs),a notable advancement in the clinical applicability of these cells. To investigate differences between two iPS cell lines (fibroblast-iPSC and hASC-iPSC),and also the gold standard human embryonic stem cell,we looked at cell stiffness as a possible indicator of cell differentiation-potential differences. We used atomic force microscopy as a tool to determine stem cell stiffness,and hence differences in material properties between cells. Human fibroblast and hASC stiffness was also ascertained for comparison. Interestingly,cells exhibited a noticeable difference in stiffness. From least to most stiff,the order of cell stiffness was as follows: hASC-iPSC,human embryonic stem cell,fibroblast-iPSC,fibroblasts,and,lastly,as the stiffest cell,hASC. In comparing hASC-iPSCs to their origin cell,the hASC,the reprogrammed cell is significantly less stiff,indicating that greater differentiation potentials may correlate with a lower cellular modulus. The stiffness differences are not dependent on cell culture density; hence,material differences between cells cannot be attributed solely to cell-cell constraints. The change in mechanical properties of the cells in response to reprogramming offers insight into how the cell interacts with its environment and might lend clues to how to efficiently reprogram cell populations as well as how to maintain their pluripotent state. View Publication

Maintenance of genomic integrity is an essential cellular function. We previously reported that the transcription factor and tumor suppressor CCAAT/enhancer binding protein δ (C/EBPδ,CEBPD; also known as NFIL-6β") promotes genomic stability. However� View Publication

Casitas B-cell lymphoma (Cbl)-family E3 ubiquitin ligases are negative regulators of tyrosine kinase signaling. Recent work has revealed a critical role of Cbl in the maintenance of hematopoietic stem cell (HSC) homeostasis,and mutations in CBL have been identified in myeloid malignancies. Here we show that,in contrast to Cbl or Cbl-b single-deficient mice,concurrent loss of Cbl and Cbl-b in the HSC compartment leads to an early-onset lethal myeloproliferative disease in mice. Cbl,Cbl-b double-deficient bone marrow cells are hypersensitive to cytokines,and show altered biochemical response to thrombopoietin. Thus,Cbl and Cbl-b play redundant but essential roles in HSC regulation,whose breakdown leads to hematological abnormalities that phenocopy crucial aspects of mutant Cbl-driven human myeloid malignancies. View Publication

Chronic myeloid leukemia (CML) is genetically characterized by the Philadelphia (Ph) chromosome,formed through a reciprocal translocation between chromosomes 9 and 22 and giving rise to the constitutively active tyrosine kinase P210 BCR/ABL1. Therapeutic strategies aiming for a cure of CML will require full eradication of Ph chromosome-positive (Ph(+)) CML stem cells. Here we used gene-expression profiling to identify IL-1 receptor accessory protein (IL1RAP) as up-regulated in CML CD34(+) cells and also in cord blood CD34(+) cells as a consequence of retroviral BCR/ABL1 expression. To test whether IL1RAP expression distinguishes normal (Ph(-)) and leukemic (Ph(+)) cells within the CML CD34(+)CD38(-) cell compartment,we established a unique protocol for conducting FISH on small numbers of sorted cells. By using this method,we sorted cells directly into drops on slides to investigate their Ph-chromosome status. Interestingly,we found that the CML CD34(+)CD38(-)IL1RAP(+) cells were Ph(+),whereas CML CD34(+)CD38(-)IL1RAP(-) cells were almost exclusively Ph(-). By performing long-term culture-initiating cell assays on the two cell populations,we found that Ph(+) and Ph(-) candidate CML stem cells could be prospectively separated. In addition,by generating an anti-IL1RAP antibody,we provide proof of concept that IL1RAP can be used as a target on CML CD34(+)CD38(-) cells to induce antibody-dependent cell-mediated cytotoxicity. This study thus identifies IL1RAP as a unique cell surface biomarker distinguishing Ph(+) from Ph(-) candidate CML stem cells and opens up a previously unexplored avenue for therapy of CML. View Publication

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Tumor-initiating cells (TICs) are defined by their ability to form tumors after xenotransplantation in immunodeficient mice and appear to be relatively rare in most human cancers. Recent data in melanoma indicate that the frequency of TICs increases dramatically via more permissive xenotransplantation conditions,raising the possibility that the true frequency of TICs has been greatly underestimated in most human tumors. We compared the growth of human pancreatic,non-small cell lung,and head and neck carcinomas in NOD/SCID and NSG mice. Although TIC frequency was detected up to 10-fold higher in NSG mice,it remained low (textless1 in 2500 cells) in all cases. Moreover,aldehyde dehydrogenase-positive (ALDH(+)) and CD44(+)CD24(+) cells,phenotypically distinct cells enriched in TICs,were equally tumorigenic in NOD/SCID and NSG mice. Our findings demonstrate that TICs are rare in these cancers and that the identification of TICs and their frequency in other human malignancies should be validated via primary tumors and highly permissive xenotransplantation conditions. View Publication

Mesenchymal stromal cells (MSCs) have important immunosuppressive properties,but the mechanisms and soluble factors involved in these effects remain unclear. We have studied prostaglandin-E2 (PGE2) as a possible candidate implied in adipose tissue-derived MSCs (Ad-MSCs) immunosuppressive properties over dendritic cells and T lymphocytes,compared to bone marrow derived MSCs (BM-MSCs). We found that both MSCs inhibited the maturation of myeloid-DCs and plasmocytoid-DCs. High levels of PGE2 were detected in DCs/MSCs co-cultures. Its blockade with indomethacin (IDM) allowed plasmocytoid-DCs but not myeloid-DCs maturation. Additionally,high levels of PGE2 were found in co-cultures in which Ad-MSCs or BM-MSCs inhibited activated T cells proliferation and pro-inflammatory cytokines production. PGE2 blockade by IDM preserved T lymphocytes proliferation but did not restore the pro-inflammatory cytokines secretion. However,an increased expression of transcription factors and cytokines genes involved in the Th1/Th2 differentiation pathway was detected in the T cells co-cultured with Ad-MSCs,but not with BM-MSCs. In conclusion,we propose that PGE2 is a soluble factor mediating most of the immunosuppressive effects of Ad-MSCs and BM-MSCs over p-DCs maturation and activated T lymphocytes proliferation and cytokine secretion. View Publication