ALBERT

Description: Liver and lymph node sinusoidal endothelial cell C-type lectin (LSECtin [CLEC4G]) is a C-type lectin encoded within the liver/lymph node–specific intercellular adhesion molecule-3–grabbing nonintegrin (L-SIGN)/dendritic cell–specific intercellular adhesion molecule-3–grabbing nonintegrin (DC-SIGN)/CD23 gene cluster. LSECtin expression has been previously described as restricted to sinusoidal endothelial cells of the liver and lymph node. We now report LSECtin expression in human peripheral blood and thymic dendritic cells isolated ex vivo. LSECtin is also detected in monocyte-derived macrophages and dendritic cells at the RNA and protein level. In vitro, interleukin-4 (IL-4) induces the expression of 3 LSECtin alternatively spliced isoforms, including a potentially soluble form (Δ2 isoform) and a shorter version of the prototypic molecule (Δ3/4 isoform). LSECtin functions as a pathogen receptor, because its expression confers Ebola virus–binding capacity to leukemic cells. Sugar-binding studies indicate that LSECtin specifically recognizes N-acetyl-glucosamine, whereas no LSECtin binding to Mannan- or N-acetyl-galactosamine–containing matrices are observed. Antibody or ligand-mediated engagement triggers a rapid internalization of LSECtin,which is dependent on tyrosine and diglutamic-containing motifs within the cytoplasmic tail. Therefore, LSECtin is a pathogen-associated molecular pattern receptor in human myeloid cells. In addition, our results suggest that LSECtin participates in antigen uptake and internalization, and might be a suitable target molecule in vaccination strategies.

Description: Introduction: Mantle cell lymphoma (MCL) is a mature B-cell lymphoma comprising up 5% of non-Hodgkins lymphomas. Although the prognosis for MCL patients has improved in recent years, the outlook for those with advanced or recurrent disease remains poor and the role of hematopoietic stem cell transplantation is unclear. The HyperCVAD-M/A regimen (fractionated high-dose cyclophosphamide, vincristine, doxorubicin and prednisolone alternated with methotraxate and cytarabine) has yielded encouraging results when combined with autologous stem cell transplantation (ASCT). In an effort to improve these results further, we have combined rituximab in vivo purging and post-transplant consolidation with HyperCVAD-M/A plus ASCT. Methods: Patients aged

Description: The need for safer gene therapy vectors was highlighted by the occurrence of three cases of retroviral vector-induced leukemia in children after the cure of severe combined immunodeficiency by gene therapy. These severe adverse events enhanced the development of new gene therapy vector systems, which aim to reduce influence of insertions on integrity and expression of genomic host DNA. Lentiviral vectors with self-inactivating (SIN) long terminal repeats (LTRs) have no LTR enhancer activity and are not expected to produce insertional gene activation. In our study we analyzed the integrations sites of three different lentiviral SIN-HIV-based- vectors. These vectors differed in their internal elements (Promotor, Transgene, WPRE) which allowed us to investigate whether internal elements are influencing target site selection and clone survival. A total of 1422 integration sites were analyzed at three different time points (1 day, 30 days, 60 days) after transduction of identical HeLa cells by LAM- PCR. Our results showed similar gene involvement and chromosomal distribution of integration sites for all vector types analyzed, independent of vector composition. 62–63% of the integrations were detected in Refseq genes, 82–86% were found within Refseq genes and their surrounding 10kb. Surprisingly, 271 of 1422 integration sites were clustered as common integration sites (CIS). Computer simulations allowed us to show that this high number of CIS was significantly different from a modeled random distribution of integration sites. Gene ontology analysis showed no difference in significantly overrepresented gene categories between the distinct vector types. Interestingly, we detected a time dependent increase or decrease in significance. Specific gene categories like phosphorylation, protein kinase or ATP binding activity increased in significance from freshly transduced cells (1 day) to 30 days. This observation was even more pronounced at the latest time point analyzed (60 days). Other gene categories showed the exactly opposite effect. Gene ontology analysis of freshly transduced cells showed a significant overrepresentation of genes involved in cell cycle regulation, whereas the analysis of the later time points did not show overrepresentation of this gene category. These results suggest that lentiviral SIN-HIV-based vectors may induce clonal selection in vitro independently of internal vector elements. The character of such effects as well as any putative relevance of such genotoxicity for the in vivo situation will have to be investigated in detail for the role of individual vector/cell type configurations.

Description: B-cell chronic lymphocytic leukemia (B-CLL) progression is determined by malignant cell extravasation and lymphoid tissue infiltration. We have studied the role and regulation of matrix metalloproteinase-9 (MMP-9) in B-CLL cell migration and invasion. Adhesion of B-CLL cells to the fibronectin fragment FN-H89, VCAM-1, or TNF-α–activated human umbilical vein endothelial cells (HUVECs) up-regulated MMP-9 production, measured by gelatin zymography. This effect was mediated by α4β1 integrin and required PI3-K/Akt signaling. The chemokine CXCL12 also up-regulated MMP-9, independently of α4β1 and involving ERK1/2 but not Akt activity. Accordingly, α4β1 engagement activated the PI3-K/Akt/NF-κB pathway, while CXCL12/CXCR4 interaction activated ERK1/2/c-Fos signaling. Anti–MMP-9 antibodies, the MMP-9 inhibitor TIMP-1, or transfection with 3 different MMP-9 siRNAs significantly blocked migration through Matrigel or HUVECs. Cell-associated MMP-9 was mainly at the membrane and contained the proactive and mature forms. Moreover, B-CLL cells formed podosomes upon adhesion to FN-H89, VCAM-1, or fibronectin; MMP-9 localized to podosomes in a PI3-K–dependent manner and degraded a fibronectin/gelatin matrix. Our results are the first to show that MMP-9 is physiologically regulated by α4β1 integrin and CXCL12 and plays a key role in cell invasion and transendothelial migration, thus contributing to B-CLL progression. MMP-9 could therefore constitute a target for treatment of this malignancy.

Description: There is increasing evidence to suggest that the Wnt signaling pathway plays a critical role in the pathogenesis of myeloma bone disease. In the present study, we determined whether increasing Wnt signaling within the bone marrow microenvironment in myeloma counteracts development of osteolytic bone disease. C57BL/KaLwRij mice were inoculated intravenously with murine 5TGM1 myeloma cells, resulting in tumor growth in bone and development of myeloma bone disease. Lithium chloride (LiCl) treatment activated Wnt signaling in osteoblasts, inhibited myeloma bone disease, and decreased tumor burden in bone, but increased tumor growth when 5TGM1 cells were inoculated subcutaneously. Abrogation of β-catenin activity and disruption of Wnt signaling in 5TGM1 cells by stable overexpression of a dominant-negative TCF4 prevented the LiCl-induced increase in subcutaneous growth but had no effect on LiCl-induced reduction in tumor burden within bone or on osteolysis in myeloma-bearing mice. Together, these data highlight the importance of the local microenvironment in the effect of Wnt signaling on the development of myeloma bone disease and demonstrate that, despite a direct effect to increase tumor growth at extraosseous sites, increasing Wnt signaling in the bone marrow microenvironment can prevent the development of myeloma bone disease and inhibit myeloma growth within bone in vivo.

Description: The generation of pathogen-specific immune responses is dependent on the signaling capabilities of pathogen-recognition receptors. DC-SIGN is a C-type lectin that mediates capture and internalization of viral, bacterial, and fungal pathogens by myeloid dendritic cells. DC-SIGN–interacting pathogens are thought to modulate dendritic cell maturation by interfering with intracellular signaling from Toll-like receptor molecules. We report that engagement of DC-SIGN by specific antibodies does not promote dendritic cell maturation but induces ERK1/2 and Akt phosphorylation without concomitant p38MAPK activation. DC-SIGN ligation also triggers PLCγ phosphorylation and transient increases in intracellular calcium in dendritic cells. In agreement with its signaling capabilities, a fraction of DC-SIGN molecules partitions within lipid raft–enriched membrane fractions both in DC-SIGN–transfected and dendritic cells. Moreover, DC-SIGN in dendritic cells coprecipitates with the tyrosine kinases Lyn and Syk. The relevance of the DC-SIGN–initiated signals was demonstrated in monocyte-derived dendritic cells, as DC-SIGN cross-linking synergizes with TNF-α for IL-10 release and enhances the production of LPS-induced IL-10. These results demonstrate that DC-SIGN–triggered intracellular signals modulate dendritic cell maturation. Since pathogens stimulate Th2 responses via preferential activation of ERK1/2, these results provide a molecular explanation for the ability of DC-SIGN–interacting pathogens to preferentially evoke Th2-type immune responses.

Description: Nonhomologous end-joining DNA repair factors, including Artemis, are all required for the repair of DNA double-strand breaks, which occur during the assembly of the variable antigen recognition domain of B-cell receptors and T-cell receptors through the V(D)J recombination. Mature B cells further shape their immunoglobulin repertoire on antigen recognition notably through the class switch recombination (CSR) process. To analyze the role of Artemis during CSR, we developed a mature B-cell–specific Artemis conditional knockout mouse to bypass the absence of B cells caused by its early deficit. Although CSR is not overwhelmingly affected in these mice, class switching to certain isotypes is clearly reduced both in vitro on B-cell activation and in vivo after keyhole limpet hemocyanin immunization. The reduced CSR in Artemis-deficient B cells is accompanied by the increase in DNA microhomology usage at CSR junctions, the imprint of an alternative DNA end-joining pathway. Likewise, significant increase in DNA microhomology usage is the signature of CSR junctions obtained from human RS-SCID patients harboring hypomorphic Artemis mutations. Altogether, this indicates that Artemis participates in the repair of a subset of DNA breaks generated during CSR.

Description: Transfusion dependency seems to have a major prognostic impact in patients with myelodysplastic syndrome (MDS) (Malcovati L et al. J Clin Oncol2007;25:3503). Preliminary data also suggest that the development of iron overload could influence outcome (Malcovati L et al. J Clin Oncol2005;23:7594 and Garcia-Manero G et al. Leukemia2008;22:538), but small numbers have precluded a meaningful analysis of the prognostic value of this characteristic. The main aim of this study was to evaluate the independent prognostic value of transfusion dependency (as defined in WHO-based Prognostic Scoring System [WPSS]) and iron overload (defined as serum ferritin level 〉1,000 ng/mL) in a large series of 2,994 patients (median age, 74 yr) with de novo MDS according to FAB criteria (2,107 MDS according to WHO criteria). Complete transfusional history was available in 2,241 patients (835 transfusion dependent [TD] at diagnosis, 526 TD during follow-up, and 880 non-TD) and serum ferritin levels in 1,634. Karyotyping was successfully performed in 2,074 patients, who could then be classified by the International Prognostic Scoring System (IPSS) as low (861 patients), intermediate-1 (748), intermediate-2 (311), and high-risk (154). The numbers of patients in the five risk categories defined by the WPSS (available for 1,228 patients) were 257 (21%) in very low, 385 (31%) in low, 217 (18%) in intermediate, 271 (22%) in high, and 98 (8%) in very high, closely similar to those reported in the original WPSS series. Actuarial curves of overall survival (OS) and risk of evolution to acute myeloblastic leukemia (AML) were built by Kaplan-Meier method and differences between curves compared with log-rank tests. Multivariate analyses of OS and risk of evolution to AML were performed by Cox proportional hazards regression method, with development of transfusion dependency and iron overload entered as time-dependent covariates. Other variables included in the prognostic factor analyses were age, gender, hemoglobin level, absolute WBC, PMN, and platelet counts, proportion of blasts in blood and marrow, percentage of dysplastic features in the three different hematopoietic cell lines, cytogenetics according to IPSS cytogenetic risk subgroups, FAB and WHO classifications, ferritin, beta-2 microglobulin, erythropoietin, and LDH levels at diagnosis, and IPSS and WPSS risk categories. All the previous variables showed a statistically significant relationship with OS and/or AML risk on univariante analyses. Median OS for TD patients at diagnosis, TD patients during evolution, and non-TD patients was 19, 60, and 96 months, respectively (P

Description: Retroviral vectors are commonly used gene delivery tools in clinical gene therapy providing stable integration and continuous gene expression of the transgene in the treated host cell. However, integration of the reverse transcribed vector DNA into the host genome is, by itself, a mutagenic eventthat may directly contribute to severe adverse events. The latter has dramatically been obbserved in individual cases in several, otherwise successful, gene therapy trials. Thus, a comprehensive analysis of the existing integration site pool in a transduced sample is indispensable to identify potential in vivo selection of affected cell clones and uncontrolled vector-induced cell proliferation. To date, there are several methods available to study the integration site distribution of retroviral vectors or other integrating elements as transposons. Each of these techniques makes use of restriction enzymes to digest the genomic DNA. To reveal particular vector integrations, a recognition motif of the used restriction enzyme has to be located in an appropriate distance to the integration locus in the host genome. Therefore, the genomic distribution of the recognition sequences directly impact the outcome of restriction enzyme dependent integration site analysis. We here report a validated genomic accessibility model which precisely determines the fraction of the human genome that can be analyzed with one reaction set up (i.e. restriction enzyme used). For our modeling, we used the clinically relevant linear amplification mediated PCR (LAM-PCR) as integration site analysis method of choice and the commonly used frequently cutting restriction enzymes (‘four-cutters’). We show that the most frequent four cutter motif (AATT) gives access to 54.5% of all possible integrations in the human genome, whereas the rarest distributed motif (CGCG) only identifies 2.9%. This restriction bias can be minimized by analyzing the same sample with different enzymes. A combination of the 5 most potent four cutter restriction enzymes gives access to 88.7% of the analyzable genome. Furthermore, we established an unbiased, non-restrictive integration site analysis technique based on (nr) LAM-PCR. Direct ligation of a single-stranded DNA sequence to the linear PCR product evades the need for restriction enzymes to recover integration sites. While standard LAM-PCR was done repeatedly with 3 different enzymes to detect integration sites present in lentivirally transduced single cell clones, nrLAM-PCR detected all integrations in these clones in one single reaction setup. This newly developed method comprehensively recovers genomic locations of integrating elements regardless of a restriction enzyme introduced bias. Our data show that the recovery rate of integration sites present in a transduced sample strongly depends on the restriction enzyme(s) used. However, we demonstrate that the genomic accessibility of viral integration sites indeed can be determined and minimized a priori, and that a non restrictive LAM-PCR approach circumvents the existing limitations. Analysis of the clonal inventory by these methods will allow determining the pharmacodynamics of insertional vectors with unprecedented precision, facilitating development and clinical testing of insertional vector systems.

Description: BACKGROUND: Well-differentiated systemic mastocytosis (WDSM) has recently been described as a novel form of mast cell disease. WDSM is characterized by a marked increase of bone marrow (BM) mast cells, usually with compact aggregates, with normal phenotype and morphology as well as the absence of the typical D816V somatic KIT mutation. OBJECTIVE: To describe and compare clinical, morphological, biological and molecular characteristics in a group of 18 patients who fullfilled criteria for WDSM with a group of 32 patients with indolent systemic mastocytosis (ISM). PATIENTS AND METHODS: All the patients were diagnosed on the basis of BM aspirate and biopsy findings after they were thought to have a systemic mastocytosis. A rigorous skin examination together with a clinical work-up and a complete laboratory analysis including peripheral blood count, routine biochemistry and serum tryptase levels were performed. The Mann-Whitney U and the chi-square tests were used to assess the statistical differences of continuous and categorical variables, respectively. RESULTS: WDSM patients were 4 males and 14 females with a median (range) age of 24 years (2–72) at diagnosis. Median (range) age at the time of the first observation of skin lesions was 2 years (0–41). In 16 of the 18 patients (89%), skin lesions appeared under the age of 14, five of them being younger than 1 year old. All the WDSM patients had skin involvement but the typical maculo-papular lesions were found only in 18% of patients while in the remaining 82% of cases, cutaneous lesions were plaques or nodules. Interestingly, 78% of WDSM patients had cutaneous neck involvement in contrast with only 13% in the ISM group (p