技术资料

B cell-activating factor belonging to the TNF family (BAFF) plays a critical role in B cell maturation,yet its precise role in B cell differentiation into Ig-secreting cells (ISCs) remains unclear. In this study,we find that upon isolation human naive and memory B (MB) cells have prebound BAFF on their surface,whereas germinal center (GC) B cells lack detectable levels of prebound BAFF. We attribute their lack of prebound BAFF to cell activation,because we demonstrate that stimulation of naive and MB cells results in the loss of prebound BAFF. Furthermore,the absence of prebound BAFF on GC B cells is not related to a lack of BAFF-binding receptors or an inability to bind exogenous BAFF. Instead,our data suggest that accessibility to soluble BAFF is limited within GCs,perhaps to prevent skewing of the conventional B cell differentiation program. In support of this concept,whereas BAFF significantly enhances ISC differentiation in response to T cell-dependent activation,we report for the first time the ability of BAFF to considerably attenuate ISC differentiation of MB cells in response to CpG stimulation,a form of T cell-independent activation. Our data suggest that BAFF may be providing regulatory signals during specific T cell-independent events,which protect the balance between MB cells and ISCs outside GCs. Taken together,these data define a complex role for BAFF in humoral immune responses and show for the first time that BAFF can also play an inhibitory role in B cell differentiation. View Publication

BACKGROUND The epidermal growth factor receptor (EGFR) and Notch signaling pathways have been implicated in self-renewal of normal breast stem cells. We investigated the involvement of these signaling pathways in ductal carcinoma in situ (DCIS) of the breast. METHODS Samples of normal breast tissue (n = 15),pure DCIS tissue of varying grades (n = 35),and DCIS tissue surrounding an invasive cancer (n = 7) were used for nonadherent (i.e.,mammosphere) culture. Mammosphere cultures were treated at day 0 with gefitinib (an EGFR inhibitor),DAPT (N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester) (a gamma-secretase inhibitor),or Notch 4-neutralizing antibody. Mammosphere-forming efficiency (MFE) was calculated by dividing the number of mammospheres of 60 microm or more formed by the number of single cells seeded and is expressed as a percentage. The Notch 1 intracellular domain (NICD) was detected immunohistochemically in paraffin-embedded DCIS tissue from 50 patients with at least 60 months of follow-up. All statistical tests were two-sided. RESULTS DCIS had a greater MFE than normal breast tissue (1.5% versus 0.5%,difference = 1%,95% confidence interval [CI] = 0.62% to 1.25%,Ptextless.001). High-grade DCIS had a greater MFE than low-grade DCIS (1.6% versus 1.09%,difference = 0.51%,95% CI = 0.07% to 0.94%,P = .01). The MFE of high-grade DCIS treated with gefitinib in the absence of exogenous EGF was lower than that of high-grade DCIS treated with mammosphere medium lacking gefitinib and exogenous EGF (0.56% versus 1.36%,difference 0.8%,95% CI = 0.33% to 1.4%,P = .004). Increased Notch signaling as detected by NICD staining was associated with recurrence at 5 years (P = .012). DCIS MFE was reduced when Notch signaling was inhibited using either DAPT (0.89% versus 0.51%,difference = 0.38%,95% CI = 0.2% to 0.6%,Ptextless.001) or a Notch 4-neutralizing antibody (0.97% versus 0.2%,difference = 0.77%,95% CI = 0.52% to 1.0%,Ptextless.001). CONCLUSION We describe a novel primary culture technique for DCIS. Inhibition of the EGFR or Notch signaling pathways reduced DCIS MFE. View Publication

Although butein (3,4,2',4'-tetrahydroxychalcone) is known to exhibit anti-inflammatory,anti-cancer,and anti-fibrogenic activities,very little is known about its mechanism of action. Because numerous effects modulated by butein can be linked to interference with the NF-kappaB pathway,we investigated in detail the effect of this chalcone on NF-kappaB activity. As examined by DNA binding,we found that butein suppressed tumor necrosis factor (TNF)-induced NF-kappaB activation in a dose- and time-dependent manner; suppressed the NF-kappaB activation induced by various inflammatory agents and carcinogens; and inhibited the NF-kappaB reporter activity induced by TNFR1,TRADD,TRAF2,NIK,TAK1/TAB1,and IKK-beta. We also found that butein blocked the phosphorylation and degradation of IkappaBalpha by inhibiting IkappaBalpha kinase (IKK) activation. We found the inactivation of IKK by butein was direct and involved cysteine residue 179. This correlated with the suppression of phosphorylation and the nuclear translocation of p65. In this study,butein also inhibited the expression of the NF-kappaB-regulated gene products involved in anti-apoptosis (IAP2,Bcl-2,and Bcl-xL),proliferation (cyclin D1 and c-Myc),and invasion (COX-2 and MMP-9). Suppression of these gene products correlated with enhancement of the apoptosis induced by TNF and chemotherapeutic agents; and inhibition of cytokine-induced cellular invasion. Overall,our results indicated that antitumor and anti-inflammatory activities previously assigned to butein may be mediated in part through the direct inhibition of IKK,leading to the suppression of the NF-kappaB activation pathway. View Publication

Polycomb-repressive complex 2 (PRC2)-mediated histone methylation plays an important role in aberrant cancer gene silencing and is a potential target for cancer therapy. Here we show that S-adenosylhomocysteine hydrolase inhibitor 3-Deazaneplanocin A (DZNep) induces efficient apoptotic cell death in cancer cells but not in normal cells. We found that DZNep effectively depleted cellular levels of PRC2 components EZH2,SUZ12,and EED and inhibited associated histone H3 Lys 27 methylation (but not H3 Lys 9 methylation). By integrating RNA interference (RNAi),genome-wide expression analysis,and chromatin immunoprecipitation (ChIP) studies,we have identified a prominent set of genes selectively repressed by PRC2 in breast cancer that can be reactivated by DZNep. We further demonstrate that the preferential reactivation of a set of these genes by DZNep,including a novel apoptosis affector,FBXO32,contributes to DZNep-induced apoptosis in breast cancer cells. Our results demonstrate the unique feature of DZNep as a novel chromatin remodeling compound and suggest that pharmacologic reversal of PRC2-mediated gene repression by DZNep may constitute a novel approach for cancer therapy. View Publication

Infection with a recombinant murine-feline gammaretrovirus,MoFe2,or with the parent virus,Moloney murine leukemia virus,caused significant reduction in B-lymphoid differentiation of bone marrow at 2 to 8 weeks postinfection. The suppression was selective,in that myeloid potential was significantly increased by infection. Analysis of cell surface markers and immunoglobulin H gene rearrangements in an in vitro model demonstrated normal B-lymphoid differentiation after infection but significantly reduced viability of differentiating cells. This reduction in viability may confer a selective advantage on undifferentiated lymphoid progenitors in the bone marrow of gammaretrovirus-infected animals and thereby contribute to the establishment of a premalignant state. View Publication

Murine megakaryocytes (MKs) are defined by CD41/CD61 expression and acetylcholinesterase (AChE) activity; however,their stages of differentiation in bone marrow (BM) have not been fully elucidated. In murine lineage-negative (Lin(-))/CD45(+) BM cells,we found CD41(+) MKs without AChE activity (AChE(-)) except for CD41(++) MKs with AChE activity (AChE(+)),in which CD61 expression was similar to their CD41 level. Lin(-)/CD41(+)/CD45(+)/AChE(-) MKs could differentiate into AChE(+),with an accompanying increase in CD41/CD61 during in vitro culture. Both proplatelet formation (PPF) and platelet (PLT) production for Lin(-)/CD41(+)/CD45(+)/AChE(-) MKs were observed later than for Lin(-)/CD41(++)/CD45(+)/AChE(+) MKs,whereas MK progenitors were scarcely detected in both subpopulations. GeneChip and semiquantitative polymerase chain reaction analyses revealed that the Lin(-)/CD41(+)/CD45(+)/AChE(-) MKs are assigned at the stage between the progenitor and PPF preparation phases in respect to the many MK/PLT-specific gene expressions,including beta1-tubulin. In normal mice,the number of Lin(-)/CD41(+)/CD45(+)/AChE(-) MKs was 100 times higher than that of AChE(+) MKs in BM. When MK destruction and consequent thrombocytopenia were caused by an antitumor agent,mitomycin-C,Lin(-)/CD41(+)/CD45(+)/AChE(-) MKs led to an increase in AChE(+) MKs and subsequent PLT recovery with interleukin-11 administration. It was concluded that MKs in murine BM at least in part consist of immature Lin(-)/CD41(+)/CD45(+)/AChE(-) MKs and more differentiated Lin(-)/CD41(++)/CD45(+)/AChE(+) MKs. Immature Lin(-)/CD41(+)/CD45(+)/AChE(-) MKs are a major MK population compared with AChE(+) MKs in BM and play an important role in rapid PLT recovery in vivo. View Publication

The identification of self-renewing and multipotent neural stem cells (NSCs) in the mammalian brain holds promise for the treatment of neurological diseases and has yielded new insight into brain cancer. However,the complete repertoire of signaling pathways that governs the proliferation and self-renewal of NSCs,which we refer to as the 'ground state',remains largely uncharacterized. Although the candidate gene approach has uncovered vital pathways in NSC biology,so far only a few highly studied pathways have been investigated. Based on the intimate relationship between NSC self-renewal and neurosphere proliferation,we undertook a chemical genetic screen for inhibitors of neurosphere proliferation in order to probe the operational circuitry of the NSC. The screen recovered small molecules known to affect neurotransmission pathways previously thought to operate primarily in the mature central nervous system; these compounds also had potent inhibitory effects on cultures enriched for brain cancer stem cells. These results suggest that clinically approved neuromodulators may remodel the mature central nervous system and find application in the treatment of brain cancer. View Publication

Ewing sarcoma gene EWS encodes a putative RNA-binding protein with proposed roles in transcription and splicing,but its physiological role in vivo remains undefined. Here,we have generated Ews-deficient mice and demonstrated that EWS is required for the completion of B cell development and meiosis. Analysis of Ews(-/-) lymphocytes revealed a cell-autonomous defect in precursor B lymphocyte (pre-B lymphocyte) development. During meiosis,Ews-null spermatocytes were deficient in XY bivalent formation and showed reduced meiotic recombination,resulting in massive apoptosis and complete arrest in gamete maturation. Inactivation of Ews in mouse embryonic fibroblasts resulted in premature cellular senescence,and the mutant animals showed hypersensitivity to ionizing radiation. Finally,we showed that EWS interacts with lamin A/C and that loss of EWS results in a reduced lamin A/C expression. Our findings reveal essential functions for EWS in pre-B cell development and meiosis,with proposed roles in DNA pairing and recombination/repair mechanisms. Furthermore,we demonstrate a novel role of EWS in cellular senescence,possibly through its interaction and modulation of lamin A/C. View Publication

Doublecortin (DCX) has recently been promulgated as a selective marker of cells committed to the neuronal lineage in both the developing and the adult brain. To explore the potential of DCX-positive (DCX+) cells more stringently,these cells were isolated by flow cytometry from the brains of transgenic mice expressing green fluorescent protein under the control of the DCX promoter in embryonic,early postnatal,and adult animals. It was found that virtually all of the cells (99.9%) expressing high levels of DCX (DCX(high)) in the embryonic brain coexpressed the neuronal marker betaIII-tubulin and that this population contained no stem-like cells as demonstrated by lack of neurosphere formation in vitro. However,the DCX+ population from the early postnatal brain and the adult subventricular zone and hippocampus,which expressed low levels of DCX (DCX(low)),was enriched for neurosphere-forming cells,with only a small subpopulation of these cells coexpressing the neuronal markers betaIII-tubulin or microtubule-associated protein 2. Similarly,the DCX(low) population from embryonic day 14 (E14) brain contained neurosphere-forming cells. Only the postnatal cerebellum and adult olfactory bulb contained some DCX(high) cells,which were shown to be similar to the E14 DCX(high) cells in that they had no stem cell activity. Electrophysiological studies confirmed the heterogeneous nature of DCX+ cells,with some cells displaying characteristics of immature or mature neurons,whereas others showed no neuronal characteristics whatsoever. These results indicate that DCX(high) cells,regardless of location,are restricted to the neuronal lineage or are bone fide neurons,whereas some DCX(low) cells retain their multipotentiality. View Publication

BACKGROUND The capability of human mesenchymal stem cells (hMSC) derived of adult bone marrow to undergo in vitro hepatic differentiation was investigated. RESULTS Exposure of hMSC to a cocktail of hepatogenic factors [(fibroblast growth factor-4 (FGF-4),hepatocyte growth factor (HGF),insulin-transferrin-sodium-selenite (ITS) and dexamethasone)] failed to induce hepatic differentiation. Sequential exposure to these factors (FGF-4,followed by HGF,followed by HGF+ITS+dexamethasone),however,resembling the order of secretion during liver embryogenesis,induced both glycogen-storage and cytokeratin (CK)18 expression. Additional exposure of the cells to trichostatin A (TSA) considerably improved endodermal differentiation,as evidenced by acquisition of an epithelial morphology,chronological expression of hepatic proteins,including hepatocyte-nuclear factor (HNF)-3beta,alpha-fetoprotein (AFP),CK18,albumin (ALB),HNF1alpha,multidrug resistance-associated protein (MRP)2 and CCAAT-enhancer binding protein (C/EBP)alpha,and functional maturation,i.e. upregulated ALB secretion,urea production and inducible cytochrome P450 (CYP)-dependent activity. CONCLUSION hMSC are able to undergo mesenchymal-to-epithelial transition. TSA is hereby essential to promote differentiation of hMSC towards functional hepatocyte-like cells. View Publication

View Publication

Mesenchymal stem cells (MSC) are part of the bone marrow that provides signals supporting survival and growth of bystander hematopoietic stem cells (HSC). MSC modulate also the immune response,as they inhibit proliferation of lymphocytes. In order to investigate whether MSC can support survival of T cells,we investigated MSC capacity of rescuing T lymphocytes from cell death induced by different mechanisms. We observed that MSC prolong survival of unstimulated T cells and apoptosis-prone thymocytes cultured under starving conditions. MSC rescued T cells from activation induced cell death (AICD) by downregulation of Fas receptor and Fas ligand on T cell surface and inhibition of endogenous proteases involved in cell death. MSC dampened also Fas receptor mediated apoptosis of CD95 expressing Jurkat leukemic T cells. In contrast,rescue from AICD was not associated with a significant change of Bcl-2,an inhibitor of apoptosis induced by cell stress. Accordingly,MSC exhibited a minimal capacity of rescuing Jurkat cells from chemically induced apoptosis,a process disrupting the mitochondrial membrane potential regulated by Bcl-2. These results suggest that MSC interfere with the Fas receptor regulated process of programmed cell death. Overall,MSC can inhibit proliferation of activated T cells while supporting their survival in a quiescent state,providing a model of their activity inside the HSC niche. Disclosure of potential conflicts of interest is found at the end of this article. View Publication