参考文献

HIV up-regulates cell-surface expression of specific ligands for the activating NKG2D receptor,including ULBP-1,-2,and -3,but not MICA or MICB,in infected cells both in vitro and in vivo. However,the viral factor(s) involved in NKG2D ligand expression still remains undefined. HIV-1 Vpr activates the DNA damage/stress-sensing ATR kinase and promotes G(2) cell-cycle arrest,conditions known to up-regulate NKG2D ligands. We report here that HIV-1 selectively induces cell-surface expression of ULBP-2 in primary CD4(+) T lymphocytes by a process that is Vpr dependent. Importantly,Vpr enhanced the susceptibility of HIV-1-infected cells to NK cell-mediated killing. Strikingly,Vpr alone was sufficient to up-regulate expression of all NKG2D ligands and thus promoted efficient NKG2D-dependent NK cell-mediated killing. Delivery of virion-associated Vpr via defective HIV-1 particles induced analogous biologic effects in noninfected target cells,suggesting that Vpr may act similarly beyond infected cells. All these activities relied on Vpr ability to activate the ATR-mediated DNA damage/stress checkpoint. Overall,these results indicate that Vpr is a key determinant responsible for HIV-1-induced up-regulation of NKG2D ligands and further suggest an immunomodulatory role for Vpr that may not only contribute to HIV-1-induced CD4(+) T-lymphocyte depletion but may also take part in HIV-1-induced NK-cell dysfunction. View Publication

Chemokine receptor CX3CR1(+) dendritic cells (DCs) have been suggested to sample intestinal antigens by extending transepithelial dendrites into the gut lumen. Other studies identified CD103(+) DCs in the mucosa,which,through their ability to synthesize retinoic acid (RA),appear to be capable of generating typical signatures of intestinal adaptive immune responses. We report that CD103 and CX3CR1 phenotypically and functionally characterize distinct subsets of lamina propria cells. In contrast to CD103(+) DC,CX3CR1(+) cells represent a nonmigratory gut-resident population with slow turnover rates and poor responses to FLT-3L and granulocyte/macrophage colony-stimulating factor. Direct visualization of cells in lymph vessels and flow cytometry of mouse intestinal lymph revealed that CD103(+) DCs,but not CX3CR1-expressing cells,migrate into the gut draining mesenteric lymph nodes (LNs) under steady-state and inflammatory conditions. Moreover,CX3CR1(+) cells displayed poor T cell stimulatory capacity in vitro and in vivo after direct injection of cells into intestinal lymphatics and appeared to be less efficient at generating RA compared with CD103(+) DC. These findings indicate that selectively CD103(+) DCs serve classical DC functions and initiate adaptive immune responses in local LNs,whereas CX3CR1(+) populations might modulate immune responses directly in the mucosa and serve as first line barrier against invading enteropathogens. View Publication

To define novel human NK cell markers,we generated two mAbs specific for G-protein-coupled receptor 56 (GPR56),a surface glycoprotein that appears to be involved in cell-to-cell and cell-to-matrix interactions. GPR56 has been described in selected normal tissues,and in certain tumors,while,as yet,its expression on leukocytes is unknown. In this study,we show that anti-GPR56 mAbs,among leukocytes,prevalently recognize NK cells. In particular,these mAbs brightly stain CD56(dull) CD16(+) NK cells while react poorly with CD56(bright) CD16(+/-) NK cells. Consistently,we found that GPR56 was expressed on NK cells populating inflamed peripheral tissues while it was absent in lymph node-derived NK cells. We also show that activating stimuli,such as cytokines or exposure to monocyte-derived dendritic cell,down-regulate NK cell expression of GPR56 both at the protein and at the transcriptional level. Interestingly,IL-18,known to induce de novo expression of CCR7 on CD56(dull) CD16(+) NK cells,displayed the highest capability of modulating GPR56. Thus,together with the identification of GPR56 as a novel marker capable of discriminating different NK cells subsets,our data suggest that GPR56 may take part to the mechanisms regulating NK cell migration through the blood stream,peripheral tissues and lymph nodes. View Publication

The discovery of an activating tyrosine kinase mutation JAK2V617F in myeloproliferative neoplasms (MPNs),polycythemia vera (PV),essential thrombocythemia (ET) and primary myelofibrosis (PMF) has resulted in the development of JAK2 inhibitors,of which several are being evaluated in phase I/II clinical studies. It is important to recognize that because the V617F mutation is localized in a region outside the adenosine triphosphate (ATP)-binding pocket of JAK2 enzyme,ATP-competitive inhibitors of JAK2 kinase (like the current JAK2 inhibitors in the clinic) are not likely to discriminate between wild-type and mutant JAK2 enzymes. Therefore,JAK2 inhibitors,by virtue of their near equipotent activity against wild-type JAK2 that is important for normal hematopoiesis,may have adverse myelosuppression as an expected side effect,if administered at doses that aim to completely inhibit the mutant JAK2 enzyme. While they may prove to be effective in controlling hyperproliferation of hematopoietic cells in PV and ET,they may not be able to eliminate mutant clones. On the other hand,JAK inhibitors may have great therapeutic benefit by controlling the disease for patients with MPNs who suffer from debilitating signs (eg,splenomegaly) or constitutional symptoms (which presumably result from high levels of circulating cytokines that signal through JAK enzymes). Indeed,the primary clinical benefits observed so far in MF patients have been significant reduction is splenomegaly,elimination of debilitating disease-related symptoms,and weight gain. Most importantly,patients with and without the JAK2V617F mutation appear to benefit to the same extent. In this review we summarize current clinical experience with JAK2 inhibitors in MPNs. View Publication

Neonatal hyperoxia impairs vascular and alveolar growth in mice and decreases endothelial progenitor cells. To determine the role of bone marrow-derived cells in restoration of neonatal lung structure after injury,we studied a novel bone marrow myeloid progenitor cell population from Tie2-green fluorescent protein (GFP) transgenic mice (bone marrow-derived angiogenic cells; BMDAC). We hypothesized that treatment with BMDAC would restore normal lung structure in infant mice during recovery from neonatal hyperoxia. Neonatal mice (1-day-old) were exposed to 80% oxygen for 10 days. BMDACs (1 x 10(5)),embryonic endothelial progenitor cells,mouse embryonic fibroblasts (control),or saline were then injected into the pulmonary circulation. At 21 days of age,saline-treated mice had enlarged alveoli,reduced septation,and a reduction in vascular density. In contrast,mice treated with BMDAC had complete restoration of lung structure that was indistinguishable from room air controls. BMDAC comprised 12% of distal lung cells localized to pulmonary vessels or alveolar type II (AT2) cells and persist (8.8%) for 8 wk postinjection. Coculture of AT2 cells or lung endothelial cells (luEC) with BMDAC augmented AT2 and luEC cell growth in vitro. We conclude that treatment with BMDAC after neonatal hyperoxia restores lung structure in this model of bronchopulmonary dysplasia. View Publication

MLL-AF4 fusion is a hallmark genetic abnormality in infant B-acute lymphoblastic leukemia (B-ALL) known to arise in utero. The cellular origin of leukemic fusion genes during human development is difficult to ascertain. The bone marrow (BM) microenvironment plays an important role in the pathogenesis of several hematological malignances. BM mesenchymal stem cells (BM-MSC) from 38 children diagnosed with cytogenetically different acute leukemias were screened for leukemic fusion genes. Fusion genes were absent in BM-MSCs of childhood leukemias carrying TEL-AML1,BCR-ABL,AML1-ETO,MLL-AF9,MLL-AF10,MLL-ENL or hyperdiploidy. However,MLL-AF4 was detected and expressed in BM-MSCs from all cases of MLL-AF4(+) B-ALL. Unlike leukemic blasts,MLL-AF4(+) BM-MSCs did not display monoclonal Ig gene rearrangements. Endogenous or ectopic expression of MLL-AF4 exerted no effect on MSC culture homeostasis. These findings suggest that MSCs may be in part tumor-related,highlighting an unrecognized role of the BM milieu on the pathogenesis of MLL-AF4(+) B-ALL. MLL-AF4 itself is not sufficient for MSC transformation and the expression of MLL-AF4 in MSCs is compatible with a mesenchymal phenotype,suggesting a differential impact in the hematopoietic system and mesenchyme. The absence of monoclonal rearrangements in MLL-AF4(+) BM-MSCs precludes the possibility of cellular plasticity or de-differentiation of B-ALL blasts and suggests that MLL-AF4 might arise in a population of prehematopoietic precursors. View Publication

Patients with alveolar rhabdomyosarcoma (ARMS) have poorer response to conventional chemotherapy and lower survival rates than those with embryonal RMS (ERMS). To identify compounds that preferentially block the growth of ARMS,we conducted a small-scale screen of 160 kinase inhibitors against the ARMS cell line Rh30 and ERMS cell line RD and identified inhibitors of glycogen synthase kinase 3 (GSK3),including TWS119 as ARMS-selective inhibitors. GSK3 inhibitors inhibited cell proliferation and induced apoptosis more effectively in Rh30 than RD cells. Ectopic expression of fusion protein PAX3-FKHR in RD cells significantly increased their sensitivity to TWS119. Down-regulation of GSK3 by GSK3 inhibitors or siRNA significantly reduced the transcriptional activity of PAX3-FKHR. These results suggest that GSK3 is directly involved in regulating the transcriptional activity of PAX3-FKHR. Also,GSK3 phosphorylated PAX3-FKHR in vitro,suggesting that GSK3 might regulate PAX3-FKHR activity via phosphorylation. These findings support a novel mechanism of PAX3-FKHR regulation by GSK3 and provide a novel strategy to develop GSK inhibitors as anti-ARMS therapies. View Publication

The tumor suppressor gene phosphatase and tensin homolog (PTEN) is inactivated in many human cancers. However,it is unknown whether PTEN functions as a tumor suppressor in human Philadelphia chromosome-positive leukemia that includes chronic myeloid leukemia (CML) and B-cell acute lymphoblastic leukemia (B-ALL) and is induced by the BCR-ABL oncogene. By using our mouse model of BCR-ABL-induced leukemias,we show that Pten is down-regulated by BCR-ABL in leukemia stem cells in CML and that PTEN deletion causes acceleration of CML development. In addition,overexpression of PTEN delays the development of CML and B-ALL and prolongs survival of leukemia mice. PTEN suppresses leukemia stem cells and induces cell-cycle arrest of leukemia cells. Moreover,PTEN suppresses B-ALL development through regulating its downstream gene Akt1. These results demonstrate a critical role of PTEN in BCR-ABL-induced leukemias and suggest a potential strategy for the treatment of Philadelphia chromosome-positive leukemia. View Publication

Blood of both humans and mice contains 2 main monocyte subsets. Here,we investigated the extent of their similarity using a microarray approach. Approximately 270 genes in humans and 550 genes in mice were differentially expressed between subsets by 2-fold or more. More than 130 of these gene expression differences were conserved between mouse and human monocyte subsets. We confirmed numerous of these differences at the cell surface protein level. Despite overall conservation,some molecules were conversely expressed between the 2 species' subsets,including CD36,CD9,and TREM-1. Other differences included a prominent peroxisome proliferator-activated receptor gamma (PPARgamma) signature in mouse monocytes,which is absent in humans,and strikingly opposed patterns of receptors involved in uptake of apoptotic cells and other phagocytic cargo between human and mouse monocyte subsets. Thus,whereas human and mouse monocyte subsets are far more broadly conserved than currently recognized,important differences between the species deserve consideration when models of human disease are studied in mice. View Publication

Gfi-1B is a transcriptional repressor that is crucial for erythroid differentiation: inactivation of the GFI1B gene in mice leads to embryonic death due to failure to produce differentiated red cells. Accordingly,GFI1B expression is tightly regulated during erythropoiesis,but the mechanisms involved in such regulation remain partially understood. We here identify HMGB2,a high-mobility group HMG protein,as a key regulator of GFI1B transcription. HMGB2 binds to the GFI1B promoter in vivo and up-regulates its trans-activation most likely by enhancing the binding of Oct-1 and,to a lesser extent,of GATA-1 and NF-Y to the GFI1B promoter. HMGB2 expression increases during erythroid differentiation concomitantly to the increase of GfI1B transcription. Importantly,knockdown of HMGB2 in immature hematopoietic progenitor cells leads to decreased Gfi-1B expression and impairs their erythroid differentiation. We propose that HMGB2 potentiates GATA-1-dependent transcription of GFI1B by Oct-1 and thereby controls erythroid differentiation. View Publication