技术资料

Human embryonic stem (hES) cells have enormous potential for clinical applications. However,one major challenge is to achieve high cell recovery rate after cryopreservation. Understanding how the conventional cryopreservation protocol fails to protect the cells is a prerequisite for developing efficient and successful cryopreservation methods for hES cell lines and banks. We investigated how the stimuli from cryopreservation result in apoptosis,which causes the low cell recovery rate after cryopreservation. The level of reactive oxygen species (ROS) is significantly increased,F-actin content and distribution is altered,and caspase-8 and caspase-9 are activated after cryopreservation. p53 is also activated and translocated into nucleus. During cryopreservation apoptosis is induced by activation of both caspase-8 through the extrinsic pathway and caspase-9 through the intrinsic pathway. However,exactly how the extrinsic pathway is activated is still unclear and deserves further investigation. View Publication

Deregulation of the phosphoinositide-3-OH kinase (PI(3)K) pathway has been implicated in numerous pathologies including cancer,diabetes,thrombosis,rheumatoid arthritis and asthma. Recently,small-molecule and ATP-competitive PI(3)K inhibitors with a wide range of selectivities have entered clinical development. In order to understand the mechanisms underlying the isoform selectivity of these inhibitors,we developed a new expression strategy that enabled us to determine to our knowledge the first crystal structure of the catalytic subunit of the class IA PI(3)K p110 delta. Structures of this enzyme in complex with a broad panel of isoform- and pan-selective class I PI(3)K inhibitors reveal that selectivity toward p110 delta can be achieved by exploiting its conformational flexibility and the sequence diversity of active site residues that do not contact ATP. We have used these observations to rationalize and synthesize highly selective inhibitors for p110 delta with greatly improved potencies. View Publication

Slow-onset adaptive changes that arise from sustained antidepressant treatment,such as enhanced adult hippocampal neurogenesis and increased trophic factor expression,play a key role in the behavioral effects of antidepressants. alpha(2)-Adrenoceptors contribute to the modulation of mood and are potential targets for the development of faster acting antidepressants. We investigated the influence of alpha(2)-adrenoceptors on adult hippocampal neurogenesis. Our results indicate that alpha(2)-adrenoceptor agonists,clonidine and guanabenz,decrease adult hippocampal neurogenesis through a selective effect on the proliferation,but not the survival or differentiation,of progenitors. These effects persist in dopamine beta-hydroxylase knock-out (Dbh(-/-)) mice lacking norepinephrine,supporting a role for alpha(2)-heteroceptors on progenitor cells,rather than alpha(2)-autoreceptors on noradrenergic neurons that inhibit norepinephrine release. Adult hippocampal progenitors in vitro express all the alpha(2)-adrenoceptor subtypes,and decreased neurosphere frequency and BrdU incorporation indicate direct effects of alpha(2)-adrenoceptor stimulation on progenitors. Furthermore,coadministration of the alpha(2)-adrenoceptor antagonist yohimbine with the antidepressant imipramine significantly accelerates effects on hippocampal progenitor proliferation,the morphological maturation of newborn neurons,and the increase in expression of brain derived neurotrophic factor and vascular endothelial growth factor implicated in the neurogenic and behavioral effects of antidepressants. Finally,short-duration (7 d) yohimbine and imipramine treatment results in robust behavioral responses in the novelty suppressed feeding test,which normally requires 3 weeks of treatment with classical antidepressants. Our results demonstrate that alpha(2)-adrenoceptors,expressed by progenitor cells,decrease adult hippocampal neurogenesis,while their blockade speeds up antidepressant action,highlighting their importance as targets for faster acting antidepressants. View Publication

Clonal analysis is important for many areas of hematopoietic stem cell research,including in vitro cell expansion,gene therapy,and cancer progression and treatment. A common approach to measure clonality of retrovirally transduced cells is to perform integration site analysis using Southern blotting or polymerase chain reaction-based methods. Although these methods are useful in principle,they generally provide a low-resolution,biased,and incomplete assessment of clonality. To overcome those limitations,we labeled retroviral vectors with random sequence tags or barcodes." On integration� View Publication

The immunodeficiency disorder,X-linked agammaglobulinemia (XLA),results from mutations in the gene encoding Bruton tyrosine kinase (Btk). Btk is required for pre-B cell clonal expansion and B-cell antigen receptor signaling. XLA patients lack mature B cells and immunoglobulin and experience recurrent bacterial infections only partially mitigated by life-long antibody replacement therapy. In pursuit of definitive therapy for XLA,we tested ex vivo gene therapy using a lentiviral vector (LV) containing the immunoglobulin enhancer (Emu) and Igbeta (B29) minimal promoter to drive B lineage-specific human Btk expression in Btk/Tec(-/-) mice,a strain that reproduces the features of human XLA. After transplantation of EmuB29-Btk-LV-transduced stem cells,treated mice showed significant,albeit incomplete,rescue of mature B cells in the bone marrow,peripheral blood,spleen,and peritoneal cavity,and improved responses to T-independent and T-dependent antigens. LV-treated B cells exhibited enhanced B-cell antigen receptor signaling and an in vivo selective advantage in the peripheral versus central B-cell compartment. Secondary transplantation showed sustained Btk expression,viral integration,and partial functional responses,consistent with long-term stem cell marking; and serial transplantation revealed no evidence for cellular or systemic toxicity. These findings strongly support pursuit of B lineage-targeted LV gene therapy in human XLA. View Publication

Autophagy that is induced by starvation or cellular stress can enable cancer cell survival by sustaining energy homeostasis and eliminating damaged organelles and proteins. In response to stress,cancer cells have been reported to accumulate the protein p62/SQSTM1 (p62),but its role in the regulation of autophagy is controversial. Here,we report that the plant phytoalexin resveratrol (RSV) triggers autophagy in imatinib-sensitive and imatinib-resistant chronic myelogenous leukemia (CML) cells via JNK-dependent accumulation of p62. JNK inhibition or p62 knockdown prevented RSV-mediated autophagy and antileukemic effects. RSV also stimulated AMPK,thereby inhibiting the mTOR pathway. AMPK knockdown or mTOR overexpression impaired RSV-induced autophagy but not JNK activation. Lastly,p62 expression and autophagy in CD34+ progenitors from patients with CML was induced by RSV,and disrupting autophagy protected CD34+ CML cells from RSV-mediated cell death. We concluded that RSV triggered autophagic cell death in CML cells via both JNK-mediated p62 overexpression and AMPK activation. Our findings show that the JNK and AMPK pathways can cooperate to eliminate CML cells via autophagy. View Publication

PURPOSE: To evaluate the expression of stem cell-related markers at the cellular level in human breast tumors of different subtypes and histologic stage. EXPERIMENTAL DESIGN: We performed immunohistochemical analyses of 12 proteins [CD44,CD24,ALDH1,vimentin,osteonectin,EPCR,caveolin 1,connexin 43,cytokeratin 18 (CK18),MUC1,claudin 7,and GATA3] selected based on their differential expression in breast cancer cells with more differentiated and stem cell-like characteristics in 47 cases of invasive ductal carcinoma (IDC) only,135 cases of IDC with ductal carcinoma in situ (DCIS),35 cases of DCIS with microinvasion,and 58 cases of pure DCIS. We also analyzed 73 IDCs with adjacent DCIS to determine the differences in the expression of markers by histology within individual tumors. CD44+/CD24- and CD24-/CD24+ cells were detected using double immunohistochemistry. RESULTS: CD44 and EPCR expression was different among the four histologic groups and was lower in invasive compared with in situ tumors,especially in luminal A subtype. The expression of vimentin,osteonectin,connexin 43,ALDH1,CK18,GATA3,and MUC1 differed by tumor subtype in some histologic groups. ALDH1-positive cells were more frequent in basal-like and HER2+ than in luminal tumors. CD44+/CD24- cells were detected in 69% of all tumors with 100% of the basal-like and 52% of HER2+ tumors having some of these cells. CONCLUSIONS: Our findings suggest that in breast cancer,the frequency of tumor cells positive for stem cell-like and more differentiated cell markers varies according to tumor subtype and histologic stage. View Publication

Memantine is classified as an NMDA receptor antagonist. We recently reported that memantine promoted the proliferation of neural progenitor cells and the production of mature granule neurons in the adult hippocampus. However,the molecular mechanism responsible for the memantine-induced promotion of cellular proliferation remains unknown. In this study we searched for a factor that mediates memantine-induced cellular proliferation,and found that pigment epithelium-derived factor (PEDF),a broad-acting neurotrophic factor,is up-regulated in the dentate gyrus of adult mice after the injection of memantine. PEDF mRNA expression increased significantly by 3.5-fold at 1 day after the injection of memantine. In addition,the expression level of PEDF protein also increased by 1.8-fold at 2 days after the injection of memantine. Immunohistochemical study using anti-PEDF antibody showed that the majority of the PEDF-expressing cells were protoplasmic and perivascular astrocytes. Using a neurosphere assay,we confirmed that PEDF enhanced cellular proliferation under the presence of fibroblast growth factor-2 (FGF-2) and epidermal growth factor (EGF) but was not involved in the multilineage potency of hippocampal progenitor cells. Over expression of PEDF by adeno-associated virus,however,did not stimulate cellular proliferation,suggesting PEDF per se does not promote cellular proliferation in vivo. These findings suggest that the memantine induced PEDF up-regulation is involved in increased proliferation of hippocampal progenitor cells. View Publication

Lysine-specific demethylase 1 (LSD1) functions as a transcriptional coregulator by modulating histone methylation. Its role in neural stem cells has not been studied. We show here for the first time that LSD1 serves as a key regulator of neural stem cell proliferation. Inhibition of LSD1 activity or knockdown of LSD1 expression led to dramatically reduced neural stem cell proliferation. LSD1 is recruited by nuclear receptor TLX,an essential neural stem cell regulator,to the promoters of TLX target genes to repress the expression of these genes,which are known regulators of cell proliferation. The importance of LSD1 function in neural stem cells was further supported by the observation that intracranial viral transduction of the LSD1 small interfering RNA (siRNA) or intraperitoneal injection of the LSD1 inhibitors pargyline and tranylcypromine led to dramatically reduced neural progenitor proliferation in the hippocampal dentate gyri of wild-type adult mouse brains. However,knockout of TLX expression abolished the inhibitory effect of pargyline and tranylcypromine on neural progenitor proliferation,suggesting that TLX is critical for the LSD1 inhibitor effect. These findings revealed a novel role for LSD1 in neural stem cell proliferation and uncovered a mechanism for neural stem cell proliferation through recruitment of LSD1 to modulate TLX activity. View Publication

Transplantation studies have demonstrated the existence of mammary progenitor cells with the ability to self-renew and regenerate a functional mammary gland. Although these progenitors are the likely targets for oncogenic transformation,correlating progenitor populations with certain oncogenic stimuli has been difficult. Cyclin D1 is required for lobuloalveolar development during pregnancy and lactation as well as MMTV-ErbB2- but not MMTV-Wnt1-mediated tumorigenesis. Using a kinase-deficient cyclin D1 mouse,we identified two functional mammary progenitor cell populations,one of which is the target of MMTV-ErbB2. Moreover,cyclin D1 activity is required for the self-renewal and differentiation of mammary progenitors because its abrogation leads to a failure to maintain the mammary epithelial regenerative potential and also results in defects in luminal lineage differentiation. View Publication

Constitutive JAK2 activation in hematopoietic cells by the JAK2V617F mutation recapitulates myeloproliferative neoplasm (MPN) phenotypes in mice,establishing JAK2 inhibition as a potential therapeutic strategy. Although most polycythemia vera patients carry the JAK2V617F mutation,half of those with essential thrombocythemia or primary myelofibrosis do not,suggesting alternative mechanisms for constitutive JAK-STAT signaling in MPNs. Most patients with primary myelofibrosis have elevated levels of JAK-dependent proinflammatory cytokines (eg,interleukin-6) consistent with our observation of JAK1 hyperactivation. Accordingly,we evaluated the effectiveness of selective JAK1/2 inhibition in experimental models relevant to MPNs and report on the effects of INCB018424,the first potent,selective,oral JAK1/JAK2 inhibitor to enter the clinic. INCB018424 inhibited interleukin-6 signaling (50% inhibitory concentration [IC(50)] = 281nM),and proliferation of JAK2V617F(+) Ba/F3 cells (IC(50) = 127nM). In primary cultures,INCB018424 preferentially suppressed erythroid progenitor colony formation from JAK2V617F(+) polycythemia vera patients (IC(50) = 67nM) versus healthy donors (IC(50) textgreater 400nM). In a mouse model of JAK2V617F(+) MPN,oral INCB018424 markedly reduced splenomegaly and circulating levels of inflammatory cytokines,and preferentially eliminated neoplastic cells,resulting in significantly prolonged survival without myelosuppressive or immunosuppressive effects. Preliminary clinical results support these preclinical data and establish INCB018424 as a promising oral agent for the treatment of MPNs. View Publication

Activating mutations in KRAS and BRAF are found in more than 30% of all human tumours and 40% of melanoma,respectively,thus targeting this pathway could have broad therapeutic effects. Small molecule ATP-competitive RAF kinase inhibitors have potent antitumour effects on mutant BRAF(V600E) tumours but,in contrast to mitogen-activated protein kinase kinase (MEK) inhibitors,are not potent against RAS mutant tumour models,despite RAF functioning as a key effector downstream of RAS and upstream of MEK. Here we show that ATP-competitive RAF inhibitors have two opposing mechanisms of action depending on the cellular context. In BRAF(V600E) tumours,RAF inhibitors effectively block the mitogen-activated protein kinase (MAPK) signalling pathway and decrease tumour growth. Notably,in KRAS mutant and RAS/RAF wild-type tumours,RAF inhibitors activate the RAF-MEK-ERK pathway in a RAS-dependent manner,thus enhancing tumour growth in some xenograft models. Inhibitor binding activates wild-type RAF isoforms by inducing dimerization,membrane localization and interaction with RAS-GTP. These events occur independently of kinase inhibition and are,instead,linked to direct conformational effects of inhibitors on the RAF kinase domain. On the basis of these findings,we demonstrate that ATP-competitive kinase inhibitors can have opposing functions as inhibitors or activators of signalling pathways,depending on the cellular context. Furthermore,this work provides new insights into the therapeutic use of ATP-competitive RAF inhibitors. View Publication