技术资料

Stem cells from bone marrow,skeletal muscle and possibly other tissues can be identified by the 'side-population' (SP) phenotype. Although it has been assumed that expression of ABC transporters is responsible for this phenotype,the specific molecules involved have not been defined. Here we show that expression of the Bcrp1 (also known as Abcg2 murine/ABCG2 human) gene is a conserved feature of stem cells from a wide variety of sources. Bcrp1 mRNA was expressed at high levels in primitive murine hematopoietic stem cells,and was sharply downregulated with differentiation. Enforced expression of the ABCG2 cDNA directly conferred the SP phenotype to bone-marrow cells and caused a reduction in maturing progeny both in vitro and in transplantation-based assays. These results show that expression of the Bcrp1/ABCG2 gene is an important determinant of the SP phenotype,and that it might serve as a marker for stem cells from various sources. View Publication

Two distinct dendritic cell (DC) subpopulations have been evidenced in mice on the basis of their differential CD8alpha expression and their localization in lymphoid organs. Several reports suggest that CD8alpha(+) and CD8alpha(-) DC subsets could be functionally different. In this study,using a panel of MHC class I- and/or class II-restricted peptides,we analyzed CD4(+) and CD8(+) T cell responses obtained after i.v. injection of freshly purified peptide-pulsed DC subsets. First,we showed that both DC subsets efficiently induce specific CTL responses and Th1 cytokine production in the absence of CD4(+) T cell priming. Second,we showed that in vivo activation of CD4(+) T cells by CD8alpha(+) or CD8alpha(-) DC,injected i.v.,leads to a nonpolarized Th response with production of both Th1 and Th2 cytokines. The CD8alpha(-) subset induced a higher production of Th2 cytokines such as IL-4 and IL-10 than the CD8alpha(+) subset. However,IL-5 was produced by CD4(+) T cells activated by both DC subsets. When both CD4(+) and CD8(+) T cells were primed by DC injected i.v.,a similar pattern of cytokines was observed,but,under these conditions,Th1 cytokines were mainly produced by CD8(+) T cells,while Th2 cytokines were produced by CD4(+) T cells. Thus,this study clearly shows that CD4(+) T cell responses do not influence the development of specific CD8(+) T cell cytotoxic responses induced either by CD8alpha(+) or CD8alpha(-) DC subsets. View Publication

Sir2p is an NAD(+)-dependent histone deacetylase required for chromatin-dependent silencing in yeast. In a cell-based screen for inhibitors of Sir2p,we identified a compound,splitomicin,that creates a conditional phenocopy of a sir2 deletion mutant in Saccharomyces cerevisiae. Cells grown in the presence of the drug have silencing defects at telomeres,silent mating-type loci,and the ribosomal DNA. In addition,whole genome microarray experiments show that splitomicin selectively inhibits Sir2p. In vitro,splitomicin inhibits NAD(+)-dependent histone deacetylase activity (HDA) of the Sir2 protein. Mutations in SIR2 that confer resistance to the drug map to the likely acetylated histone tail binding domain of the protein. By using splitomicin as a chemical genetic probe,we demonstrate that continuous HDA of Sir2p is required for maintaining a silenced state in nondividing cells. View Publication

The human ATP-binding cassette superfamily G (White) member 2 (ABCG2) gene and its murine homologue breast cancer resistance protein 1 (Bcrp1) are recently described ATP-binding cassette transporters associated with drug resistance in tumor cell lines,including the MCF-7 cell line,selected for its resistance to mitoxantrone (MCF-7/MitoR). Infection of MCF-7 cells with the retroviral vector containing ABCG2 cDNA (G1-ABCG2) resulted in cells (MCF-7/ABCG2) that were resistant to mitoxantrone at levels similar to those observed in MCF-7/MitoR cells. Previous studies have shown that pluripotent hematopoietic stem cells overexpress the multidrug-resistant transport (MDR1) gene and efflux rhodamine,a substrate for the MDR1 transporter. Other studies have identified a primitive hematopoietic stem cell population,or side population (SP) cells,which are identified by their efflux of the fluorescent dye,Hoechst 33342. In an attempt to identify the transport genes responsible for this phenotype,we examined the uptake of Hoechst 33342 into MCF-7,MCF-7/MitoR,and MCF-7 cells infected with a retroviral vector expressing the ABCG2 gene (MCF-7/ABCG2). MCF-7/MitoR cells as well as MCF-7/ABCG2 cells demonstrated lower levels of Hoechst 33342 uptake compared with the parental MCF-7 cells. We also examined the level of the mouse Bcrp1 RNA in SP cells and non-SP cells isolated from mouse hematopoietic cells. Mouse SP cells expressed relatively high levels of Bcrp1 mRNA relative to non-SP cells. These results suggest that Hoechst 33342 is a substrate for the ABCG2 transporter and that ABCG2/Bcrp1 expression may serve as a marker for hematopoietic stem cells in hematopoietic cells. View Publication

microRNA (miRNA) expression profiles are often characteristic of specific cell types. The mouse mammary epithelial cell line,Comma-Dbeta,contains a population of self-renewing progenitor cells that can reconstitute the mammary gland. We purified this population and determined its miRNA signature. Several microRNAs,including miR-205 and miR-22,are highly expressed in mammary progenitor cells,while others,including let-7 and miR-93,are depleted. Let-7 sensors can be used to prospectively enrich self-renewing populations,and enforced let-7 expression induces loss of self-renewing cells from mixed cultures. View Publication

It is well known that hepatic stellate cells (HSC) develop into cells,which are thought to contribute to liver fibrogenesis. Recent data suggest that HSC are progenitor cells with the capacity to differentiate into cells of endothelial and hepatocyte lineages. The present study shows that beta-catenin-dependent canonical Wnt signaling is active in freshly isolated HSC of rats. Mimicking of the canonical Wnt pathway in cultured HSC by TWS119,an inhibitor of the glycogen synthase kinase 3beta,led to reduced beta-catenin phosphorylation,induced nuclear translocation of beta-catenin,elevated glutamine synthetase production,impeded synthesis of alpha-smooth muscle actin and Wnt5a,but promoted the expression of glial fibrillary acidic protein,Wnt10b,and paired-like homeodomain transcription factor 2c. In addition,canonical Wnt signaling lowered DNA synthesis and hindered HSC from entering the cell cycle. The findings demonstrate that beta-catenin-dependent Wnt signaling maintains the quiescent state of HSC and,similar to stem and progenitor cells,influences their developmental fate. View Publication

Many agents are active in multiple myeloma,but the majority of patients relapse. This clinical pattern suggests most cancer cells are eliminated,but cells with the clonogenic potential to mediate tumor regrowth are relatively chemoresistant. Our previous data suggested that CD138(+) multiple myeloma plasma cells cannot undergo long-term proliferation but rather arise from clonogenic CD138(neg) B cells. We compared the relative sensitivity of these distinct cell types to clinical antimyeloma agents and found that dexamethasone,lenadilomide,bortezomib,and 4-hydroxycyclophosphamide inhibited CD138(+) multiple myeloma plasma cells but had little effect on CD138(neg) precursors in vitro. We further characterized clonogenic multiple myeloma cells and stained cell lines using the Hoechst side population and Aldefluor assays. Each assay identified CD138(neg) cells suggesting that they possess high drug efflux capacity and intracellular drug detoxification activity. We also found that multiple myeloma cells expressing the memory B-cell markers CD20 and CD27 could give rise to clonogenic multiple myeloma growth in vitro and engraft immunodeficient nonobese diabetes/severe combined immunodeficient mice during both primary and secondary transplantation. Furthermore,both the side population and Aldefluor assays were capable of identifying circulating clonotypic memory B-cell populations within the peripheral blood of multiple myeloma patients. Our results suggest that circulating clonotypic B-cell populations represent multiple myeloma stem cells,and the relative drug resistance of these cells is mediated by processes that protect normal stem cells from toxic injury. View Publication

OBJECTIVE: In this study,the alternative splicing product of vasohibin 1 (VASH1B) was analyzed in direct comparison to the major isoform (VASH1A) for antiangiogenic effects on endothelial colony forming cells (ECFCs) from peripheral blood and on human umbilical vein endothelial cells (HUVECs). METHODS AND RESULTS: Expression studies in primary human endothelial cells revealed that both vasohibin proteins,hVASH1A and hVASH1B,localized in the nucleus and cytoplasm. Adenoviruses carrying the cDNA for VASH1A/B and purified recombinant proteins were used to study the function of both molecules in ECFCs and HUVECs. Recombinant VASH1A protein did not inhibit cell proliferation,tube formation,or vessel growth in vivo in the chick chorioallantoic membrane (CAM) assay,but promoted endothelial cell migration in vitro. The VASH1B protein had an inhibitory effect on cell proliferation,migration,tube formation,and inhibited blood vessel formation in the CAM assay. Adenoviral overexpression of VASH1B,but not of VASH1A,resulted in inhibition of endothelial cell growth,migration,and capillary formation. Interestingly,overexpression of VASH1A and B induced apoptosis in proliferating human fibroblasts,but did not affect cell growth of keratinocytes. CONCLUSIONS: Our data point out that alternative splicing of the VASH1 pre-mRNA transcript generates a potent antiangiogenic protein. View Publication

Our previous studies have shown that z-guggulsterone,a constituent of Indian Ayurvedic medicinal plant Commiphora mukul,inhibits the growth of human prostate cancer cells by causing apoptosis. We now report a novel response to z-guggulsterone involving the inhibition of angiogenesis in vitro and in vivo. The z-guggulsterone treatment inhibited capillary-like tube formation (in vitro neovascularization) by human umbilical vein endothelial cells (HUVEC) and migration by HUVEC and DU145 human prostate cancer cells in a concentration- and time-dependent manner. The z- and E-isomers of guggulsterone seemed equipotent as inhibitors of HUVEC tube formation. The z-guggulsterone-mediated inhibition of angiogenesis in vitro correlated with the suppression of secretion of proangiogenic growth factors [e.g.,vascular endothelial growth factor (VEGF) and granulocyte colony-stimulating factor],down-regulation of VEGF receptor 2 (VEGF-R2) protein level,and inactivation of Akt. The z-guggulsterone-mediated suppression of DU145 cell migration was increased by knockdown of VEGF-R2 protein level. Ectopic expression of constitutively active Akt in DU145 cells conferred protection against z-guggulsterone-mediated inhibition of cell migration. Oral gavage of 1 mg z-guggulsterone/d (five times/wk) to male nude mice inhibited in vivo angiogenesis in DU145-Matrigel plug assay as evidenced by a statistically significant decrease in tumor burden,microvessel area (staining for angiogenic markers factor VIII and CD31),and VEGF-R2 protein expression. In conclusion,the present study reveals that z-guggulsterone inhibits angiogenesis by suppressing the VEGF-VEGF-R2-Akt signaling axis. Together,our results provide compelling rationale for further preclinical and clinical investigation of z-guggulsterone for its efficacy against prostate cancer. View Publication

Hematopoietic stem cells (HSCs) are the basis of bone marrow transplantation and are attractive target cells for hematopoietic gene therapy,but these important clinical applications have been severely hampered by difficulties in ex vivo expansion of HSCs. In particular,the use of cord blood for adult transplantation is greatly limited by the number of HSCs. Previously we identified angiopoietin-like proteins and IGF-binding protein 2 (IGFBP2) as new hormones that,together with other factors,can expand mouse bone marrow HSCs in culture. Here,we measure the activity of multipotent human severe combined immunodeficient (SCID)-repopulating cells (SRCs) by transplantation into the nonobese diabetic SCID (NOD/SCID) mice; secondary transplantation was performed to evaluate the self-renewal potential of SRCs. A serum-free medium containing SCF,TPO,and FGF-1 or Flt3-L cannot significantly support expansion of the SRCs present in human cord blood CD133+ cells. Addition of either angiopoietin-like 5 or IGF-binding protein 2 to the cultures led to a sizable expansion of HSC numbers,as assayed by NOD/SCID transplantation. A serum-free culture containing SCF,TPO,FGF-1,angiopoietin-like 5,and IGFBP2 supports an approximately 20-fold net expansion of repopulating human cord blood HSCs,a number potentially applicable to several clinical processes including HSC transplantation. View Publication

Advancement in our understanding of the biology of adult stem cells and their therapeutic potential relies heavily on meaningful functional assays that can identify and measure stem cell activity in vivo and in vitro. In the mammalian nervous system,neural stem cells (NSCs) are often studied using a culture system referred to as the neurosphere assay. We previously challenged a central tenet of this assay,that all neurospheres are derived from a NSC,and provided evidence that it overestimates NSC frequency,rendering it inappropriate for quantitation of NSC frequency in relation to NSC regulation. Here we report the development and validation of the neural colony-forming cell assay (NCFCA),which discriminates stem from progenitor cells on the basis of their proliferative potential. We anticipate that the NCFCA will provide additional clarity in discerning the regulation of NSCs,thereby facilitating further advances in the promising application of NSCs for therapeutic use. View Publication

Proteasome inhibition is a new strategy in cancer therapy. We synthesized three new peptide aldehyde inhibitors linked to the benzamide derivative structure to use their cytotoxic activity against malignant melanoma cells. Of these,10 displayed the highest cytotoxicity (0.18 +/- 0.16 microM). A radiosynthesis of the iodine aldehyde was performed. Its drug biodistribution showed that some selectivity of the benzamide group toward malignant melanoma tissue was conserved. View Publication