In JoVE (1)

Other Publications (17)

Articles by Alice M. S. Cheung in JoVE

Other articles by Alice M. S. Cheung on PubMed

Raf/MEK/MAPK Signaling Stimulates the Nuclear Translocation and Transactivating Activity of FOXM1c

Journal of Cell Science. Feb, 2005  |  Pubmed ID: 15671063

The forkhead box (FOX) transcription factor FOXM1 is ubiquitously expressed in proliferating cells. FOXM1 expression peaks at the G2/M phase of the cell cycle and its functional deficiency in mice leads to defects in mitosis. To investigate the role of FOXM1 in the cell cycle, we used synchronized hTERT-BJ1 fibroblasts to examine the cell cycle-dependent regulation of FOXM1 function. We observed that FOXM1 is localized mainly in the cytoplasm in cells at late-G1 and S phases. Nuclear translocation occurs just before entry into the G2/M phase and is associated with phosphorylation of FOXM1. Consistent with the dependency of FOXM1 function on mitogenic signals, nuclear translocation of FOXM1 requires activity of the Raf/MEK/MAPK signaling pathway and is enhanced by the MAPK activator aurintricarboxylic acid. This activating effect was suppressed by the MEK1/2 inhibitor U0126. In transient reporter assays, constitutively active MEK1 enhances the transactivating effect of FOXM1c, but not FOXM1b, on the cyclin B1 promoter. RT-PCR analysis confirmed that different cell lines and tissues predominantly express the FOXM1c transcript. Mutations of two ERK1/2 target sequences within FOXM1c completely abolish the MEK1 enhancing effect, suggesting a direct link between Raf/MEK/MAPK signaling and FOXM1 function. Importantly, inhibition of Raf/MEK/MAPK signaling by U0126 led to suppression of FOXM1 target gene expression and delayed progression through G2/M, verifying the functional relevance of FOXM1 activation by MEK1. In summary, we provide the first evidence that Raf/MEK/MAPK signaling exerts its G2/M regulatory effect via FOXM1c.

Stem Cell Model of Hematopoiesis

Current Stem Cell Research & Therapy. Sep, 2006  |  Pubmed ID: 18220875

Hematopoietic stem cells (HSC) are characterized by their capacity of self-renewal, multi-lineage differentiation, and the ability to rescue lethally irradiated hosts. Both murine and human studies have attempted to characterize and purify HSC based on surface phenotypes, metabolic markers, in-vitro clonogenic and in-vivo competitive repopulation assays. The cell-fate of HSC is under intrinsic regulation by various transcription factors, including Hox and SCL genes, cyclin-dependent kinase inhibitors and telomerase, and extrinsic regulation by various signaling pathways involved in embryonic development, including the Notch, Wnt and bone morphogenetic proteins (BMP) pathways. Recent advances in genome research and gene profiling technologies have begun to unravel the regulatory mechanism of HSC by novel genes with hitherto unknown functions in hematopoiesis. The stem cell model of hematopoiesis has also shed light on the concepts of leukemic stem cells (LSC), which involves the presence of a rare population of cells that share the essential HSC attributes of self-renewing, replication and differentiation into progenies of leukemic blasts.

All-trans Retinoic Acid Induces Proliferation of an Irradiated Stem Cell Supporting Stromal Cell Line AFT024

Experimental Hematology. Jan, 2007  |  Pubmed ID: 17198874

We have previously shown that all-trans retinoic acid (ATRA) enhanced the maintenance of early human hematopoietic progenitor cells (HPCs) in the presence of an irradiated stromal cell line AFT024. In this study, we examined the effects of ATRA on the stromal cell component with particular reference to cellular proliferation and gene expression.

FoxM1c Counteracts Oxidative Stress-induced Senescence and Stimulates Bmi-1 Expression

The Journal of Biological Chemistry. Jun, 2008  |  Pubmed ID: 18408007

The Forkhead box transcription factor FoxM1 is expressed in proliferating cells. When it was depleted in mice and cell lines, cell cycle defects and chromosomal instability resulted. Premature senescence was observed in embryonic fibroblasts derived from FoxM1 knock-out mice, but the underlying cause has remained unclear. To investigate whether FoxM1 can protect cells against stress-induced premature senescence, we established NIH3T3 lines with doxycycline-inducible overexpression of FoxM1c. Treatment of these lines with sublethal doses (20 and 100 microm) of H(2)O(2) induced senescence with senescence-associated beta-galactosidase expression and elevated levels of p53 and p21. Induction of FoxM1c expression markedly suppressed senescence and expression of p53 and p21. Consistent with down-regulation of the p19(Arf)-p53 pathway, p19(Arf) levels decreased while expression of the Polycomb group protein Bmi-1 was induced. That Bmi-1 is a downstream target of FoxM1c was further supported by the dose-dependent induction of Bmi-1 by FoxM1c at both the protein and mRNA levels, and FoxM1 and Bmi-1 reached maximal levels in cells at the G(2)/M phase. Depletion of FoxM1 by RNA interference decreased Bmi-1 expression. Using Bmi-1 promoter reporters with wild-type and mutated c-Myc binding sites and short hairpin RNAs targeting c-Myc, we further demonstrated that FoxM1c activated Bmi-1 expression via c-Myc, which was recently reported to be regulated by FoxM1c. Our results reveal a functional link between FoxM1c, c-Myc, and Bmi-1, which are major regulators of tumorigenesis. This link has important implications for the regulation of cell proliferation and senescence by FoxM1 and Bmi-1.

A Comparative Study of Bone Marrow and Peripheral Blood CD34+ Myeloblasts in Acute Myeloid Leukaemia

British Journal of Haematology. Feb, 2009  |  Pubmed ID: 19055666

To examine the differences between primitive bone marrow (BM) and peripheral blood (PB) myeloblasts in acute myeloid leukaemia (AML), we compared CD34(+) myeloblasts of paired BM and PB samples from 14 AML patients in terms of surface phenotype, homing and engraftment in a xenogeneic transplantation model, and gene expression, based on microarray studies and quantitative polymerase chain reaction. While there was no significant difference in surface phenotypes between these two populations, in vivo assay showed significantly better homing potential of PB CD34(+) cells than BM CD34(+) cells. Significant correlation between homing and engraftment in AML samples was also noted. In addition, gene expression profiling of CD34(+) cells from five paired BM and PB leukaemic samples showed that genes involved in G-protein and prostaglandin signalling, chemotaxis and stress response, cell proliferation and apoptosis were down-regulated in PB CD34(+) myeloblasts. These data suggested that circulating primitive myeloblasts in AML are functionally different from those residing in the marrow compartment, and such differences may be partly regulated by the BM microenvironment.

FLT3/internal Tandem Duplication Subclones in Acute Myeloid Leukemia Differ in Their Engraftment Potential in NOD/SCID Mice

Leukemia Research. Jan, 2010  |  Pubmed ID: 19683812

In this study, we tested if FLT3/internal tandem duplication (ITD) in acute myeloid leukemia (AML) might occur at different hierarchical stages during leukemogenesis. In 56 AML cases, 10 showed FLT3/ITD (single ITD=5; multiple ITD=5). Myeloblasts from seven cases (CD34-selected=4; unselected=3) were transplanted into NOD/SCID mice. Five cases engrafted successfully into 14 mice. Two patients carried single FLT3/ITD subclones, which were maintained during primary and secondary transplantations. In three patients with multiple FLT3/ITD subclones, some subclones persisted or expanded while others diminished upon transplantation. Their different engraftment capabilities in NOD/SCID mice supported the proposition that FLT3/ITD might occur at different stages during leukemogenesis.

Successful Engraftment by Leukemia Initiating Cells in Adult Acute Lymphoblastic Leukemia After Direct Intrahepatic Injection into Unconditioned Newborn NOD/SCID Mice

Experimental Hematology. Jan, 2010  |  Pubmed ID: 19837128

Xenogeneic transplantation has been the gold standard for enumeration of leukemia initiating cells in acute myeloid and lymphoblastic leukemia (ALL). Most transplantation models have required conditioning in which the recipients were either irradiated or treated with chemotherapy prior to injection of human leukemia cells. In this study, we reported an undescribed model in which adult ALL cells were injected into unconditioned newborn nonobese diabetic severe combined immunodeficient mice via an intrahepatic route.

Differential NOD/SCID Mouse Engraftment of Peripheral Blood CD34+ Cells and JAK2V617F Clones from Patients with Myeloproliferative Neoplasms

Leukemia Research. Oct, 2010  |  Pubmed ID: 20170959

We evaluated the NOD/SCID engraftment of CD34(+) cells from polycythemia vera (PV) and secondary polycythemia patients (SP) and the JAK2V617F clone before and after transplantation. Peripheral blood CD34(+) cells were transplanted intra-femorally. In the injected BM, successful engraftment (>0.1%) occurred in 8/26 mice transplanted with CD34+ cells from 5/13 PV patients (median: 4.26%, range: 0.3-5.56%), in contrast to 0/14 mice from 9 SP patients (P=0.017). The engrafting PV cells were of multi-lineage. JAK2V617F/total JAK2 ratios decreased after transplantation (initial: 65.9% versus 6-week: 13.0%, P=0.001). Essential thrombocythemia (ET) BM cells also exhibited a similar decrease in JAK2V617F clone. The results suggested that events in addition to JAK2V617F are involved in the pathogenesis of PV and ET.

Sorafenib Treatment of FLT3-ITD(+) Acute Myeloid Leukemia: Favorable Initial Outcome and Mechanisms of Subsequent Nonresponsiveness Associated with the Emergence of a D835 Mutation

Blood. May, 2012  |  Pubmed ID: 22368270

Internal tandem duplication (ITD) of the fms-related tyrosine kinase-3 (FLT3) gene occurs in 30% of acute myeloid leukemias (AMLs) and confers a poor prognosis. Thirteen relapsed or chemo-refractory FLT3-ITD(+) AML patients were treated with sorafenib (200-400 mg twice daily). Twelve patients showed clearance or near clearance of bone marrow myeloblasts after 27 (range 21-84) days with evidence of differentiation of leukemia cells. The sorafenib response was lost in most patients after 72 (range 54-287) days but the FLT3 and downstream effectors remained suppressed. Gene expression profiling showed that leukemia cells that have become sorafenib resistant expressed several genes including ALDH1A1, JAK3, and MMP15, whose functions were unknown in AML. Nonobese diabetic/severe combined immunodeficiency mice transplanted with leukemia cells from patients before and during sorafenib resistance recapitulated the clinical results. Both ITD and tyrosine kinase domain mutations at D835 were identified in leukemia initiating cells (LICs) from samples before sorafenib treatment. LICs bearing the D835 mutant have expanded during sorafenib treatment and dominated during the subsequent clinical resistance. These results suggest that sorafenib have selected more aggressive sorafenib-resistant subclones carrying both FLT3-ITD and D835 mutations, and might provide important leads to further improvement of treatment outcome with FLT3 inhibitors.

Distinct but Phenotypically Heterogeneous Human Cell Populations Produce Rapid Recovery of Platelets and Neutrophils After Transplantation

Blood. Apr, 2012  |  Pubmed ID: 22374695

Delayed recovery of mature blood cells poses a serious, expensive, and often life-threatening problem for many stem cell transplantation recipients, particularly if heavily pretreated and serving as their own donor, or having a CB transplantation as the only therapeutic option. Importantly, the different cells required to ensure a rapid, as well as a permanent, hematopoietic recovery in these patients remain poorly defined. We now show that human CB and mobilized peripheral blood (mPB) collections contain cells that produce platelets and neutrophils within 3 weeks after being transplanted into sublethally irradiated NOD/scid-IL-2Rγc-null mice. The cells responsible for these 2 outputs are similarly distributed between the aldehyde dehydrogenase-positive and -negative subsets of lineage marker-negative CB and mPB cells, but their overall frequencies vary independently in individual samples. In addition, their total numbers can be seen to be much (> 30-fold) lower in a single "average" CB transplantation compared with a single "average" mPB transplantation (normalized for a similar weight of the recipient), consistent with the published differential performance in adult patients of these 2 transplantation products. Experimental testing confirmed the clinical relevance of the surrogate xenotransplantation assay for quantifying cells with rapid platelet regenerative activity, underscoring its potential for future applications.

Enhanced Normal Short-term Human Myelopoiesis in Mice Engineered to Express Human-specific Myeloid Growth Factors

Blood. Jan, 2013  |  Pubmed ID: 23233660

Better methods to characterize normal human hematopoietic cells with short-term repopulating activity cells (STRCs) are needed to facilitate improving recovery rates in transplanted patients.We now show that 5-fold more human myeloid cells are produced in sublethally irradiated NOD/SCID-IL-2Receptor-γchain-null (NSG) mice engineered to constitutively produce human interleukin-3, granulocyte-macrophage colony-stimulating factor and Steel factor (NSG-3GS mice) than in regular NSG mice 3 weeks after an intravenous injection of CD34 human cord blood cells. Importantly, the NSG-3GS mice also show a concomitant and matched increase in circulating mature human neutrophils. Imaging NSG-3GS recipients of lenti-luciferase-transduced cells showed that human cells being produced 3 weeks posttransplant were heterogeneously distributed, validating the blood as a more representative measure of transplanted STRC activity. Limiting dilution transplants further demonstrated that the early increase in human granulopoiesis in NSG-3GS mice reflects an expanded output of differentiated cells per STRC rather than an increase in STRC detection.

Analysis of the Clonal Growth and Differentiation Dynamics of Primitive Barcoded Human Cord Blood Cells in NSG Mice

Blood. Oct, 2013  |  Pubmed ID: 24030380

Human cord blood (CB) offers an attractive source of cells for clinical transplants because of its rich content of cells with sustained repopulating ability in spite of an apparent deficiency of cells with rapid reconstituting ability. Nevertheless, the clonal dynamics of nonlimiting CB transplants remain poorly understood. To begin to address this question, we exposed CD34+ CB cells to a library of barcoded lentiviruses and used massively parallel sequencing to quantify the clonal distributions of lymphoid and myeloid cells subsequently detected in sequential marrow aspirates obtained from 2 primary NOD/SCID-IL2Rγ(-/-) mice, each transplanted with ∼10(5) of these cells, and for another 6 months in 2 secondary recipients. Of the 196 clones identified, 68 were detected at 4 weeks posttransplant and were often lympho-myeloid. The rest were detected later, after variable periods up to 13 months posttransplant, but with generally increasing stability throughout time, and they included clones in which different lineages were detected. However, definitive evidence of individual cells capable of generating T-, B-, and myeloid cells, for over a year, and self-renewal of this potential was also obtained. These findings highlight the caveats and utility of this model to analyze human hematopoietic stem cell control in vivo.

Clonal Analysis Via Barcoding Reveals Diverse Growth and Differentiation of Transplanted Mouse and Human Mammary Stem Cells

Cell Stem Cell. Feb, 2014  |  Pubmed ID: 24440600

Cellular barcoding offers a powerful approach to characterize the growth and differentiation activity of large numbers of cotransplanted stem cells. Here, we describe a lentiviral genomic-barcoding and analysis strategy and its use to compare the clonal outputs of transplants of purified mouse and human basal mammary epithelial cells. We found that both sources of transplanted cells produced many bilineage mammary epithelial clones in primary recipients, although primary clones containing only one detectable mammary lineage were also common. Interestingly, regardless of the species of origin, many clones evident in secondary recipients were not detected in the primary hosts, and others that were changed from appearing luminal-restricted to appearing bilineage. This barcoding methodology has thus revealed conservation between mice and humans of a previously unknown diversity in the growth and differentiation activities of their basal mammary epithelial cells stimulated to grow in transplanted hosts.

High-throughput Genotyping of CRISPR/Cas9-mediated Mutants Using Fluorescent PCR-capillary Gel Electrophoresis

Scientific Reports. Oct, 2015  |  Pubmed ID: 26498861

Recent advances in the engineering of sequence-specific synthetic nucleases provide enormous opportunities for genetic manipulation of gene expression in order to study their cellular function in vivo. However, current genotyping methods to detect these programmable nuclease-induced insertion/deletion (indel) mutations in targeted human cells are not compatible for high-throughput screening of knockout clones due to inherent limitations and high cost. Here, we describe an efficient method of genotyping clonal CRISPR/Cas9-mediated mutants in a high-throughput manner involving the use of a direct lysis buffer to extract crude genomic DNA straight from cells in culture, and fluorescent PCR coupled with capillary gel electrophoresis. This technique also allows for genotyping of multiplexed gene targeting in a single clone. Overall, this time- and cost-saving technique is able to circumvent the limitations of current genotyping methods and support high-throughput screening of nuclease-induced mutants.

Early Production of Human Neutrophils and Platelets Posttransplant Is severely compromised by Growth Factor Exposure

Experimental Hematology. Jul, 2016  |  Pubmed ID: 27090409

The critical human cells that produce neutrophils and platelets within 3 weeks in recipients of hematopoietic transplants are thought to produce these mature blood cells with the same kinetics in sublethally irradiated immunodeficient mice. Quantification of their numbers indicates their relative underrepresentation in cord blood (CB), likely explaining the clinical inadequacy of single CB units in rescuing hematopoiesis in myelosuppressed adult patients. We here describe that exposure of CD34(+) CB cells ex vivo to growth factors that markedly expand their numbers and colony-forming cell content also rapidly (within 24 hours) produce a significant and sustained net loss of their original short-term repopulating activity. This loss of short-term in vivo repopulating activity affects early platelet production faster than early neutrophil output, consistent with their origin from distinct input populations. Moreover, this growth factor-mediated loss is not abrogated by published strategies to increase progenitor homing despite evidence that the effect on rapid neutrophil production is paralleled in time and amount by a loss of the homing of their committed clonogenic precursors to the bone marrow. These results highlight the inability of in vitro or phenotype assessments to reliably predict clinical engraftment kinetics of cultured CB cells.

Homoharringtonine (omacetaxine Mepesuccinate) As an Adjunct for FLT3-ITD Acute Myeloid Leukemia

Science Translational Medicine. Oct, 2016  |  Pubmed ID: 27708062

An in vitro drug-screening platform on patient samples was developed and validated to design personalized treatment for relapsed/refractory acute myeloid leukemia (AML). Unbiased clustering and correlation showed that homoharringtonine (HHT), also known as omacetaxine mepesuccinate, exhibited preferential antileukemia effect against AML carrying internal tandem duplication of fms-like tyrosine kinase 3 (FLT3-ITD). It worked synergistically with FLT3 inhibitors to suppress leukemia growth in vitro and in xenograft mouse models. Mechanistically, the effect was mediated by protein synthesis inhibition and reduction of short-lived proteins, including total and phosphorylated forms of FLT3 and its downstream signaling proteins. A phase 2 clinical trial of sorafenib and HHT combination treatment in FLT3-ITD AML patients resulted in complete remission (true or with insufficient hematological recovery) in 20 of 24 patients (83.3%), reduction of ITD allelic burden, and median leukemia-free and overall survivals of 12 and 33 weeks. The regimen has successfully bridged five patients to allogeneic hematopoietic stem cell transplantation and was well tolerated in patients unfit for conventional chemotherapy, including elderly and heavily pretreated patients. This study validated the principle and clinical relevance of in vitro drug testing and identified an improved treatment for FLT3-ITD AML. The results provided the foundation for phase 2/3 clinical trials to ascertain the clinical efficacy of FLT3 inhibitors and HHT in combination.

Analysis of Parameters That Affect Human Hematopoietic Cell Outputs in Mutant C-kit-immunodeficient Mice

Experimental Hematology. Apr, 2017  |  Pubmed ID: 28087429

Xenograft models are transforming our understanding of the output capabilities of primitive human hematopoietic cells in vivo. However, many variables that affect posttransplantation reconstitution dynamics remain poorly understood. Here, we show that an equivalent level of human chimerism can be regenerated from human CD34(+) cord blood cells transplanted intravenously either with or without additional radiation-inactivated cells into 2- to 6-month-old NOD-Rag1(-/-)-IL2Rγc(-/-) (NRG) mice given a more radioprotective conditioning regimen than is possible in conventionally used, repair-deficient NOD-Prkdc(scid/scid)-IL2Rγc(-/-) (NSG) hosts. Comparison of sublethally irradiated and non-irradiated NRG mice and W(41)/W(41) derivatives showed superior chimerism in the W(41)-deficient recipients, with some differential effects on different lineage outputs. Consistently superior outputs were observed in female recipients regardless of their genotype, age, or pretransplantation conditioning, with greater differences apparent later after transplantation. These results define key parameters for optimizing the sensitivity and minimizing the intraexperimental variability of human hematopoietic xenografts generated in increasingly supportive immunodeficient host mice.

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