scholarly journals c-Myc inhibition is critical for HSC expansion and Rad51 expression

2018 ◽  
Author(s):  
Merve Aksoz ◽  
Esra Albayrak ◽  
Galip Servet Aslan ◽  
Raife Dilek Turan ◽  
Lamia Yazgi Alyazici ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cell ◽  
Kinase Inhibitor ◽  
Ex Vivo ◽  
Fold Increase ◽  
Hematopoietic Stem ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Nos Inhibitor ◽  
Kinetics Of

c-Myc plays a major role in the maintenance of glycolytic metabolism and hematopoietic stem cell (HSC) quiescence. Targeting modulators of HSC quiescence and metabolism could lead to HSC cell cycle entry with concomitant expansion. Here we show that c-Myc inhibitor 10074-G5 treatment leads to 2-fold increase in murine LSKCD34low HSC compartment post 7 days. In addition, c-Myc inhibition increases CD34+ and CD133+ human HSC number. c-Myc inhibition leads to downregulation of glycolytic and cyclin-dependent kinase inhibitor (CDKI) gene expression ex vivo and in vivo. In addition, c-Myc inhibition upregulates major HDR modulator Rad51 expression in hematopoietic cells. Besides, c-Myc inhibition does not alter proliferation kinetics of endothelial cells, fibroblasts or adipose derived mesenchymal stem cells, however; it limits bone marrow derived mesenchymal stem cell proliferation. We further demonstrate that a cocktail of c-Myc inhibitor 10074-G5 along with tauroursodeoxycholic acid (TUDCA) and i-NOS inhibitor L-NIL provides a robust HSC maintenance and expansion ex vivo as evident by induction of all stem cell antigens analyzed. Intriguingly, the cocktail of c-Myc inhibitor 10074-G5, TUDCA and L-NIL improves HDR related gene expression. These findings provide tools to improve ex vivo HSC maintenance and expansion, autologous HSC transplantation and gene editing through modulation of HSC glycolytic and HDR pathways.

c-Myc Inhibitor 10074-G5 Induces Murine and Human Hematopoietic Stem and Progenitor Cell Expansion and HDR Modulator Rad51 Expression

2019 ◽  
Vol 19 (6) ◽  
pp. 479-494 ◽  
Author(s):  
Merve Aksoz ◽  
Esra Albayrak ◽  
Galip Servet Aslan ◽  
Raife Dilek Turan ◽  
Lamia Yazgi Alyazici ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cell ◽  
Kinase Inhibitor ◽  
Ex Vivo ◽  
Fold Increase ◽  
Hematopoietic Stem ◽  
Cell Cycle Entry ◽  
Nos Inhibitor ◽  
Kinetics Of

Background:c-Myc plays a major role in the maintenance of glycolytic metabolism and hematopoietic stem cell (HSC) quiescence.Objective:Targeting modulators of HSC quiescence and metabolism could lead to HSC cell cycle entry with concomitant expansion.Methods and Results:Here we show that c-Myc inhibitor 10074-G5 treatment leads to 2-fold increase in murine LSKCD34low HSC compartment post 7 days. In addition, c-Myc inhibition increases CD34+ and CD133+ human HSC number. c-Myc inhibition leads to downregulation of glycolytic and cyclindependent kinase inhibitor (CDKI) gene expression ex vivo and in vivo. In addition, c-Myc inhibition upregulates major HDR modulator Rad51 expression in hematopoietic cells. Besides, c-Myc inhibition does not alter proliferation kinetics of endothelial cells, fibroblasts or adipose-derived mesenchymal stem cells, however, it limits bone marrow derived mesenchymal stem cell proliferation. We further demonstrate that a cocktail of c-Myc inhibitor 10074-G5 along with tauroursodeoxycholic acid (TUDCA) and i-NOS inhibitor L-NIL provides a robust HSC maintenance and expansion ex vivo as evident by induction of all stem cell antigens analyzed. Intriguingly, the cocktail of c-Myc inhibitor 10074-G5, TUDCA and L-NIL improves HDR related gene expression.Conclusion:These findings provide tools to improve ex vivo HSC maintenance and expansion, autologous HSC transplantation and gene editing through modulation of HSC glycolytic and HDR pathways.

scholarly journals Identification of novel regulators of hematopoietic stem cell development through refinement of stem cell localization and expression profiling

Blood ◽  
2009 ◽  
Vol 114 (21) ◽  
pp. 4645-4653 ◽  
Author(s):  
Maria I. Mascarenhas ◽  
Aimée Parker ◽  
Elaine Dzierzak ◽  
Katrin Ottersbach
Keyword(s):  
Gene Expression ◽  
Stem Cell ◽  
Expression Profiling ◽  
Gene Expression Analysis ◽  
Kinase Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Hematopoietic Stem ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Cell Localization ◽  
Before And After

Abstract The first adult-repopulating hematopoietic stem cells (HSCs) are detected starting at day 10.5 of gestation in the aorta-gonads-mesonephros (AGM) region of the mouse embryo. Despite the importance of the AGM in initiating HSC production, very little is currently known about the regulators that control HSC emergence in this region. We have therefore further defined the location of HSCs in the AGM and incorporated this information into a spatial and temporal comparative gene expression analysis of the AGM. The comparisons included gene expression profiling (1) in the newly identified HSC-containing region compared with the region devoid of HSCs, (2) before and after HSC emergence in the AGM microenvironment, and (3) on populations enriched for HSCs and their putative precursors. Two genes found to be up-regulated at the time and place where HSCs are first detected, the cyclin-dependent kinase inhibitor p57Kip2/Cdkn1c and the insulin-like growth factor 2, were chosen for further analysis. We demonstrate here that they play a novel role in AGM hematopoiesis. Interestingly, many genes involved in the development of the tissues surrounding the dorsal aorta are also up-regulated during HSC emergence, suggesting that the regulation of HSC generation occurs in coordination with the development of other organs.

Screen for Small Molecules Capable of Expanding Human Hematopoietic Stem Cell Ex Vivo

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1919-1919
Author(s):  
Iman Hatem Fares ◽  
Jalila Chagraoui ◽  
Jana Krosl ◽  
Denis-Claude Roy ◽  
Sandra Cohen ◽  
...  
Keyword(s):  
Stem Cell ◽  
Hematopoietic Stem Cell ◽  
Mononuclear Cells ◽  
Conflicts Of Interest ◽  
Ex Vivo ◽  
Fold Increase ◽  
Hematopoietic Stem ◽  
Cd34 Cells

Abstract Abstract 1919 Hematopoietic stem cell (HSC) transplantation is a life saving procedure whose applicability is restricted by the lack of suitable donors, by poor responsiveness to mobilization regimens in preparation of autologous transplantations, by insufficient HSC numbers in individual cord blood units, and by the inability to sufficiently amplify HSCs ex vivo. Characterization of Stemregenin (SR1), an aryl hydrocarbon receptor (AHR) antagonist that promotes HSC expansion, provided a proof of principle that low molecular weight (LMW) compounds have the ability to promote HSC expansion. To identify novel putative agonists of HSC self-renewal, we initiated a high throughput screen (HTS) of a library comprising more than 5,000 LMW molecules using the in vitro maintenance of the CD34+CD45RA- phenotype as a model system. Our study was based on the fact that mobilized peripheral blood-derived CD34+CD45RA- cells cultured in media supplemented with: stem cell factor, thrombopoietin, FLT3 ligand and interleukin 6, would promote the expansion of mononuclear cells (MNC) concomitant with a decrease in CD34+CD45RA- population and HSC depletion. LMW compounds preventing this loss could therefore act as agonists of HSC expansion. In a 384-well plate, 2000 CD34+cells were initially cultured/well in 50μl medium comprising 1μM test compounds or 0.1% DMSO (vehicle). The proportions of CD34+CD45RA− cells were determined at the initiation of experiment and after a 7-day incubation. Six of 5,280 LMW compounds (0.11%) promoted CD34+CD45RA− cell expansion, and seventeen (0.32%) enhanced differentiation as determined by the increase in proportions of CD34−CD45RA+ cells compared to control (DMSO). The 6 LMW compounds promoting expansion of the CD34+CD45RA− cell population were re-analyzed in a secondary screen. Four out of these 6 molecules suppressed the transcriptional activity of AHR, suggesting that these compounds share the same molecular pathway as SR1 in stimulating HSC expansion, thus they were not further characterized. The remaining 2 compounds promoted, similar to SR1 or better, a 10-fold and 35-fold expansion of MNC during 7 and 12-day incubations, respectively. The expanded cell populations comprised 65–75% of CD34+ cells compared to 12–30% determined for DMSO controls. During 12-day incubation with these compounds, the numbers of CD34+ cells increased ∼25-fold over their input values, or ∼ 6-fold above the values determined for controls. This expansion of CD34+ cells was associated with a ∼5-fold increase in the numbers of multilineage CFC (granulocyte, erythroid, monocyte, and megakaryocyte, or CFU-GEMM) compared to that found in DMSO control cultures. The ability of the 2 newly identified compounds to expand functional HSCs is currently being evaluated in vivo usingimmunocompromised mice. In conclusion, results of our initial screen suggest that other mechanism, besides inhibition of AhR, are at play for expansion of human HSC. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Hematopoietic stem cell exhaustion impacted by p18INK4C and p21Cip1/Waf1 in opposite manners

Blood ◽  
2006 ◽  
Vol 107 (3) ◽  
pp. 1200-1206 ◽  
Author(s):  
Hui Yu ◽  
Youzhong Yuan ◽  
Hongmei Shen ◽  
Tao Cheng
Keyword(s):  
Stem Cell ◽  
Kinase Inhibitor ◽  
Cell Cycle Regulators ◽  
Transplant Recipients ◽  
Differentiation Potential ◽  
Hematopoietic Stem ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Molecular Bases

AbstractTransplantation-associated stress can compromise the hematopoietic potential of hematopoietic stem cells (HSCs). As a consequence, HSCs may undergo “exhaustion” in serial transplant recipients, for which the cellular and molecular bases are not well understood. Hematopoietic exhaustion appears to be accelerated in the absence of p21Cip1/Waf1 (p21), a cyclin-dependent kinase inhibitor (CKI) in irradiated hosts. Our recent study demonstrated that unlike loss of p21, deletion of p18INK4C (p18), a distinct CKI, results in improved long-term engraftment, largely because of increased self-renewing divisions of HSCs in vivo. We show here that HSCs deficient in p18 sustained their competitiveness to wild-type HSCs from unmanipulated young mice, and retained multilineage differentiation potential after multiple rounds of serial bone marrow transfer over a period of more than 3 years. Further, p18 absence significantly decelerated hematopoietic exhaustion caused by p21 deficiency. Such an effect was shown to occur at the stem cell level, likely by a counteracting mechanism against the cellular senescence outcome. Our current study provides new insights into the distinct impacts of these cell-cycle regulators on HSC exhaustion and possibly HSC aging as well under proliferative stress, thereby offering potential pharmacologic targets for sustaining the durability of stressed HSCs in transplantation or elderly patients.

scholarly journals Regenerative Response in Ischemic Brain Restricted by p21cip1/waf1

2004 ◽  
Vol 199 (7) ◽  
pp. 937-945 ◽  
Author(s):  
Jianhua Qiu ◽  
Yasushi Takagi ◽  
Jun Harada ◽  
Neil Rodrigues ◽  
Michael A. Moskowitz ◽  
...  
Keyword(s):  
Stem Cell ◽  
Brain Injury ◽  
Kinase Inhibitor ◽  
Neural Regeneration ◽  
Cell Reactivity ◽  
Hematopoietic Stem ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Regenerative Response

Neural precursor cells from adults have exceptional proliferative and differentiative capability in vitro yet respond minimally to in vivo brain injury due to constraining mechanisms that are poorly defined. We assessed whether cell cycle inhibitors that restrict stem cell populations in other tissues may participate in limiting neural stem cell reactivity in vivo. The cyclin-dependent kinase inhibitor, p21cip1/waf1 (p21), maintains hematopoietic stem cell quiescence, and we evaluated its role in the regenerative response of neural tissue after ischemic injury using the mice deficient in p21. Although steady-state conditions revealed no increase in primitive cell proliferation in p21-null mice, a significantly larger fraction of quiescent neural precursors was activated in the hippocampus and subventricular zone after brain ischemia. The hippocampal precursors migrated and differentiated into a higher number of neurons after injury. Therefore, p21 is an intrinsic suppressor to neural regeneration after brain injury and may serve as a common molecular regulator restricting proliferation among stem cell pools from distinct tissue types.

scholarly journals Cyclin-Dependent Kinase Inhibitor p21 Controls Adult Neural Stem Cell Expansion by Regulating Sox2 Gene Expression

2013 ◽  
Vol 12 (1) ◽  
pp. 88-100 ◽  
Author(s):  
M. Ángeles Marqués-Torrejón ◽  
Eva Porlan ◽  
Ana Banito ◽  
Esther Gómez-Ibarlucea ◽  
Andrés J. Lopez-Contreras ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cell ◽  
Neural Stem Cell ◽  
Cell Expansion ◽  
Kinase Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Adult Neural Stem Cell ◽  
Stem Cell Expansion ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Sox2 Gene

scholarly journals Hyperactive Nras and Dose Reduction of Tet2 Collaborate to Dys-Regulate Hematopoietic Stem Cells and Promote Leukemogenesis

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1204-1204
Author(s):  
Xi Jin ◽  
Tingting Qin ◽  
Nathanael G Bailey ◽  
Meiling Zhao ◽  
Kevin B Yang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cell ◽  
Double Mutant ◽  
Mutant Mice ◽  
Cytokine Signaling ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Single Mutant ◽  
Tet2 Mutation

Abstract Activating mutations in RAS and somatic loss-of-function mutations in the ten-eleven translocation 2 (TET2) are frequently detected in hematologic malignancies. Global genomic sequencing revealed the co-occurrence of RAS and TET2 mutations in chronic myelomonocytic leukemias (CMMLs) and acute myeloid leukemias (AMLs), suggesting that the two mutations collaborate to induce malignant transformation. However, how the two mutations interact with each other, and the effects of co-existing RAS and TET2 mutations on hematopoietic stem cell (HSC) function and leukemogenesis, remains unknown. In this study, we generated conditional Mx1-Cre+;NrasLSL-G12D/+;Tet2fl/+mice (double mutant) and activated the expression of mutant Nras and Tet2 in hematopoietic tissues with poly(I:C) injections. Double mutant mice had significantly reduced survival compared to mice expressing only NrasG12D/+ or Tet2+/-(single mutants). Hematopathology and flow-cytometry analyses showed that these mice developed accelerated CMML-like phenotypes with higher myeloid cell infiltrations in the bone marrow and spleen as compared to single mutants. However, no cases of AML occurred. Given that CMML is driven by dys-regulated HSC function, we examined stem cell competitiveness, self-renewal and proliferation in double mutant mice at the pre-leukemic stage. The absolute numbers of HSCs in 10-week old double mutant mice were comparable to that observed in wild type (WT) and single mutant mice. However, double mutant HSCsdisplayed significantly enhanced self-renewal potential in colony forming (CFU) replating assays. In vivo competitive serial transplantation assays using either whole bone marrow cells or 15 purified SLAM (CD150+CD48-Lin-Sca1+cKit+) HSCs showed that while single mutant HSCs have increased competitiveness and self-renewal compared to WT HSCs, double mutants have further enhanced HSC competitiveness and self-renewal in primary and secondary transplant recipients. Furthermore, in vivo BrdU incorporation demonstrated that while Nras mutant HSCs had increased proliferation rate, Tet2 mutation significantly reduced the level of HSC proliferation in double mutants. Consistent with this, in vivo H2B-GFP label-retention assays (Liet. al. Nature 2013) in the Col1A1-H2B-GFP;Rosa26-M2-rtTA transgenic mice revealed significantly higher levels of H2B-GFP in Tet2 mutant HSCs, suggesting that Tet2 haploinsufficiency reduced overall HSC cycling. Overall, these findings suggest that hyperactive Nras signaling and Tet2 haploinsufficiency collaborate to enhance HSC competitiveness through distinct functions: N-RasG12D increases HSC self-renewal, proliferation and differentiation, while Tet2 haploinsufficiency reduces HSC proliferation to maintain HSCs in a more quiescent state. Consistent with this, gene expression profiling with RNA sequencing on purified SLAM HSCs indicated thatN-RasG12D and Tet2haploinsufficiencyinduce different yet complementary cellular programs to collaborate in HSC dys-regulation. To fully understand how N-RasG12D and Tet2dose reduction synergistically modulate HSC properties, we examined HSC response to cytokines important for HSC functions. We found that when HSCs were cultured in the presence of low dose stem cell factor (SCF) and thrombopoietin (TPO), only Nras single mutant and Nras/Tet2 double mutant HSCs expanded, but not WT or Tet2 single mutant HSCs. In the presence of TPO and absence of SCF, HSC expansion was only detected in the double mutants. These results suggest that HSCs harboring single mutation of Nras are hypersensitive to cytokine signaling, yet the addition of Tet2 mutation allows for further cytokine independency. Thus, N-RasG12D and Tet2 dose reduction collaborate to promote cytokine signaling. Together, our data demonstrate that hyperactive Nras and Tet2 haploinsufficiency collaborate to alter global HSC gene expression and sensitivity to stem cell cytokines. These events lead to enhanced HSC competitiveness and self-renewal, thus promoting transition toward advanced myeloid malignancy. This model provides a novel platform to delineate how mutations of signaling molecules and epigenetic modifiers collaborate in leukemogenesis, and may identify opportunities for new therapeutic interventions. Disclosures No relevant conflicts of interest to declare.

Quantification of Drug-Induced mRNA in Human Whole Blood ex vivo

2008 ◽  
Vol 1 ◽  
pp. CMBD.S507 ◽  
Author(s):  
Masato Mitsuhashi ◽  
Katsuya Endo ◽  
Kazuhiko Obara ◽  
Hiroshi Izutsu ◽  
Taishi Ishida ◽  
...  
Keyword(s):  
Whole Blood ◽  
Kinase Inhibitor ◽  
Ex Vivo ◽  
Fold Increase ◽  
Drug Induced ◽  
Human Whole Blood ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Sensitivity Tests ◽  
Data Points ◽  
Mrna Markers

Apoptosis was induced in heparinized human whole blood by 3 different ways (radiation, bleomycin, or etoposide), and various mRNA were quantified using the method we reported (Clin. Chem. 2006; 52:634-642). We found that cyclin-dependent kinase inhibitor 1A (p21) and p53 upregulated modulator of apoptosis (PUMA) were the most sensitive and universal mRNA markers of apoptosis in leukocytes. In order to define positive and negative responses, a synthetic RNA was spiked into the lysis buffer and the fold increase was calculated. As a result, 837/880 (95.1%) of data points stayed between 0.75 and 1.5 fold increase, and 874/880 (99.3%) were within 0.5-2.0 fold increase. When blood samples from 40 healthy adults were stimulated with 22 different drugs, more than 75% of the samples responded to bleomycin (1 μM), idarubicin (2 μM), vincristine (1 μM), daunorubicin (2 μM), cytarabine (10 μM), to induce p21 and/or PUMA mRNA, and approximately 25% showed no induction. Significant correlation was found between p21 and PUMA mRNA responses, and between daunorubicin and cytarabine, idarubicin, and vincristine for both p21 and PUMA. The quantification of drug-induced mRNA in whole blood will be considered as ex vivo, and is a suitable platform for biomarker screening as well as a model system for drug sensitivity tests in future.

Ex-Vivo Expansion of Multipotent CD133+ Stem Cells with VEGF, FLT3l and SCGF.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4147-4147
Author(s):  
Sonja Loges ◽  
Martin Butzal ◽  
Uta Fischer ◽  
Ursula M. Gehling ◽  
Dieter K. Hossfeld ◽  
...  
Keyword(s):  
Stem Cells ◽  
Endothelial Cells ◽  
Stem Cell ◽  
Culture System ◽  
Ex Vivo ◽  
Ex Vivo Expansion ◽  
Facs Analysis ◽  
Hematopoietic Stem ◽  
Large Numbers

Abstract The rare CD133+ stem cell population contains both hematopoietic and endothelial progenitors. Successful ex-vivo expansion of this multipotent population would therefore be of great benefit in many clinical settings including stem cell transplantation and gene therapy. We developed a cell culture system containing the recombinant human cytokines vascular endothelial growth factor (VEGF), FLT3 ligand (FLT3L) and stem cell growth factor (SCGF) for ex-vivo expansion of purified human CD133+ stem cells obtained from leukapheresis products from patients pre-treated with G-CSF. FACS analysis, colony assays and NOD-SCID transplantation studies were performed to monitor stem cell and endothelial phenotype in-vitro and in-vivo. Cultivation with VEGF, FLT3L and SCGF induced a mean 2200-fold increase of total cell counts in 5 weeks. FACS analysis revealed persistence of 6–15% CD133+ stem cells indicating proliferation and survival of primitive hematopoietic stem cells. 5–6% of the proliferating cells expressed the endothelial markers CD144 (VE-Cadherin) and von-Willebrand factor (vWF). Ex-vivo expanded stem cells could be differentiated into adherent endothelial cells after withdrawal of SCGF and FLT3L allowing generation of large numbers of endothelial cells. Colony-assays showed an increase of hematopoietic and endothelial colonies after 5 weeks of ex-vivo expansion indicating simultaneous proliferation of hematopoietic and endothelial precursors under the established culture conditions (CFU-E 60-fold, CFU-GEMM 48-fold, CFU-GM 59-fold, CFU-G 99-fold, CFU-M 1356-fold and CFU-EC 1843-fold). To assess in-vivo functionality, hematopoietic stem cells expanded ex-vivo for 7, 14, 21 and 32 days were transplanted into sublethally irradiated NOD-SCID mice. For each expansion period, the mean percentage of anti-human CD45 positive bone marrow cells 3 months post-transplantation was 11, 3, 3 and 1%, respectively. Human CD45+ cells for each set of experiments contained a mean of 15, 26, 8 and 32% T-cells (CD3+), 9, 0, 7 and 21% B-cells (CD19+), 24, 2, 2 and 11% monocytes (CD14+), 21, 3, 1 and 12% granulocytes (CD33+) and 19, 37, 44 and 24% stem cells (CD34+) (d7 (n=5), d14 (n=4), d21 (n=7) and d32 (n=6) respectively). Our experiments showed multilineage engraftment of human stem cells expanded for more than 4 weeks ex-vivo. Therefore our culture system provides a tool to generate large numbers of human stem and endothelial cells for clinical purposes.

Prolonged High-Level Detection of Retrovirally Marked Hematopoietic Cells in Nonhuman Primates after Transduction of CD34+ Progenitors Using Clinically Feasible Methods.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1137-1137
Author(s):  
Tong Wu ◽  
Hyeoung Joon Kim ◽  
Stephanie E. Sellers ◽  
Kristin E. Meade ◽  
Brian A. Agricola ◽  
...  
Keyword(s):  
Stem Cell ◽  
Gene Transfer ◽  
Nonhuman Primates ◽  
Ex Vivo ◽  
Hematopoietic Stem ◽  
Retroviral Transduction ◽  
Colony Pcr ◽  
High Level

Abstract Low-level retroviral transduction and engraftment of hematopoietic long-term repopulating cells in large animals and humans remain primary obstacles to the successful application of hematopoietic stem cell(HSC) gene transfer in humans. Recent studies have reported improved efficiency by including stromal cells(STR), or the fibronectin fragment CH-296(FN), and various cytokines such as flt3 ligand(FLT) during ex vivo culture and transduction in nonhuman primates. In this work, we extend our studies using the rhesus competitive repopulation model to further explore optimal and transduction in the presence of either preformed autologous STR or immobilized FN. Long-term clinically relevant gene marking levels in multiple hematopoietic lineages from both conditions were demonstrated in vivo by semiquantitative PCR, colony PCR, and genomic Southern blotting, suggesting that FN could replace STR in ex vivo transduction protocols. Second, we compared transduction on FN in the presence of IL-3, IL-6, stem cell factor(SCF), and FLT(our best cytokine combination in prior studies)with a combination of megakaryocyte growth and development factor(MGDF), SCF, and FLT. Gene marking levels were equivalent in these animals, with no significant effect on retroviral gene transfer efficiency assessed in vivo by the replacement of IL-3 and IL-6 with MGDF. Our results indicate that SCF/G-CSF-mobilized PB CD34+ cells are transduced with equivalent efficiency in the presence of either STR or FN, with stable long-term marking of multiple lineages at levels of 10–15% and transient marking as high as 54%. These results represent an advance in the field of HSC gene transfer using methods easily applied in the clinical setting.

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