Functional Analysis of Leukemia-Associated PTPN11 Mutations in Primary Hematopoietic Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2423-2423
Author(s):  
Suzanne Schubbert ◽  
Kenneth Lieuw ◽  
Sara L. Rowe ◽  
Connie M. Lee ◽  
XiaXin Li ◽  
...  
Keyword(s):  
Growth Factor ◽  
Bone Marrow Cells ◽  
Fetal Liver ◽  
Hematopoietic Cells ◽  
Colony Growth ◽  
Sh2 Domain ◽  
Receptor Protein ◽  
Juvenile Myelomonocytic Leukemia ◽  
Erythroid Progenitor ◽  
Gm Csf

Abstract The PTPN11 gene encodes SHP-2, a non-receptor protein tyrosine phosphatase (PTPase) that relays signals from activated growth factor receptors to p21ras (Ras), Src family kinases, and other signaling molecules. Germ-line, missense mutations in PTPN11 account for approximately 50% of cases of the human developmental disorder Noonan Syndrome (NS). More recently, PTPN11 mutations have been identified in approximately 35% of children with juvenile myelomonocytic leukemia (JMML) without NS and have also been detected in other lymphoid and myeloid malignancies. Interestingly, almost all of these leukemia-associated mutations introduce amino acid substitutions within the N-SH2 domain of SHP-2 that are largely distinct from those found in NS. We have assessed the functional consequences of leukemia-associated PTPN11 mutations in primary hematopoietic cells. Expression of an E76K mutant SHP-2 in murine fetal liver and bone marrow cells confers a hypersensitive pattern of colony-forming unit granulocyte-macrophage (CFU-GM) colony growth in response to granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 3 (IL-3). Specifically, cells expressing E76K mutant SHP-2 display enhanced colony growth at low concentrations of growth factor compared to cells expressing wild-type (WT) SHP-2 protein. Mutant colonies are significantly larger with an abnormal, spreading morphology. E76K-expressing cells also form CFU-GM colonies in the absence of growth factor. The catalytic activity of the E76K mutant is required for aberrant colony growth as expressing the E76K mutation in the context of defective phosphatase activity (C463S) abolishes hypersensitive CFU-GM growth. Mutant E76K expression also enhances the growth of immature progenitor cells with high repopulating potential (HPP-CFC and LPP-CFC) in response to GM-CSF and IL-3 and perturbs erythroid progenitor colony growth. In addition, expressing the E76K mutation results in more pronounced growth factor hypersensitivity than another leukemia-associated SHP-2 mutation (D61Y), and both of these mutations confer a stronger hematopoietic phenotype than the common N308S substitution found in patients with NS.

scholarly journals Functional analysis of leukemia-associated PTPN11 mutations in primary hematopoietic cells

Blood ◽  
2005 ◽  
Vol 106 (1) ◽  
pp. 311-317 ◽  
Author(s):  
Suzanne Schubbert ◽  
Kenneth Lieuw ◽  
Sara L. Rowe ◽  
Connie M. Lee ◽  
XiaXin Li ◽  
...  
Keyword(s):  
Tyrosine Phosphatase ◽  
Hematopoietic Cells ◽  
Colony Growth ◽  
Juvenile Myelomonocytic Leukemia ◽  
Primary Role ◽  
Gm Csf ◽  
Functional Consequences ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Normal Differentiation

PTPN11 encodes the protein tyrosine phosphatase SHP-2, which relays signals from growth factor receptors to Ras and other effectors. Germline PTPN11 mutations underlie about 50% of Noonan syndrome (NS), a developmental disorder that is associated with an elevated risk of juvenile myelomonocytic leukemia (JMML). Somatic PTPN11 mutations were recently identified in about 35% of patients with JMML; these mutations introduce amino acid substitutions that are largely distinct from those found in NS. We assessed the functional consequences of leukemia-associated PTPN11 mutations in murine hematopoietic cells. Expressing an E76K SHP-2 protein induced a hypersensitive pattern of granulocyte-macrophage colony-forming unit (CFU-GM) colony growth in response to granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 3 (IL-3) that was dependent on SHP-2 catalytic activity. E76K SHP-2 expression also enhanced the growth of immature progenitor cells with high replating potential, perturbed erythroid growth, and impaired normal differentiation in liquid cultures. In addition, leukemia-associated SHP-2 mutations conferred a stronger phenotype than a germline mutation found in patients with NS. Mutant SHP-2 proteins induce aberrant growth in multiple hematopoietic compartments, which supports a primary role of hyperactive Ras in the pathogenesis of JMML.

scholarly journals Inducible production of human macrophage growth factor, CSF-1

Blood ◽  
1986 ◽  
Vol 68 (3) ◽  
pp. 633-639 ◽  
Author(s):  
P Ralph ◽  
MK Warren ◽  
MT Lee ◽  
J Csejtey ◽  
JF Weaver ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Growth Factor ◽  
Bone Marrow Cells ◽  
Colony Growth ◽  
Northern Analysis ◽  
Human Macrophage ◽  
Nonspecific Esterase ◽  
Mouse Bone Marrow ◽  
Serum Free ◽  
Murine Bone Marrow

A panel of human cell lines was screened for production of colony- stimulating factor-1 (CSF-1) using a specific radioreceptor assay and criterion of macrophage colony growth in mouse bone marrow culture. The pancreatic carcinoma lines MIA PaCa and PANC were found to secrete high levels of CSF-1. In a bone marrow proliferation assay, the activities from these two lines were blocked by a CSF-1 specific neutralizing antiserum, confirming the predominant content of this macrophage growth factor. MIA PaCA cells stopped secreting CSF-1 when transferred to various serum-free media. Serum-free production could be reinitiated by phorbol myristic acetate (PMA). Purified CSF-1 from serum-free MIA PaCa cells stimulated the formation of 14-day colonies from total and nonadherent mononuclear human bone marrow cells. Most of the colonies consisted exclusively of large, dispersed macrophages that were intensely stained for nonspecific esterase. Although similar numbers of human 14-day colonies were stimulated by CSF-1 and other CSFs, more CSF- 1 was required for the proliferation of human as compared with murine bone marrow progenitors. Northern analysis of mRNA from induced-MIA PaCa cells, using a human CSF-1 oligonucleotide probe, revealed multiple species of CSF-1 mRNA ranging from 1.5 to 4.5 kilobases (kb). Uninduced, serum-free cultures showed only the largest mRNA species, suggesting that serum removal interfered with CSF-1 mRNA processing related to synthesis and/or secretion of the protein. Regulation of the production of CSF-1 may be an important physiological process in hematopoiesis and macrophage functioning.

scholarly journals Inducible production of human macrophage growth factor, CSF-1

Blood ◽  
1986 ◽  
Vol 68 (3) ◽  
pp. 633-639 ◽  
Author(s):  
P Ralph ◽  
MK Warren ◽  
MT Lee ◽  
J Csejtey ◽  
JF Weaver ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Growth Factor ◽  
Bone Marrow Cells ◽  
Colony Growth ◽  
Northern Analysis ◽  
Human Macrophage ◽  
Nonspecific Esterase ◽  
Mouse Bone Marrow ◽  
Serum Free ◽  
Murine Bone Marrow

Abstract A panel of human cell lines was screened for production of colony- stimulating factor-1 (CSF-1) using a specific radioreceptor assay and criterion of macrophage colony growth in mouse bone marrow culture. The pancreatic carcinoma lines MIA PaCa and PANC were found to secrete high levels of CSF-1. In a bone marrow proliferation assay, the activities from these two lines were blocked by a CSF-1 specific neutralizing antiserum, confirming the predominant content of this macrophage growth factor. MIA PaCA cells stopped secreting CSF-1 when transferred to various serum-free media. Serum-free production could be reinitiated by phorbol myristic acetate (PMA). Purified CSF-1 from serum-free MIA PaCa cells stimulated the formation of 14-day colonies from total and nonadherent mononuclear human bone marrow cells. Most of the colonies consisted exclusively of large, dispersed macrophages that were intensely stained for nonspecific esterase. Although similar numbers of human 14-day colonies were stimulated by CSF-1 and other CSFs, more CSF- 1 was required for the proliferation of human as compared with murine bone marrow progenitors. Northern analysis of mRNA from induced-MIA PaCa cells, using a human CSF-1 oligonucleotide probe, revealed multiple species of CSF-1 mRNA ranging from 1.5 to 4.5 kilobases (kb). Uninduced, serum-free cultures showed only the largest mRNA species, suggesting that serum removal interfered with CSF-1 mRNA processing related to synthesis and/or secretion of the protein. Regulation of the production of CSF-1 may be an important physiological process in hematopoiesis and macrophage functioning.

scholarly journals Platelet Factor 4 and Other CXC Chemokines Support the Survival of Normal Hematopoietic Cells and Reduce the Chemosensitivity of Cells to Cytotoxic Agents

Blood ◽  
1997 ◽  
Vol 89 (7) ◽  
pp. 2328-2335 ◽  
Author(s):  
Zhong Chao Han ◽  
Min Lu ◽  
Junmin Li ◽  
Mai Defard ◽  
Bernadette Boval ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Growth Factor ◽  
Cell Lines ◽  
Cancer Cell ◽  
Bone Marrow Cells ◽  
Hematopoietic Cells ◽  
Platelet Factor 4 ◽  
Cytotoxic Agents ◽  
Platelet Factor ◽  
Cd34 Cells

Abstract The effects of platelet factor 4 (PF4) on the viability and chemosensitivity of normal hematopoietic cells and cancer cell lines were studied to determine the mechanisms whereby PF4 functions as either an inhibitor or a protector and to evaluate its clinical significance. Two other chemokines, interleukin-8 (IL-8) and neutrophil-activating peptide-2 (NAP-2), were also studied in comparison to PF4. Using a tetrazolium salt assay for cell viability, we observed that PF4 at 1 to 50 μg/mL supported the viability of normal human bone marrow cells. Approximately 45% of cells cultured for 48 hours survived, whereas 80% or more survived in the presence of PF4 5 μg/mL. PF4 also supported the viability of CD34+ cord blood (CB) cells and protected them from apoptosis induced by transforming growth factor β1 (TGFβ1) and cytotoxic drugs. Pretreatment of CD34+ cells by PF4, but not by TGFβ1, caused an increase in the number of megakaryocyte colonies after these cells were replated in secondary cultures. Flow cytometry analysis showed that when CD34+ cells were preincubated with PF4 or TGFβ1 for 12 days in hematopoietic growth factor–rich medium, an increased number of remaining CD34+ cells was observed only for PF4-treated cells. Furthermore, PF4 significantly reduced the chemosensitivity of bone marrow cells, as shown by its ability to increase the 50% inhibition concentration (IC50) of several cytotoxic agents. Like PF4, IL-8 and NAP-2 at 0.1, 0.6, and 1 μg/mL supported the survival of myeloid progenitors, including colony-forming units granulocyte, erythroblast, monocyte, megakaryocyte (CFU-GEMM), CFU-megakaryocyte (CFU-MK), CFU–granulocyte/macrophage (CFU-GM), and burst-forming units–erythroblast (BFU-E), and reduced their sensitivity to the toxicity of etoposide (ETP). Protamine sulfate at 1 to 100 μg/mL showed no such activity of PF4. Interestingly, the three chemokines failed to affect significantly the viability and chemosensitivity of three leukemic and two other tumor cell lines. Based on these results, we conclude for the first time that PF4 and IL-8 and NAP-2 support the survival of normal hematopoietic precursors and protect them from the toxicity of chemotherapeutic agents. Because such activities are unique to normal hematopoietic cells but not to the cancer cell lines evaluated, a potential clinical application of these molecules in the treatment of cancer is suggested.

scholarly journals Pregnancy-Secreted Acid Phosphatase, Uteroferrin, Enhances Fetal Erythropoiesis

Endocrinology ◽  
2014 ◽  
Vol 155 (11) ◽  
pp. 4521-4530 ◽  
Author(s):  
Wei Ying ◽  
Haiqing Wang ◽  
Fuller W. Bazer ◽  
Beiyan Zhou
Keyword(s):  
Acid Phosphatase ◽  
Progenitor Cells ◽  
Fetal Liver ◽  
Hematopoietic Cells ◽  
Erythroid Progenitor ◽  
Colony Forming Unit ◽  
Erythroid Progenitor Cells ◽  
Uterine Glands ◽  
Fetal Erythropoiesis

Abstract Uteroferrin (UF) is a progesterone-induced acid phosphatase produced by uterine glandular epithelia in mammals during pregnancy and targeted to sites of hematopoiesis throughout pregnancy. The expression pattern of UF is coordinated with early fetal hematopoietic development in the yolk sac and then liver, spleen, and bone to prevent anemia in fetuses. Our previous studies suggested that UF exerts stimulatory impacts on hematopoietic progenitor cells. However, the precise role and thereby the mechanism of action of UF on hematopoiesis have not been investigated previously. Here, we report that UF is a potent regulator that can greatly enhance fetal erythropoiesis. Using primary fetal liver hematopoietic cells, we observed a synergistic stimulatory effect of UF with erythropoietin and other growth factors on both burst-forming unit-erythroid and colony-forming unit-erythroid formation. Further, we demonstrated that UF enhanced erythropoiesis at terminal stages using an in vitro culture system. Surveying genes that are crucial for erythrocyte formation at various stages revealed that UF, along with erythropoietin, up-regulated transcription factors required for terminal erythrocyte differentiation and genes required for synthesis of hemoglobin. Collectively, our results demonstrate that UF is a cytokine secreted by uterine glands in response to progesterone that promotes fetal erythropoiesis at various stages of pregnancy, including burst-forming unit-erythroid and colony-forming unit-erythroid progenitor cells and terminal stages of differentiation of hematopoietic cells in the erythroid lineage.

Mechanism of Oncogenesis by Leukemia-Associated Mutants of Shp2 (PTPN11).

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 199-199
Author(s):  
M. Golam Mohi ◽  
Heike Keilhack ◽  
Sarah Cohen ◽  
Christina Boulton ◽  
Toshiyuki Araki ◽  
...  
Keyword(s):  
Early Stage ◽  
Biological Effects ◽  
Lymphoblastic Leukemia ◽  
Genetic Disorder ◽  
Tyrosine Phosphatase ◽  
Sh2 Domain ◽  
Juvenile Myelomonocytic Leukemia ◽  
Myeloproliferative Disease ◽  
Murine Bone Marrow ◽  
Gm Csf

Abstract Juvenile Myelomonocytic Leukemia (JMML) is a clonal hematopoietic disorder of childhood that is principally characterized by proliferation of cells of the granulocytic and monocytic lineages. Previous studies showed that Ras or Nf1 mutations contribute to ~65% cases of JMML. More recently, mutations in the protein tyrosine phosphatase Shp2 (PTPN11) have been found in ~35% of sporadic JMML, and at lower incidence in acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and childhood B-cell acute lymphoblastic leukemia (B-ALL). Interestingly, germline mutations of Shp2 cause the autosomal dominant genetic disorder Noonan Syndrome (NS) and NS patients may have an increased incidence of JMML. Nearly all disease-associated Shp2 mutations affect residues known to control catalytic activity. NS and JMML mutations can involve the same residues, but when they do, the latter are less conservative, suggesting that they may be more activated. We have compared the biochemical and biological effects of NS and JMML mutations. When produced as recombinant proteins in bacteria, nearly all NS mutations studied showed increased PTP activity. However, the JMML mutations E76K and D61Y have the highest activity, resembling the fully active mutant E76A that we defined earlier. Retroviral-mediated expression of E76K or D61Y, but not wild type (WT) Shp2 in murine bone marrow (BM) cells results in cytokine-independent myeloid colony outgrowth, as well as hypersensitivity to both IL-3 and GM-CSF. Notably, NS- associated mutants (e.g., D61G or N308D) also could transform BM cells to factor-independence, but yielded far fewer colonies. Transformation by the leukemia-associated E76K mutant required the phosphatase activity and intact FLVRE motifs in the Shp2 SH2 domains. Gab2, a major Shp2 SH2 domain binding protein, also was required for transformation. When retrovirally transduced BM cells were transplanted into lethally irradiated recipients, E76K and D61Y but not WT Shp2 evoked fatal myeloproliferative disease (MPD) in 30–40% of recipients characterized by splenomegaly, leukocytosis, neutrophilia and monocytosis with occasional anemia and thrombocytopenia. Another ~20% showed less severe MPD at early stage and ultimately succumbed to T-ALL at later times. Histological analysis of mice dying MPD revealed BM and spleen packed with myeloid cells and livers with perivascular myeloid infiltrates. Flow cytometry on BM and spleen confirmed the presence of MPD. Moreover, BM from E76K and D61Y transplanted recipients exhibited enhanced factor-independent colony formation. Furthermore, mast cells derived from E76K and D61Y transplanted mice exhibit increased proliferation and enhanced activation of Erk, Akt and Stat5 in response to IL-3. In contrast, mice with a knock-in mutation of NS (D61G) displayed only a mild MPD. These data support a model in which leukemia-associated mutants of Shp2 are strong hypermorphs that enhance signaling via βc cytokines, whereas NS mutants are less severe gain of function alleles. Our results provide the first evidence that Shp2 mutants have a causal role in leukemogenesis and therefore, Shp2 is the first bona fide PTP proto-oncogene.

Forced Overexpression of Ahi-1 Confers a Proliferative Advantage on Primitive Murine Hematopoietic Cells and Enhances the Effects of BCR-ABL.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2573-2573
Author(s):  
Leon Zhou ◽  
Ashley Ringrose ◽  
Xiaoyan Jiang
Keyword(s):  
Bone Marrow ◽  
Growth Factor ◽  
Proliferative Activity ◽  
Insertional Mutagenesis ◽  
Bone Marrow Cells ◽  
Integration Site ◽  
Hematopoietic Cells ◽  
Chronic Phase ◽  
Biological Behavior ◽  
Pcr Analysis

Abstract Ahi-1 (Abelson helper integration site-1) is a novel gene that is commonly activated by proviral insertional mutagenesis in v-abl or myc-induced murine leukemias and lymphomas. Ahi-1 encodes a unique protein with known signaling features including SH3 and WD40-repeat domains but its normal function is unknown. Involvement of Ahi-1 in leukemogenesis is suggested by the high frequency of Ahi-1 mutations seen in certain virus-induced murine leukemias and by the gross perturbations seen in the expression of human AHI-1 and its isoforms in several human leukemic cell lines, as well as in the primary lin−CD34+CD38− leukemic stem cell-enriched population in patients with chronic phase CML. To further investigate the role of Ahi-1 as a potential co-operating oncogene relevant to BCR-ABL-mediated leukemogenesis, we compared the biological behavior of primitive murine hematopoietic cells from the bone marrow of 5-FU-treated adult C57BL/6 mice after their transduction with MSCV-Ahi-1-IRES-YFP, MSCV-BCR-ABL-IRES-GFP retroviruses, either alone or in combination. Quantitative real-time RT-PCR analysis of RNA from FACS-purified lin−YFP+ (Ahi-1+), lin−GFP+ (BCR-ABL+) and lin−YFP+GFP+ (Ahi-1+ + BCR-ABL+)-transduced bone marrow cells showed that Ahi-1 transcripts were present at 40-fold higher levels in the Ahi-1-transduced cells by comparison to the control cells transduced with the empty MIY vector. Immediately post-transduction, the Ahi-1-transduced cells produced a similar number of colonies as the MIY-transduced control cells in semi-solid cultures containing Steel factor (SF) + IL-3 + IL-6 + EPO, although a small proportion of the Ahi-1+ CFCs (~10%) were already growth factor-independent. In addition, the proliferative activity of the FACS-purified lin−YFP+ (Ahi-1+) cells (as indicated by the rate of expansion of viable cells in a week in liquid cultures containing SF, IL-3, and IL-6) was ~3-fold higher than in cultures initiated with control (lin−YFP+) cells. Moreover, after 4 weeks in longterm culture-initiating cell (LTC-IC) assays, the Ahi-1+ cells produced 2x more CFCs than the control cells. All of these endpoints (proliferative activity, growth factor-dependence and CFC output in LTC-IC assays) are also perturbed by BCR-ABL transduction. Interestingly, in cells that were co-transduced with Ahi-1 and BCR-ABL, all of these effects were further enhanced as compared to cells transduced with either BCR-ABL alone (2–4-fold) or Ahi-1 alone (3–6-fold). Thus, overexpression of Ahi-1 alone deregulates the proliferation control of primitive murine hematopoietic cells and this is additive with the effects of BCR-ABL, suggesting that Ahi-1 and BCR-ABL can cooperate to promote the progression of BCR-ABL-associated diseases like CML.

Phase II Window Study of the Farnesyltransferase Inhibitor R115777 (Zarnestra®) in Untreated Juvenile Myelomonocytic Leukemia (JMML): A Children’s Oncology Group Study.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2587-2587 ◽  
Author(s):  
Robert P. Castleberry ◽  
Mignon L. Loh ◽  
Nalini Jayaprakash ◽  
April Peterson ◽  
Vicky Casey ◽  
...  
Keyword(s):  
Phase Ii ◽  
Initial Dosage ◽  
Colony Growth ◽  
Juvenile Myelomonocytic Leukemia ◽  
Cell Transplant ◽  
Monocyte Count ◽  
Similar Frequency ◽  
Gm Csf ◽  
The Impact

Abstract JMML is a rare and often fatal leukemia of young children exhibiting unique clinical, hematopoietic and genetic features including GM-CSF hypersensitivity, and mutations of NF1, RAS, and PTPN11. Ras proteins control a number of cell signaling events becoming activated in part by the addition of a farnesyl moiety via farnesyl protein transferase (FTPase). Given that hyperactive Ras is central to JMML pathogenesis, it is intuitive that an FTPase is an appropriate therapeutic target in JMML. One FTPase inhibitor, L739,749, has previously been shown to abrogate spontaneous in vitro colony growth in 9 JMML samples (Blood 95:639, 2000). R115777 is a potent in vitro and in vivo inhibitor of FTPase, abrogating the growth of H-ras, K-ras and N-ras transformed tumors. In humans, it is well tolerated with the dose-limiting toxicities being myelosuppression and diarrhea. To assess the efficacy and toxicity of R115777 in JMML, a phase II window study was conducted as a part of COG study AAML0122 in newly diagnosed patients who were given the option of receiving this agent prior to cytosine arabinoside, fludarabine and 13-cis retinoic acid followed by stem cell transplant. R115777 was administered PO BID for 21 days with a 7 day rest for two courses in the absence of disease progression or excessive toxicity. The starting dosage in the first 11 patients was 200mg/m2 with escalation in subsequent patients to 300mg/m2 if the initial dosage was tolerated. Overall response was based upon changes in WBC and organomegaly. The impact of R115777 upon in vitro spontaneous colony growth, GM-CSF hypersensitivity and farnesylation was monitored. A total of 47 patients were accrued: M:F=30:17, median (med) age 15 mos. (1–76); med WBC 30X109/L (4–151); med monocyte count 18X109/L (1–55); med platelet count 58X109/L (2–587); elevated fetal hemoglobin 30 (65%). RAS and PTPN11 mutations were tested in 42 cases and inhibition of prenylation in 33. R115777 was well tolerated at both dosages with the most common grade 3/4 toxicities being thrombocytopenia (40%), anemia (40%), neutropenia (15%), and diarrhea (6%). There were no deaths during the trial. The table details the responses in patients receiving one course (N=47) and 2 courses (N=38) of R115777. The 9 patients not receiving two courses were removed from study due to lack of response or progressive disease. WBC ONLY 0VERALL (WBC & organomegaly) COURSE #1 CR CR PR MR SD PD Total     200mg/m2 6 0 4 4 2 1 11     300mg/m2 18 1 17 9 4 5 36 COURSE #2     200mg/m2 6 0 6 1 2 1 10     300mg/m2 17 2 14 7 2 3 28 FTPase activity was inhibited in 13/15 cases (med 71%; range 38–91%) with similar frequency and degree of inhibition at both dosages of R115777. There was no relationship between FTPase inhibition or response and the presence of RAS/PTPN11 mutations or inhibition of prenylation in an HJ2 assay. In conclusion, R115777 provides an overall CR/PR rate of 58% with no significant differences between the two dosages (p=0.7). This agent should be considered in the future management of JMML.

scholarly journals β common receptor inactivation attenuates myeloproliferative disease in Nf1 mutant mice

Blood ◽  
2006 ◽  
Vol 109 (4) ◽  
pp. 1687-1691 ◽  
Author(s):  
Andrew Kim ◽  
Kelly Morgan ◽  
Diane E. Hasz ◽  
Stephen M. Wiesner ◽  
Jennifer O. Lauchle ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Cells ◽  
Neurofibromatosis Type ◽  
Therapeutic Benefit ◽  
Juvenile Myelomonocytic Leukemia ◽  
Myeloproliferative Disease ◽  
Hematopoietic Stem ◽  
Gm Csf ◽  
Common Receptor ◽  
Receptor Inactivation

Abstract Neurofibromatosis type 1 (NF1) syndrome is caused by germline mutations in the NF1 tumor suppressor, which encodes neurofibromin, a GTPase activating protein for Ras. Children with NF1 are predisposed to juvenile myelomonocytic leukemia (JMML) and lethally irradiated mice given transplants with homozygous Nf1 mutant (Nf1−/−) hematopoietic stem cells develop a fatal myeloproliferative disorder (MPD) that models JMML. We investigated the requirement for signaling through the GM-CSF receptor to initiate and sustain this MPD by generating Nf1 mutant hematopoietic cells lacking the common β chain (Beta c) of the GM-CSF receptor. Mice reconstituted with Nf1−/−, beta c−/− stem cells did not develop evidence of MPD despite the presence of increased number of immature hematopoietic progenitors in the bone marrow. Interestingly, when the Mx1-Cre transgene was used to inactivate a conditional Nf1 mutant allele in hematopoietic cells, concomitant loss of beta c−/−reduced the severity of the MPD, but did not abrogate it. Whereas inhibiting GM-CSF signaling may be of therapeutic benefit in JMML, our data also demonstrate aberrant proliferation of Nf1−/−myeloid progenitors that is independent of signaling through the GM-CSF receptor.

scholarly journals Mechanisms that regulate the cell cycle status of very primitive hematopoietic cells in long-term human marrow cultures. II. Analysis of positive and negative regulators produced by stromal cells within the adherent layer

Blood ◽  
1991 ◽  
Vol 78 (1) ◽  
pp. 110-117 ◽  
Author(s):  
CJ Eaves ◽  
JD Cashman ◽  
RJ Kay ◽  
GJ Dougherty ◽  
T Otsuka ◽  
...  
Keyword(s):  
Growth Factor ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Transforming Growth Factor ◽  
Hematopoietic Cells ◽  
Dominant Negative ◽  
Mrna Levels ◽  
Tgf Beta ◽  
Gm Csf

Numerous factors that can influence the proliferation and differentiation in vitro of cells at various stages of hematopoiesis have been identified, but the mechanisms used by stromal cells to regulate the cycling status of the most primitive human hematopoietic cells are still poorly understood. Previous studies of long-term cultures (LTC) of human marrow have suggested that cytokine-induced variations in stromal cell production of one or more stimulators and inhibitors of hematopoiesis may be important. To identify the specific regulators involved, we performed Northern analyses on RNA extracted from human marrow LTC adherent layers, or stromal cell types derived from or related to those present in the adherent layer. These analyses showed marked increases in interleukin-1 beta (IL-1 beta), IL-6, and granulocyte colony-stimulating factor (G-CSF) mRNA levels within 8 hours after treatments that lead to the activation within 2 days of primitive hematopoietic progenitors in such cultures. Increases in granulocyte-macrophage (GM)-CSF and M-CSF mRNA were also sometimes seen. Bioassays using cell lines responsive to G-CSF, GM-CSF, and IL-6 showed significant elevation in growth factor levels 24 hours after IL- 1 beta stimulation. Neither IL-3 nor IL-4 mRNA was detectable at any time. In contrast, transforming growth factor-beta (TGF-beta) mRNA and nanogram levels of TGF-beta bioactivity in the medium were detected at all times in established LTC, and these levels were not consistently altered by any of the manipulations that stimulated hematopoietic growth factor production and primitive progenitor cycling. We also found that addition of anti-TGF-beta antibody could prolong or reactivate primitive progenitor proliferation when added to previously stimulated or quiescent cultures, respectively. Together, these results indicate a dominant negative regulatory role of endogenously produced TGF-beta in unperturbed LTC, with activation of primitive hematopoietic cells being achieved by mechanisms that stimulate stromal cells to produce G-CSF, GM-CSF, and IL-6. Given the similarities between the LTC system and the marrow microenvironment, it seems likely that the control of human stem cell activation in vivo may involve similar variations in the production of these factors by stromal cells.

Sign in / Sign up

Export Citation Format

Share Document