Lineage-specific hematopoietic growth factors

A glycosylated recombinant human granulocyte colony stimulating factor produced in a novel protein production system (AVI-014) in healthy subjects: a first-in human, single dose, controlled study

Background

AVI-014 is an egg white-derived, recombinant, human granulocyte colony-stimulating factor (G-CSF). This healthy volunteer study is the first human investigation of AVI-014.

Methods

24 male and female subjects received a single subcutaneous injection of AVI-014 at 4 or 8 mcg/kg. 16 control subjects received 4 or 8 mcg/kg of filgrastim (Neupogen, Amgen) in a partially blinded, parallel fashion.

Results

The Geometric Mean Ratio (GMR) (90% CI) of 4 mcg/kg AVI-014/filgrastim AUC(0–72 hr) was 1.00 (0.76, 1.31) and Cmax was 0.86 (0.66, 1.13). At the 8 mcg/kg dose, the AUC(0–72) GMR was 0.89 (0.69, 1.14) and Cmax was 0.76 (0.58, 0.98). A priori pharmacokinetic bioequivalence was defined as the 90% CI of the GMR bounded by 0.8–1.25. Both the white blood cell and absolute neutrophil count area under the % increase curve AUC(0–9 days) and Cmax (maximal % increase from baseline)GMR at 4 and 8 mcg/kg fell within the 0.5–2.0 a priori bound set for pharmacodynamic bioequivalence. The CD 34+ % increase curve AUC(0–9 days) and Cmax GMR for both doses was ~1, but 90% confidence intervals were large due to inherent variance, and this measure did not meet pharmacodynamic bioequivalence. AVI-014 demonstrated a side effect profile similar to that of filgrastim.

Conclusion

AVI-014 has safety, pharmacokinetic, and pharmacodynamic properties comparable to filgrastim at an equal dose in healthy volunteers. These findings support further investigation in AVI-014.

Endothelial progenitor cell infusion induces hematopoietic stem cell reconstitution in vivo

Hematopoietic stem cells (HSCs) reside in association with bone marrow (BM) sinusoidal vessels in vivo, but the function of BM endothelial cells (ECs) in regulating hematopoiesis is unclear. We hypothesized that hematopoietic regeneration following injury is regulated by BM ECs. BALB/c mice were treated with total body irradiation (TBI) and then infused with C57Bl6-derived endothelial progenitor cells (EPCs) to augment endogenous BM EC activity. TBI caused pronounced disruption of the BM vasculature, BM hypocellularity, ablation of HSCs, and pancytopenia in control mice, whereas irradiated, EPC-treated mice displayed accelerated recovery of BM sinusoidal vessels, BM cellularity, peripheral blood white blood cells (WBCs), neutrophils, and platelets, and a 4.4-fold increase in BM HSCs. Systemic administration of anti-VE-cadherin antibody significantly delayed hematologic recovery in both EPC-treated mice and irradiated, non-EPC-treated mice compared with irradiated controls. These data demonstrate that allogeneic EPC infusions can augment hematopoiesis and suggest a relationship between BM microvascular recovery and hematopoietic reconstitution in vivo.

Bone marrow aspirate and biopsy: a pathologist's perspective. II. interpretation of the bone marrow aspirate and biopsy

Bone marrow examination has become increasingly important for the diagnosis and treatment of hematologic and other illnesses. Morphologic evaluation of the bone marrow aspirate and biopsy has recently been supplemented by increasingly sophisticated ancillary assays, including immunocytochemistry, cytogenetic analysis, flow cytometry, and molecular assays. With our rapidly expanding knowledge of the clinical and biologic diversity of leukemia and other hematologic neoplasms, and an increasing variety of therapeutic options, the bone marrow examination has became more critical for therapeutic monitoring and planning optimal therapy. Sensitive molecular techniques, in vitro drug sensitivity testing, and a number of other special assays are available to provide valuable data to assist these endeavors. Fortunately, improvements in bone marrow aspirate and needle technology has made the procurement of adequate specimens more reliable and efficient, while the use of conscious sedation has improved patient comfort. The procurement of bone marrow specimens was reviewed in the first part of this series. This paper specifically addresses the diagnostic interpretation of bone marrow specimens and the use of ancillary techniques.

Zinc transporters ZnT1 (Slc30a1), Zip8 (Slc39a8), and Zip10 (Slc39a10) in mouse red blood cells are differentially regulated during erythroid development and by dietary zinc deficiency

Zinc is essential for normal erythroid cell functions and therefore intracellular zinc homeostasis during erythroid differentiation is tightly regulated. However, a characterization of zinc transporters in erythrocytes has not been conducted. The membrane fraction of mature mouse RBC was screened for zinc transporter expression using western analysis as a first step in the characterization process. ZnT1, Zip8, and Zip10 were detected among the 12 transporter proteins tested. We examined expression of these zinc transporters during erythropoietin (EPO)-induced differentiation of splenic erythroid progenitor cells into reticulocytes. Both Zip8 and Zip10 mRNA increased by 2-6 h after addition of EPO to the cells. In contrast, maximal RNA levels for the zinc transporter ZnT1 and erythroid delta-aminolevulinic acid synthase were only produced by 24 h after EPO. We confirmed these changes in transcript abundance by western analysis. Dietary zinc status influences zinc-dependent functions of RBC. To determine whether the identified zinc transporters respond to dietary zinc status, mice were fed a zinc-deficient or control diet. Incorporation of (65)Zn into erythrocytes in vitro was significantly increased in cells from the zinc-deficient mice. Western analysis and densitometry revealed that erythrocyte Zip10 was upregulated and ZnT1 was downregulated in the zinc-depleted mice. Zip8 was not affected by restricted zinc intake. Collectively, these data suggest that the zinc transporters ZnT1, Zip8, and Zip10 are important for zinc homeostasis in erythrocytes and that ZnT1 and Zip10 respond to the dietary zinc supply.

Hemoglobin research and the origins of molecular medicine

Much of our understanding of human physiology, and of many aspects of pathology, has its antecedents in laboratory and clinical studies of hemoglobin. Over the last century, knowledge of the genetics, functions, and diseases of the hemoglobin proteins has been refined to the molecular level by analyses of their crystallographic structures and by cloning and sequencing of their genes and surrounding DNA. In the last few decades, research has opened up new paradigms for hemoglobin related to processes such as its role in the transport of nitric oxide and the complex developmental control of the alpha-like and beta-like globin gene clusters. It is noteworthy that this recent work has had implications for understanding and treating the prevalent diseases of hemoglobin, especially the use of hydroxyurea to elevate fetal hemoglobin in sickle cell disease. It is likely that current research will also have significant clinical implications, as well as lessons for other aspects of molecular medicine, the origin of which can be largely traced to this research tradition.

The determinants of granulocyte yield in 1198 granulocyte concentrates collected from unrelated volunteer donors mobilized with dexamethasone and granulocyte-colony-stimulating factor: a 13-year experience

BACKGROUND

The combination of granulocyte-colony-stimulating factor (G-CSF [filgrastim]) and dexamethasone (G-CSF/dex) is an effective granulocyte mobilization regimen, but the variables that affect donor neutrophil response and granulocyte collection yield are not well characterized.

STUDY DESIGN AND METHODS

A computerized database containing records of 1198 granulocyte collections from 137 unrelated volunteer apheresis donors during a 13-year period was retrospectively analyzed. Donors were categorized by age, sex, and cumulative number of granulocyte donations. Complete blood counts at baseline and after G-CSF/dex stimulation were recorded. The outcome variables include the preprocedure absolute neutrophil count (preANC), which reflects G-CSF/dex stimulation, and the granulocyte product yield per liter processed (BagGranYield/L).

RESULTS

Higher baseline ANC and platelet (PLT) counts were significantly associated with higher preANC while a larger number of prior granulocytapheresis procedures was associated with lower preANC. Total filgrastim dose (used in weight-based dosing) did not significantly impact preANC or the granulocyte yield; weight-based dosing at 5 microg per kg and a uniform 480-microg dose produced equivalent preANC. PreANC and weight were the key determinants of granulocyte yield (BagGranYield/L).

CONCLUSION

Apheresis donors with higher baseline PLT counts and ANCs have higher ANCs after G-CSF/dex stimulation; donor age, weight, and sex do not have a significant impact. A uniform G-CSF dose of 480 microg is as effective as weight-based dosing at 5 microg per kg. Donor ANC monitoring should be considered after serial granulocytapheresis procedures.

Tumor-vascular interactions and tumor dormancy

Tumor progression is dependent on a number of sequential steps, including initial tumor-vascular interactions and recruitment of blood vessels (i.e., the angiogenic switch), as well as tumor cells interacting with the surrounding microenvironment and its different components. Failure of a microscopic tumor to complete one or more of these early stages may lead to delayed clinical manifestation of the cancer and a state of stable non-progressing disease (i.e., tumor dormancy). In this review, some of the clinical and experimental evidence is summarized, suggesting that microscopic human cancers, either primary, recurrent or metastatic, can remain in an asymptomatic, non-detectable, and occult state for a long period of time. We also review current experimental human tumor dormancy models which closely recapitulate clinically observed delay in tumor progress.

Miscreant myeloproliferative disorder stem cells

Myeloproliferative disorders (MPDs), typified by robust marrow and extramedullary hematopoiesis, have a propensity to progress to acute leukemia. Although the hematopoietic stem cell (HSC) origin of MPDs was suggested over 30 years ago, only recently the HSC-specific effects of MPD molecular mutations have been investigated. The pivotal role of BCR-ABL in chronic myeloid leukemia (CML) development provided the rationale for targeted therapy, which greatly reduced mortality rates. However, BCR-ABL inhibitor-resistant CML HSCs persist that may be a reservoir for relapse. This has provided the impetus for investigating molecular mechanisms governing the production of recalcitrant HSC. Comparatively little was known about the molecular events driving BCR-ABL-negative MPDs until seminal studies revealed that a large proportion of MPD patients harbor a JAK2-activating point mutation, JAK2V617F. Although JAK2 activation appears to be central to BCR-ABL-negative MPD pathogenesis, its effects may be cell type and context specific. Recent evidence suggests that acquired mutations misdirect differentiation and survival of the MPD-initiating stem cell resulting in the production of aberrant self-renewing progenitors that subvert the microenvironment leading to leukemia stem cell generation and leukemic transformation. Thus, combined therapies targeting aberrant molecular pathways may be required to redirect miscreant MPD stem cells.

Molecular drug targets in myeloproliferative neoplasms: mutant ABL1, JAK2, MPL, KIT, PDGFRA, PDGFRB and FGFR1

Therapeutically validated oncoproteins in myeloproliferative neoplasms (MPN) include BCR-ABL1 and rearranged PDGFR proteins. The latter are products of intra- (e.g. FIP1L1-PDGFRA) or inter-chromosomal (e.g.ETV6-PDGFRB) gene fusions. BCR-ABL1 is associated with chronic myelogenous leukaemia (CML) and mutant PDGFR with an MPN phenotype characterized by eosinophilia and in addition, in case of FIP1L1-PDGFRA, bone marrow mastocytosis. These genotype-phenotype associations have been effectively exploited in the development of highly accurate diagnostic assays and molecular targeted therapy. It is hoped that the same will happen in other MPN with specific genetic alterations: polycythemia vera (JAK2V617F and other JAK2 mutations), essential thrombocythemia (JAK2V617F and MPL515 mutations), primary myelofibrosis (JAK2V617F and MPL515 mutations), systemic mastocytosis (KITD816V and other KIT mutations) and stem cell leukaemia/lymphoma (ZNF198-FGFR1 and other FGFR1 fusion genes). The current review discusses the above-listed mutant molecules in the context of their value as drug targets.

Effects of sepsis on neonatal thrombopoiesis

We serially evaluated the effects of sepsis and/or necrotizing enterocolitis (NEC) on neonatal thrombopoiesis, using a panel of tests that included platelet counts, thrombopoietin concentrations (Tpo), circulating megakaryocyte progenitor concentrations (CMPs), and reticulated platelets (RPs). Variables analyzed included sepsis type, time after onset of sepsis, platelet counts, and gestational (GA) and postconceptional ages (PCA). Twenty neonates were enrolled. Ten had Gram-negative, six had Gram-positive, and four had presumed sepsis. Four neonates had NEC stage II or higher, and six developed thrombocytopenia. Overall, septic neonates had significantly elevated Tpo concentrations and circulating megakaryocyte progenitors. The highest Tpo levels were associated with Gram-negative or presumed sepsis. RP percentages were increased only in neonates with low platelet counts, while RP counts (RP% x platelet count) were elevated in neonates with high platelet counts. Our findings suggest that septic neonates up-regulate Tpo production, leading to increased megakaryocytopoiesis and platelet release, although the degree of upregulation is moderate. The changes in RP% and RP count most likely reflect increased thrombopoiesis with variable degrees of platelet consumption. In addition, our findings suggest that different factors, likely including level of illness and/or specific platelet or bacterial products, can down-regulate the magnitude of the thrombopoietic response.

Hematopoietic progenitor cells and interleukin-stimulated endothelium: expansion and differentiation of myeloid precursors

BACKGROUND

Cytokine-stimulated endothelial cells (EC) propagate hematopoietic progenitor cell (HPC) expansion. However, the effects on the functional capacities of cultured progenitors have not been evaluated. HPC were assessed by flow cytometry, colony and cobblestone assays and long-term cultures (LTC) after culturing in the supernatant of EC stimulated by IL-1beta, IL-3 or IL-6.

RESULTS

EC incubation with IL-6 did not improve cell expansion in comparison to non-stimulated EC supernatant, while the HPCs' phenotype and functional capacities were retained. In contrast, IL-1beta and IL-3 stimulation resulted in a 10- and 100-fold increase in cell numbers with more than 90% of these cells being CD33(+). Plating efficiencies and LTC initiating cells were greatest in IL-6 supernatants, whereas the highest numbers of burst-forming units were observed using IL-3. IL-1beta supernatants diminished the number of 5-week cobblestone-areas, whereas the number of 2-week cobblestone areas remained equal to freshly isolated HPC. Fewer 2-week cobblestones and greater amounts of 5-week cobblestones were observed with IL-6 and IL-3. Expanded progenitors from all interleukin conditions were further matured into functional granulocytes.

CONCLUSION

IL-1beta and IL-3 stimulated endothelium induces proliferation and differentiation of myeloid precursors, while IL-6 treatment induced a benefit of HPC survival.

EPO in combination with G-CSF improves mobilization effectiveness after chemotherapy with ifosfamide, epirubicin and etoposide and reduces costs during mobilization and transplantation of autologous hematopoietic progenitor cells

A successful stem cell harvest is a prerequisite for peripheral blood SCT. We investigated the number of CD34(+) cells mobilized, the number of leukaphereses needed and the expenses of treatment for 28 patients with multiple myeloma randomly assigned to receive either G-CSF alone or G-CSF+EPO for stem cell mobilization after chemotherapy with ifosfamide, epirubicin and etoposide. All patients treated with G-CSF+EPO reached the threshold of 6 x 10(6) CD34(+) cells per kg body weight (kgbw), with a mean of 1.3 leukaphereses. On average 15.4 x 10(6) CD34(+) cells/kgbw were collected. In the G-CSF-alone group, the mean number of leukaphereses was 1.8, and 12.6 x 10(6) CD34(+) cells/kgbw were collected, and two patients failed the threshold. Overall costs per patient for mobilization and leukaphereses were 8339 euro (G-CSF+EPO) and 8842 euro (G-CSF). After transplantation, fewer blood transfusions (0.6 versus 1.3, P=0.05), fewer days on antibiotics (2.3 versus 6.1, P=0.02) and a shorter hospital stay (15.2 versus 17.8, P=0.06) were noted in the G-CSF+EPO group resulting in a 19.2% reduction of costs for each transplant (P=0.018). In summary, EPO improves the mobilization efficiency of G-CSF and so reduces costs of mobilization and SCT.

Incomplete restoration of Mpl expression in the mpl-/- mouse produces partial correction of the stem cell-repopulating defect and paradoxical thrombocytosis

Expression of Mpl is restricted to hematopoietic cells in the megakaryocyte lineage and to undifferentiated progenitors, where it initiates critical cell survival and proliferation signals after stimulation by its ligand, thrombopoietin (TPO). As a result, a deficiency in Mpl function in patients with congenital amegakaryocytic thrombocytopenia (CAMT) and in mpl(-/-) mice produces profound thrombocytopenia and a severe stem cell-repopulating defect. Gene therapy has the potential to correct the hematopoietic defects of CAMT by ectopic gene expression that restores normal Mpl receptor activity. We rescued the mpl(-/-) mouse with a transgenic vector expressing mpl from the promoter elements of the 2-kb region of DNA just proximal to the natural gene start site. Transgene rescued mice exhibit thrombocytosis but only partial correction of the stem cell defect. Furthermore, they show very low-level expression of Mpl on platelets and megakaryocytes, and the transgene-rescued megakaryocytes exhibit diminished TPO-dependent kinase phosphorylation and reduced platelet production in bone marrow chimeras. Thrombocytosis is an unexpected consequence of reduced Mpl expression and activity. However, impaired TPO homeostasis in the transgene-rescued mice produces elevated plasma TPO levels, which serves as an unchecked stimulus to drive the observed excessive megakaryocytopoiesis.

Effects of aerobic exercise training in anemic cancer patients receiving darbepoetin alfa: a randomized controlled trial

BACKGROUND

Anemia in patients with solid tumors is a common problem that is associated with impaired exercise capacity, increased fatigue, and lower quality of life (QoL). Erythropoiesis-stimulating agents (ESAs) have been shown to improve these outcomes; however, it is unknown if additional benefits can be achieved with aerobic exercise training.

METHODS

We conducted a single-center, prospective, randomized, controlled trial in 55 mild-to-moderately anemic patients with solid tumors. Patients were randomized to either darbepoetin alfa alone (DAL, n = 29) or darbepoetin alfa plus aerobic exercise training (DEX; n = 26). The DEX group performed aerobic exercise training three times per week at 60%-100% of baseline exercise capacity for 12 weeks. The primary endpoint was QoL assessed by the Functional Assessment of Cancer Therapy-Anemia scale. Secondary endpoints were fatigue, cardiorespiratory fitness (VO(2peak)), hemoglobin (Hb) response, and darbepoetin alfa dosing.

RESULTS

Intention-to-treat analyses indicated significant improvements in QoL and fatigue in both groups over time but there were no between-group differences. The DEX group had a significantly greater VO(2peak) than the DAL group (mean group difference, +3.0 ml/kg per minute; 95% confidence interval, 1.2-4.7; p = .001) and there were borderline significant differences in favor of the DEX group for Hb response and darbepoetin alfa dosing.

CONCLUSIONS

Aerobic exercise training did not improve QoL or fatigue beyond the established benefits of DAL but it did result in favorable improvements in exercise capacity and a more rapid Hb response with lower dosing requirements. Our results may be useful to clinicians despite the more recent restrictions on the indications for ESAs.

Delineating the cellular pathways of hematopoietic lineage commitment

The prevailing model for adult hematopoiesis postulates that the first lineage commitment step results in a strict separation of common myeloid and common lymphoid pathways. However, the recent identification of granulocyte/monocyte (GM)-lymphoid restricted lymphoid-primed multipotent progenitors (LMPPs) and primitive common myeloid progenitors (CMPs) within the "HSC" compartment provide compelling support for establishment of independent GM-megakaryocyte/erythroid (GM-MkE) and GM-lymphoid commitment pathways as decisive early lineage fate decisions. These changes in lineage potentials are corroborated by corresponding changes in multilineage transcriptional priming, as LMPPs down-regulate MkE priming but become GM-lymphoid transcriptionally primed, whereas CMPs are GM-MkE primed. These distinct biological and molecular relationships are established already in the fetal liver.

MicroRNAs, the immune system and rheumatic disease

MicroRNAs (miRNAs) are short noncoding RNA molecules that modulate the expression of multiple target genes at the post-transcriptional level and are implicated in a wide array of cellular and developmental processes. In hematopoietic cells, miRNA levels are dynamically regulated during lineage differentiation and also during the course of the immune response. Mouse models have provided good evidence for miRNAs being key players in the establishment of hematopoietic lineages. Furthermore, miRNA-dependent alterations in gene expression in hematopoietic cells are critical for mounting an appropriate immune response to a wide range of pathogens, spontaneously emerging tumors, and autoimmune cells. Deregulation of hematopoietic-specific miRNA expression results in defects in both central and peripheral tolerance, hematopoietic malignancies, and sometimes both. Abnormal expression of miRNAs-which is implicated in inflammation-has also been found in patients with rheumatoid arthritis. These findings identify miRNAs as critical targets for immunomodulatory drug development.

WP1066, a novel JAK2 inhibitor, suppresses proliferation and induces apoptosis in erythroid human cells carrying the JAK2 V617F mutation

PURPOSE

The discovery of an activating somatic mutation in codon 617 of the gene encoding the Janus kinase (JAK)-2 (JAK2 V617F) in patients with myeloproliferative disorders has opened new avenues for the development of targeted therapies for these malignancies. However, no effective JAK2 inhibitors are currently available for clinical use.

EXPERIMENTAL DESIGN

We investigated the activity of (E)-3(6-bromopyridin-2-yl)-2-cyano-N-(S0-1phenylethyl)acrylamide (WP1066), a novel analogue of the JAK2 inhibitor AG490, in JAK2 V617F-positive erythroleukemia HEL cells and in blood cells from patients with polycythemia vera.

RESULTS

We found that WP1066 significantly inhibited JAK2 and its downstream signal transducer and activator of transcription-3, signal transducer and activator of transcription-5, and extracellular signal-regulated kinase-1/2 pathways in a dose- and time-dependent manner. As a result, WP1066 concentrations in the low micromolar range induced time- and dose-dependent antiproliferative and proapoptotic effects in HEL cells. As expected, WP1066 inhibited the proliferation of peripheral blood hematopoietic progenitors of patients with polycythemia vera carrying the JAK2 V617F mutation in a dose-dependent manner.

CONCLUSIONS

Our data suggest that WP1066 is active both in vitro and ex vivo and should be further developed for the treatment of neoplasms expressing the JAK2 V617F mutation.

Repairing the human brain after stroke. II. Restorative therapies

Spontaneous behavioral recovery is usually limited after stroke, making stroke a leading source of disability. A number of therapies in development aim to improve patient outcomes not by acutely salvaging threatened tissue, but instead by promoting repair and restoration of function in the subacute or chronic phase after stroke. Examples include small molecules, growth factors, cell-based therapies, electromagnetic stimulation, device-based strategies, and task-oriented and repetitive training-based interventions. Stage of development across therapies varies widely, from preclinical to late-phase clinical trials. The optimal methods to prescribe such therapies require further studies, for example, to best identify appropriate patients or to guide features of dosing. Likely, anatomic, functional, and behavioral measures of brain state, as well as measures of injury, will each be useful in this regard. Considerations for clinical trials of restorative therapies are provided, emphasizing both similarities and points of divergence with acute stroke clinical trial design.

Myelophil, a mixture of Astragali Radix and Salviae Radix extract, moderates toxic side effects of fluorouracil in mice

AIM

To evaluate the efficacy of Myelophil, an extract containing Astragali Radix and Salviae Radix, for reducing complications induced by 5-fluorouracil (5-FU) in a gastrointestinal cancer model.

METHODS

We injected 5-FU into mice and then administered Myelophil to examine the ability of the drug to treat the side effects of 5-FU in mice. Peripheral blood counts, histological examinations, and colony-forming assays of bone marrow were conducted, followed by swimming tests and assessment of survival times.

RESULTS

Myelophil restored red and white blood cells and platelets in blood, and recovered cell density in bone marrow to levels comparable to those observed within the control group. In addition, Myelophil significantly increased colony-forming unit granulocyte-macrophage (CFU-GM) and CFU-erythroid (CFU-E) compared to the control group. We confirmed that interleukin-3 gene expression was upregulated by Myelophil in spleen cells. Myelophil administration also doubled the survival rate of mice that were severely myelosuppressed as a result of 5-FU injection at a lethal dose of 70%. Finally, the swimming performance of mice significantly improved as a result of Myelophil treatment.

CONCLUSION

These results provide experimental evidence in support of clinical applications of Myelophil to minimize 5-FU-induced myelosuppression and improve general post-chemotherapy health.

Morphological and functional platelet abnormalities in Berkeley sickle cell mice

Berkeley sickle cell mice are used as animal models of human sickle cell disease but there are no reports of platelet studies in this model. Since humans with sickle cell disease have platelet abnormalities, we studied platelet morphology and function in Berkeley mice (SS). We observed elevated mean platelet forward angle light scatter (FSC) values (an indirect measure of platelet volume) in SS compared to wild type (WT) (37+/-3.2 vs. 27+/-1.4, mean+/-SD; p<0.001), in association with moderate thrombocytopenia (505+/-49 x 10(3)/microl vs. 1151+/-162 x 10(3)/microl; p<0.001). Despite having marked splenomegaly, SS mice had elevated levels of Howell-Jolly bodies and "pocked" erythrocytes (p<0.001 for both) suggesting splenic dysfunction. SS mice also had elevated numbers of thiazole orange positive platelets (5+/-1% vs. 1+/-1%; p<0.001), normal to low plasma thrombopoietin levels, normal plasma glycocalicin levels, normal levels of platelet recovery, and near normal platelet life spans. Platelets from SS mice bound more fibrinogen and antibody to P-selectin following activation with a threshold concentration of a protease activated receptor (PAR)-4 peptide compared to WT mice. Enlarged platelets are associated with a predisposition to arterial thrombosis in humans and some humans with SCD have been reported to have large platelets. Thus, additional studies are needed to assess whether large platelets contribute either to pulmonary hypertension or the large vessel arterial occlusion that produces stroke in some children with sickle cell disease.

JAK and MPL mutations in myeloid malignancies

The Janus family of non-receptor tyrosine kinases (JAK1, JAK2, JAK3 and tyrosine kinase 2) transduces signals downstream of type I and II cytokine receptors via signal transducers and activators of transcription (STATs). JAK3 is important in lymphoid and JAK2 in myeloid cell proliferation and differentiation. The thrombopoietin receptor MPL is one of several JAK2 cognate receptors and is essential for myelopoiesis in general and megakaryopoiesis in particular. Germline loss-of-function (LOF) JAK3 and MPL mutations cause severe combined immunodeficiency and congenital amegakaryocytic thrombocytopenia, respectively. Germline gain-of-function (GOF) MPL mutation (MPLS505N) causes familial thrombocytosis. Somatic JAK3 (e.g. JAK3A572V, JAK3V722I, JAK3P132T) and fusion JAK2 (e.g. ETV6-JAK2, PCM1-JAK2, BCR-JAK2) mutations have respectively been described in acute megakaryocytic leukemia and acute leukemia/chronic myeloid malignancies. However, current attention is focused on JAK2 (e.g. JAK2V617F, JAK2 exon 12 mutations) and MPL (e.g. MPLW515L/K/S, MPLS505N) mutations associated with myeloproliferative neoplasms (MPNs). A JAK2 mutation, primarily JAK2V617F, is invariably associated with polycythemia vera (PV). The latter mutation also occurs in the majority of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF). MPL mutational frequency in MPNs is substantially less (<10%). In general, despite a certain degree of genotype - phenotype correlations, the prognostic relevance of harbouring one of these mutations, or their allele burden when present, remains dubious. Regardless, based on the logical assumption that amplified JAK-STAT signalling is central to the pathogenesis of PV, ET and PMF, several anti-JAK2 tyrosine kinase inhibitors have been developed and are currently being tested in humans with these disorders.

In vivo isolation and characterization of stem cells with diverse phenotypes using growth factor impregnated biomatrices

Background

The stimulation to differentiate into specific cell types for somatic stem cells is largely due to a series of internal and external signals coming from the microenvironment that surrounds the stem cell. Even though intensive research has been made, the basic mechanisms of plasticity and/or the molecules regulating stem cells proliferation and differentiation are not completely determined. Potential answers concerning the problems could be derived from the studies of stem cells in culture.

Methodology/Principle Findings

We combine a new procedure (using the matrigel biopolymer supplemented with a selected cytokine/growth factor) with classic techniques such as light, confocal and electron microscopy, immunohistochemistry and cell culture, to perform an analysis on stem cells involved in the leech (Hirudo medicinalis) repair tissues. The leech has a relative anatomical simplicity and is a reliable model for studying a variety of basic events, such as tissue repair, which has a striking similarity with vertebrate responses. Our data demonstrate that the injection of an appropriate combination of the matrigel biopolymer supplemented with a selected cytokine/growth factor in the leech Hirudo medicinalis is a remarkably effective tool for isolating a specific cell population in vivo. A comparative analysis of biopolymer in vivo sorted stem cells indicates that VEGF recruited cells of a hematopoietic/endothelial phenotype whereas MCP-1/CCL2 isolated cells that were of an early myeloid lineage.

Conclusion

Our paper describes, for the first time, a method allowing not only the isolation of a specific cell population in relation to the cytokine utilized but also the possibility to culture a precise cell type whose isolation is otherwise quite difficult. This approach could be broadly applied to isolate stem cells of diverse origins based on the recruitment stimuli employed.

Down-regulation of Mpl marks the transition to lymphoid-primed multipotent progenitors with gradual loss of granulocyte-monocyte potential

Evidence for a novel route of adult hematopoietic stem-cell lineage commitment through Lin-Sca-1+Kit+Flt3hi (LSKFlt3hi) lymphoid-primed multipotent progenitors (LMPPs) with granulocyte/monocyte (GM) and lymphoid but little or no megakaryocyte/erythroid (MkE) potential was recently challenged, as LSKFlt3hi cells were reported to possess MkE potential. Herein, residual (1%-2%) MkE potential segregated almost entirely with LSKFlt3hi cells expressing the thrombopoietin receptor (Mpl), whereas LSKFlt3hiMpl- LMPPs lacked significant MkE potential in vitro and in vivo, but sustained combined GM and lymphoid potentials, and coexpressed GM and lymphoid but not MkE transcriptional lineage programs. Gradually increased transcriptional lymphoid priming in single LMPPs from Rag1GFP mice was shown to occur in the presence of maintained GM lineage priming, but gradually reduced GM lineage potential. These functional and molecular findings reinforce the existence of GM/lymphoid-restricted progenitors with dramatically down-regulated probability for committing toward MkE fates, and support that lineage restriction occurs through gradual rather than abrupt changes in specific lineage potentials.

Severe thrombocytosis and anemia associated with celiac disease in a young female patient: a case report

INTRODUCTION

Platelet counts exceeding 1.000 x 103/microl are usually considered secondary to another cause, particularly to chronic myeloproliferative disease (CMPD). Reactive thrombocytosis due to iron deficiency rarely exceeds platelet counts of 700 x 103/microl.

CASE PRESENTATION

Here we report the case of a young woman presenting with clinical signs of severe anemia. Laboratory findings confirmed an iron-deficiency anemia associated with severe thrombocytosis of 1703 x 103/microl. Macroscopic gastrointestinal and genitourinary tract bleeding was excluded. The excessive elevation of platelets, slightly elevated lactate dehydrogenase and slightly elevated leukocytes along with the absence of other inflammation parameters raised the suspicion of an underlying hematological disease. However, bone marrow evaluation could not prove the suspected diagnosis of a CMPD, especially essential thrombocythemia (ET). In the further clinical course the platelet count returned to normal after raising the hemoglobin to a level close to normal range with erythrocyte transfusion, and normalization of serum iron and decline of erythropoietin. Finally, following small bowel biopsy, despite the absence of typical clinical signs, celiac disease was diagnosed. After discharge from hospital the patient was commenced on a gluten-free diet and her hemoglobin almost completely normalized in the further follow-up period.

CONCLUSION

This case illustrates the rare constellation of an extreme thrombocytosis most likely secondary to iron deficiency due to celiac disease. This represents, to the best of the authors' knowledge, the highest reported platelet count coincident with iron deficiency. A potential mechanism for the association of iron-deficiency anemia and thrombocytosis is discussed. Even in the presence of 'atypically' high platelets one should consider the possibility of reactive thrombocytosis. Extreme thrombocytosis could emerge in the case of iron deficiency secondary to celiac disease.

Second cancers in patients with the Ewing sarcoma family of tumours

BACKGROUND

Patients are at risk of second malignancies (SM) after treatment for Ewing sarcoma family of tumours (ESFT).

METHODS

We performed a retrospective review of 237 patients with ESFT treated at our institution from September 1979 through to February 2004. Cumulative incidence (CI) of SM by the type of malignancy and treatment was estimated.

RESULTS

Twelve patients with SM were identified. Secondary leukaemia (SL) developed in 8 patients (2 ALL, 6 MDS/AML), a median 2.6 years (range 1.4-19.6 years) after diagnosis of ESFT. Four patients had secondary solid tumours, a median 8.0 years (range 7.4-9.4 years) after the ESFT diagnosis. Five- and 10-year estimates of the CI of SM were 3.0+/-1.1% and 4.7+/-1.5%, respectively. Patients treated on recent protocols with higher cumulative doses or an increased dose intensity of alkylators and epipodophyllotoxins and the use of G-CSF had a higher estimated CI of SL than those in earlier studies (5-year CI 6.4+/-2.4% versus 0.0+/-0.0%, respectively, P=0.004).

CONCLUSIONS

Patients with ESFT are at risk for SM after treatment. The cumulative incidence of SM is higher with the current treatment protocols and may be related to the intensification of chemotherapeutic agents.

Clinical implications of JAK2 mutations in myeloproliferative disorders

The V617F mutation of JAK2 is the key molecular event in 90% of polycythaemia vera (PV), 50% of essential thrombocythaemia (ET) and 50% of primary myelofibrosis (PMF). JAK2 exon 12 and MPLW515 mutations are less frequent. Because JAK2 V617F is specific for myeloid neoplasms, and because it can be detected in peripheral blood granulocytes, it offers a powerful tool that facilitates the diagnosis of these BCR-ABL negative myeloproLiferative disorders. These discoveries provide the rationale for a revision of the current WHO diagnostic criteria for PV, ET and PMF and could ultimately lead to the development of a specific targeted therapy.

TRPC3 is the erythropoietin-regulated calcium channel in human erythroid cells

Erythropoietin (Epo) stimulates a significant increase in the intracellular calcium concentration ([Ca(2+)](i)) through activation of the murine transient receptor potential channel TRPC2, but TRPC2 is a pseudogene in humans. TRPC3 expression increases on normal human erythroid progenitors during differentiation. Here, we determined that erythropoietin regulates calcium influx through TRPC3. Epo stimulation of HEK 293T cells transfected with Epo receptor and TRPC3 resulted in a dose-dependent increase in [Ca(2+)](i), which required extracellular calcium influx. Treatment with the phospholipase C (PLC) inhibitor U-73122 or down-regulation of PLCgamma1 by RNA interference inhibited the Epo-stimulated increase in [Ca(2+)](i) in TRPC3-transfected HEK 293T cells and in primary human erythroid precursors, demonstrating a requirement for PLC. TRPC3 associated with PLCgamma, and substitution of predicted PLCgamma Src homology 2 binding sites (Y226F, Y555F, Y648F, and Y674F) on TRPC3 reduced the interaction of TRPC3 with PLCgamma and inhibited the rise in [Ca(2+)](i). Substitution of Tyr(226) alone with phenylalanine significantly reduced the Epo-stimulated increase in [Ca(2+)](i) but not the association of PLCgamma with TRPC3. PLC activation results in production of inositol 1,4,5-trisphosphate (IP(3)). To determine whether IP(3) is involved in Epo activation of TRPC3, TRPC3 mutants were prepared with substitution or deletion of COOH-terminal IP(3) receptor (IP(3)R) binding domains. In cells expressing TRPC3 with mutant IP(3)R binding sites and Epo receptor, interaction of IP(3)R with TRPC3 was abolished, and Epo-modulated increase in [Ca(2+)](i) was reduced. Our data demonstrate that Epo modulates TRPC3 activation through a PLCgamma-mediated process that requires interaction of PLCgamma and IP(3)R with TRPC3. They also show that TRPC3 Tyr(226) is critical in Epo-dependent activation of TRPC3. These data demonstrate a redundancy of TRPC channel activation mechanisms by widely different agonists.

Microarray-based CGH detects chromosomal mosaicism not revealed by conventional cytogenetics

Somatic chromosomal mosaicism is a well-established cause for birth defects, mental retardation, and, in some instances, specific genetic syndromes. We have developed a clinically validated, targeted BAC clone array as a platform for comparative genomic hybridization (aCGH) to enable detection of a wide range of pathologic copy number changes in DNA. It is designed to provide high sensitivity to detect well-characterized submicroscopic micro-deletion and duplication disorders while at the same time minimizing detection of variation of uncertain clinical significance. In the course of studying 2,585 samples submitted to our clinical laboratory, chromosomal mosaicism was detected in 12 patient samples; 10 of these cases were reported to have had a normal blood chromosome analysis. This enhanced ability of aCGH to detect mosaicism missed by routine chromosome analysis may be due to some combination of testing multiple cell lineages and/or failure of cytogenetically abnormal T lymphocytes to respond to mitogens. This suggests that aCGH may detect somatic chromosomal mosaicism that would be missed by conventional cytogenetics.

Megakaryocyte and platelet biology: getting your FAKs straight

In this issue of Blood, Hitchcock and colleagues show that the nonreceptor tyrosine kinase FAK plays a critical role in regulating megakaryocyte maturation and platelet function in vivo.

Canadian supportive care recommendations for the management of neutropenia in patients with cancer

Hematologic toxicities of cancer chemotherapy are common and often limit the ability to provide treatment in a timely and dose-intensive manner. These limitations may be of utmost importance in the adjuvant and curative intent settings. Hematologic toxicities may result in febrile neutropenia, infections, fatigue, and bleeding, all of which may lead to additional complications and prolonged hospitalization. The older cancer patient and patients with significant comorbidities may be at highest risk of neutropenic complications. Colony-stimulating factors (csfs) such as filgrastim and pegfilgrastim can effectively attenuate most of the neutropenic consequences of chemotherapy, improve the ability to continue chemotherapy on the planned schedule, and minimize the risk of febrile neutropenia and infectious morbidity and mortality. The present consensus statement reviews the use of csfs in the management of neutropenia in patients with cancer and sets out specific recommendations based on published international guidelines tailored to the specifics of the Canadian practice landscape. We review existing international guidelines, the indications for primary and secondary prophylaxis, the importance of maintaining dose intensity, and the use of csfs in leukemia, stem-cell transplantation, and radiotherapy. Specific disease-related recommendations are provided related to breast cancer, non-Hodgkin lymphoma, lung cancer, and gastrointestinal cancer. Finally, csf dosing and schedules, duration of therapy, and associated acute and potential chronic toxicities are examined.

Critical role of thrombopoietin in maintaining adult quiescent hematopoietic stem cells

The role of cytokines in regulation of hematopoietic stem cells (HSCs) remains poorly understood. Herein we demonstrate that thrombopoietin (THPO) and its receptor, MPL, are critically involved in postnatal steady-state HSC maintenance, reflected in a 150-fold reduction of HSCs in adult Thpo(-/-) mice. Further, whereas THPO and MPL proved not required for fetal HSC expansion, HSC expansion posttransplantation was highly MPL and THPO dependent. The distinct role of THPO in postnatal HSC maintenance is accompanied by accelerated HSC cell-cycle kinetics in Thpo(-/-) mice and reduced expression of the cyclin-dependent kinase inhibitors p57(Kip2) and p19(INK4D) as well as multiple Hox transcription factors. Although also predicted to be an HSC viability factor, BCL2 failed to rescue the HSC deficiency of Thpo(-/-) mice. Thus, THPO regulates posttransplantation HSC expansion as well as the maintenance of adult quiescent HSCs, of critical importance to avoid postnatal HSC exhaustion.

Transcriptional control of erythropoiesis: emerging mechanisms and principles

Transcriptional networks orchestrate fundamental biological processes, including hematopoiesis, in which hematopoietic stem cells progressively differentiate into specific progenitors cells, which in turn give rise to the diverse blood cell types. Whereas transcription factors recruit coregulators to chromatin, leading to targeted chromatin modification and recruitment of the transcriptional machinery, many questions remain unanswered regarding the underlying molecular mechanisms. Furthermore, how diverse cell type-specific transcription factors function cooperatively or antagonistically in distinct cellular contexts is poorly understood, especially since genes in higher eukaryotes commonly encompass broad chromosomal regions (100 kb and more) and are littered with dispersed regulatory sequences. In this article, we describe an important set of transcription factors and coregulators that control erythropoiesis and highlight emerging transcriptional mechanisms and principles. It is not our intent to comprehensively survey all factors implicated in the transcriptional control of erythropoiesis, but rather to underscore specific mechanisms, which have potential to be broadly relevant to transcriptional control in diverse systems.

TLR agonists induce the differentiation of human bone marrow CD34+ progenitors into CD11c+ CD80/86+ DC capable of inducing a Th1-type response

We recently reported that human bone marrow hematopoietic CD34(+) progenitors express functional Toll-like receptors (TLR) and can differentiate into myeloid cells just by stimulation with resiquimod (R848), a specific agonist for TLR7/8. However, the mechanisms by which R848 induces cell differentiation, the effects of other TLR agonists and the functionality of the differentiated cells are not known. Comparable to R848, loxoribine (a TLR7 agonist) and Pam(3)CSK(4) (a TLR2 agonist) induced cytokine production and cell differentiation along the myeloid lineage. R848 and loxoribine were more effective than Pam(3)CSK(4) at inducing the lineage-negative (CD11c(+) CD14(-)) dendritic cells (DC), whereas Pam(3)CSK(4) was more effective at inducing CD11c(+) CD14(+) monocytes. Both cell subsets expressed CD80/CD86 and HLA-DR molecules; however, they showed differential expression of CD1a, CD1b, CD1c, CD11b, CD206 and CD207 markers when compared with each other. Cell differentiation into DC was significantly inhibited by an anti-TNF-alpha nonoclonal antibody. The CD11c(+) CD14(-) subset was isolated and shown to be more potent in stimulating an alloreaction than the CD11c(+) CD14(+) subset. Collectively, these data highlight the differential effects of TLR agonists on human bone marow CD34(+) progenitor cells and provide a new opportunity for generating functional DC that would be useful in cancer vaccination.

Risks and benefits of erythropoiesis-stimulating agents in cancer management

Anemia is frequently diagnosed in patients with cancer and its treatment is an important clinical problem. The deficiency in red blood cells (RBCs) can be a debilitating problem, and anemia correlates with poor performance status, deteriorates quality of life, and may negatively influence the prognosis of cancer patients. The development of recombinant human erythropoietins (rhEPO) provides a therapeutic option in patients with mild to moderate anemia. However, clinical experience demonstrates that more than half of anemic cancer patients are not treated. There is clear evidence that rhEPO reliably increases haemoglobin (Hb) levels in patients suffering from cancer-related or treatment-associated anemia. The dosing and management of these patients should strictly follow evidence-based guidelines of the clinical societies, as well as the manufacturer's recommendations. Furthermore, treatment of patients beyond the correction of anemia must be regarded as potentially harmful and should only be conducted in an experimental clinical setting. In this review, recently published recommendations and standards for the use of rhEPO will be discussed.

Current status of growth factors in the treatment of acute myeloid and lymphoblastic leukemia

The safety of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with acute leukemia has been well established in numerous clinical trials. The primary aim of these studies was to determine whether CSFs, when used as adjuncts to intensive chemotherapy, reduced the duration of neutropenia, prevented febrile neutropenia, infections, and hospitalization rates, and improved response and overall outcome in patients with acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL). Despite considerable efforts in divers clinical settings, the potential advantages of hematopoietic growth factors in the management of these leukemias remain inconclusive. In general, individual published trials have shown declines in the incidence and/or duration of neutropenia but have not consistently demonstrated a reduction in the overall frequency of infectious complications or the duration of hospitalization. Most protocols also have failed to show a benefit in terms of disease-free or overall survival. Nevertheless, improvements in "soft" clinical end points, such as incidence of severe infections, may be clinically important and contribute, even if only incrementally, to the patient's quality of life. Selection of those patients likely to benefit from growth factors in a specific clinical setting is a worthwhile endeavour.

Chronic myeloproliferative disorders: the role of tyrosine kinases in pathogenesis, diagnosis and therapy

The term chronic myeloproliferative disorders was originally used by Damashek to describe the link amongst a group of acquired blood diseases. Recent molecular genetic analysis has provided a scientific basis for this observation. Underlying myeloproliferative disorders are acquired abnormalities of tyrosine kinase genes. These may be chromosomal translocations resulting in the creation of a fusion kinase gene, examples of which include ABL, FGFR, and PDGFR as seen in disorders CML, 8p11 myeloproliferative syndrome, atypical CML and chronic eosinophilic leukaemia. The second group of tyrosine kinase abnormalities are point mutations in JAK2, a cytosolic TK. This abnormality is seen in 30-97% of cases of MPD with the phenotype PV, ET or CIMF.

Mice lacking three myeloid colony-stimulating factors (G-CSF, GM-CSF, and M-CSF) still produce macrophages and granulocytes and mount an inflammatory response in a sterile model of peritonitis

To assess the combined role of G-CSF, GM-CSF, and M-CSF in myeloid cell production, mice deficient in all three myeloid CSFs were generated (G-/-GM-/-M-/- mice). G-/-GM-/-M-/- mice share characteristics found in mice lacking individual cytokines: they are toothless and osteopetrotic and furthermore acquire alveolar proteinosis that is more severe than that found in either GM-/- or G-/-GM-/- mice. G-/-GM-/-M-/- mice have a significantly reduced lifespan, which is prolonged by antibiotic administration, suggesting compromised ability to control bacterial infection. G-/-GM-/-M-/- mice have circulating neutrophils and monocytes, albeit at significantly reduced numbers compared with wild-type mice, but surprisingly, have more circulating monocytes than M-/- mice and more circulating neutrophils than G-/-GM-/- mice. Due to severe osteopetrosis, G-/-GM-/-M-/- mice show diminished numbers of myeloid cells, myeloid progenitors, and B lymphocytes in the bone marrow, but have significantly enhanced compensatory splenic hemopoiesis. Although G-/-GM-/-M-/- mice have a profound deficiency of myeloid cells in the resting peritoneal cavity, the animals mount a moderate cellular response in a model of sterile peritonitis. These data establish that in the absence of G-CSF, GM-CSF, and M-CSF, additional growth factor(s) can stimulate myelopoiesis and acute inflammatory responses.