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Karl Staser,
Su-Jung Park,
Steven D Rhodes,
Yi Zeng,
Yong Zheng He,
Matthew A Shew,
Jeffrey R Gehlhausen,
Donna Cerabona,
Keshav Menon,
Shi Chen,
Zejin Sun,
Jin Yuan, David A Ingram,
Grzegorz Nalepa,
Feng-Chun Yang,
D Wade Clapp
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ABSTRACT: Neurofibromatosis type 1 (NF1) predisposes individuals to the development of juvenile myelomonocytic leukemia (JMML), a fatal myeloproliferative disease (MPD). In genetically engineered murine models, nullizygosity of Nf1, a tumor suppressor gene that encodes a Ras-GTPase-activating protein, results in hyperactivity of Raf/Mek/Erk in hematopoietic stem and progenitor cells (HSPCs). Activated Erk1/2 phosphorylate kinases and transcription factors with myriad mitogenic roles in diverse cell types. However, genetic studies examining Erk1/2's differential and/or combined control of normal and Nf1-deficient myelopoiesis are lacking. Moreover, prior studies relying on chemical Mek/Erk inhibitors have reached conflicting conclusions in normal and Nf1-deficient mice. Here, we show that while single Erk1 or Erk2 disruption did not grossly compromise myelopoiesis, dual Erk1/2 disruption rapidly ablated granulocyte and monocyte production in vivo, diminished progenitor cell number, and prevented HSPC proliferation in vitro. Genetic disruption of Erk1/2 in the context of Nf1 nullizygosity (Mx1Cre+Nf1flox/floxErk1-/-Erk2flox/flox) fully protects against the development of MPD. Collectively, we identified a fundamental requirement for Erk1/2 signaling in normal and Nf1-deficient hematopoiesis, elucidating a critical hematopoietic function for Erk1/2 while genetically validating highly selective Mek/Erk inhibitors in a leukemia that is otherwise resistant to traditional therapy.
The Journal of clinical investigation 12/2012; · 15.39 Impact Factor
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Brian K Stansfield,
Waylan K Bessler,
Raghuveer Mali,
Julie A Mund,
Brandon Downing,
Fang Li,
Kara N Sarchet,
Matthew R Distasi,
Simon J Conway,
Reuben Kapur, David A Ingram
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ABSTRACT: Mutations in the NF1 tumor suppressor gene cause Neurofibromatosis type 1 (NF1). Neurofibromin, the protein product of NF1, functions as a negative regulator of Ras activity. Some NF1 patients develop cardiovascular disease, which represents an under-recognized disease complication and contributes to excess morbidity and mortality. Specifically, NF1 patients develop arterial occlusion resulting in tissue ischemia and sudden death. Murine studies demonstrate that heterozygous inactivation of Nf1 (Nf1+/-) in bone marrow cells enhances neointima formation following arterial injury. Macrophages infiltrate Nf1+/- neointimas, and NF1 patients have increased circulating inflammatory monocytes in their peripheral blood. Therefore, we tested the hypothesis that heterozygous inactivation of Nf1 in myeloid cells is sufficient for neointima formation. Specific ablation of a single copy of the Nf1 gene in myeloid cells alone mobilizes a discrete pro-inflammatory murine monocyte population via a cell autonomous and gene-dosage dependent mechanism. Further, lineage-restricted heterozygous inactivation of Nf1 in myeloid cells is sufficient to reproduce the enhanced neointima formation observed in Nf1+/- mice compared to WT controls and homozygous inactivation of Nf1 in myeloid cells amplified the degree of arterial stenosis after arterial injury. Treatment of Nf1+/- mice with rosuvastatin, a stain with anti-inflammatory properties, significantly reduced neointima formation compared to control. These studies identify neurofibromin-deficient myeloid cells as critical cellular effectors of Nf1+/- neointima formation and propose a potential therapeutic for NF1 cardiovascular disease.
Human Molecular Genetics 11/2012; · 7.64 Impact Factor
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Kent A Robertson,
Grzegorz Nalepa,
Feng-Chun Yang,
Daniel C Bowers,
Chang Y Ho,
Gary D Hutchins,
James M Croop,
Terry A Vik,
Scott C Denne,
Luis F Parada, [......],
Mervyn D Cohen,
James W Fletcher,
Jeffrey B Travers,
Karl W Staser,
Melissa W Lee,
Marcie R Sherman,
Cynthia J Davis,
Lucy C Miller, David A Ingram,
D Wade Clapp
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ABSTRACT: BACKGROUND: Plexiform neurofibromas are slow-growing chemoradiotherapy-resistant tumours arising in patients with neurofibromatosis type 1 (NF1). Currently, there are no viable therapeutic options for patients with plexiform neurofibromas that cannot be surgically removed because of their proximity to vital body structures. We undertook an open-label phase 2 trial to test whether treatment with imatinib mesylate can decrease the volume burden of clinically significant plexiform neurofibromas in patients with NF1. METHODS: Eligible patients had to be aged 3-65 years, and to have NF1 and a clinically significant plexiform neurofibroma. Patients were treated with daily oral imatinib mesylate at 220 mg/m(2) twice a day for children and 400 mg twice a day for adults for 6 months. The primary endpoint was a 20% or more reduction in plexiform size by sequential volumetric MRI imaging. Clinical data were analysed on an intention-to-treat basis; a secondary analysis was also done for those patients able to take imatinib mesylate for 6 months. This trial is registered with ClinicalTrials.gov, number NCT01673009. FINDINGS: Six of 36 patients (17%, 95% CI 6-33), enrolled on an intention-to-treat basis, had an objective response to imatinib mesylate, with a 20% or more decrease in tumour volume. Of the 23 patients who received imatinib mesylate for at least 6 months, six (26%, 95% CI 10-48) had a 20% or more decrease in volume of one or more plexiform tumours. The most common adverse events were skin rash (five patients) and oedema with weight gain (six). More serious adverse events included reversible grade 3 neutropenia (two), grade 4 hyperglycaemia (one), and grade 4 increases in aminotransferase concentrations (one). INTERPRETATION: Imatinib mesylate could be used to treat plexiform neurofibromas in patients with NF1. A multi-institutional clinical trial is warranted to confirm these results. FUNDING: Novartis Pharmaceuticals, the Indiana University Simon Cancer Centre, and the Indiana University Herman B Wells Center for Pediatric Research.
The lancet oncology 10/2012; · 14.47 Impact Factor
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ABSTRACT: We have identified a novel hierarchy of human endothelial colony-forming cells (ECFCs) that are functionally defined by their proliferative and clonogenic potential and in vivo vessel-forming ability. The rhesus monkey provides an excellent model in which to examine the changes in circulating concentrations and functions of ECFCs since this nonhuman primate possesses a long lifespan and has been used extensively to model age-related processes that occur in humans.
Endothelial cells (ECs) derived from rhesus monkey ECFCs share a cell-surface phenotype similar to human cord blood ECFCs, rapidly form capillary-like structures in vitro, and form endothelial-lined vessels in vivo upon implantation in immunodeficient mice in an age-dependent manner. Of interest, although ECFCs from the oldest monkeys formed capillary-like structures in vitro, the cells failed to form inosculating vessels when implanted in vivo and displayed a deficiency in cytoplasmic vacuolation in vitro; a critical first step in vasculogenesis.
Utilizing previously established clonogenic assays for defining different subpopulations of human ECFCs, we have shown that a hierarchy of ECFCs, identical to human cells, can be isolated from the peripheral blood of rhesus monkeys, and that the frequency of the circulating cells varies with age. These studies establish the rhesus monkey as an important preclinical model for evaluating the role and function of circulating ECFCs in vascular homeostasis and aging.
Peripheral blood samples were collected from 40 healthy rhesus monkeys from birth to 24 years of age for ECFC analysis including immunophenotyping, clonogenic assays, and in vivo vessel formation.
Pediatric Research 02/2012; 71(2):156-61. · 2.70 Impact Factor
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ABSTRACT: We sought to identify and characterize 2 distinct populations of bona fide circulating endothelial cells, including the endothelial colony-forming cell (ECFC), by polychromatic flow cytometry (PFC), colony assays, immunomagnetic selection, and electron microscopy.
Mononuclear cells from human umbilical cord blood and peripheral blood were analyzed using our recently published PFC protocol. A population of cells containing both ECFCs and mature circulating endothelial cells was determined by varying expressions of CD34, CD31, and CD146 but not AC133 and CD45. After immunomagnetic separation, these cells failed to form hematopoietic colonies, yet clonogenic endothelial colonies with proliferative potential were obtained, thus verifying their identity as ECFCs. The frequency of ECFCs were increased in cord blood and were extremely rare in the peripheral blood of healthy adults. We also detected another mature endothelial cell population in the circulation that was apoptotic. Finally, when comparing this new protocol with a prior method, we determined that the present protocol identifies circulating endothelial cells, whereas the earlier protocol identified extracellular vesicles.
Two populations of circulating endothelial cells, including the functionally characterized ECFC, are now identifiable in human cord blood and peripheral blood by PFC.
Arteriosclerosis Thrombosis and Vascular Biology 01/2012; 32(4):1045-53. · 6.37 Impact Factor
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ABSTRACT: An important consideration in bone regeneration is the need for expedited neovascularization within the defect site. Formation of a vascular network is critical for cell viability and normal function leading to tissue regeneration, but spontaneous angiogenesis is too slow to yield sufficient vessel formation. In this pilot study, human umbilical cord blood (hUCB)-derived endothelial colony forming cells (ECFCs) were evaluated for in vivo vasculogenesis in the macropores of biphasic calcium phosphate (BCP)/bone morphogenetic protein-2 (BMP-2) bone tissue engineering constructs. Constructs were implanted on the abdominal wall of NOD/SCID mice for 4 weeks. This study demonstrated in vivo vasculogenesis by human ECFCs within the macropore space of BCP/BMP-2 constructs. The human ECFC-derived vessels anastomosed with the host vasculature and perfused vessels were visible in the very center of the 5mm diameter, 2.5mm tall scaffolds. Additionally, the vessels were evenly distributed throughout the construct. This study suggests that scaffolds containing ECFCs have significant potential for expedited neovascularization in bony defects.
Acta biomaterialia 07/2011; 7(12):4222-8. · 3.98 Impact Factor
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ABSTRACT: Endothelial colony-forming cells (ECFCs) are endothelial progenitor cells that circulate at low concentration in human umbilical cord and adult peripheral blood and are largely resident in blood vessels. ECFCs not only appear to be critical for normal vascular homeostasis and repair but may also contribute to tumor angiogenesis and response to therapy. To begin to characterize the potential role of ECFCs during the treatment of tumors in children and adults with radiation, we characterized the X-ray sensitivity of cord and adult blood-derived ECFCs. We found both cord blood and adult ECFCs to be highly radiation sensitive (3 Gy resulted in >90% killing without induction of apoptosis). The X-ray survival curves suggested reduced potential for repair capacity, but X-ray fractionation studies demonstrated that all the ECFCs exhibited repair when the radiation was fractionated. Finally, the mechanisms of X-ray-induced cell death for cord blood and adult ECFCs were different at low and high dose. At low dose, all ECFCs appear to die by mitotic death/catastrophe. However, at high radiation doses (≥ 10 Gy) cord blood ECFCs underwent p53 stabilization and Bax-dependent apoptosis as well as p21-dependent G₁ and G₂/M cell cycle checkpoints. By contrast, after 10 Gy adult ECFCs undergo only large-scale radiation-induced senescence, which is a cellular phenotype linked to premature development of atherosclerosis and vasculopathies. These data demonstrate that the ECFC response to radiation is dose-dependent and developmentally regulated and may provide potential mechanistic insight into their role in tumor and normal tissue response after ionizing radiation treatment.
Radiation Research 06/2011; 176(2):208-16. · 2.68 Impact Factor
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ABSTRACT: Pediatric solid tumors depend upon angiogenesis for their growth and metastases. A new polychromatic flow cytometry (PFC) protocol has revealed circulating cells of hematopoietic and endothelial lineages from the peripheral blood (PB) of healthy individuals, and has defined the different cell types involved in the growth of tumor vasculature that are critical in angiogenesis.
PB was collected from both healthy children and children with different malignant solid tumors and the mononuclear cells (MNCs) were subsequently isolated. PFC was applied and the MNCs were evaluated for proangiogenic and nonangiogenic circulating progenitor cells (CPCs), endothelial colony forming cells (ECFCs), and mature endothelial cells using the markers CD45, CD31, AC133, CD34, CD14, CD235a, CD41a, and a viability marker.
ECFCs and CPCs were significantly elevated in patients at day 21 compared to controls. The ratio of proangiogenic to nonangiogenic CPCs was significantly elevated compared to controls at baseline and returned to healthy baseline levels following treatment.
We describe the successful identification of these hematopoietic and endothelial progenitor cells in both healthy children and children with solid tumors. In addition, this is a potential discovery of novel predictive biomarkers for future clinical trials.
Cytometry Part B Clinical Cytometry 05/2011; 80(5):335-8. · 2.53 Impact Factor
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ABSTRACT: The purpose of this study was to examine whether women with gestational diabetes mellitus (GDM) and their offspring have reduced endothelial progenitor cell subsets and vascular reactivity.
Women with GDM, healthy control subjects, and their infants participated. Maternal blood and cord blood were assessed for colony-forming unit-endothelial cells and endothelial progenitor cell subsets with the use of polychromatic flow cytometry. Cord blood endothelial colony-forming cells were enumerated. Vascular reactivity was tested by laser Doppler imaging.
Women with GDM had fewer CD34, CD133, CD45, and CD31 cells (circulating progenitor cells [CPCs]) at 24-32 weeks' gestation and 1-2 days after delivery, compared with control subjects. No differences were detected in colony-forming unit-endothelial cells or colony-forming unit-endothelial cells. In control subjects, CPCs were higher in the third trimester, compared with the postpartum period. Cord blood from GDM pregnancies had reduced CPCs. Vascular reactivity was not different between GDM and control subjects.
The normal physiologic increase in CPCs during pregnancy is impaired in women with GDM, which may contribute to endothelial dysfunction and GDM-associated morbidities.
American journal of obstetrics and gynecology 12/2010; 204(3):254.e8-254.e15. · 3.28 Impact Factor
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ABSTRACT: To evaluate whether counts of circulating colony forming unit-endothelial cells (CFU-ECs), cells co-expressing CD34, CD133, and CD31 (CD34+CD133+CD31+), and CD34+CD45- cells are altered in adolescents with type 1 diabetes and if the changes in counts correlate with endothelial dysfunction.
Adolescents with diabetes (ages 18 to 22 years) and race- and sex-matched control subjects were studied. We assessed circulating CFU-ECs, using colony assays, and CD34+CD133+CD31+ and CD34+CD45- cells, using poly-chromatic flow cytometry. CFU-ECs and CD34+CD133+CD31+ are hematopoietic-derived progenitors that inversely correlate with cardiovascular risk in adults. CD34+CD45- cells are enriched for endothelial cells with robust vasculogenic potential. Vascular reactivity was tested by laser Doppler iontophoresis.
Subjects with diabetes had lower CD34+CD133+CD31+ cells, a trend toward reduced CFU-ECs, and increased CD34+CD45- cells compared with control subjects. Endothelium-dependent vasodilation was impaired in subjects with diabetes, which correlated with reductions in circulating CD34+CD133+CD31+ cells.
Long-term sequelae of type 1 diabetes include vasculopathies. Endothelial progenitor cells promote vascular health by facilitating endothelial integrity and function. Lower CD34+CD133+CD31+ cells may be a harbinger of future macrovascular disease risk. Higher circulating CD34+CD45- cells may reflect ongoing endothelial damage. These cells are potential biomarkers to guide therapeutic interventions to enhance endothelial function and to prevent progression to overt vascular disease.
The Journal of pediatrics 10/2010; 157(4):540-6. · 4.02 Impact Factor
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Myka L Estes,
Julie A Mund,
Laura E Mead,
Daniel N Prater,
Shanbao Cai,
Haiyan Wang,
Karen E Pollok,
Michael P Murphy,
Caroline S T An,
Edward F Srour, David A Ingram,
Jamie Case
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ABSTRACT: Defining whether human circulating proangiogenic cells represent a subset of the hematopoietic system and express CD45 or are hematopoietic derivatives that do not express CD45 (and are called endothelial progenitor cells) remains controversial. We have previously developed a polychromatic flow cytometry (PFC) protocol to isolate subsets of hematopoietic cells and we now identify the circulating pool of CD34(+)CD45(dim) cells representing functional circulating hematopoietic stem and progenitor cells (CHSPCs) that can be separated on the basis of AC133 expression and report that the AC133(+) subset of the CHSPCs enhances the growth of tumor blood vessels in vivo in immunodeficient mice. In addition, the ratio of AC133(+) proangiogenic CHSPCs to AC133(-) nonangiogenic CHSPCs unambiguously correlates with the severity of the clinical state of patients with peripheral arterial disease. In sum, a PFC protocol validated via in vitro and in vivo analyses, can be used to interrogate the roles of human hematopoietic elements in the growth and maintenance of the vasculature.
Cytometry Part A 09/2010; 77(9):831-9. · 3.73 Impact Factor
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ABSTRACT: An assay for circulating cell subsets in human peripheral blood by flow cytometry is used as a biomarker to determine cardiovascular disease risk and tumor responsiveness to chemotherapy since endothelial progenitor cells (EPCs) function in vasculogenesis and angiogenesis. Despite analytical advances in polychromatic flow cytometry (PFC), conventional approaches are routinely utilized to enumerate and isolate EPCs, which has led to varied results in clinical studies, potential cellular misidentification, and thus a lack of a plausible biological explanation for how purported EPCs function. Herein, a reproducible PFC protocol is provided to identify a rare circulating endothelial colony-forming cell (ECFC) with proliferative potential, along with a population of circulating progenitor cells (CPCs) in which the ratio analysis distinguishes between healthy and disease populations. In sum, a reliable PFC protocol, which can be used to investigate the roles of human hematopoietic and endothelial elements in the growth and maintenance of the vasculature, is described.
Current protocols in cytometry / editorial board, J. Paul Robinson, managing editor ... [et al.] 04/2010; Chapter 9:Unit 9.33.1-11.
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ABSTRACT: To test the hypothesis that the robust expansion of bovine corneal endothelial cells (BCECs) in vitro is due to the presence of individual endothelial cells with various levels of proliferative potential.
BCECs and bovine vascular endothelial cells (ECs) derived from aorta, coronary artery, and pulmonary artery were cultivated in optimized medium. These cell populations were confirmed by morphologic features, functional assays, and gene expression profiles. Moreover, ECs were plated in a single-cell clonogenic assay to evaluate colony-forming ability.
Both corneal and vascular ECs were confirmed to be pure populations of endothelium uncontaminated with hematopoietic cells. A complete hierarchy of endothelial colony-forming cells (ECFCs) was identified in BCECs by a single-cell clonogenic assay. The distribution of the various types of ECFCs was similar to the control ECs removed from the systemic vessels.
Cultured BCECs display clonal proliferative properties similar to those of vascular ECs.
Investigative ophthalmology & visual science 03/2010; 51(8):3943-9. · 3.43 Impact Factor
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ABSTRACT: Neurofibromatosis type 1 (NF1) results from mutations in the NF1 tumor suppressor gene, which encodes the protein neurofibromin. NF1 patients display diverse clinical manifestations, including vascular disease, which results from neointima formation and vessel occlusion. However, the pathogenesis of NF1 vascular disease remains unclear. Vessel wall homeostasis is maintained by complex interactions between vascular and bone marrow-derived cells (BMDCs), and neurofibromin regulates the function of each cell type. Therefore, utilizing cre/lox techniques and hematopoietic stem cell transplantation to delete 1 allele of Nf1 in endothelial cells, vascular smooth muscle cells, and BMDCs alone, we determined which cell lineage is critical for neointima formation in vivo in mice. Here we demonstrate that heterozygous inactivation of Nf1 in BMDCs alone was necessary and sufficient for neointima formation after vascular injury and provide evidence of vascular inflammation in Nf1+/- mice. Further, analysis of peripheral blood from NF1 patients without overt vascular disease revealed increased concentrations of inflammatory cells and cytokines previously linked to vascular inflammation and vasoocclusive disease. These data provide genetic and cellular evidence of vascular inflammation in NF1 patients and Nf1+/- mice and provide a framework for understanding the pathogenesis of NF1 vasculopathy and potential therapeutic and diagnostic interventions.
The Journal of clinical investigation 02/2010; 120(3):859-70. · 15.39 Impact Factor
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ABSTRACT: Neonatal hyperoxia impairs vascular and alveolar growth in mice and decreases endothelial progenitor cells. To determine the role of bone marrow-derived cells in restoration of neonatal lung structure after injury, we studied a novel bone marrow myeloid progenitor cell population from Tie2-green fluorescent protein (GFP) transgenic mice (bone marrow-derived angiogenic cells; BMDAC). We hypothesized that treatment with BMDAC would restore normal lung structure in infant mice during recovery from neonatal hyperoxia. Neonatal mice (1-day-old) were exposed to 80% oxygen for 10 days. BMDACs (1 x 10(5)), embryonic endothelial progenitor cells, mouse embryonic fibroblasts (control), or saline were then injected into the pulmonary circulation. At 21 days of age, saline-treated mice had enlarged alveoli, reduced septation, and a reduction in vascular density. In contrast, mice treated with BMDAC had complete restoration of lung structure that was indistinguishable from room air controls. BMDAC comprised 12% of distal lung cells localized to pulmonary vessels or alveolar type II (AT2) cells and persist (8.8%) for 8 wk postinjection. Coculture of AT2 cells or lung endothelial cells (luEC) with BMDAC augmented AT2 and luEC cell growth in vitro. We conclude that treatment with BMDAC after neonatal hyperoxia restores lung structure in this model of bronchopulmonary dysplasia.
AJP Lung Cellular and Molecular Physiology 12/2009; 298(3):L315-23. · 3.66 Impact Factor
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American Journal of Respiratory and Critical Care Medicine 10/2009; 180(6):488-90. · 11.08 Impact Factor
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ABSTRACT: Rapid induction and maintenance of blood flow through new vascular networks is essential for successfully treating ischemic tissues and maintaining function of engineered neo-organs. We have previously shown that human endothelial progenitor cells (EPCs) form functioning vessels in mice, but these are limited in number and persistence; and also that human adipose stromal cells (ASCs) are multipotent cells with pericytic properties which can stabilize vascular assembly in vitro. In this study, we tested whether ASCs would cooperate with EPCs to coassemble vessels in in vivo implants. Collagen implants containing EPCs, ASCs, or a 4:1 mixture of both were placed subcutaneously into NOD/SCID mice. After a range of time periods, constructs were explanted and evaluated with regard to vascular network assembly and cell fate; and heterotypic cell interactions were explored by targeted molecular perturbations. The density and complexity of vascular networks formed by the synergistic dual-cell system was many-fold higher than found in implants containing either ASCs or EPCs alone. Coimplantation of ASCs and EPCs with either pancreatic islets or adipocytes produced neoorgans populated by these parenchymal cells, as well as by chimeric human vessels conducting flow. This study is the first to demonstrate prompt and consistent assembly of a vascular network by human ASCs and endothelial cells and vascularization by these cells of parenchymal cells in implants. Mixture of these 2 readily available, nontransformed human cell types provides a practical approach to tissue engineering, therapeutic revascularization, and in vivo studies of human vasculogenesis.
Circulation Research 06/2009; 104(12):1410-20. · 9.49 Impact Factor
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ABSTRACT: Preterm birth and hyperoxic exposure increase the risk for bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by impaired vascular and alveolar growth. Endothelial progenitor cells, such as self-renewing highly proliferative endothelial colony-forming cells (ECFCs), may participate in vascular repair. The effect of hyperoxia on ECFC growth is unknown.
We hypothesize that umbilical cord blood (CB) from premature infants contains more ECFCs with greater growth potential than term CB. However, preterm ECFCs may be more susceptible to hyperoxia.
ECFC colonies were quantified by established methods and characterized by immunohistochemistry and flow cytometry. Growth kinetics were assessed in room air and hyperoxia (FI(O(2)) = 0.4).
Preterm CB (28-35 wk gestation) yielded significantly more ECFC colonies than term CB. Importantly, we found that CD45(-)/CD34(+)/CD133(+)/VEGFR-2(+) cell number did not correlate with ECFC colony count. Preterm ECFCs demonstrated increased growth compared with term ECFCs. Hyperoxia impaired growth of preterm but not term ECFCs. Treatment with superoxide dismutase and catalase enhanced preterm ECFC growth during hyperoxia.
Preterm ECFCs appear in increased numbers and proliferate more rapidly but have an increased susceptibility to hyperoxia compared with term ECFCs. Antioxidants protect preterm ECFCs from hyperoxia.
American Journal of Respiratory and Critical Care Medicine 06/2009; 180(5):454-61. · 11.08 Impact Factor
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ABSTRACT: Interest in the regulation of blood vessel formation as a mechanism to permit unregulated tumor cell growth was a prescient hypothesis of Dr. Judah Folkman nearly 3 decades ago. Understanding the cellular and molecular mechanisms that affect the recruitment, expansion, and turnover of the tumor microvasculature continues to evolve. While the fundamental paradigms for improving blood flow to growing, injured, diseased, or tumor infiltrated tissues are well known, the potential role of bone marrow derived circulating endothelial progenitor cells (EPCs) to function as postnatal vasculogenic precursors for tumor microvasculature has become a controversial premise. We will briefly review some recently published high profile papers that appear to derive polar interpretations for the role of EPCs in the angiogenic switch and discuss possible reasons for the disparate views in work conducted in both mouse and man.
Biochimica et Biophysica Acta 05/2009; 1796(1):50-4. · 4.66 Impact Factor
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Jayme D Allen,
Zahara M Jaffer,
Su-Jung Park,
Sarah Burgin,
Clemens Hofmann,
Mary Ann Sells,
Shi Chen,
Ethel Derr-Yellin,
Elizabeth G Michels,
Andrew McDaniel,
Waylan K Bessler, David A Ingram,
Simon J Atkinson,
Jeffrey B Travers,
Jonathan Chernoff,
D Wade Clapp
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ABSTRACT: Mast cells are key participants in allergic diseases via activation of high-affinity IgE receptors (FcepsilonRI) resulting in release of proinflammatory mediators. The biochemical pathways linking IgE activation to calcium influx and cytoskeletal changes required for intracellular granule release are incompletely understood. We demonstrate, genetically, that Pak1 is required for this process. In a passive cutaneous anaphylaxis experiment, W(sh)/W(sh) mast cell-deficient mice locally reconstituted with Pak1(-/-) bone marrow-derived mast cells (BMMCs) experienced strikingly decreased allergen-induced vascular permeability compared with controls. Consistent with the in vivo phenotype, Pak1(-/-) BMMCs exhibited a reduction in FcepsilonRI-induced degranulation. Further, Pak1(-/-) BMMCs demonstrated diminished calcium mobilization and altered depolymerization of cortical filamentous actin (F-actin) in response to FcepsilonRI stimulation. These data implicate Pak1 as an essential molecular target for modulating acute mast cell responses that contribute to allergic diseases.
Blood 02/2009; 113(12):2695-705. · 9.90 Impact Factor
