Subfractions Of Cells Research Articles

In Vivo miRNA Decoy Screen Reveals miR-124a as a Suppressor of Melanoma Metastasis.

Melanoma is a highly prevalent cancer with an increasing incidence worldwide and high metastatic potential. Brain metastasis is a major complication of the disease, as more than 50% of metastatic melanoma patients eventually develop intracranial disease. MicroRNAs (miRNAs) have been found to play an important role in the tumorigenicity of different cancers and have potential as markers of disease outcome. Identification of relevant miRNAs has generally stemmed from miRNA profiling studies of cells or tissues, but these approaches may have missed miRNAs with relevant functions that are expressed in subfractions of cancer cells. We performed an unbiased in vivo screen to identify miRNAs with potential functions as metastasis suppressors using a lentiviral library of miRNA decoys. Notably, we found that a significant fraction of melanomas that metastasized to the brain carried a decoy for miR-124a, a miRNA that is highly expressed in the brain/neurons. Additional loss- and gain-of-function in vivo validation studies confirmed miR-124a as a suppressor of melanoma metastasis and particularly of brain metastasis. miR-124a overexpression did not inhibit tumor growth in vivo, underscoring that miR-124a specifically controls processes required for melanoma metastatic growth, such as seeding and growth post-extravasation. Finally, we provide proof of principle of this miRNA as a promising therapeutic agent by showing its ability to impair metastatic growth of melanoma cells seeded in distal organs. Our efforts shed light on miR-124a as an antimetastatic agent, which could be leveraged therapeutically to impair metastatic growth and improve patient survival.

Efficient delivery of oncolytic enterovirus by carrier cell line NK-92

Many members of the enterovirus family are considered as promising oncolytic agents; however, their systemic administration is largely inefficient due to the rapid neutralization of the virus in the circulation and the barrier functions of the endothelium. We aimed to evaluate natural killer cells as carriers for the delivery of oncolytic enteroviruses, which would combine the effects of cell immunotherapy with virotherapy. We tested four strains of nonpathogenic enteroviruses against the glioblastoma cell line panel and evaluated the produced infectious titers. Next, we explored whether these virus strains could be delivered to the tumor by natural killer cell line NK-92, which is being actively evaluated as a clinically acceptable therapeutic. Several strains of enteroviruses demonstrated oncolytic properties, but only coxsackievirus A7 (CVA7) could replicate in NK-92 cells efficiently. We compared the delivery efficiency of CVA7 in vivo, using NK-92 cells and direct intravenous administration, and found significant advantages of cell delivery even after a single injection. This suggests that the NK-92 cell line can be utilized as a vehicle for the delivery of the oncolytic strain of CVA7, which would improve the clinical potential of this viral oncolytic for the treatment of glioblastoma multiforme and other forms of cancer.

Sub-Fractions of Red Blood Cells Respond Differently to Shear Exposure Following Superoxide Treatment.

Red blood cell (RBC) deformability is an essential component of microcirculatory function that appears to be enhanced by physiological shear stress, while being negatively affected by supraphysiological shears and/or free radical exposure. Given that blood contains RBCs with non-uniform physical properties, whether all cells equivalently tolerate mechanical and oxidative stresses remains poorly understood. We thus partitioned blood into old and young RBCs which were exposed to phenazine methosulfate (PMS) that generates intracellular superoxide and/or specific mechanical stress. Measured RBC deformability was lower in old compared to young RBCs. PMS increased total free radicals in both sub-populations, and RBC deformability decreased accordingly. Shear exposure did not affect reactive species in the sub-populations but reduced RBC nitric oxide synthase (NOS) activation and intriguingly increased RBC deformability in old RBCs. The co-application of PMS and shear exposure also improved cellular deformability in older cells previously exposed to reactive oxygen species (ROS), but not in younger cells. Outputs of NO generation appeared dependent on cell age; in general, stressors applied to younger RBCs tended to induce S-nitrosylation of RBC cytoskeletal proteins, while older RBCs tended to reflect markers of nitrosative stress. We thus present novel findings pertaining to the interplay of mechanical stress and redox metabolism in circulating RBC sub-populations.

Gene expression profiling in adipose tissue of Sprague Dawley rats identifies olfactory receptor 984 as a potential obesity treatment target

The aim of the study was to identify and functionally characterize novel candidate gene/s involved in the development of resistance to diet-induced obesity in rats. In a high-fat-diet (HFD) study of rats, we found subgroups which either developed resistance to HFD-induced obesity (DR) or showed an obesity-prone phenotype (DIO). Gene expression analysis in 10 samples (5 DIO vs 5 DR) was performed. The most promising gene, OR6C3 (orthologous with rat Olr984 and mouse Olfr788) was measured by qRT-PCR in paired samples of human visceral (Vis) and subcutaneous (SC) adipose tissue (AT) (n = 225) and in sub-fractions of adipocytes and cells of stromal vascular fraction. Gene expression analyses showed Olr984 with significantly reduced mRNA expression in DR rats. In the Vis AT of human samples we found an up-regulation of OR6C3 compared to SC AT, independent of gender, glucose tolerance or type 2 diabetes. We observed significantly lower levels of SC AT OR6C3 mRNA in subjects with obesity compared to those with normal-weight or overweight. OR6C3 is more expressed in SVF than in adipocytes. Olr984 could be a novel candidate gene related to diet-induced obesity in rats. Variation in human AT mRNA expression is related to obesity parameters and glucose homeostasis and linked to the regulatory role of insulin on the Olr984.

Cancer imaging in the era of precision treatment: present and future

Cancer imaging in the era of precision treatment: present and future

Multiple blocks in the engagement of oxidative phosphorylation in putative ovarian cancer stem cells: implication for maintenance therapy with glycolysis inhibitors.

Survival rate in ovarian cancer has not improved since chemotherapy was introduced a few decades ago. The dismal prognosis is mostly due to disease recurrence where majority of the patients succumb to the disease. The demonstration that tumors are comprised of subfractions of cancer cells displaying heterogeneity in stemness potential, chemoresistance, and tumor repair capacity suggests that recurrence may be driven by the chemoresistant cancer stem cells. Thus to improve patient survival, novel therapies should eradicate this cancer cell population. We show that in contrast to the more differentiated ovarian cancer cells, the putative CD44+/MyD88+ ovarian cancer stem cells express lower levels of pyruvate dehydrogenase, Cox-I, Cox-II, and Cox-IV, and higher levels of UCP2. Together, this molecular phenotype establishes a bioenergetic profile that prefers the use of glycolysis over oxidative phosphorylation to generate ATP. This bioenergetic profile is conserved in vivo and therefore a maintenance regimen of 2-deoxyglucose administered after Paclitaxel treatment is able to delay the progression of recurrent tumors and decrease tumor burden in mice. Our findings strongly suggest the value of maintenance with glycolysis inhibitors with the goal of improving survival in ovarian cancer patients.

Phenotyping of Human Melanoma Cells Reveals a Unique Composition of Receptor Targets and a Subpopulation Co-Expressing ErbB4, EPO-R and NGF-R

Malignant melanoma is a life-threatening skin cancer increasingly diagnosed in the western world. In advanced disease the prognosis is grave. Growth and metastasis formation in melanomas are regulated by a network of cytokines, cytokine-receptors, and adhesion molecules. However, little is known about surface antigens and target expression profiles in human melanomas. We examined the cell surface antigen profile of human skin melanoma cells by multicolor flow cytometry, and compared their phenotype with 4 melanoma cell lines (A375, 607B, Mel-Juso, SK-Mel28). Melanoma cells were defined as CD45−/CD31− cells co-expressing one or more melanoma-related antigens (CD63, CD146, CD166). In most patients, melanoma cells exhibited ErbB3/Her3, CD44/Pgp-1, ICAM-1/CD54 and IGF-1-R/CD221, but did not express CD20, ErbB2/Her2, KIT/CD117, AC133/CD133 or MDR-1/CD243. Melanoma cell lines were found to display a similar phenotype. In most patients, a distinct subpopulation of melanoma cells (4–40%) expressed the erythropoietin receptor (EPO-R) and ErbB4 together with PD-1 and NGF-R/CD271. Both the EPO-R+ and EPO-R− subpopulations produced melanoma lesions in NOD/SCID IL-2Rgammanull (NSG) mice in first and secondary recipients. Normal skin melanocytes did not express ErbB4 or EPO-R, but expressed a functional KIT receptor (CD117) as well as NGF-R, ErbB3/Her3, IGF-1-R and CD44. In conclusion, melanoma cells display a unique composition of surface target antigens and cytokine receptors. Malignant transformation of melanomas is accompanied by loss of KIT and acquisition of EPO-R and ErbB4, both of which are co-expressed with NGF-R and PD-1 in distinct subfractions of melanoma cells. However, expression of EPO-R/ErbB4/PD-1 is not indicative of a selective melanoma-initiating potential.

Sub-Sets of Cancer Stem Cells Differ Intrinsically in Their Patterns of Oxygen Metabolism

The glycolytic response of hypoxic cells is primarily mediated by the hypoxia inducible factor alpha (HIF-1α) but even in the presence of abundant oxygen tumours typically show high rates of glycolysis. Higher levels of HIF-1α in tumours are associated with a poorer prognosis and up-regulation of markers of epithelial mesenchymal transition (EMT) due to HIF-1α actions. We have recently shown that EMT occurs within the CD44high cancer stem cell (CSC) fraction and that epithelial and EMT CSCs are distinguished by high and low ESA expression, respectively. We here show that hypoxia induces a marked shift of the CSC fraction towards EMT leading to altered cell morphology, an increased proportion of CD44high/ESAlow cells, patterns of gene expression typical of EMT, and enhanced sphere-forming ability. The size of EMT fractions returned to control levels in normoxia indicating a reversible process. Surprisingly, however, even under normoxic conditions a fraction of EMT CSCs was present and maintained high levels of HIF-1α, apparently due to actions of cytokines such as TNFα. Functionally, this EMT CSC fraction showed decreased mitochondrial mass and membrane potential, consumed far less oxygen per cell, and produced markedly reduced levels of reactive oxygen species (ROS). These differences in the patterns of oxygen metabolism of sub-fractions of tumour cells provide an explanation for the general therapeutic resistance of CSCs and for the even greater resistance of EMT CSCs. They also identify potential mechanisms for manipulation of CSCs.

Identification and Isolation of Slow-Dividing Cells in Human Glioblastoma Using Carboxy Fluorescein Succinimidyl Ester (CFSE)

Tumor heterogeneity represents a fundamental feature supporting tumor robustness and presents a central obstacle to the development of therapeutic strategies(1). To overcome the issue of tumor heterogeneity, it is essential to develop assays and tools enabling phenotypic, (epi)genetic and functional identification and characterization of tumor subpopulations that drive specific disease pathologies and represent clinically relevant targets. It is now well established that tumors exhibit distinct sub-fractions of cells with different frequencies of cell division, and that the functional criteria of being slow cycling is positively associated with tumor formation ability in several cancers including those of the brain, breast, skin and pancreas as well as leukemia(2-8). The fluorescent dye carboxyfluorescein succinimidyl ester (CFSE) has been used for tracking the division frequency of cells in vitro and in vivo in blood-borne tumors and solid tumors such as glioblastoma(2,7,8). The cell-permeant non-fluorescent pro-drug of CFSE is converted by intracellular esterases into a fluorescent compound, which is retained within cells by covalently binding to proteins through reaction of its succinimidyl moiety with intracellular amine groups to form stable amide bonds(9). The fluorescent dye is equally distributed between daughter cells upon divisions, leading to the halving of the fluorescence intensity with every cell division. This enables tracking of cell cycle frequency up to eight to ten rounds of division(10). CFSE retention capacity was used with brain tumor cells to identify and isolate a slow cycling subpopulation (top 5% dye-retaining cells) demonstrated to be enriched in cancer stem cell activity(2). This protocol describes the technique of staining cells with CFSE and the isolation of individual populations within a culture of human glioblastoma (GBM)-derived cells possessing differing division rates using flow cytometry(2). The technique has served to identify and isolate a brain tumor slow-cycling population of cells by virtue of their ability to retain the CFSE labeling.

Identification and Isolation of Slow-Dividing Cells in Human Glioblastoma Using Carboxy Fluorescein Succinimidyl Ester (CFSE)

Tumor heterogeneity represents a fundamental feature supporting tumor robustness and presents a central obstacle to the development of therapeutic strategies1. To overcome the issue of tumor heterogeneity, it is essential to develop assays and tools enabling phenotypic, (epi)genetic and functional identification and characterization of tumor subpopulations that drive specific disease pathologies and represent clinically relevant targets. It is now well established that tumors exhibit distinct sub-fractions of cells with different frequencies of cell division, and that the functional criteria of being slow cycling is positively associated with tumor formation ability in several cancers including those of the brain, breast, skin and pancreas as well as leukemia2-8. The fluorescent dye carboxyfluorescein succinimidyl ester (CFSE) has been used for tracking the division frequency of cells in vitro and in vivo in blood-borne tumors and solid tumors such as glioblastoma2,7,8. The cell-permeant non-fluorescent pro-drug of CFSE is converted by intracellular esterases into a fluorescent compound, which is retained within cells by covalently binding to proteins through reaction of its succinimidyl moiety with intracellular amine groups to form stable amide bonds9. The fluorescent dye is equally distributed between daughter cells upon divisions, leading to the halving of the fluorescence intensity with every cell division. This enables tracking of cell cycle frequency up to eight to ten rounds of division10. CFSE retention capacity was used with brain tumor cells to identify and isolate a slow cycling subpopulation (top 5% dye-retaining cells) demonstrated to be enriched in cancer stem cell activity2. This protocol describes the technique of staining cells with CFSE and the isolation of individual populations within a culture of human glioblastoma (GBM)-derived cells possessing differing division rates using flow cytometry2. The technique has served to identify and isolate a brain tumor slow-cycling population of cells by virtue of their ability to retain the CFSE labeling.

Abstract 784A: Profiling pancreatic cancer metabolism and tumor microenvironment for therapy

Abstract Pancreatic cancers have one of the highest fatality rates among all cancers and their response to therapies is highly variable. We have recently shown that inhibition of lactate dehydrogenase A (LDHA) and glutaminase (GLS) through small drug-like molecules causes pancreatic tumor regression. These studies indicate that targeting the metabolic reprogramming of cancer cells is a promising new approach to pancreatic cancer therapy. In order to translate these metabolic inhibitors to the clinic, our goal is to characterize and enable targeted selection of patients based on predicted metabolic response. Although genetic mutations may ultimately be the prime causes of early stage cancer, they can also lead to changes in cancer metabolism which enable cancer cells to proliferate and survive even under the hypoxic and nutrient-deprived conditions often encountered in the tumor microenvironment. The biochemical changes in cancer cells, which determine their behavior in terms of growth, survival and mobility, represent a functional readout of responses to external agents. We hypothesize that the metabolites of tumors that are sensitive to metabolic inhibitors are measurably different from those of resistant ones. We can therefore propose these metabolites as potential functional predictors of response. The proposed research will also study the metabolic reprogramming of cancer cells in the tumor microenvironment that can affect pancreatic cancer sensitivity to LDHA and GLS inhibition. The proposed experiments will use Metabolomics technology to trace the metabolic prototypes of pancreatic orthotopic xenografts to identify the metabolic signature of FX11 or BPTES-sensitive tumors as compared to resistant ones. For an analysis of the effects due to the tumor hypoxic microenvironment, we will use our innovative tool, the HypoxCR reporter system, which can simultaneously detect hypoxic cells and proliferating cells to define the effects of the pancreatic cancer tumor microenvironment on their sensitivity to metabolic inhibitors. This will be the first evaluation of the hypoxic tumor microenvironment in regards to how it affects the response of subfractions of pancreatic orthotopic xenograft tumor cells to metabolic inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 784A. doi:1538-7445.AM2012-784A

Abstract 483: CXCR6, a newly defined biomarker of tissue-specific stem cell asymmetric self-renewal, identifies more aggressive human melanoma cancer stem cells

Abstract Background- A fundamental problem in cancer research is identifying the cell type that is capable of sustaining neoplastic growth and its origin from normal tissue cells. Recent investigations of a variety of tumor types have shown that phenotypically identifiable and isolable subfractions of cells possess the tumor-forming ability. In the present paper, using two lineage-related human melanoma cell lines, primary melanoma line IGR39 and its metastatic derivative line IGR37, two main contributes are reported. The first one is the first phenotypic evidence to support the origin of melanoma CSCs from mutated tissue-specific stem cells and the second one is the identification of a more aggressive subpopulation CXCR6+ in melanoma. Methods/Findings- We defined CXCR6 as a new biomarker for tissue-specific stem cell asymmetric self-renewal. Thus, the relationship between melanoma formation and ABCG2 and CXCR6 expression was investigated. Consistent with their non-metastatic character, unsorted IGR39 cells formed significantly smaller tumors than unsorted IGR37 cells. In addition, ABCG2+ tumors gave a 2-fold greater mass than tumors from unsorted cells or ABCG2- cells. Furthermore, CXCR6+ cells produced more aggressive tumors. These findings show that CXCR6 identifies a more discrete subpopulation of cultured human melanoma cells with a more aggressive melanoma cancer stem cell phenotype than cells selected on the basis of ABCG2, and CXCR6+/ABCG2+ expression. Conclusions/Significance- The association of more aggressive tumor phenotype with asymmetric self-renewal phenotype reveals a previously unrecognized aspect of tumor cell physiology. Namely, the retention of some tissue-specific stem cell attributes, like the ability to preserve self-phenotype, impacts the natural history of human tumor development. Knowledge of this new aspect of tumor progression may provide new targets for cancer prevention and treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 483. doi:10.1158/1538-7445.AM2011-483

CXCR6, a Newly Defined Biomarker of Tissue-Specific Stem Cell Asymmetric Self-Renewal, Identifies More Aggressive Human Melanoma Cancer Stem Cells

BackgroundA fundamental problem in cancer research is identifying the cell type that is capable of sustaining neoplastic growth and its origin from normal tissue cells. Recent investigations of a variety of tumor types have shown that phenotypically identifiable and isolable subfractions of cells possess the tumor-forming ability. In the present paper, using two lineage-related human melanoma cell lines, primary melanoma line IGR39 and its metastatic derivative line IGR37, two main observations are reported. The first one is the first phenotypic evidence to support the origin of melanoma cancer stem cells (CSCs) from mutated tissue-specific stem cells; and the second one is the identification of a more aggressive subpopulation of CSCs in melanoma that are CXCR6+.Methods/FindingsWe defined CXCR6 as a new biomarker for tissue-specific stem cell asymmetric self-renewal. Thus, the relationship between melanoma formation and ABCG2 and CXCR6 expression was investigated. Consistent with their non-metastatic character, unsorted IGR39 cells formed significantly smaller tumors than unsorted IGR37 cells. In addition, ABCG2+ cells produced tumors that had a 2-fold greater mass than tumors produced by unsorted cells or ABCG2- cells. CXCR6+ cells produced more aggressive tumors. CXCR6 identifies a more discrete subpopulation of cultured human melanoma cells with a more aggressive MCSC phenotype than cells selected on the basis of the ABCG2+ phenotype alone.Conclusions/SignificanceThe association of a more aggressive tumor phenotype with asymmetric self-renewal phenotype reveals a previously unrecognized aspect of tumor cell physiology. Namely, the retention of some tissue-specific stem cell attributes, like the ability to asymmetrically self-renew, impacts the natural history of human tumor development. Knowledge of this new aspect of tumor development and progression may provide new targets for cancer prevention and treatment.

Relapsed AML Patients with Mutational Shifts Harbor An Oligoclonal Primitive Cell Compartment at Presentation; Evidence for Clonal Selection towards Relapse

AbstractAbstract 751Previously we observed instability of type I/II mutations between diagnosis and relapse in a large portion (38%) of relapsed AML patients and this was associated with outcome (Bachas et al, Blood, 2010). Such instabilities may be explained by clonal selection during disease progression from oligoclonal initial AML populations. This hypothesis was tested in 6 AML patients with recurrent disease and mutational shifts between diagnosis and relapse. We determined the mutation profiles of mature and of immature subfractions of AML cells in initial diagnosis samples and related these to the corresponding relapse samples. Small amounts of cells (<50 cells) from mature and immature AML subfractions were sorted, followed by direct PCR assays for the detection of the frequently instable FMS like tyrosine kinase 3 (FLT3) internal tandem duplication (ITD), Wilms Tumor 1 (WT1) and RAS mutations and the relatively stable Nucleophosmin 1 (NPM1) mutation. AML blasts were cell sorted based on CD45dim expression and primitive cell populations were defined by CD34/CD38 co-expression and refined based on the expression of CD133 and CD117. A lineage infidelity (Lininf) marker was used for designation of aberrant cells (Van Rhenen et al, Leukemia, 2007). Lymphocytes were sorted based on scatter properties and CD45bright expression and were regarded as wild type controls of primary patient material in mutation analyses. Immunophenotypes, cytogenetics and minimal residual disease (MRD) status were routinely assessed in our laboratory. Our results are indicative of an oligoclonal immature AML cell compartment at presentation: the immature CD45dimCD34+CD38dim/- compartments of initial samples were more heterogeneous according to their mutation profiles, when compared to the bulk of mature CD45dimCD34+ blast cells. Mutation profiles differed for at least one molecular marker among immature subfractions of the initial samples within 5 out of 6 patients. In the remaining patient, the mutation profiles were identical among sorted fractions of the initial sample. When comparing these data with the mutation profile of the bulk of AML cells of the relapse samples, in the latter patient and 2 out of the 5 above referred heterogeneous patients, mutational shifts could not be retraced to any subfraction of the initial sample. Strikingly, in the 3 other patients we found evidence for the clonal selection of a minor immature subclone of the initial sample, with a specific mutation profile that was predominantly present at relapse. In two of these patients we detected FLT3/ITD mutations of specific lengths, which were predominantly present at relapse, in a CD34+CD38−Lininf or CD34+CD38dimLininf subfraction of the initial sample. This ITD was undetectable in the bulk of AML cells by standard diagnostics. Similarly, in the other patient with clonal selection, the CD34+CD38−Lininf compartment of the initial sample was enriched for a WT1 exon 7 mutation that predominated at relapse, whereas no WT1 mutations were detected in the bulk of AML cells at presentation. In concordance with these observations, immunophenotype and MRD data also suggested a clonal selection in these patients. In the 3 patients that did show a mutational shift, but lacked direct indications for clonal selection, a de novo mutation may have been induced during therapy. Alternatively, the use of additional immunophenotypical and molecular markers may be required for these samples to identify the relevant subclones. The key finding of our study is that we could detect in the immature fraction of initial samples of 3 AML patients a rare and otherwise undetectable subclone with a distinctive mutational profile that was predominant in the bulk of AML cells at relapse. This has several clinical implications: risk group stratification based on the presence of mutations that are associated with prognosis can be refined by genetic characterization of oligoclonal immature AML subpopulations that may play a role in the development of relapse. In addition, early and accurate detection of these subclones will be crucial in the prevention of relapse by accurate timing and application of targeted treatment. In conclusion, our results underline the concept of oligoclonality in AML and the involvement of clonal selection of immature chemoresistant subclones in the development of relapse. This study was supported by the Dutch Cancer Society (VU2005-3666). Disclosures:No relevant conflicts of interest to declare.

Characterization of human embryonic stem cell-derived hematopoietic progenitor phenotype

Differentiation of human embryonic stem cells (hESCs) into hematopoietic lineages using various methods has been reported. However, the phenotype that precisely defines the hematopoietic progenitor compartment with clonogenic activities has yet to be determined. Here, we measured and characterized progenitor function of subfractions of cells prospectively isolated from human embryoid bodies (hEBs) during hematopoietic differentiation basing on surface markers CD45, CD34, CD43, and CD38. We report that hematopoietic progenitors predominantly resided in the CD45(+) subset. CD43(+) cells lacking CD45 expression were largely devoid of progenitor activity. However, progenitor activity and multipotentiality was more enriched in CD45(+) cells co-expressing CD43. CD45(+) subset co-expressing CD34 but lacking CD38 expression (CD45(+)CD34(+)CD38(-)) were further enriched for CFU capacity compared to the CD45(+)CD34(+)CD38(+) subset. Our study demonstrates a role of CD43 in enriching hematopoietic progenitors derived from hEBs and reveals a hierarchical organization of hESC-derived hematopoietic progenitor compartments defined by phenotypic markers.

Localization of Enolase in the Subfractions of a Breast Cancer Cell Line

Enolase detected on the cell surface may be a receptor for certain ligands, especially for plasminogen. It is important for the pathogen invasiveness and in the development of a tumour. Therefore, we sought to preliminarily determine the enolase location and catalytic activity in the subfractions of MCF-7 cells. The latter was done on intact cells and in subfractions of MCF-7 cells. We identified enolase by immunoblotting. The binding of human plasminogen to enolase was performed by immunoblotting using monoclonal antibodies against plasminogen. The intact MCF-7 cells demonstrated activity of enolase. Enolase in postnuclear and perinuclear fractions is catalyticly active too. We identified the enolase protein in immunoblots of these fractions, except for the nuclear subfraction. These results provide evidence that enolase is present on the intact surface of MCF-7 cells and in post- and perinuclear fractions. The surface protein maintained catalytic activity, which suggests that its location in the plasma membrane didn't change the active centre of the enzyme.

Subfractions of white cells associated with body mass and fitness

Subfractions of white cells associated with body mass and fitness

Problems associated with routine PIXE analysis in quantifying elemental concentrations of leukocytes from Coronary Artery Bypass Grafting (CABG) surgery patients

Whole blood from patients undergoing Coronary Artery Bypass Grafting (CABG) operations was separated into leukocyte subfractions of polymorphonuclearcytes (PMN) and peripheral blood mononuclear cells (PBMC). Blood samples were collected and analyzed at various timepoints to determine the elemental composition to provide a better understanding of recovery mechanisms and to indicate complications that may occur post-operatively. Proton induced X-ray emission (PIXE) analysis and Rutherford backscattering spectrometry (RBS) using the University of Surrey microprobe was employed to determine the concentrations of a range of elements. Accurate two-dimensional PIXE analysis however, requires knowledge of the sample matrix composition. These samples, on the other hand, showed varying thickness, lacked matrix homogeneity and displayed non-uniform trace element distribution. This paper discusses the results and problems associated with routine PIXE analysis and demonstrates the potential ability of ion beam analysis (IBA) depth profiling software, previously unused in PIXE analysis, to model a RBS spectrum of inhomogeneous, multi-layered samples prior to performing PIXE analysis.

In vitro characterization of a human neural progenitor cell coexpressing SSEA4 and CD133

The stage-specific embryonic antigen 4 (SSEA4) is commonly used as a cell surface marker to identify the pluripotent human embryonic stem (ES) cells. Immunohistochemistry on human embryonic central nervous system revealed that SSEA4 is detectable in the early neuroepithelium, and its expression decreases as development proceeds. Flow cytometry analysis of forebrain-derived cells demonstrated that the SSEA4-expressing cells are enriched in the neural stem/progenitor cell fraction (CD133(+)), but are rarely codetected with the neural stem cell (NSC) marker CD15. Using a sphere-forming assay, we showed that both subfractions CD133(+)/SSEA4(+) and CD133(+)/CD15(+) isolated from the embryonic forebrain are enriched in neurosphere-initiating cells. In addition CD133, SSEA4, and CD15 expression is sustained in the expanded neurosphere cells and also mark subfractions of neurosphere-initiating cells. Therefore, we propose that SSEA4 associated with CD133 can be used for both the positive selection and the enrichment of neural stem/progenitor cells from human embryonic forebrain.

A Novel Rat Homolog of the Saccharomyces cerevisiae Ubiquitin-Conjugating Enzymes UBC4 and UBC5 with Distinct Biochemical Features Is Induced during Spermatogenesis

The Saccharomyces cerevisiae ubiquitin-conjugating enzymes (E2s) UBC4 and UBC5 are essential for degradation of short-lived and abnormal proteins. We previously identified rat cDNAs encoding two E2s with strong sequence similarity to UBC4 and UBC5. These E2 isoforms are widely expressed in rat tissues, consistent with a fundamental cellular function for these E2s. We now report a new isoform, 8A, which despite having >91% amino acid identity with the other isoforms, shows several novel features. Expression of the 8A isoform appears restricted to the testis, is absent in early life, but is induced during puberty. Hypophysectomy reduced expression of the 8A isoform. In situ hybridization studies indicated that 8A mRNA is expressed mainly in round spermatids. Immunoblot analyses showed that 8A protein is found not only in subfractions of germ cells enriched in round spermatids but also in subfractions containing residual bodies extruded from more mature elongated spermatids, indicating that the protein possesses a longer half-life than the mRNA. Unlike all previously identified mammalian and plant homologs of S. cerevisiae UBC4, which possess a basic pI, the 8A isoform is unique in possessing an acidic pI. The small differences in sequence between the 8A isoform and other rat isoforms conferred differences in biochemical function. The 8A isoform was less effective than an isoform with a basic pI or ineffective in conjugating ubiquitin to certain fractions of testis proteins. Thus, although multiple isoforms of a specific E2 may exist to ensure performance of a critical cellular function, our data demonstrate, for the first time, that multiple genes also permit highly specialized regulation of expression of specific isoforms and that subtle differences in E2 primary structure can dictate conjugation of ubiquitin to different subsets of cellular proteins.