Optimization of a flow cytometric method for the simultaneous measurement of cell surface antigen, DNA content, and in vitro BrdUrd incorporation into normal and malignant hematopoietic cells

ISWI ATPase Smarca5 Regulates Differentiation of Thymocytes Undergoing β-Selection

Development of lymphoid progenitors requires a coordinated regulation of gene expression, DNA replication, and gene rearrangement. Chromatin-remodeling activities directed by SWI/SNF2 superfamily complexes play important roles in these processes. In this study, we used a conditional knockout mouse model to investigate the role of Smarca5, a member of the ISWI subfamily of such complexes, in early lymphocyte development. Smarca5 deficiency results in a developmental block at the DN3 stage of αβ thymocytes and pro-B stage of early B cells at which the rearrangement of Ag receptor loci occurs. It also disturbs the development of committed (CD73⁺) γδ thymocytes. The αβ thymocyte block is accompanied by massive apoptotic depletion of β-selected double-negative DN3 cells and premitotic arrest of CD4/CD8 double-positive cells. Although Smarca5-deficient αβ T cell precursors that survived apoptosis were able to undergo a successful TCRβ rearrangement, they exhibited a highly abnormal mRNA profile, including the persistent expression of CD44 and CD25 markers characteristic of immature cells. We also observed that the p53 pathway became activated in these cells and that a deficiency of p53 partially rescued the defect in thymus cellularity (in contrast to early B cells) of Smarca5-deficient mice. However, the activation of p53 was not primarily responsible for the thymocyte developmental defects observed in the Smarca5 mutants. Our results indicate that Smarca5 plays a key role in the development of thymocytes undergoing β-selection, γδ thymocytes, and also B cell progenitors by regulating the transcription of early differentiation programs.

Detecting Hematopoietic Stem Cell Proliferation Using BrdU Incorporation

Cellular quiescence is a key component of hematopoietic stem cell (HSC) homeostasis; therefore, a reliable method to measure HSC cell division is critical in many studies. However, measuring the proliferation rate of largely quiescent and rare populations of cells can be challenging. Bromo-deoxyuridine (BrdU) incorporation into replicating DNA is a commonly used and highly reproducible method to detect cell division history. Here, we describe a protocol for BrdU incorporation analysis in hematopoietic stem and progenitor cells that can provide a sensitive measure of cell division even in rare cell populations. In combination with flow cytometry, this method can be generalized to analyze other cell populations and other tissues as identified by cell surface markers.

Activation of Antigen-Specific CD8(+) T Cells by Poly-DL-Lactide/Glycolide (PLGA) Nanoparticle-Primed Gr-1(high) Cells

PURPOSE

The aim of this study was to investigate the induction of antigen-specific T cell activation and cell cycle modulation by a poly-DL-lactide/glycolide (PLGA) nanoparticle (NP)-primed CD11b(+)Gr-1(high) subset isolated from mouse bone marrow.

METHODS

PLGA NPs containing the ovalbumin (OVA) antigen were prepared using the double emulsion and solvent evaporation method, and protein release rate and cell viability were determined. The Lin2(¯)CD11b(+)Gr-1(high)Ly6c(low) (Gr-1(high)) subset was sorted from the bone marrow of C57BL/6 J mice by fluorescence-activated cell sorting (FACS) and co-cultured with OT-I CD8(+) splenic T cells. Proliferation of OT-I CD8(+) T cells was monitored, and cell cycles were determined by 5-bromo-2'-deoxyuridine (BrdU) labeling.

RESULTS

Treatment of Gr-1(high) cells with PLGA/OVA NPs upregulated expression of the SIINFEKL-H2K(b) complex in the context of MHC I. Co-cultures of OT-I CD8(+) T cells with the PLGA/OVA NP-primed Gr-1(high) cells induced the proliferation of T cells in vitro and modulated cell division and morphology. Treatment of Gr-1(high) cells with PLGA/OVA NPs also induced cell apoptosis and necrosis.

CONCLUSION

This study demonstrated the function of PLGA/OVA NPs in the activation of OT-I CD8(+) T cells and the capability of cross-presentation via the Gr-1(high) polymorphonuclear subset from mouse bone marrow.

Antileukemic potential of PEGylated gold nanoparticle conjugated with protein toxin (NKCT1) isolated from Indian cobra (Naja kaouthia) venom

Limited efficacy of current first-line treatment for leukemia calls attention for further development of efficient strategies. Recently, much attention has been given to nanoparticle-based drug delivery systems loaded with dual drugs to improve current disease therapies by overcoming toxicity. In the present study, we document to explore an approach to conjugate gold nanoparticles (GNPs) with protein toxin (NKCT1), a protein toxin from the Indian cobra (Naja kaouthia) venom, and to establish its antileukemic activity. GNP was prepared by NaBH₄ reduction method. UV–vis spectroscopy of GNP showed the absorbance at 530 nm for plasma resonance. Dynamic light scattering (DLS) size of GNPs was 2–8 nm and the GNP-NKCT1 was 68–122 nm. CD spectra of GNP-NKCT1 showed change in percentage of β-turn as compared with NKCT1. GNP-NKCT1 significantly inhibited leukemic cell growth in dose- and time-dependent manner by two- to threefold more than NKCT1. For human leukemic lymphoma cell line and human myelogenous leukemic cell line, the IC50 dose was found to be 1.2 and 0.75 μg/ml, respectively, observed by trypan blue exclusion method and tetrazolium bromide reduction assay. Flow cytometric analysis showed appreciable number of both cell lines in early and late apoptotic stages and arrested cell cycle in the G1 phase by GNP-NKCT1. Resilient power of leukemic cell line after wound healing and migration or invasive power of the cell line was significantly low in GNP-NKCT1-treated plate than the control plate. These analyses reveal that GNP-NKCT1 possesses significant and selective anticancer activity, likely by inducing programmed cell death through mitochondrial and/or lysosomal pathway.

Involvement of intrinsic mitochondrial pathway in neosergeolide-induced apoptosis of human HL-60 leukemia cells: the role of mitochondrial permeability transition pore and DNA damage

CONTEXT

Quassinoids are biologically active secondary metabolites found exclusively in the Simaroubaceae family of plants. These compounds generally present important biological properties, including cytotoxic and antitumor properties.

OBJECTIVE

In the present study, the cytotoxic effects of neosergeolide, a quassinoid isolated from Picrolemma sprucei Hook. f., were evaluated in human promyelocytic leukemia cells (HL-60).

MATERIALS AND METHODS

Cytotoxicity and antiproliferative effects were evaluated by the MTT assay, May-Grünwald-Giemsa's staining, BrdU incorporation test, and flow cytometry procedures. The comet assay and micronuclei analysis were applied to determine the genotoxic and mutagenic potential of neosergeolide.

RESULTS

After 24 h exposure, neosergeolide strongly inhibited cancer cell proliferation (IC₅₀ 0.1 µM), and its activity seemed to be selective to tumor cells because it had no antiproliferative effect on human peripheral blood mononuclear cells (PBMC) at tested concentrations. Apoptosis was induced at submicromolar concentrations (0.05, 0.1, and 0.2 µM) as evidenced by morphological changes, mitochondrial depolarization, phosphatidylserine externalization, caspases activation, and internucleosomal DNA fragmentation. Additionally, neosergeolide effects were prevented by cyclosporine A (CsA), an inhibitor of the mitochondrial permeability transition (MPT) pore, which reinforced the participation of intrinsic pathways in the apoptotic process induced by this natural quassinoid. Direct DNA damage was further confirmed by comet assay and cytokinesis-block micronucleus test.

DISCUSSION AND CONCLUSION

The present study provided experimental evidence to support the underlying mechanism of action involved in the neosergeolide-mediated apoptosis. In addition, no antiproliferative effect or DNA damage effect of neosergeolide was evident in PBMC, highlighting its therapeutic potential.

Cytometry of DNA replication and RNA synthesis: Historical perspective and recent advances based on "click chemistry"

This review covers progress in the development of cytometric methodologies designed to assess DNA replication and RNA synthesis. The early approaches utilizing autoradiography to detect incorporation of (3) H- or (14) C-labeled thymidine were able to identify the four fundamental phases of the cell cycle G(1) , S, G(2) , and M, and by analysis of the fraction of labeled mitosis (FLM), to precisely define the kinetics of cell progression through these phases. Analysis of (3) H-uridine incorporation and RNA content provided the means to distinguish quiescent G(0) from cycling G(1) cells. Subsequent progress in analysis of DNA replication was based on the use of BrdU as a DNA precursor and its detection by the quenching of the fluorescence intensity of DNA-bound fluorochromes such as Hoechst 33358 or acridine orange as measured by flow cytometry. Several variants of this methodology have been designed and used in studies to detect anticancer drug-induced perturbations of cell cycle kinetics. The next phase of method development, which was particularly useful in studies of the cell cycle in vivo, including clinical applications, relied on immunocytochemical detection of incorporated halogenated DNA or RNA precursors. This approach however was hampered by the need for DNA denaturation, which made it difficult to concurrently detect other cell constituents for multiparametric analysis. The recently introduced "click chemistry" approach has no such limitation and is the method of choice for analysis of DNA replication and RNA synthesis. This method is based on the use of 5-ethynyl-2'deoxyuridine (EdU) as a DNA precursor or 5-ethynyluridine (EU) as an RNA precursor and their detection with fluorochrome-tagged azides utilizing a copper (I) catalyzed [3+2] cycloaddition. Several examples are presented that illustrate incorporation of EdU or EU in cells subjected to DNA damage detected as histone H2AX phosphorylation that have been analyzed by flow or laser scanning cytometry.

Synthesis and cytotoxicity screening of substituted isobenzofuranones designed from anacardic acids

This work is part of a large program, which seeks to discover new antitumor isobenfuranones designed from anacardic acids. The synthetic strategy for the construction of the title compounds takes into consideration the use of inexpensive anacardic acids (2), the major natural cashew (Anacardium occidentale) nut-shell phenolic lipid, and features one-pot construction of fused-ring aromatic gamma-lactones, phthalides. The cytotoxicity screening in different human cancer cell lines (HL-60 leukemia, SF295 glioblastoma and MDA-MB435 melanoma) by the MTT assay showed that acyclic precursor (6), and isobenfuranones (1a and 1b) are active compounds. Interestingly, 1a exhibits significant antiproliferative effect against HL-60 cells and moderate activity against SF295 and MDA-MB435 cell lines. Analysis of mechanisms involved in the cytotoxic activity showed that active compounds were leading to DNA damage, triggering apoptosis or necrosis induction.

Side population of a murine mantle cell lymphoma model contains tumour-initiating cells responsible for lymphoma maintenance and dissemination

‘Cancer stem cells’ or ‘tumour initiating cells’ in B-cell non-Hodgkin lymphomas have not been demonstrated, although some studies focused on other cancer types suggest that such populations exist and represent tumour cells resistant to therapy and involved in relapse. These cells may also represent a putative neoplastic ‘cell of origin’ in lymphomas, but there is little substantive data to support this suggestion. Using cell lines derived from a recently established murine IL-14α× c-Myc double transgenic/mantle cell lymphoma-blastoid variant model, heretofore referred to as DTG cell lines, we identified a subset of cells within the side population (SP) with features of ‘tumour-initiating cells’. These features include higher expression of ABCG2 and BCL-2, longer telomere length, greater self-renewal ability and higher in vitro clonogenic and in vivo tumorigenic capacities compared with non-SP. In addition, in vitro viability studies demonstrated that the non-SP lymphoma subpopulation has a limited lifespan in comparison with the SP fraction. Syngenic transplant studies showed that non-SP derived tumours, in comparison to the SP-derived tumours, exhibit greater necrosis/apoptosis and less systemic dissemination capability. In conclusion, our data support the interpretation that the DTG SP fraction contains a cell population highly capable of tumour maintenance and systemic dissemination and lends support to the concept that ‘tumour-initiating cells’ occur in lymphomas.

Establishment and characterization of 4 new human pancreatic cancer cell lines: evidences of different tumor phenotypes

OBJECTIVES

Pancreatic cancer still remains a challenge for its biological complexity and lack of effective therapeutic strategies. Establishing new pancreatic cancer cell lines is therefore of paramount importance to clarify its biology.

METHODS

We established and characterized 4 new pancreatic cancer cell lines (PP78, PP109, PP117, and PP161) according to their genetic (K-Ras, TP53, CDKN2A, and MADH4; DNA fingerprinting; karyotype), cytostructural (cytokeratins 7, 8, 18, and 19 vimentin, and ezrin), and functional profiles (doubling time; migration assay).

RESULTS

K-Ras, TP53, and CDKN2A gene alterations were detected in all 4 of them. Each cell line had a unique DNA profile revealed by DNA fingerprinting. A complex karyotype with numerous structural and numeric chromosomal abnormalities was present in each cell line. All 4 cell lines showed positivity for cytokeratins 7, 8, and 18. All but PP78 expressed cytokeratin 19, whereas vimentin was expressed only in PP117 and PP78 cells. A different ezrin cellular distribution was noticed in PP78 and PP117, being mostly located at membrane ruffles. This peculiar distribution was associated with the strongest migratory capability.

CONCLUSIONS

Our results seem to confirm the pancreatic ductal adenocarcinoma heterogeneity; in fact, the same genetic abnormalities (K-Ras, TP53, and CDKN2A) may have different effects on tumor biology depending on cellular differentiation.

Cytotoxic activity of a dichloromethane extract and fractions obtained from Eudistoma vannamei (Tunicata: Ascidiacea)

This study consists of the bioassay-guided fractionation of the dichloromethane extract from Eudistoma vannamei and the pharmacological characterization of the active fractions. The dried hydromethanolic extract dissolved in aqueous methanol was partitioned with dichloromethane and chromatographed on a silica gel flash column. The anti-proliferative effect was monitored by the MTT assay. Four of the latest fractions, numbered 14 to 17, which held many chemical similarities amongst each other, were found to be the most active. The selected fractions were tested for viability, proliferation and death induction on cultures of HL-60 promyeloblastic leukemia cells. The results suggested that the observed cytotoxicity is related to apoptosis induction.

Antileukemic effects of Didemnum psammatodes (Tunicata: Ascidiacea) constituents

Chemical investigation of the methanolic extract of the ascidian Didemnum psammatodes has led to the identification of fourteen known compounds: three methyl esters (methyl myristate, methyl palmitate and methyl stearate), four steroids (cholesterol, campesterol, stigmasterol and beta-sitosterol), two fatty acids (palmitic acid and stearic acid), three glyceryl ethers {(1,2-propanediol, 3-(heptadecyloxy), batyl alcohol and 1,2-propanediol, 3-[(methyloctadecyl)oxy]} and two nucleosides (thymidine and 2'-deoxyguanosine). Their structures were proposed by NMR and comparison with literature data and GC analysis in comparison with authentic sample. The cytotoxic activity of these compounds was evaluated against human leukemia cell line panel using the MTT assay. The mixture of the three methyl esters was the most active group of compounds, showing antiproliferative and cytotoxic effects. Further studies on their mode of action suggest that these activities are connected with inhibition of DNA synthesis and induction of both necrosis and apoptosis.

Myelodysplasia and anemia of chronic disease in human tumor necrosis factor-alpha transgenic mice

TNF-alpha is a pleitropic cytokine that expresses both pro- and anti-inflammatory activity and transgenic mice expressing human tumor necrosis factor-alpha (TNF-alpha) exhibit a progressive polyarthritis that models rheumatoid arthritis (RA). One of the common comorbidities of RA is anemia of chronic disease (ACD). The purpose of these experiments was to study the changes in the bone marrow and peripheral blood that accompany polyarthritis in TNF-alpha transgenic mice in an effort to better understand the pathogenesis of myelodysplasia and ACD. Polychromatic cytometry, hematology and serum cytokine analysis were used to study the pathogenesis of ACD in human TNF-alpha transgenic mice. Our hematological evaluation revealed a mild, compensated, microcytic hypochromic anemia, and monocytosis. In the bone marrow, we observed alterations in cell kinetics, decreased relative expression of transferrin receptor and increased apoptosis and cell death in several late precursor cell populations. Although significant levels of human TNF-alpha were found in the serum, neither change in serum murine erythropoietin nor any significant difference observed in serum levels of murine IL-beta, IL-5, IL-6, IL-10, IL-12(p70), IL-17, TNF-alpha, IFNgamma, GM-CSF, MIP-1alphaJE, MCP-5 was observed. Tg197 mice develop a compensated, microcytic, hypochromic anemia, and a functional iron deficiency by 9 weeks of age. Changes in peripheral blood are reflected in alterations in cell kinetics, transferrin receptor expression and markedly increased apoptosis and cell death in the bone marrow indicating that TNF-alpha may contribute to myelodysplasia in ACD. Moreover, since human TNF-alpha can interact only with murine TNFR1, our data suggest that TNFR1 may play an important role in the development of ACD.

Malignant catarrhal fever induced by alcelaphine herpesvirus 1 is associated with proliferation of CD8+ T cells supporting a latent infection

Alcelaphine herpesvirus 1 (AlHV-1), carried by wildebeest asymptomatically, causes malignant catarrhal fever (WD-MCF) when cross-species transmitted to a variety of susceptible species of the Artiodactyla order. Experimentally, WD-MCF can be induced in rabbits. The lesions observed are very similar to those described in natural host species. Here, we used the rabbit model and in vivo 5-Bromo-2'-Deoxyuridine (BrdU) incorporation to study WD-MCF pathogenesis. The results obtained can be summarized as follows. (i) AlHV-1 infection induces CD8(+) T cell proliferation detectable as early as 15 days post-inoculation. (ii) While the viral load in peripheral blood mononuclear cells remains below the detection level during most of the incubation period, it increases drastically few days before death. At that time, at least 10% of CD8(+ )cells carry the viral genome; while CD11b(+), IgM(+) and CD4(+) cells do not. (iii) RT-PCR analyses of mononuclear cells isolated from the spleen and the popliteal lymph node of infected rabbits revealed no expression of ORF25 and ORF9, low or no expression of ORF50, and high or no expression of ORF73. Based on these data, we propose a new model for the pathogenesis of WD-MCF. This model relies on proliferation of infected CD8(+) cells supporting a predominantly latent infection.

Pharmacodynamics of Recombinant Human Erythropoietin in Murine Bone Marrow

PURPOSE

Originally approved for three times/week dosing, recombinant human erythropoietin (rhEPO) is now often used at weekly intervals. We have studied rhEPO in mice to better understand why the extended dosing interval retains efficacy.

METHODS

C57Bl/6 mice received a single sc. dose of rhEPO (3,000 IU/kg). Bone marrow and blood were collected at 8 h and 1, 2, 5 and 7 days. Staining for TER-119 and CD71, pulse labeling with bromodeoxyuridine, annexin-V binding and vital staining with 7-aminoactinomycin D: were used cell cycle and apoptosis in erythroblasts by four color flow cytometry.

RESULTS

A wave of proliferation and/or maturation progressed through all erythroblasts, resulting in the emigration of immature reticulocytes into the periphery. An increase in the fraction of erythroblasts in S and G2M was found, but suppression of apoptosis was not.

CONCLUSIONS

Most of the effects of rhEPO occurred 48 h after dosing, when the concentration of rhEPO was less than 1% of Cmax, suggesting that the processes set in motion by rhEPO can continue after rhEPO concentrations fall. Our observation of apoptosis in erythroblasts even when rhEPO concentrations were high suggests that regulatory mechanisms which down-regulate erythropoiesis are also engaged.

Neuronal cell cycle re-entry mediates Alzheimer disease-type changes

Evidence showing the ectopic re-expression of cell cycle-related proteins in specific vulnerable neuronal populations in Alzheimer disease led us to formulate the hypothesis that neurodegeneration, like cancer, is a disease of inappropriate cell cycle control. To test this notion, we used adenoviral-mediated expression of c-myc and ras oncogenes to drive postmitotic primary cortical neurons into the cell cycle. Cell cycle re-entry in neurons was associated with increased DNA content, as determined using BrdU and DAPI, and the re-expression of cyclin B1, a marker for the G2/M phase of the cell cycle. Importantly, we also found that cell cycle re-entry in primary neurons leads to tau phosphorylation and conformational changes similar to that seen in Alzheimer disease. This study establishes that the cell cycle can be instigated in normally quiescent neuronal cells and results in a phenotype that shares features of degenerative neurons in Alzheimer disease. As such, our neuronal cell model may be extremely valuable for the development of novel therapeutic strategies.

Differential and nonredundant roles of phospholipase Cgamma2 and phospholipase Cgamma1 in the terminal maturation of NK cells

NK cells play a central role in mediating innate immune responses. Activation of NK cells results in cytotoxicity, cytokine, and chemokine secretions. In this study, we show that in mice with targeted deletion of phospholipase Cgamma (PLCgamma)2, one of the key signal transducers, there are profound effects on the development and terminal maturation of NK cells. Lack of PLCgamma2 significantly impaired the ability of lineage-committed NK precursor cells to acquire subset-specific Ly49 receptors and thereby terminal maturation of NK cells. Overexpression of isozyme, PLCgamma1, in PLCgamma2-deficient NK cells resulted in the successful Ly49 acquisition and terminal maturation of the NK cells; however, it could only partially rescue NKG2D-mediated cytotoxicity with no cytokine production. Furthermore, PLCgamma2-deficient NK cells failed to mediate antitumor cytotoxicity and inflammatory cytokine production, displaying a generalized hyporesponsiveness. Our results strongly demonstrate that PLCgamma1 and PLCgamma2 play nonredundant and obligatory roles in NK cell ontogeny and in its effector functions.

Effects of transient PTH on early proliferation, apoptosis, and subsequent differentiation of osteoblast in primary osteoblast cultures

In primary calvarial osteoblast cultures derived from transgenic mice expressing green fluorescent protein (GFP) under the control of 3.6-kb Col1a1 promoter, the emergence of GFP signal marks the transition of multipotential osteoprogenitors into preosteoblasts. Early transient treatment (days 1-7) of these cultures with parathyroid hormone (PTH) has an anabolic effect that is not associated with an increase in total DNA content or cell number in day 21 cultures. In the present study, the effect of early PTH treatment on cell proliferation and apoptosis was examined in greater detail in GFP(+) and GFP(-) cells using flow cytometry. In preconfluent cultures, PTH significantly reduced the proportion of cells in S phase but increased those in G(0)/G(1) and G(2)+M phases in both GFP(+) and GFP(-) subpopulations. PTH decreased apoptosis only in GFP(-) but not GFP(+) cells, indicating an increased survival of GFP(-) cells. In contrast, PTH did not change the amounts of cell proliferation and apoptosis seen in either compartment after these cultures reached confluence. To further assess the effect of early PTH treatment on osteogenic differentiation, secondary cultures of sorted GFP(+) or GFP(-) cells were obtained from day 7 primary cultures that had been treated for 1 wk with PTH. This treatment resulted in larger areas of GFP expression accompanied by increased xylenol orange/von Kossa staining in the secondary cultures of GFP fractions. Early transient PTH treatment appears to enhance the commitment of progenitor cells to an osteogenic fate and results in a higher proportion of cells that achieve full osteoblast differentiation.

Dissemination of bovine leukemia virus-infected cells from a newly infected sheep lymph node

To investigate the early establishment of bovine leukemia virus (BLV) infection, we injected BLV-infected or mock-infected allogeneic cells into the shoulder of sheep in which an efferent lymphatic duct of the draining prescapular lymph node had been cannulated. Rare mononuclear cells acting as centers of BLV infection in culture were present within 4 to 6 days in efferent lymph and within 6 to 10 days in blood. Soon after BLV injection, immunoglobulin M+ (IgM+) and CD8+ cells increased in efferent lymph and oscillated reciprocally in frequency. CD8+ blasts increased on days 4 to 6, when infectious centers increased 100-fold in lymph. On days 6 and 7, both lymph and blood were enriched with CD8+ cells that were labeled late on day 5 with an intravenous pulse of 5-bromo-2'-deoxyuridine (BrdU). Lymph, but not blood, was enriched with BrdU+ B cells on day 7. Capsid-specific antibodies became detectable in efferent lymph on days 6 to 8 and surface glycoprotein-specific antibodies on day 9, preceding their detection in serum by 9 to 14 days. Systemic dissemination of BLV-infected cells was thus accompanied by an increase in proliferating CD8+ cells and the onset of BLV-specific antibodies in lymph. Infectious centers reached maximum frequencies of 0.2% in lymph by days 11 to 13, and then their frequencies increased by 5- to 40-fold in blood cells, suggesting that many infected blood cells do not recirculate back into lymph. Beginning on days 10 to 13, a subpopulation of B cells having high levels of surface IgM increased sharply in peripheral blood. Such cells were not present in lymph. After a day 16 pulse of BrdU, recently proliferated cells that stained intensely for surface IgM appeared in blood within 15 h. Predominantly B lymphocytes contained the viral capsid protein when lymph and blood cells were cultured briefly to allow BLV expression. However, both early in lymph and later in blood, BrdU+ B cells greatly exceeded productively infected cells, indicating that new BLV infections stimulate proliferation of two different populations of B cells.

Establishment of a pediatric HSCT program in a public hospital in Chile

BACKGROUND

In Chile, survival estimates for pediatric patients with cancer are comparable to those in the United States and Western Europe. Approximately 80% of these patients are treated at government-supported centers, and an estimated 65% are cured. We reasoned that cure rates could be further improved if transplantation with hematopoietic stem cells were available for patients with chemotherapy-resistant malignancy.

PATIENTS AND METHODS

Physicians and nurses were selected to be trained in international centers, and a transplantation unit was developed at Luis Calvo Mackenna Hospital in Santiago. Between October 1999 and December 2003, 59 patients received transplants. Of these, 42 were from HLA-matched family members and 11 were autologous.

RESULTS

The 3-year event-free survival estimate was 72 +/- 10% overall, and it was 81 +/- 10% for the subgroup treated with matched related transplants. Peritransplant mortality was 6.6%. The average cost for an allogeneic transplant in our unit was 50,000 US dollars.

CONCLUSIONS

We are encouraged by this experience as well as by the overall survival rates and hope to expand the program. Our goal is to extend treatment to all children in the country for whom HSCT is indicated, including those who do not have HLA-identical family donors.

CXCR3 surface expression in human airway epithelial cells: cell cycle dependence and effect on cell proliferation

We recently demonstrated that human bronchial epithelial cells (HBEC) constitutively express the CXC chemokine receptor CXCR3, which when activated, induces directed cell migration. The present study in HBEC examined the relative expression of the CXCR3 splice variants CXCR3-A and -B, cell cycle dependence of CXCR3 expression, and the effects of the CXCR3 ligand, the interferon-gamma-inducible CXC chemokine I-TAC/CXCL11, on DNA synthesis and cell proliferation. Both CXCR3-A and -B mRNA, assessed by real-time RT-PCR, were expressed in normal HBEC (NHBEC) and the HBEC line 16-HBE. However, CXCR3-B mRNA was 39- and 6-fold greater than CXCR3-A mRNA in NHBEC and 16-HBE, respectively. Although most HBEC (>80%) assessed by flow cytometry and immunofluorescence microscopy contained intracellular CXCR3, only a minority (<40%) expressed it on the cell surface. In this latter subset of cells, most (>75%) were in the S + G(2)/M phases of the cell cycle. Stimulation of CXCR3 with I-TAC enhanced thymidine incorporation and cell proliferation and increased p38 and ERK1/2 phosphorylation. These data indicate that 1) human airway epithelial cells primarily express CXCR3-B mRNA, 2) surface expression of CXCR3 is largely confined to the S + G(2)/M phases of the cell cycle, and 3) activation of CXCR3 induces DNA synthesis, cell proliferation, and activation of MAPK pathways. We speculate that activation of CXCR3 exerts a mitogenic effect in HBEC, which may be important during airway mucosal injury in obstructive airway diseases such as asthma and chronic obstructive pulmonary disease.

Activation of human T lymphocytes under conditions similar to those that occur during exposure to microgravity: A proteomics study

A number of experiments, conducted under microgravity conditions, i.e. in space shuttle biolaboratories or in ground based systems simulating the conditions occurring in microgravity, show that in hypogravity, in vitro human lymphocyte activation is severely impaired. However, very early stimulation steps of T lymphocytes are not compromised, since CD69 receptor, the earliest membrane activation marker, is expressed by T cells at a level comparable to that observed on 1 g activated lymphocytes. Since CD69 engagement, together with submitogenic doses of phorbol esters, transduces an activation signal to T lymphocytes, we undertook a comparative study on the stimulation mediated through this receptor on human CD3+ cells cultured under conditions similar to those which occur during exposure to microgravity, i.e. in clinorotation, or at 1 g. During the early hours of activation, increased levels of intracellular calcium and increased mitochondrial membrane potential were detectable in clinorotating as well as in 1 g cells. However, after 48 hours clinorotation, interleukin 2 production by T lymphocytes was significantly reduced and cell proliferation was greatly decreased. By means of a differential proteomics approach on T cells activated in clinorotation or at 1 g for 48 hours, we were able to detect statistically significant quantitative protein alterations. Seven proteins with modified expression values were identified; they are involved in nucleic acids processing, proteasome regulation and cytoskeleton structure.

Investigation of the susceptibility of human cell lines to bovine herpesvirus 4 infection: demonstration that human cells can support a nonpermissive persistent infection which protects them against tumor necrosis factor alpha-induced apoptosis

Bovine herpesvirus 4 (BoHV-4) is a gammaherpesvirus that has a worldwide distribution in the population of cattle. Many factors make human contamination by BoHV-4 likely to occur. In this study, we performed in vitro experiments to assess the risk and the consequences of human infection by BoHV-4. First, by using a recombinant BoHV-4 strain expressing enhanced green fluorescent protein under the control of the human cytomegalovirus immediate-early gene promoter, we tested 21 human cell lines for their sensitivity and their permissiveness to BoHV-4 infection. These experiments revealed that human cell lines from lymphoid and myeloid origins were resistant to infection, whereas epithelial cells, carcinoma cells, or adenocarcinoma cells isolated from various organs were sensitive but poorly permissive to BoHV-4 infection. Second, by using the HeLa cell line as a model of human cells sensitive but not permissive to BoHV-4 infection, we investigated the resistance of infected cells to apoptosis and the persistence of the infection through cellular divisions. The results obtained can be summarized as follows. (i) BoHV-4 nonpermissive infection of HeLa cells protects them against tumor necrosis factor alpha-induced apoptosis. (ii) BoHV-4 infection of HeLa cells persists in cell culture; however, the percentage of infected cells decreases with time due to erratic transmission of the viral genome through cell division. (iii) BoHV-4 infection has no effect on the rate of HeLa cell division. Altogether, these data suggest that BoHV-4 could infect humans. This study also stresses the importance of considering the insidious effects of nonpermissive infection when the biosafety of animal gammaherpesviruses for humans is being considered.

The IL-12 Signature: NK Cell Terminal CD56+high Stage and Effector Functions

We report that human peripheral NK cells expressing high CD56 levels (CD56(+high)) are terminally differentiated cells indistinguishable from mature NK cells recently activated in the presence of IL-12, and not a functionally distinct NK-cell subset or progenitors to mature CD56(+low) NK cells. CD56(+high) NK cells coexpress all differentiation Ags constitutive or inducible in mature (CD56(+)) NK cells, except CD16, present at lower level than on most mature NK cells. Also, activation markers, activating receptors and adhesion molecules, and most inducible receptors are expressed exclusively and constitutively and are inducible at higher levels on CD56(+high) than on CD56(+low) NK cells. Consistent with their activated phenotype, many CD56(+high) NK cells are cycling and mediate heightened effector functions (proliferation, IFN-gamma and IL-10 but not IL-13 production) in response to IL-12 and other NK cell-specific stimuli. Conversely, IL-12 induces on CD56(+low) NK cells all markers constitutively expressed on the CD56(+high) NK cells, concomitantly preventing the IL-2 (and IL-15)-inducible expression of NKp44 and CD16 re-expression after immune complex-induced down-modulation, and CD56(-/+low) NK cells acquire a CD56(+high) NK cell phenotype in short term in vitro culture with IL-12. The significance of these findings to the NK cell-mediated regulation of immune responses and NK cell development is discussed.

Proliferation and apoptosis in acute and chronic leukemias and myelodysplastic syndrome

Clonal expansion of leukemic cells is thought to be due to proliferation in excess of apoptosis. To define and compare proliferation and apoptosis between various leukemias and myelodysplastic syndrome (MDS), we measured proliferating cell nuclear antigen (PCNA) and bromodeoxyuridine (BrdU) incorporation as surrogate markers for proliferation and caspase 3 activity and annexin V surface binding as surrogate markers for activation of the apoptotic cascade in patients with MDS, chronic myelomonocytic leukemia (CMML), acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML). We found high proliferation in bone marrow cells from MDS and CMML as measured by PCNA and BrdU incorporation. The lowest level of proliferation was found in CLL. Apoptosis was also highest in MDS and CMML as measured by annexin V and caspase 3 activity. Unexpectedly, we found no significant difference in proliferation in bone marrow CD34+ cells from various leukemias or MDS. Apoptosis was significantly higher in bone marrow CD34+ cells from MDS and CML in chronic phase as compared to CD34+ cells from AML patients. Our results illustrate differences in proliferation and apoptosis between acute and chronic leukemias and MDS. These differences may have diagnostic and therapeutic implications.

Decrease in apoptosis and increase in polyploidization of megakaryocytes by stem cell factor during ex vivo expansion of human cord blood CD34+ cells using thrombopoietin

Thrombopoietin (TPO) is widely used for ex vivo expansion of hematopoietic stem cells. Previously, we have reported that TPO induces a characteristic pattern of apoptosis, and the TPO-induced apoptosis is closely associated with megakaryocyte (MK) differentiation. In the present study, several cytokines, flt3-ligand, stem cell factor (SCF), interleukin-3 (IL-3), IL-6, IL-11, leukemia inhibitory factor, G-CSF, and erythropoietin, which are known to affect megakaryocytopoiesis, have been evaluated to elucidate their effects on the TPO-induced apoptosis. Measurement of apoptosis by flow cytometry revealed that only SCF absolutely reduced the TPO-induced apoptosis in MK fractions, particularly in the late phase of ex vivo expansion. Platelet production was demonstrated by electron microscopy in a later phase when SCF was added. Simultaneous measurement of DNA contents with immunophenotyping demonstrated a significant increase in polyploidization in the CD41+ cell fraction when cultured with SCF. These results suggested that SCF not only inhibited premature senescence but also enhanced maturation of the differentiating cells of MK lineage during ex vivo expansion using TPO.

Megakaryothrombopoiesis during ex vivo expansion of human cord blood CD34+ cells using thrombopoietin

Thrombopoietin (TPO) is one of the most promising stimulants for ex vivo expansion of haematopoietic stem cells. Previously, we have found that TPO induces a characteristic pattern of apoptosis during ex vivo expansion of human cord blood (CB) CD34+ cells and that the TPO-induced apoptotic cells belong to megakaryocyte (MK) lineage. In this study, we have examined the maturation of MK and platelet production in association with the TPO-induced apoptosis. CD34+ cells, purified from human CB, were expanded in serum-free conditions stimulated with TPO. Apoptosis was confirmed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL) assay and electron microscopy (EM). Simultaneous measurement of DNA content and immunophenotyping revealed that the cells with higher DNA content (>8 N) constituted less than 5% of the CD41+ fractions until day 14, implying premature apoptosis of MKs before full polyploidization. Nevertheless, EM observation showed not only platelet territories but also newly produced platelets in which granules and microfilaments could be identified. Furthermore, flow cytometry demonstrated that the platelet fraction expressed P-selectin and an activation motif on GPIIb/IIIa recognized by monoclonal antibody PAC-1 upon stimulation with adenosine diphosphate (ADP). In addition, periodic acid-Schiff (PAS)-positive materials and nonspecific esterase activities could be demonstrated. Therefore, it is suggested that platelet production and the accompanying processes, rather than apoptosis only, be hastened during the ex vivo expansion of CB CD34+ cells when using TPO.

Immune reconstitution after autologous peripheral blood progenitor cell transplantation: effect of interleukin-15 on T-cell survival and effector functions

OBJECTIVE

The aim of this study was to evaluate the occurrence of T-cell spontaneous apoptosis (A(spont)) and its modulation in vitro by the interleukin-2 receptor (IL-2R) gamma-chain (gammac)-signaling cytokine IL-15 in patients transplanted with autologous peripheral blood progenitor cells (PBPC) for hematologic malignancies.

MATERIALS AND METHODS

Patients were examined on days 30-60, 60-90, and 90-120 after PBPC infusion. Dissipation of mitochondrial transmembrane potential, a hallmark of T-cell apoptosis, has been detected using the fluorescent probe 3,3'-dihexyloxacarbocyanine iodide, after short-term T-cell culture in the absence or presence of exogenous cytokines. Expression of Bcl-2 family members has been studied by flow cytometry and reverse transcriptase polymerase chain reaction. T-cell proliferative responses to recall antigens have been estimated in autologous mixed leukocyte cultures.

RESULTS

A(spont) was seen in 45% +/- 6% of CD4(+) and 55% +/- 6% of CD8(+) T cells cultured in the absence of cytokines. Of interest, IL-15 and, to a lesser extent, its structural cousin IL-2 counteracted T-cell A(spont) by inhibiting the processing of caspase-3 and up-regulating Bcl-2 mRNA and protein levels. Cell division tracking confirmed that IL-15 did not rescue T cells from A(spont) by promoting proliferation but rather acted as a genuine survival factor. Addition of a gammac-blocking antibody to cytokine-conditioned cultures abrogated both apoptosis inhibition and Bcl-2 induction by IL-15, suggesting involvement of the IL-2Rgammac signal transduction pathway. Whereas cytokine-unprimed posttransplant T cells mounted inadequate responses to recall antigens, T cells conditioned with IL-15 expanded vigorously, indicating restoration of antigen-specific proliferation.

CONCLUSIONS

T cells recovering after autologous PBPC transplantation are highly susceptible to spontaneous apoptosis in vitro. This phenomenon can be counteracted by the gammac-signaling cytokine IL-15. These findings suggest that IL-15 might be a promising immunomodulating agent to improve postgrafting T-cell function.

Dynamic cell cycle kinetics in vitro and in vivo in myelodysplastic syndromes with special reference to the influence of hematopoietic growth factors

We have investigated the effect of HGF in vivo and in vitro in MDS using a recently developed FCM assay involving the simultaneous measurement of cell surface antigens, DNA content, and BrdUrd or IodUrd incorporation. This allows for the determination of the dynamic cell kinetic parameters: LI, T(s), and T(pot) and we observed that in vitro HGF stimulation resulted in a significant decrease in mean T(pot) values from 6.6 to 3.5 days. Importantly, we demonstrated that in vivo GM-CSF administration to patients with RAEB resulted in a shortening of T(pot) within the 2 first weeks of GM-CSF treatment.

Soluble CD40 ligand induces selective proliferation of lymphoma cells in primary mantle cell lymphoma cell cultures

Interaction between CD40 and the CD40 ligand (CD40L) is critical for the survival and proliferation of B cells during immunopoiesis. However, the role of CD40L in the pathogenesis of malignant lymphomas is ambiguous. Primary mantle cell lymphoma (MCL) cells were cultured in the presence of recombinant human CD40L trimer (huCD40LT), and a significant time- and dose-dependent induction of DNA synthesis was observed in thymidine incorporation assays (n = 7,P &lt; .04). The maximal rate of DNA synthesis was reached at huCD40LT doses of 100 ng/mL and above after 4 days of culture, but a significant increase of DNA synthesis was detected already at doses of 1 ng/mL (P = .03). HuCD40LT never inhibited the basal level of DNA synthesis. These findings established 400 ng/mL of huCD40LT for 4 days as standard conditions in the system. Under these conditions, huCD40LT significantly increased the proportion of cells in the S/G2/M phases of the cell cycle in 4 of 7 studied cases, while the fraction of apoptotic cells remained unchanged (n = 7). HuCD40LT also induced expression of CD80/B7-1, CD86/B7-2, and CD95/Fas and up-regulated the expression of HLA-DR (n = 6). With the use of bromodeoxyuridine incorporation in triple-color flow cytometric analysis, it was found that huCD40LT induced cell-cycle progression in light chain–restricted cells only, of which a median of 14% (range, 0.5% to 29%; n = 4) returned to G0/1 phase DNA content after bromodeoxyuridine incorporation, demonstrating completion of at least one cell cycle in the presence of huCD40LT. Thus, primary clonal MCL cells are activated and can proliferate in the presence of huCD40LT as a single agent.

Soluble CD40 ligand induces selective proliferation of lymphoma cells in primary mantle cell lymphoma cell cultures

Interaction between CD40 and the CD40 ligand (CD40L) is critical for the survival and proliferation of B cells during immunopoiesis. However, the role of CD40L in the pathogenesis of malignant lymphomas is ambiguous. Primary mantle cell lymphoma (MCL) cells were cultured in the presence of recombinant human CD40L trimer (huCD40LT), and a significant time- and dose-dependent induction of DNA synthesis was observed in thymidine incorporation assays (n = 7,P < .04). The maximal rate of DNA synthesis was reached at huCD40LT doses of 100 ng/mL and above after 4 days of culture, but a significant increase of DNA synthesis was detected already at doses of 1 ng/mL (P = .03). HuCD40LT never inhibited the basal level of DNA synthesis. These findings established 400 ng/mL of huCD40LT for 4 days as standard conditions in the system. Under these conditions, huCD40LT significantly increased the proportion of cells in the S/G2/M phases of the cell cycle in 4 of 7 studied cases, while the fraction of apoptotic cells remained unchanged (n = 7). HuCD40LT also induced expression of CD80/B7-1, CD86/B7-2, and CD95/Fas and up-regulated the expression of HLA-DR (n = 6). With the use of bromodeoxyuridine incorporation in triple-color flow cytometric analysis, it was found that huCD40LT induced cell-cycle progression in light chain–restricted cells only, of which a median of 14% (range, 0.5% to 29%; n = 4) returned to G0/1 phase DNA content after bromodeoxyuridine incorporation, demonstrating completion of at least one cell cycle in the presence of huCD40LT. Thus, primary clonal MCL cells are activated and can proliferate in the presence of huCD40LT as a single agent.

Ultraviolet-induced detection of halogenated pyrimidines: simultaneous analysis of DNA replication and cellular markers

BACKGROUND

We describe a new nonenzymatic methodology that allows the simultaneous detection of DNA replication and other cellular markers such as immunophenotyping. DNA replicating cells are identified by their incorporation of halogenated thymidine analogs, e.g., 5-bromo-deoxyuridine (BrdUrd).

METHODS

Irradiation with ultraviolet (UV)-B or UV-A light in the presence of Hoechst 33258 and subsequent treatment with a hypotonic buffer makes BrdUrd accessible to monoclonal antibodies (mAb), thus allowing its sensitive detection.

RESULTS

The photolysis of BrdUrd in DNA with UV light is sequence dependent and results in DNA damage, allowing the detection of remaining BrdUrd using hypotonic conditions. However, treatment with other inducers of single or double- strand breaks of DNA such as gamma irradiation or hydrogen peroxide did not allow BrdUrd detection. The new methodology is compatible with both mild crosslinking fixation, i.e., aldehydes, or coagulative fixation, i.e., alcohols. The successful identification of CD34+, CD138+, or CD19+ cells out of heterogeneous cell suspensions and their cell-cycle analysis are described. Results correlated very well with acid denaturation (r = 0.972). The average coefficient of variation (CV) of G(1) in the DNA histogram was smaller than 5%, resulting in good preservation of DNA distribution. Also, the signal-to-noise ratio was almost twice as high as for 2N acid denaturation, facilitating convenient discrimination of BrdUrd-positive cells.

CONCLUSIONS

In contrast to previous approaches, this methodology eliminates the need for any additional enzymatic treatment such as DNA digestion or strand-break labeling after UV irradiation. The method is fast, convenient, and inexpensive and should be able to promote the use of halogenated pyrimidines in basic and clinical research of cancer, immunology, and pharmacology.

Dynamic cell cycle kinetics of normal CD34+ cells and CD38+/- subsets of haemopoietic progenitor cells in G-CSF-mobilized peripheral blood

Using a recently developed flow cytometric assay for the simultaneous measurement of cell surface antigens, DNA content and bromodeoxyuridine incorporation, we have for the first time determined the labelling index (LI), the duration of the S-phase (Ts) and the potential doubling time (Tpot) of purified CD34+ cells mobilized by G-CSF from 10 normal donors. Although CD34+ cells were not actively cycling immediately following purification, up to 5% could nevertheless traverse cell cycle without exogenous stimulation during the first 24 h of culture. In addition, it was possible to induce CD34+ cells to enter cycling by stimulation with haemopoietic growth factors (IL-3, IL-6 and SCF), resulting in median Tpot values of 18.2 d at 21 h, 7.7 d at 29 h, and 4.5 d at 37 h. Importantly, stimulation of CD34+ cells was seen almost exclusively within the CD38+ subset (mean Tpot value 2.8 d), whereas CD38- cells were not recruited into cycle (mean Tpot value 35.9 d). In conclusion, although cell cycle entry and progression can easily be induced in differentiated CD34+/CD38+ cells, immature CD34+/CD38- cells will remain dormant in most of the clinical and laboratory stimulation protocols hitherto employed. This assay can be used to obtain detailed cell cycle kinetics in leucocyte subsets in health and disease.