Retinoic acid differentiation of HL-60 cells promotes cytoskeletal polarization

Magnetic field and nuclear spin influence on the DNA synthesis rate

The rate of a chemical reaction can be sensitive to the isotope composition of the reactants, which provides also for the sensitivity of such "spin-sensitive" reactions to the external magnetic field. Here we demonstrate the effect of the external magnetic field on the enzymatic DNA synthesis together with the effect of the spin-bearing magnesium ions ([Formula: see text]Mg). The rate of DNA synthesis monotonously decreased with the external magnetic field induction increasing in presence of zero-spin magnesium ions ([Formula: see text]Mg). On the contrary, in the presence of the spin-bearing magnesium ions, the dependence of the reaction rate on the magnetic field induction was non-monotonous and possess a distinct minimum at 80-100 mT. To describe the observed effect, we suggested a chemical scheme and biophysical mechanism considering a competition between Zeeman and Fermi interactions in the external magnetic field.

Interphase epichromatin: last refuge for the 30-nm chromatin fiber?

"Interphase epichromatin" describes the surface of chromatin located adjacent to the interphase nuclear envelope. It was discovered in 2011 using a bivalent anti-nucleosome antibody (mAb PL2-6), now known to be directed against the nucleosome acidic patch. The molecular structure of interphase epichromatin is unknown, but is thought to be heterochromatic with a high density of "exposed" acidic patches. In the 1960s, transmission electron microscopy of fixed, dehydrated, sectioned, and stained inactive chromatin revealed "unit threads," frequently organized into parallel arrays at the nuclear envelope, which were interpreted as regular helices with ~ 30-nm center-to-center distance. Also observed in certain cell types, the nuclear envelope forms a "sandwich" around a layer of closely packed unit threads (ELCS, envelope-limited chromatin sheets). Discovery of the nucleosome in 1974 led to revised helical models of chromatin. But these models became very controversial and the existence of in situ 30-nm chromatin fibers has been challenged. Development of cryo-electron microscopy (Cryo-EM) gave hope that in situ chromatin fibers, devoid of artifacts, could be structurally defined. Combining a contrast-enhancing phase plate and cryo-electron tomography (Cryo-ET), it is now possible to visualize chromatin in a "close-to-native" situation. ELCS are particularly interesting to study by Cryo-ET. The chromatin sheet appears to have two layers of ~ 30-nm chromatin fibers arranged in a criss-crossed pattern. The chromatin in ELCS is continuous with adjacent interphase epichromatin. It appears that hydrated ~ 30-nm chromatin fibers are quite rare in most cells, possibly confined to interphase epichromatin at the nuclear envelope.

Radiation-Chemical Biotechnology for Producing Ultrashort (50-100n) Single-Chain Polydeoxyribonucleotides with Anticancer Activity

The fundamental possibility of obtaining ultrashort (50n-100n) single-stranded polydeoxyribonucleotides by the method of radiation-chemical destruction of total yeast DNA was established and their anticancer activity was shown.

Antiviral potential of plant polysaccharide nanoparticles actuating non-specific immunity

The development of high-end targeted drugs and vaccines against modern pandemic infections, such as COVID-19, can take a too long time that lets the epidemic spin up and harms society. However, the countermeasures must be applied against the infection in this period until the targeted drugs became available. In this regard, the non-specific, broad-spectrum anti-viral means could be considered as a compromise allowing overcoming the period of trial. One way to enhance the ability to resist the infection is to activate the nonspecific immunity using a suitable driving-up agent, such as plant polysaccharides, particularly our drug Panavir isolated from the potato shoots. Earlier, we have shown the noticeable anti-viral and anti-bacterial activity of Panavir. Here we demonstrate the pro-inflammation activity of Panavir, which four-to-eight times intensified the ATP and MIF secretion by HL-60 cells. This effect was mediated by the active phagocytosis of the Panavir particles by the cells. We hypothesized the physiological basis of the Panavir proinflammatory activity is mediated by the indol-containing compounds (auxins) present in Panavir and acting as a plant analog of serotonin.

Nuclear Morphological Remodeling in Human Granulocytes Is Linked to Prenylation Independently from Cytoskeleton

Nuclear shape modulates cell behavior and function, while aberrant nuclear morphologies correlate with pathological phenotype severity. Nevertheless, functions of specific nuclear morphological features and underlying molecular mechanisms remain poorly understood. Here, we investigate a nucleus-intrinsic mechanism driving nuclear lobulation and segmentation concurrent with granulocyte specification, independently from extracellular forces and cytosolic cytoskeleton contributions. Transcriptomic regulation of cholesterol biosynthesis is equally concurrent with nuclear remodeling. Its putative role as a regulatory element is supported by morphological aberrations observed upon pharmacological impairment of several enzymatic steps of the pathway, most prominently the sterol ∆14-reductase activity of laminB-receptor and protein prenylation. Thus, we support the hypothesis of a nuclear-intrinsic mechanism for nuclear shape control with the putative involvement of the recently discovered GGTase III complex. Such process could be independent from or complementary to the better studied cytoskeleton-based nuclear remodeling essential for cell migration in both physiological and pathological contexts such as immune system function and cancer metastasis.

Reliable and mobile all-fiber modular optical tweezers

Miniaturization and integration of optical tweezers are attractive. Optical fiber-based trapping systems allow optical traps to be realized in miniature systems, but the optical traps in these systems lack reliability or mobility. Here, we present the all-fiber modular optical tweezers (AFMOTs), in which an optical trap can be reliably created and freely moved on a sample substrate. Two inclined optical fibers are permanently fixed to a common board, rendering a modular system where fiber alignments are maintained over months. The freely movable optical trap allows particles to be trapped in their native locations. As a demonstration, we applied AFMOTs to trap and deform freely floating individual cells. By the cell mechanical responses, we differentiated the nontumorigenic breast epithelial cell line (MCF10A) from its cancerous PTEN mutants (MCF10 PTEN-/-). To further expand the functionalities, three modalities of AFMOTs are demonstrated by changing the types of fibers for both the optical trap creation and particle position detection. As a miniature and modular system that creates a reliable and mobile optical trap, AFMOTs can find potential applications ranging from point-of-care diagnostics to education, as well as helping transition the optical trapping technology from the research lab to the field.

L, D-Polydeoxyribonucleotides to provide an essential inhibitory effect on DNA polymerase β of human myeloid leukemia HL60 cells

The inhibitory effect of D and L-polynucleotides of a given length (40-50n) on the catalytic activity of DNA polymerase β isolated from chromatin cells of acute myeloid leukemia HL-60 was evaluated. The synthesized L enantiomer was found to have a higher inhibitory activity than the synthesized and isolated D enantiomers of polynucleotides. The work also proposes a biophysical model that describes this effect.

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The inhibitory activity of L, D-polydeoxyribonucleotides of various compositions was evaluated.

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Inhibition of DNA polymerase β is due to a nonspecific interaction between the enzyme and the substrate.

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L-polynucleotide exhibits the highest inhibiting activity, compared to the D-enantiomers.

Lamin A/C and the Immune System: One Intermediate Filament, Many Faces

Nuclear envelope lamin A/C proteins are a major component of the mammalian nuclear lamina, a dense fibrous protein meshwork located in the nuclear interior. Lamin A/C proteins regulate nuclear mechanics and structure and control cellular signaling, gene transcription, epigenetic regulation, cell cycle progression, cell differentiation, and cell migration. The immune system is composed of the innate and adaptive branches. Innate immunity is mediated by myeloid cells such as neutrophils, macrophages, and dendritic cells. These cells produce a rapid and nonspecific response through phagocytosis, cytokine production, and complement activation, as well as activating adaptive immunity. Specific adaptive immunity is activated by antigen presentation by antigen presenting cells (APCs) and the cytokine microenvironment, and is mainly mediated by the cellular functions of T cells and the production of antibodies by B cells. Unlike most cell types, immune cells regulate their lamin A/C protein expression relatively rapidly to exert their functions, with expression increasing in macrophages, reducing in neutrophils, and increasing transiently in T cells. In this review, we discuss and summarize studies that have addressed the role played by lamin A/C in the functions of innate and adaptive immune cells in the context of human inflammatory and autoimmune diseases, pathogen infections, and cancer.

Whole-genome fingerprint of the DNA methylome during chemically induced differentiation of the human AML cell line HL-60/S4

Epigenomic regulation plays a vital role in cell differentiation. The leukemic HL-60/S4 [human myeloid leukemic cell line HL-60/S4 (ATCC CRL-3306)] promyelocytic cell can be easily differentiated from its undifferentiated promyelocyte state into neutrophil- and macrophage-like cell states. In this study, we present the underlying genome and epigenome architecture of HL-60/S4 through its differentiation. We performed whole-genome bisulphite sequencing of HL-60/S4 cells and their differentiated counterparts. With the support of karyotyping, we show that HL-60/S4 maintains a stable genome throughout differentiation. Analysis of differential Cytosine-phosphate-Guanine dinucleotide methylation reveals that most methylation changes occur in the macrophage-like state. Differential methylation of promoters was associated with immune-related terms. Key immune genes, CEBPA, GFI1, MAFB and GATA1 showed differential expression and methylation. However, we observed the strongest enrichment of methylation changes in enhancers and CTCF binding sites, implying that methylation plays a major role in large-scale transcriptional reprogramming and chromatin reorganisation during differentiation. Correlation of differential expression and distal methylation with support from chromatin capture experiments allowed us to identify putative proximal and long-range enhancers for a number of immune cell differentiation genes, including CEBPA and CCNF Integrating expression data, we present a model of HL-60/S4 differentiation in relation to the wider scope of myeloid differentiation.

Effect of iron overload from multi walled carbon nanotubes on neutrophil-like differentiated HL-60 cells

Multi walled carbon nanotubes (MWCNTs) are one of the most intensively explored nanomaterials because of their unique physical and chemical properties. Due to the widespread use of MWCNTs, it is important to investigate their effects on human health. The precise mechanism of MWCNT toxicity has not been fully elucidated. The present study was designed to examine the mechanisms of MWCNT toxicity toward human promyelocytic leukemia HL-60 cells. First, we found that MWCNTs decreased the viability of neutrophil-like differentiated HL-60 cells but not undifferentiated HL-60 cells. Because neutrophil-like differentiated HL-60 cells exhibit enhanced phagocytic activity, the cytotoxicity of MWCNTs is dependent on the intracellularly localized MWCNTs. Next, we revealed that the cytotoxicity of MWCNTs is correlated with the intracellular accumulation of iron that is released from the engulfed MWCNTs in an acidic lysosomal environment. The intracellular accumulation of iron was repressed by treatment with cytochalasin D, a phagocytosis inhibitor. In addition, our results indicated that iron overload enhanced the release of interleukin-8 (IL-8), a chemokine that activates neutrophils, and subsequently elevated intracellular calcium concentration ([Ca²⁺]_i). Finally, we found that the sustained [Ca²⁺]_i elevation resulted in the loss of mitochondrial membrane potential and the increase of caspase-3 activity, thereby inducing apoptotic cell death. These findings suggest that the iron overload caused by engulfed MWCNTs results in the increase of IL-8 production and the elevation of [Ca²⁺]_i, thereby activating the mitochondria-mediated apoptotic pathway.

Carcinoembryonic antigen cell adhesion molecule 1 inhibits the antitumor effect of neutrophils in tongue squamous cell carcinoma

Carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1), a transmembrane glycoprotein, has multiple functions. In tongue squamous cell carcinoma (TSCC), CEACAM1 overexpression is correlated with neutrophil infiltration, and both are associated with poor clinical outcomes. However, the mechanism underlying CEACAM1's effect on neutrophil function in TSCC remains unclear. We cocultured tongue carcinoma cells overexpressing CEACAM1‐4L, CEACAM1‐4S and differentiated HL‐60 cells. This significantly upregulated the expression of MMP‐9, interleukin 8, and VEGF‐A in the differentiated HL‐60 cells and downregulated the expression of TNF‐α, relative to vector and blank control groups (P < 0.05). Additionally, CEACAM1 overexpression in tongue carcinoma cells weakened the cytotoxicity of differentiated HL‐60 cells in the coculture system (P < 0.05). Thus, CEACAM1 expression in TSCC may induce an antitumor to protumor transformation of neutrophils. We performed qRT‐PCR and ELISA to evaluate the underlying mechanism, and found that CEACAM1 expression in tongue carcinoma cells upregulated transforming growth factor β1 (TGF‐β1) expression, while blocking of TGF‐β1 inhibited the neutrophils’ changes in the coculture system. Immunohistochemical analysis of clinical specimens revealed strong expression of TGF‐β1 protein in TSCC. TGF‐β1 expression was positively correlated with CEACAM1 expression, lymph node metastasis, and tumor recurrence. Double immunofluorescence results revealed colocalization of CEACAM1 and TGF‐β1 protein in TSCC. A xenograft nude mouse model revealed that CEACAM1 overexpression in TSCC promoted tumor formation and growth, and was associated with more neutrophils infiltration. Our results indicate that CEACAM1 overexpression in TSCC may induce transformation of neutrophils from antitumor to protumor type via TGF‐β1, which may further promote tumor progression.

Bulk tumour cell migration in lung carcinomas might be more common than epithelial-mesenchymal transition and be differently regulated

Background

Epithelial-to-mesenchymal transition (EMT) is one mechanism of carcinoma migration, while complex tumour migration or bulk migration is another - best demontrated by tumour cells invading blood vessels.

Methods

Thirty cases of non-small cell lung carcinomas were used for identifying genes responsible for bulk cell migration, 232 squamous cell and adenocarcinomas to identify bulk migration rates. Genes expressed differently in the primary tumour and in the invasion front were regarded as relevant in migration and further validated in 528 NSCLC cases represented on tissue microarrays (TMAs) and metastasis TMAs.

Results

Markers relevant for bulk cancer cell migration were regulated differently when compared with EMT: Twist expressed in primary tumour, invasion front, and metastasis was not associated with TGFβ1 and canonical Wnt, as Slug, Snail, and Smads were negative and β-Catenin expressed membraneously. In the majority of tumours, E-Cadherin was downregulated at the invasive front, but not absent, but, coexpressed with N-Cadherin. Vimentin was coexpressed with cytokeratins at the invasion site in few cases, whereas fascin expression was seen in a majority. Expression of ERK1/2 was downregulated, PLCγ was only expressed at the invasive front and in metastasis. Brk and Mad, genes identified in Drosophila border cell migration, might be important for bulk migration and metastasis, together with invadipodia proteins Tks5 and Rab40B, which were only upregulated at the invasive front and in metastasis. CXCR1 was expressed equally in all carcinomas, as opposed to CXCR2 and 4, which were only expressed in few tumours.

Conclusion

Bulk cancer cell migration seems predominant in AC and SCC. Twist, vimentin, fascin, Mad, Brk, Tsk5, Rab40B, ERK1/2 and PLCγ are associated with bulk cancer cell migration. This type of migration requires an orchestrated activation of proteins to keep the cells bound to each other and to coordinate movement. This hypothesis needs to be proven experimentally.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4640-y) contains supplementary material, which is available to authorized users.

Transcriptomes reflect the phenotypes of undifferentiated, granulocyte and macrophage forms of HL-60/S4 cells

To understand the chromatin changes underlying differential gene expression during induced differentiation of human leukemic HL-60/S4 cells, we conducted RNA-Seq analysis on quadruplicate cultures of undifferentiated, granulocytic- and macrophage-differentiated cell forms. More than half of mapped genes exhibited altered transcript levels in the differentiated cell forms. In general, more genes showed increased mRNA levels in the granulocytic form and in the macrophage form, than showed decreased levels. The majority of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were significantly enriched in genes that exhibited differential transcript levels after either RA or TPA treatment. Changes in transcript levels for groups of genes with characteristic protein phenotypes, such as genes encoding cytoplasmic granular proteins, nuclear envelope and cytoskeletal proteins, cell adhesion proteins, and proteins involved in the cell cycle and apoptosis illustrate the profound differences among the various cell states. In addition to the transcriptome analyses, companion karyotyping by M-FISH of undifferentiated HL-60/S4 cells revealed a plethora of chromosome alterations, compared with normal human cells. The present mRNA profiling provides important information related to nuclear shape changes (e.g., granulocyte lobulation), deformability of the nuclear envelope and linkage between the nuclear envelope and cytoskeleton during induced myeloid chromatin differentiation.

Nucleosome repositioning during differentiation of a human myeloid leukemia cell line

Cell differentiation is associated with changes in chromatin organization and gene expression. In this study, we examine chromatin structure following differentiation of the human myeloid leukemia cell line (HL-60/S4) into granulocytes with retinoic acid (RA) or into macrophage with phorbol ester (TPA). We performed ChIP-seq of histone H3 and its modifications, analyzing changes in nucleosome occupancy, nucleosome repeat length, eu-/heterochromatin redistribution and properties of epichromatin (surface chromatin adjacent to the nuclear envelope). Nucleosome positions changed genome-wide, exhibiting a specific class of alterations involving nucleosome loss in extended (∼1kb) regions, pronounced in enhancers and promoters. Genes that lost nucleosomes at their promoters showed a tendency to be upregulated. On the other hand, nucleosome gain did not show simple effects on transcript levels. The average genome-wide nucleosome repeat length (NRL) did not change significantly with differentiation. However, we detected an approximate 10 bp NRL decrease around the haematopoietic transcription factor (TF) PU.1 and the architectural protein CTCF, suggesting an effect on NRL proximal to TF binding sites. Nucleosome occupancy changed in regions associated with active promoters in differentiated cells, compared with untreated HL-60/S4 cells. Epichromatin regions revealed an increased GC content and high nucleosome density compared with surrounding chromatin. Epichromatin showed depletion of major histone modifications and revealed enrichment with PML body-associated genes. In general, chromatin changes during HL-60/S4 differentiation appeared to be more localized to regulatory regions, compared with genome-wide changes among diverse cell types studied elsewhere.

Retinoic acid induces hypersegmentation and enhances cytotoxicity of neutrophils against cancer cells

Hypersegmentation of nuclei is considered a distinct characteristic of the antitumoral phenotype of neutrophils. Retinoic acid, a metabolite of retinol, reorganizes and induces segmentation of the nucleus during the differentiation of neutrophils. However, the role of retinoic acid in the phenotype polarization of neutrophils has not been fully established. Here, we investigated the effect of retinoic acid on phenotype polarization of neutrophils. Retinoic acid-induced the hypersegmentation of human neutrophils via retinoic acid receptors and mTOR pathways. Retinoic acid-induced hypersegmented neutrophils enhanced neutrophil extracellular traps (NETs) formation in response to phorbol-12-myristate 13-acetate (PMA) and fMLP (N-Formylmethionine-leucyl-phenylalanine) stimulation, and increased cytotoxicity against various tumor cells. Moreover, retinoic acid treatment attenuated tumor growth in a murine model of tumor. Taken together, these results suggests that retinoic acid induces the phenotype polarization of neutrophils to exert antitumor effects.

Dystroglycan Depletion Impairs Actin-Dependent Functions of Differentiated Kasumi-1 Cells

Background

Dystroglycan has recently been characterised in blood tissue cells, as part of the dystrophin glycoprotein complex involved in the differentiation process of neutrophils.

Purpose

In the present study we have investigated the role of dystroglycan in the human promyelocytic leukemic cell line Kasumi-1 differentiated to macrophage-like cells.

Methods

We characterised the pattern expression and subcellular distribution of dystroglycans in non-differentiated and differentiated Kasumi-1 cells.

Results

Our results demonstrated by WB and flow cytometer assays that during the differentiation process to macrophages, dystroglycans were down-regulated; these results were confirmed with qRT-PCR assays. Additionally, depletion of dystroglycan by RNAi resulted in altered morphology and reduced properties of differentiated Kasumi-1 cells, including morphology, migration and phagocytic activities although secretion of IL-1β and expression of markers of differentiation are not altered.

Conclusion

Our findings strongly implicate dystroglycan as a key membrane adhesion protein involved in actin-based structures during the differentiation process in Kasumi-1 cells.

Cytotoxic Activity of Highly Purified Silver Nanoparticles Sol Against Cells of Human Immune System

The widespread use of silver nanoparticles (AgN) in the articles of common use justifies the need to investigate their effects on the human body. Nanosilver toxicity of highly purified, stable, and well-characterized Ag sol toward human immune cells at various differentiation stages has been studied. Human promyelocytic leukemia cells (HL-60) were differentiated to granulocytes using dimethyl sulfoxide and to macrophage-like cells by phorbol ester. Human monocytic cells (U-937) were differentiated to monocytes and macrophages by phorbol ester. In the presence of AgN, different changes of their survival time were observed depending on cell differentiation. Differentiated cells showed a significantly higher resistance than the non-differentiated cells, depending on the contact time and AgN concentration. In the presence of AgN at concentration of 25 mg/l, fraction of non-differentiated cells alive after 24 h was equal to 45 %; for granulocytes this number increased to 75 % and for macrophages to 65 %. The presence of AgN increases the levels of intracellular antioxidant -glutathione and of nitric oxide - one of inflammation mediators. By checking the effect caused by effluent obtained from AgN sol purification resulting at AgN sol purification, it was proved that cytotoxity should be attributed to the action of silver particles themselves.

A microfluidic technique to probe cell deformability

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an efficient manner. Typically, data for ~10(2) cells can be acquired within a 1 hr experiment. An automated image analysis program enables efficient post-experiment analysis of image data, enabling processing to be complete within a few hours. Our device geometry is unique in that cells must deform through a series of micron-scale constrictions, thereby enabling the initial deformation and time-dependent relaxation of individual cells to be assayed. The applicability of this method to human promyelocytic leukemia (HL-60) cells is demonstrated. Driving cells to deform through micron-scale constrictions using pressure-driven flow, we observe that human promyelocytic (HL-60) cells momentarily occlude the first constriction for a median time of 9.3 msec before passaging more quickly through the subsequent constrictions with a median transit time of 4.0 msec per constriction. By contrast, all-trans retinoic acid-treated (neutrophil-type) HL-60 cells occlude the first constriction for only 4.3 msec before passaging through the subsequent constrictions with a median transit time of 3.3 msec. This method can provide insight into the viscoelastic nature of cells, and ultimately reveal the molecular origins of this behavior.

The fundamental role of mechanical properties in the progression of cancer disease and inflammation

The role of mechanical properties in cancer disease and inflammation is still underinvestigated and even ignored in many oncological and immunological reviews. In particular, eight classical hallmarks of cancer have been proposed, but they still ignore the mechanics behind the processes that facilitate cancer progression. To define the malignant transformation of neoplasms and finally reveal the functional pathway that enables cancer cells to promote cancer progression, these classical hallmarks of cancer require the inclusion of specific mechanical properties of cancer cells and their microenvironment such as the extracellular matrix as well as embedded cells such as fibroblasts, macrophages or endothelial cells. Thus, this review will present current cancer research from a biophysical point of view and will therefore focus on novel physical aspects and biophysical methods to investigate the aggressiveness of cancer cells and the process of inflammation. As cancer or immune cells are embedded in a certain microenvironment such as the extracellular matrix, the mechanical properties of this microenvironment cannot be neglected, and alterations of the microenvironment may have an impact on the mechanical properties of the cancer or immune cells. Here, it is highlighted how biophysical approaches, both experimental and theoretical, have an impact on the classical hallmarks of cancer and inflammation. It is even pointed out how these biophysical approaches contribute to the understanding of the regulation of cancer disease and inflammatory responses after tissue injury through physical microenvironmental property sensing mechanisms. The recognized physical signals are transduced into biochemical signaling events that guide cellular responses, such as malignant tumor progression, after the transition of cancer cells from an epithelial to a mesenchymal phenotype or an inflammatory response due to tissue injury. Moreover, cell adaptation to mechanical alterations, in particular the understanding of mechano-coupling and mechano-regulating functions in cell invasion, appears as an important step in cancer progression and inflammatory response to injuries. This may lead to novel insights into cancer disease and inflammatory diseases and will overcome classical views on cancer and inflammation. In addition, this review will discuss how the physics of cancer and inflammation can help to reveal whether cancer cells will invade connective tissue and metastasize or how leukocytes extravasate and migrate through the tissue. In this review, the physical concepts of cancer progression, including the tissue basement membrane a cancer cell is crossing, its invasion and transendothelial migration as well as the basic physical concepts of inflammatory processes and the cellular responses to the mechanical stress of the microenvironment such as external forces and matrix stiffness, are presented and discussed. In conclusion, this review will finally show how physical measurements can improve classical approaches that investigate cancer and inflammatory diseases, and how these physical insights can be integrated into classical tumor biological approaches.

Genome regulation at the peripheral zone: lamina associated domains in development and disease

The nuclear periphery has been implicated in gene regulation and it has been proposed that proximity to the nuclear lamina and inner nuclear membrane (INM) leads to gene repression. More recently, it appears that there is a correlation and interdependence between lamina associated domains (LADs), the epigenome and overall three-dimensional architecture of the genome. However, the mechanisms of such organization at the 'peripheral zone' and the functional significance of these associations are poorly understood. The role these domains play in development and disease is an active and exciting area of research, expanding our knowledge of how the three-dimensional (3D) genome is regulated.

Magnetic isotope and magnetic field effects on the DNA synthesis

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases β with isotopic ions (24)Mg(2+), (25)Mg(2+) and (26)Mg(2+) in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases β carrying (24)Mg(2+) and (26)Mg(2+) ions with spinless, non-magnetic nuclei (24)Mg and (26)Mg. However, (25)Mg(2+) ions with magnetic nucleus (25)Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases β with (24)Mg(2+) and (26)Mg(2+) ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases β with Zn(2+) ions carrying magnetic (67)Zn and non-magnetic (64)Zn nuclei, respectively. A new, ion-radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion-radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc).

Nuclear envelope composition determines the ability of neutrophil-type cells to passage through micron-scale constrictions

Neutrophils are characterized by their distinct nuclear shape, which is thought to facilitate the transit of these cells through pore spaces less than one-fifth of their diameter. We used human promyelocytic leukemia (HL-60) cells as a model system to investigate the effect of nuclear shape in whole cell deformability. We probed neutrophil-differentiated HL-60 cells lacking expression of lamin B receptor, which fail to develop lobulated nuclei during granulopoiesis and present an in vitro model for Pelger-Huët anomaly; despite the circular morphology of their nuclei, the cells passed through micron-scale constrictions on similar timescales as scrambled controls. We then investigated the unique nuclear envelope composition of neutrophil-differentiated HL-60 cells, which may also impact their deformability; although lamin A is typically down-regulated during granulopoiesis, we genetically modified HL-60 cells to generate a subpopulation of cells with well defined levels of ectopic lamin A. The lamin A-overexpressing neutrophil-type cells showed similar functional characteristics as the mock controls, but they had an impaired ability to pass through micron-scale constrictions. Our results suggest that levels of lamin A have a marked effect on the ability of neutrophils to passage through micron-scale constrictions, whereas the unusual multilobed shape of the neutrophil nucleus is less essential.

Cell types can be distinguished by measuring their viscoelastic recovery times using a micro-fluidic device

We introduce a simple micro-fluidic device containing an actuated flexible membrane, which allows the viscoelastic characterization of cells in small volumes of suspension by loading them in compression and observing the cell deformation in time. From this experiment, we can determine the characteristic time constant of recovery of the cell. To validate the device, two cell types known to have different cytoskeletal structures, 3T3 fibroblasts and HL60 cells, are tested. They show a substantially different response in the device and can be clearly distinguished on the basis of the measured characteristic recovery time constant. Also, the effect of breaking down the actin network, a main mechanical component of the cytoskeleton, by a treatment with Cytochalasin D, results in a substantial increase of the measured characteristic recovery time constant. Experimental variations in loading force, loading time, and surface treatment of the device also influence the measured characteristic recovery time constant significantly. The device can therefore be used to distinguish between cells with different mechanical structure in a quantitative way, and makes it possible to study changes in the mechanical response due to cell treatments, changes in the cell’s micro-environment, and mechanical loading conditions.

An epichromatin epitope: persistence in the cell cycle and conservation in evolution

Interphase nuclear architecture is disrupted and rapidly reformed with each cell division cycle. Successive cell generations exhibit a "memory" of this nuclear architecture, as well as for gene expression. Furthermore, many features of nuclear and mitotic chromosome structure are recognizably species and tissue specific. We wish to know what properties of the underlying chromatin structure may determine these conserved features of nuclear architecture. Employing a particular mouse autoimmune anti-nucleosome monoclonal antibody (PL2-6), combined with deconvolution immunofluorescence microscopy, we present evidence for a unique epitope (involving a ternary complex of histones H2A and H2B and DNA) which is localized only at the exterior chromatin surface of interphase nuclei and mitotic chromosomes in mammalian, invertebrate and plant systems. As only the surface chromatin region is identified with antibody PL2-6, we have assigned it the name "epichromatin". We describe an "epichromatin hypothesis", suggesting that epichromatin may have a unique evolutionary conserved conformation which facilitates interaction with the reforming post-mitotic nuclear envelope and a rapid return of interphase nuclear architecture.

An in vitro model for Pelger-Huët anomaly: stable knockdown of lamin B receptor in HL-60 cells

The principal human blood granulocyte (neutrophil) possesses a lobulated and deformable nucleus, important to facilitate rapid egress from blood vessels as these cells migrate to sites of bacterial or fungal infection. This unusual nuclear shape is a product of elevated levels of an integral membrane protein of the nuclear envelope lamin B receptor (LBR) and of decreased amounts of lamin A/C. In humans, a genetic deficiency of LBR produces Pelger-Huët anomaly, resulting in blood neutrophils that exhibit hypolobulated nuclei with redistributed heterochromatin. Structural changes in nuclear architecture occur during granulopoiesis within bone marrow. The exact mechanisms of this nuclear shape change and of heterochromatin redistribution remain largely unknown. As a tool to facilitate analysis of these mechanisms, a stable LBR knockdown subline of HL-60 cells was established. During in vitro granulopoiesis induced with retinoic acid, the LBR knockdown cells retain an ovoid shaped nucleus with reduced levels of lamin A/C; while, the parent cells develop highly lobulated nuclei. In contrast, macrophage forms induced in LBR knockdown cells by in vitro treatment with phorbol ester were indistinguishable from the parent cells, judged by both nuclear shape and attached cell morphology. The capability of differentiation of LBR knockdown HL-60 cells should facilitate a detailed analysis of the molecular relationship between LBR levels, granulocyte nuclear shape and heterochromatin distribution.

Effect of arsenic trioxide (Trisenox) on actin organization in K-562 erythroleukemia cells

Actin is one of the cytoskeletal proteins that take part in many cellular processes. The aim of this study was to show the influence of Trisenox (arsenic trioxide), on the cytoplasmic and nuclear F-actin organization. Arsenic trioxide is the proapoptotic factor. Together with increasing doses, it caused the increase in the number of cells undergoing apoptosis. Under arsenic trioxide treatment, cytoplasmic and nuclear F-actin (polymerized form of G-actin) was found reorganized. It was transformed into granulated structures. In cytometer studies fluorescence intensity of cytoplasmic F-actin after ATO treatment decreasing urgently in comparison to control. The obtained results may suggest the involvement of F-actin in apoptosis, especially in chromatin reorganization.

The influence of Trisenox on actin organization in HL-60 cells

The aim of this study was to show the influence of Trisenox (arsenic trioxide, ATO) on cytoplasmic and nuclear F-actin organization in HL-60 human leukemia cell line. Changes in localization were determined with the use of fluorescence microscopy and flow cytometry. Alterations, in both cytoplasmic and nuclear actin, were observed in cells exposed to ATO. F-actin network underwent accumulation and formed aggregates, that were very often placed under the cell membrane in whole cells and at the periphery of isolated nuclei. Addition of ATO also induced apoptosis and a decrease in G2 phase cells. These results suggest the influence of actin on the formation of apoptotic bodies and also participation of this protein in apoptotic alterations within nuclei, i.e. chromatin reorganization.

The regulatory role of cell mechanics for migration of differentiating myeloid cells

Migration of cells is important for tissue maintenance, immune response, and often altered in disease. While biochemical aspects, including cell adhesion, have been studied in detail, much less is known about the role of the mechanical properties of cells. Previous measurement methods rely on contact with artificial surfaces, which can convolute the results. Here, we used a non-contact, microfluidic optical stretcher to study cell mechanics, isolated from other parameters, in the context of tissue infiltration by acute promyelocytic leukemia (APL) cells, which occurs during differentiation therapy with retinoic acid. Compliance measurements of APL cells reveal a significant softening during differentiation, with the mechanical properties of differentiated cells resembling those of normal neutrophils. To interfere with the migratory ability acquired with the softening, differentiated APL cells were exposed to paclitaxel, which stabilizes microtubules. This treatment does not alter compliance but reduces cell relaxation after cessation of mechanical stress six-fold, congruent with a significant reduction of motility. Our observations imply that the dynamical remodeling of cell shape required for tissue infiltration can be frustrated by stiffening the microtubular system. This link between the cytoskeleton, cell mechanics, and motility suggests treatment options for pathologies relying on migration of cells, notably cancer metastasis.

Nuclear envelope-limited chromatin sheets (ELCS) and heterochromatin higher order structure

The interphase nucleus and nuclear envelope can acquire a myriad of shapes in normal or pathological cell states. There exist a wide variety of indentations and invaginations, of protrusions and evaginations. It has been difficult to classify and name all of these nuclear shapes and, consequently, a barrier to understanding the biochemical and biophysical causes. This review focuses upon one type of nuclear envelope shape change, named "nuclear envelope-limited chromatin sheets" (ELCS), which appears to involve exaggerated nuclear envelope growth, carrying with it one or more layers of approximately 30 nm diameter heterochromatin. A hypothesis on the formation of ELCS is proposed, relating higher order heterochromatin structure in an interphase nucleus, nuclear envelope growth, and nuclear envelope-heterochromatin interactions.

Gene expression analysis of human promyelocytic leukemia HL-60 cell differentiation and cytotoxicity induced by natural and synthetic retinoids

AIMS

This study analyzed gene expression profiles of human promyelocytic leukemia HL-60 cells treated with natural and synthetic retinoids (ATRA, RII and R9158), in an attempt to investigate the structure-function relationship of the retinoids in inducing cell differentiation and cytotoxicity.

MAIN METHODS

Flow cytometry was used to determine cell cycle changes in HL-60 cells following treatment (1.0 muM) with natural and synthetic retinoids (ATRA, RII and R9158), and cDNA microarrays were used to monitor the gene expression profiles of HL-60 cells treated with the various retinoids.

KEY FINDINGS

Consistent with retinoid-induced cell differentiation, treatment with these three retinoids correlated with an increase in the percentage of cells arrested in the G1/G0 phase of the cell cycle. Microarray analysis showed upregulation of known differentiation genes, adhesion molecules, and the oxidase activation pathway following retinoid treatment. Differential expression of several genes was observed in HL-60 cells treated with the three retinoids. For example, tissue remodeling protein genes, ubiquitin genes, and signal transduction genes were highly expressed in ATRA- and R9158-treated HL-60 cells, but remained unchanged in HL-60 cells treated with RII.

SIGNIFICANCE

The above findings suggest that the differentiation of HL-60 cells induced by the three retinoids occurs through similar pathways, and that there exists a structure-function relationship regarding retinoids and the induction of cell differentiation and cytotoxicity.

Molecular recognition of acute myeloid leukemia using aptamers

Cell surface proteins can play important roles in cancer pathogenesis. Comprehensive understanding of the surface protein expression patterns of tumor cells and, consequently, the pathogenesis of tumor cells, depends on molecular probes against these proteins. To be effectively used for tumor diagnosis, classification and therapy, such probes would be capable of specific binding to targeted tumor cells. Molecular aptamers, designer DNA/RNA probes, can address this challenge by recognizing proteins, peptides and other small molecules with high affinity and specificity. Through a process known as cell-SELEX, we used live acute myeloid leukemia (AML) cells to select a group of DNA aptamers that can recognize acute myeloid leukemia cells with dissociation constants (Kds) in the nanomolar range. Interestingly, one aptamer (KH1C12), compared with two control cell lines (K562 and NB4), showed significant selectivity to the target AML cell line (HL60) and could recognize the target cells within a complex mixture of normal bone marrow aspirates. The other two aptamers KK1B10 and KK1D04 recognize targets associated with monocytic differentiation. Our studies demonstrate that the selected aptamers can be used as a molecular tool for further understanding surface protein expression patterns on tumor cells and thus providing a foundation for effective molecular analysis of leukemia and its subcategories.

The LINC-less granulocyte nucleus

The major blood granulocyte (neutrophil) is rapidly recruited to sites of bacterial and fungal infections. It is a highly malleable cell, allowing it to squeeze out of blood vessels and migrate through tight tissue spaces. The human granulocyte nucleus is lobulated and exhibits a paucity of nuclear lamins, increasing its capability for deformation. The present study examined the existence of protein connections between the nuclear envelope and cytoskeletal elements (the LINC complex) in differentiated cell states (i.e. granulocytic, monocytic and macrophage) of the human leukemic cell line HL-60, as well as in human blood leukocytes. HL-60 granulocytes exhibited a deficiency of several LINC complex proteins (i.e. nesprin 1 giant, nesprin 2 giant, SUN1, plectin and vimentin); whereas, the macrophage state revealed nesprin 1 giant, plectin and vimentin. Both states possessed SUN2 in the nuclear envelope. Parallel differences were observed with some of the LINC complex proteins in isolated human blood leukocytes, including macrophage cells derived from blood monocytes. The present study documenting the paucity of LINC complex proteins in granulocytic forms, in combination with previous data on granulocyte nuclear shape and nuclear envelope composition, suggest the hypothesis that these adaptations evolved to facilitate granulocyte cellular malleability.

Granulocytic nuclear differentiation of lamin B receptor-deficient mouse EPRO cells

OBJECTIVE

Lamin B receptor (LBR) is an integral protein of the inner nuclear membrane. Recent studies have demonstrated that genetic deficiency of LBR during granulopoiesis results in hypolobulation of the mature neutrophil nucleus, as observed in human Pelger-Huët anomaly and mouse ichthyosis (ic). In this study, we utilized differentiated early promyelocytes (EPRO cells) that were derived from the bone marrow of homozygous and heterozygous ichthyosis mice to examine changes to the expression of nuclear envelope proteins and heterochromatin structure that result from deficient LBR expression.

MATERIALS AND METHODS

Wild-type (+/+), heterozygous (+/ic), and homozygous (ic/ic) granulocytic forms of EPRO cells were analyzed for the expression of multiple lamins and inner nuclear envelope proteins by immunostaining and immunoblotting techniques. The heterochromatin architecture was also examined by immunostaining for histone lysine methylation.

RESULTS

Wild-type (+/+) and heterozygous (+/ic) granulocytic forms revealed ring-shaped nuclei and contained LBR within the nuclear envelope; ic/ic granulocytes exhibited smaller ovoid nuclei devoid of LBR. The pericentric heterochromatin of undifferentiated and granulocytic ic/ic cells was condensed into larger spots and shifted away from the nuclear envelope, compared to +/+ and +/ic cell forms. Lamin A/C, which is normally not present in mature granulocytes, was significantly elevated in LBR-deficient EPRO cells.

CONCLUSIONS

Our observations suggest roles for LBR during granulopoiesis, which can involve augmenting nuclear membrane growth, facilitating compartmentalization of heterochromatin, and promoting downregulation of lamin A/C expression.

Mouse neutrophils lacking lamin B-receptor expression exhibit aberrant development and lack critical functional responses

OBJECTIVE

The capacity of neutrophils to eradicate bacterial infections is dependent on normal development and activation of functional responses, which include chemotaxis and generation of oxygen radicals during the respiratory burst. A unique feature of the neutrophil is its highly lobulated nucleus, which is thought to facilitate chemotaxis, but may also play a role in other critical neutrophil functions. Nuclear lobulation is dependent on expression of the inner nuclear envelope protein, the lamin B receptor (LBR), mutations of which cause hypolobulated neutrophil nuclei in human Pelger-Huët anomaly and the "ichthyosis" (ic) phenotype in mice. In this study, we have investigated roles for LBR in mediating neutrophil development and activation of multiple neutrophil functions, including chemotaxis and the respiratory burst.

MATERIALS AND METHODS

A progenitor EML cell line was generated from an ic/ic mouse, and derived cells that lacked LBR expression were induced to mature neutrophils and then examined for abnormal morphology and functional responses.

RESULTS

Neutrophils derived from EML-ic/ic cells exhibited nuclear hypolobulation identical to that observed in ichthyosis mice. The ic/ic neutrophils also displayed abnormal chemotaxis, supporting the notion that nuclear segmentation augments neutrophil extravasation. Furthermore, promyelocytic forms of ic/ic cells displayed decreased proliferative responses and produced a deficient respiratory burst upon terminal maturation.

CONCLUSIONS

Our studies of promyelocytes that lack LBR expression have identified roles for LBR in regulating not only the morphologic maturation of the neutrophil nucleus, but also proliferative and functional responses that are critical to innate immunity.

The human granulocyte nucleus: Unusual nuclear envelope and heterochromatin composition

The human blood granulocyte (neutrophil) is adapted to find and destroy infectious agents. The nucleus of the human neutrophil has a segmented appearance, consisting of a linear or branched array of three or four lobes. Adequate levels of lamin B receptor (LBR) are necessary for differentiation of the lobulated nucleus. The levels of other components of the nuclear envelope may also be important for nuclear shape determination. In the present study, immunostaining and immunoblotting procedures explored the levels of various components of the nuclear envelope and heterochromatin, comparing freshly isolated human neutrophils with granulocytic forms of HL-60 cells, a tissue culture model system. In comparison to granulocytic HL-60 cells, blood neutrophil nuclear envelopes contain low-to-negligible amounts of LBR, lamins A/C, B1 and B2, LAP2beta and emerin. Surprisingly, a "mitotic" chromosome marker, H3(S10)phos, is elevated in neutrophil nuclei, compared to granulocytic HL-60 cells. Furthermore, neutrophil nuclei appear to be more fragile to methanol fixation, than observed with granulocytic HL-60 cells. Thus, the human neutrophil nucleus appears to be highly specialized, possessing a paucity of nuclear envelope-stabilizing proteins. In consequence, the neutrophil nucleus appears to be very malleable, supporting rapid migration through tight tissue spaces.

The nuclear lamina and its proposed roles in tumorigenesis: Projection on the hematologic malignancies and future targeted therapy

The nuclear lamina, a network of lamin filaments and lamin-associated proteins, is located between the inner nuclear membrane and the peripheral chromatin. The nuclear lamina is involved in numerous nuclear functions including maintaining nuclear shape, determining nuclear positioning, organizing chromatin and regulating the cell cycle, DNA replication, transcription, cell differentiation, apoptosis, and aging. Alterations in the composition of nuclear lamins and their associated proteins are currently emerging as an additional event involved in malignant transformation, tumor propagation and progression, thus identifying potential novel targets for future anti-cancer therapy. Here, we review the current knowledge on lamin expression patterns in cells of hematologic malignancies and give an overview on the roles of the nuclear lamina proteins in heterochromatin organization, apoptosis, and aging with special emphasis on the relevance in cancer development.

Involvement of proapoptotic Bcl-2 family members in terbinafine-induced mitochondrial dysfunction and apoptosis in HL60 cells

Terbinafine (TB, lamisil), a promising world widely used oral-anti-fungal agent, has been used in the treatment of superficial mycosis. In this study, we found that apoptosis but not cell growth arrest was induced by TB (1 microM, for 24 h) in human promyelocytic leukemia (HL60) cells. The apoptotic effect induced by TB in the HL60 cell was not through the general differentiation mechanisms evidenced by evaluation of three recognized markers, including CD11b, CD33, and morphological features. In addition, our results also revealed that TB-induced apoptosis was not through the cellular surface CD 95 receptor-mediated signaling pathway. We found that the mitochondria membrane in the TB-treated HL60 cells was dissipated by decreasing of the electrochemical gradient (DeltaPsi(m)) led to leakage of cytochrome c from mitochondria into cytosol. Such effects were completely blocked by in vitro transfection of the HL60 cells with Bcl-2 overexpression plasmid (HL60/Bcl-2). However, our data found that TB-mediated apoptosis could not be completely prevented in the Bcl-2 over expressed (HL60/Bcl-2) cells. Such results implied that additional mediators (such as caspase-9) other than mitochondria membrane permeability might contribute to the TB-induced cellular apoptosis signaling. This hypothesis was supported by the evidence that administration of caspases-9 specific inhibitor (z-LEHD-fmk) blocked the TB-induced apoptosis. Our studies highlight the molecular mechanisms of TB-induced apoptosis in human promyelocytic leukemia (HL60) cells.

The mechanism of granulocyte nuclear shape determination: possible involvement of the centrosome

Mature blood neutrophils (polymorphonuclear granulocytes) have characteristically complex nuclear shapes. The human neutrophil nucleus generally possesses 3-4 lobes; the mouse neutrophil nucleus frequently resembles a twisted toroid with a central hole. Myeloid tissue culture systems (e.g., human HL-60 and murine MPRO) can be induced to differentiate in vitro towards neutrophils by addition of retinoic acid, exhibiting the characteristic nuclear shape changes. Confocal immunostaining and thin-section transmission electron microscopic image data from differentiated HL-60 and MPRO cells clearly demonstrate proximity of the centrosomal region (containing dynein, gamma-tubulin and C-Nap1) to regions of granulocytic nuclear indentations. In addition, the centrosomal region, flanked by the Golgi apparatus, is shown to be present within the central hole of the toroidal mouse granulocyte nucleus. A role for the centrosomal region and associated microtubules in molding granulocytic nuclear shape is suggested.

Optical deformability as an inherent cell marker for testing malignant transformation and metastatic competence

The relationship between the mechanical properties of cells and their molecular architecture has been the focus of extensive research for decades. The cytoskeleton, an internal polymer network, in particular determines a cell's mechanical strength and morphology. This cytoskeleton evolves during the normal differentiation of cells, is involved in many cellular functions, and is characteristically altered in many diseases, including cancer. Here we examine this hypothesized link between function and elasticity, enabling the distinction between different cells, by using a microfluidic optical stretcher, a two-beam laser trap optimized to serially deform single suspended cells by optically induced surface forces. In contrast to previous cell elasticity measurement techniques, statistically relevant numbers of single cells can be measured in rapid succession through microfluidic delivery, without any modification or contact. We find that optical deformability is sensitive enough to monitor the subtle changes during the progression of mouse fibroblasts and human breast epithelial cells from normal to cancerous and even metastatic state. The surprisingly low numbers of cells required for this distinction reflect the tight regulation of the cytoskeleton by the cell. This suggests using optical deformability as an inherent cell marker for basic cell biological investigation and diagnosis of disease.

Cytoskeletal influences on nuclear shape in granulocytic HL-60 cells

BACKGROUND

During granulopoiesis in the bone marrow, the nucleus differentiates from ovoid to lobulated shape. Addition of retinoic acid (RA) to leukemic HL-60 cells induces development of lobulated nuclei, furnishing a convenient model system for nuclear differentiation during granulopoiesis. Previous studies from our laboratory have implicated nuclear envelope composition as playing important roles in nuclear shape changes. Specifically noted were: 1) a paucity of lamins A/C and B1 in the undifferentiated and RA treated cell forms; 2) an elevation of lamin B receptor (LBR) during induced granulopoiesis.

RESULTS

The present study demonstrates that perturbation of cytoskeletal elements influences nuclear differentiation of HL-60 cells. Because of cytotoxicity from prolonged exposure to cytoskeleton-modifying drugs, most studies were performed with a Bcl-2 overexpressing HL-60 subline. We have found that: 1) nocodazole prevents RA induction of lobulation; 2) taxol induces lobulation and micronuclear formation, even in the absence of RA; 3) cytochalasin D does not inhibit RA induced nuclear lobulation, and prolonged exposure induces nuclear shape changes in the absence of RA.

CONCLUSIONS

The present results, in the context of earlier data and models, suggest a mechanism for granulocytic nuclear lobulation. Our current hypothesis is that the nuclear shape change involves factors that increase the flexibility of the nuclear envelope (reduced lamin content), augment connections to the underlying heterochromatin (increased levels of LBR) and promote distortions imposed by the cytoskeleton (microtubule motors creating tension in the nuclear envelope).

Deformability-based flow cytometry

BACKGROUND

Elasticity of cells is determined by their cytoskeleton. Changes in cellular function are reflected in the amount of cytoskeletal proteins and their associated networks. Drastic examples are diseases such as cancer, in which the altered cytoskeleton is even diagnostic. This connection between cellular function and cytoskeletal mechanical properties suggests using the deformability of cells as a novel inherent cell marker.

METHODS

The optical stretcher is a new laser tool capable of measuring cellular deformability. A unique feature of this deformation technique is its potential for high throughput, with the incorporation of a microfluidic delivery of cells.

RESULTS

Rudimentary implementation of the microfluidic optical stretcher has been used to measure optical deformability of several normal and cancerous cell types. A drastic difference has been seen between the response of red blood cells and polymorphonuclear cells for a given optically induced stress. MCF-10, MCF-7, and modMCF-7 cells were also measured, showing that while cancer cells stretched significantly more (five times) than normal cells, optical deformability could even be used to distinguish metastatic cancer cells from nonmetastatic cancer cells. This trimodal distribution was apparent after measuring a mere 83 cells, which shows optical deformability to be a highly regulated cell marker.

CONCLUSIONS

Preliminary work suggests a deformability-based cell sorter similar to current fluorescence-based flow cytometry without the need for specific labeling. This could be used for the diagnosis of all diseases, and the investigation of all cellular processes, that affect the cytoskeleton.

Cytoskeletal reorganization during process of apoptosis induced by cytostatic drugs in K-562 and HL-60 leukemia cell lines

The aim of the present study was to investigate the reorganization of F-actin, vimentin and tubulin in K-562 and HL-60 cell lines during apoptosis induced by etoposide, doxorubicin and taxol. The distribution of cytoskeletal proteins was analyzed by fluorescence microscopy. Actin was also studied by confocal microscopy and at the ultrastructural level. Changes in the distribution of cytoskeletal proteins were found to be dose-dependent and appeared to be more intense in HL-60 cells. Etoposide- and doxorubicin-treated cells showed similar changes in the distribution of F-actin, vimentin and tubulin. The reorganization of cytoskeletal proteins seemed to be consistent with features of apoptosis. An increase in bright staining of F-actin, vimentin and tubulin at the site of apoptotic bodies formation was observed. Immunogold labeling of actin in HL-60 cells was associated with features typical for apoptosis, i.e. compaction and margination of nuclear chromatin. K-562 cells showed cytoplasmic actin-positivity in the cytoplasm. Significant changes in morphology of HL-60 cells were found in the following concentrations: etoposide 20, 200 microM; doxorubicin 5, 10 microM and taxol 2-10 microM. The investigated proteins seemed to be involved in the above-reported apoptotic changes. Bright staining of F-actin, vimentin and tubulin, concentrated at the site of apoptotic bodies formation might suggested importance of these proteins for this process. Moreover, the increase in actin labeling in areas of chromatin compaction and margination of nuclear chromatin especially in HL-60 cells, which are more susceptible to apoptosis might implicate that actin might be involved in the chromatin remodeling during apoptosis.