RhoA/ROCK Pathway Is Upregulated in Experimental Autoimmune Myocarditis and Is Inhibited by Simvastatin at the Stage of Myosin Light Chain Phosphorylation.

Many studies have proven the involvement of the RhoA/ROCK pathway in autoimmune and cardiovascular diseases and the beneficial effects of its downregulation. Here, we examined whether the effect of simvastatin on experimental autoimmune myocarditis (EAM) may be through targeting the Ras homolog family member A/Rho-associated coiled-coil containing kinases (RhoA/ROCK) pathway and whether previously shown downregulation of metalloproteinase 9 (MMP-9) could be associated with MLC phosphorylation. Two doses of simvastatin were administered to experimental rats with autoimmune myocarditis by gastric gavage for 3 weeks, at the stage of development of the inflammatory process. Immunohistochemical staining for RhoA and ROCK1 was evaluated semi-quantitatively with H-score. The RhoA staining showed no significant differences in expression between the groups, but the ROCK1 expression was significantly upregulated in the hearts of the EAM group and was not downregulated by simvastatin. The Western blotting analysis of the last downstream product of the RhoA/ROCK axis, phosphorylated myosin light chain (phospho-MYL9), revealed that protein content increased in EAM hearts and it was prevented by the highest dose of simvastatin. Our findings suggest that the RhoA/ROCK pathway is upregulated in EAM, and simvastatin in EAM settings inhibits the RhoA/ROCK pathway at the stage of phosphorylation of myosin light chains and provides a new insight into the molecular pathology of autoimmune myocarditis.

The role of cyclin Y in normal and pathological cells.

The family protein of cyclins, as well as cyclin-dependent kinases (CDKs) cooperating with them, are broadly researched, as a matter of their dysfunction may lead to tumor transformation. Cyclins are defined as key regulators that have a controlling function of the mammalian nuclear cell divides. Cyclin Y (CCNY) is a recently characterized member of the cyclin family and was first identified from the human testis cDNA library. It is an actin-binding protein acting through decreased actin dynamics at a steady state and during glycine-induced long-term potentiation (LTP) and involves the inhibition of cofilin activation. What is more, CCNY is a positive regulatory subunit of the CDK14/PFTK1 complexes affected by the activation of the Wnt signaling pathway in the G2/M phase by recruiting CDK14/PFTK1 to the plasma membrane and promoting phosphorylation of LRP6. The expression of CCNY has been significantly mentioned within the cell migration and invasion activity both in vivo and in vitro. The aim of this review is evaluation of the expression of CCNY in the physiology processes and compare the expression of this protein in cancer cells, taking into account the impact of the level of expression on tumor progression.

The Important Role of Endothelium and Extracellular Vesicles in the Cellular Mechanism of Aortic Aneurysm Formation.

Homeostasis is a fundamental property of biological systems consisting of the ability to maintain a dynamic balance of the environment of biochemical processes. The action of endogenous and exogenous factors can lead to internal balance disorder, which results in the activation of the immune system and the development of inflammatory response. Inflammation determines the disturbances in the structure of the vessel wall, connected with the change in their diameter. These disorders consist of accumulation in the space between the endothelium and the muscle cells of low-density lipoproteins (LDL), resulting in the formation of fatty streaks narrowing the lumen and restricting the blood flow in the area behind the structure. The effect of inflammation may also be pathological dilatation of the vessel wall associated with the development of aneurysms. Described disease entities strongly correlate with the increased migration of immune cells. Recent scientific research indicates the secretion of specific vesicular structures during migration activated by the inflammation. The review focuses on the link between endothelial dysfunction and the inflammatory response and the impact of these processes on the development of disease entities potentially related to the secretion of extracellular vesicles (EVs).

Cyclin F Downregulation Affects Epithelial-Mesenchymal Transition Increasing Proliferation and Migration of the A-375 Melanoma Cell Line.

BACKGROUND: Cyclins are well-known cell cycle regulators. The activation of cyclin-dependent kinases by cyclins allows orchestration of the complicated cell cycle machinery and drives the cell from the G1 phase to the end of the mitotic phase. In recent years, it has become evident that cyclins are involved in processes beyond the cell cycle. Cyclin F does not activate CDKs but forms part of the Skp1-Cul1-F-box (SCF) complex where it is responsible for protein target recognition and subsequent degradation in a proteasome-dependent manner. RESULTS: Here, we report that the downregulation of cyclin F in the A-375 melanoma cell line increases cell viability and colony formation in a cell cycle independent manner. Lower levels of cyclin F do not appear to affect the cell cycle, based on flow cytometry measuring BrdU incorporation and propidium iodide staining. By means of immunofluorescence staining and Western blot analysis, we observed changes in cell morphology-related markers which suggested ongoing epithelial-mesenchymal transition (EMT) in response to cyclin F downregulation. Increases in vimentin and N-cadherin protein levels, decreases in levels of epithelial markers such as ZO-1, along with changes in morphology to a spindle-like shape with the appearance of actin stress fibers, are all hallmarks of EMT. These changes are associated with increased invasive and migratory potential, based on 2D migration assays. Moreover, we observe an increase in RhoABC, talin and paxillin levels, the proteins involved in controlling cell signaling and motility. Lastly, upon knocking down cyclin F expression, we observed a decrease in thrombospondin-1 expression, suggesting a role of cyclin F in angiogenesis. CONCLUSION: Cyclin F depletion induces proliferation and EMT processes in the A-375 melanoma model.

Cyclin F is involved in response to cisplatin treatment in melanoma cell lines.

Cyclin F is a non­canonical cyclin which is a part of the SKP1­CUL1­F­box protein (SCF) E3 ubiquitin­protein ligase complex. Cyclin F is responsible for target recognition, ubiquitination, and degradation of various molecular targets. This protein also controls genome stability through the degradation of ribonucleotide reductase subunit M2 (RRM2). In the present study, the difference between cyclin F expression in cell lines derived from primary and metastatic melanoma, A375 and RPMI­7951, respectively, were investigated using a western blot analysis and flow cytometry assays. A decrease in cyclin F expression in the A375 cells and an increase in RPMI­7951 cells after cisplatin treatment were observed. These changes may be related to a mutation in p53 in the RPMI­7951 cell line. Flow cytometry was conducted to observe that the RPMI­7951 cell line exhibited greater susceptibility to cisplatin, associated with lack of proper cell cycle control. Therefore, it is possible that cyclin F may modulate drug response in melanoma. The presented data describe cyclin F as a new potential factor that contributes to drug resistance in melanoma patients.

Expression of cyclin B1, D1 and K in non­small cell lung cancer H1299 cells following treatment with sulforaphane.

Sulforaphane (SFN) was first isolated from broccoli sprout and it is present at high concentrations in plants belonging to the Cruciferae family. The chemotherapeutic and anti­cancerogenic capacities of SFN have been demonstrated by inhibition of cancer cell proliferation in several cancer cell lines. The aim of the present study was to evaluate the effect of SFN on apoptosis, cell cycle and expression of selected cell cycle­associated proteins: Cyclin B1, cyclin D1 and cyclin K in the H1299 cell line. The non­small cell lung cancer cell line H1299 was treated with increasing concentrations of SFN (5, 10 and 15 µM) for two days. After incubation, the percentage of cells in the individual cell cycle phases, as well as the percentage of necrotic and apoptotic cells, were estimated using flow cytometry. The expression of cyclins was examined by immunofluorescence staining, flow cytometry, western blot analysis and qRT­PCR. Cyclin K was characterized by nuclear localization and increased expression after treatment with SFN. The expression data were confirmed by qRT­PCR. SFN­induced cell cycle arrest was associated with a decrease in cyclin B1 expression. Cells treated with SFN were also characterized by higher cyclin D1 and cyclin K expression. These data suggest the involvement of cyclin K in response to SFN. Moreover, we investigated the prognostic value of cyclin K, CDK12 and CDK13 in adenocarcinoma patients using 'The Kaplan­Meier plotter' (KM plotter) database. It was shown that high expression of CDK12 and CDK13 but no cyclin K proteins is associated with worse overall survival among adenocarcinoma patients.

Cytoskeletal reorganization and cell death in mitoxantrone-treated lung cancer cells.

The aim of this study was to investigate the cytotoxic effect of mitoxantrone on two human non-small cell lung cancer cell lines, A549 (p53+) and H1299 (p53-). To our knowledge, this is the first study to evaluate the impact of MXT on the organization of cytoskeletal proteins. Analyses were performed using fluorescence and transmission electron microscopy, spectrophotometric techniques, flow cytometry and Western blotting. It was shown that H1299 cells are significantly more sensitive to mitoxantrone than the A549 cell line, and that the growth-inhibitory effect of the drug is dose-dependent only after longer incubation. The observed presence of ring-like microtubule structures and mitochondria surrounding the nuclei of H1299 cells could be a manifestation of increased tubulin polymerization requiring large amounts of energy, whereas the loss of actin stress fibers was presumably not the cause but rather the consequence of cell death induction. Treatment with mitoxantrone also led to the appearance of structures resembling agresomes in H1299 cells and to nucleolar segregation in both cell lines. It was demonstrated that cells arrested in the S phase were most susceptible to cell death induction, and that triggered intracellular changes led mainly to apoptosis. High concentrations induced necrosis and some H1299 cells exhibited morphological features of mitotic catastrophe.

Activity of cyclin B1 in HL-60 cells treated with etoposide.

Cyclin B1 triggers G2/M phase transition phosphorylating with its catalytical partner - Cdc2 many of the molecular targets essential for cell cycle progression. Human leukemia cell line HL-60 were treated with increasing doses of etoposide (ETP) (0.5; 0.75; 1µM) to investigate how the drug affects cell morphology, viability, cell cycle distribution and expression of cyclin B1. To achieve this aim we applied light and transmission electron microscopy to observe morphological and ultra structural changes, image-based cytometry for apoptosis evaluation and cell cycle analysis, and then we conducted immunohistochemical and immunofluorescence staining to visualize cyclin localization and expression. Quantitive data about cyclin B1 expression were obtained from flow cytometry. Etoposide caused decrease in cell viability, induced apoptosis and G2/M arrest accompanied by enhanced expression of cyclin B1. Changes in expression and localization of cyclin B1 may constitute a part of the mechanism responsible for resistance of HL-60 cells to etoposide. Our results may reflect involvement of cyclin B1 in opposite processes - apoptosis induction and maintenance of cell viability in leukemia cells. We hypothesized possible roles and pathways by which cyclin B1 takes part in drug treatment response and chemosensitivity.

The effect of sulforaphane on the cell cycle, apoptosis and expression of cyclin D1 and p21 in the A549 non-small cell lung cancer cell line.

Sulforaphane (SFN) is present in plants belonging to Cruciferae family and was first isolated from broccoli sprouts. Chemotherapeutic and anticarcinogenic properties of sulforaphane were demonstrated, however, the underlying mechanisms are not fully understood. In this study we evaluated the expression of cyclin D1 and p21 protein in SFN-treated A549 cells and correlated these results with the extent of cell death and/or cell cycle alterations, as well as determined a potential contribution of cyclin D1 to cell death. A549 cells were treated with increasing concentrations of SFN (30, 60 and 90 µM) for 24 h. Morphological and ultrastructural changes were observed using light, transmission electron microscope and videomicroscopy. Image-based cytometry was applied to evaluate the effect of SFN on apoptosis and the cell cycle. Cyclin D1 and p21 expression was determined by flow cytometry, RT-qPCR and immunofluorescence. siRNA was used to evaluate the role of cyclin D1 in the process of suforaphane-induced cell death. We found that the percentage of cyclin D1-positive cells decreased after the treatment with SFN, but at the same time mean fluorescence intensity reflecting cyclin D1 content was increased at 30 µM SFN and decreased at 60 and 90 µM SFN. Percentage of p21-positive cells increased following the treatment, with the highest increase at 60 µM SFN, at which concentration mean fluorescence intensity of this protein was also significantly increased. The 30-µM dose of SFN induced an increased G2/M phase population along with a decreased polyploid fraction of cells, which implies a functional G2/M arrest. The major mode of cell death induced by SFN was necrosis and, to a lower degree apoptosis. Transfection with cyclin D1-siRNA resulted in significantly compromised fraction of apoptotic and necrotic cells, which suggests that cyclin D1 is an important determinant of the therapeutic efficiency of SFN in the A549 cells.

Expression of cyclin A in A549 cell line after treatment with arsenic trioxide.

BACKGROUND: Arsenic trioxide (ATO) is an effective drug used in acute promyelocytic leukemia (AML). Many reports suggest that ATO can also be applied as an anticancer agent for solid tumors in the future. The influence of arsenic trioxide on the expression of different cell cycle regulators is poorly recognized. The purpose of the current study is to investigate how arsenic trioxide affects cyclin A expression and localization in the A549 cell line. MATERIALS AND METHODS: Morphological and ultrastructural changes in A549 cells were observed using light and transmission electron microscopes. Cyclin A localization was determined by immunofluorescence. Image-based cytometry was applied to evaluate the effect of arsenic trioxide on apoptosis and the cell cycle. Expression of cyclin A mRNA was quantified by real-time PCR. RESULTS: After treatment with arsenic trioxide, increased numbers of cells with cytoplasmic localization of cyclin A were observed. The doses of 10 and 15 µM ATO slightly reduced expression of cyclin A mRNA. The apoptotic phenotype of cells was poorly represented, and the Tali imagebased cytometry analysis showed low percentages of apoptotic cells. The A549 population displayed an enriched fraction of cells in G0/G1 phase in the presence of 5µM ATO, whereas starting from the higher concentrations of the drug, i.e. 10 and 15 µM ATO, the G2/M fraction was on the increase. DISCUSSION: Low expression of cyclin A in the A549 cell line may constitute a potential factor determining arsenic trioxide resistance. It could be hypothesized that the observed alterations in cyclin A expression/distribution may correlate well with changes in cell cycle regulation in our model, which in turn determines the outcome of the treatment.

The influence of arsenic trioxide on the cell cycle, apoptosis and expression of cyclin D1 in the Jurkat cell line.

Cyclin D1 drives cell cycle progression at the G1/S transition and is believed to play a significant role in tumorigenesis, contributing to efficient proliferation of many cancer cells. Consequently, it is also recognized as an end-point biomarker of therapeutic outcome for different treatment modalities in cancer. In this study we aimed to evaluate the expression and localization of cyclin D1 in arsenic trioxide (ATO) treated Jurkat cells (lymphoblastic leukemia cell line) and to correlate these results with the extent of cell death and/or cell cycle alterations. Jurkat cells were incubated with increasing concentrations of ATO (0.2, 0.6 and 1.0µM) for 24h in standard cell culture conditions. To reach our goal we performed annexin V/PI labeling for detection of cell death and RNase/PI labeling for evaluation of cell cycle distribution, which were followed by the respective flow cytometric analyses of ATO-treated Jurkat cells. Transmission electron microscopy was applied for visualization of the cell ultrastructure. For cyclin D1 estimation a biparametric cyclinD1/cell cycle assay was done and localization of the protein was shown after immuno-labeling using light microscopy (ABC procedure) and confocal fluorescence microscopy. We found that there were no significant changes in the percentages of cyclin D1-positive cells after the treatment with ATO, but at the same time mean fluorescence intensity reflecting cyclin D1 content was gradually increasing along with the cell cycle progression, irrespective of the applied dose of the drug. On the other hand, we found a nuclear-cytoplasmic shift of this protein as a major treatment-related response, which was in good accord with an increased rate of cell death and suggested that cyclin D1 cytoplasmic degradation is an important determinant of the therapeutic efficiency of ATO in the Jurkat cell line.

Expression of cyclin D1 after treatment with doxorubicin in the HL-60 cell line.

Increased levels of cyclin D1 and amplification of CCND1 gene occur in many types of cancers. We have followed the expression of cyclin D1 after treatment with doxorubicin with reference to cell death and other possible therapeutic implications. The effect of the treatment on the cell cycle, survival, intracellular level (flow cytometry), and intracellular localization of cyclin D1 (fluorescence microscopy) and expression of CCND1 (real-time RT-PCR) was investigated in HL-60 cells. An increase in the fluorescence intensity of cyclin D1 occurred after treatment with 0.15 and 0.3 µM doxorubicin. This tendency was confirmed by real-time RT-PCR. Expression of CCND1 in relation to the reference gene PBGD was increased in cells exposed to 0.15 µM doxorubicin. Concomitantly, some alterations in the regulation of the G0/G1, S, and G2/M checkpoints occurred, accompanied by changes in the polyploid fraction of the population. This was particularly evident at 0.3 µM doxorubicin, at which concentration the rate of cell death was also clearly higher. In conclusion, depending on the concentration used, alterations in cell death and the number of S, G2/M, and polyploid cells may correspond with cyclin D1 levels. This, in turn, may reflect an important role of the protein as one of the possible survival/point-of-no-return regulators dependent on its concentration, which seems especially plausible in the context of more prominent cell death in the above-mentioned fractions of cells.

[Involvement of Rho proteins in G1 phase cell cycle progression]. / Udzial bialek Rho w regulacji postepu fazy G1 cyklu komórkowego.

 Rho proteins, including RhoA, Rac1 and Cdc42, are members of the Ras superfamily of monomeric GTP-binding proteins, which are well-known regulators of the cytoskeleton. Numerous studies have shown that an intact cytoskeleton is required for cell cycle progression through G1 phase as well as mitosis and cytokinesis. Because of their role in both cytoskeletal rearrangement and mitogenic signaling, Rho family proteins are key mediators of cell cycle progression. In this paper, we review the current state of knowledge concerning the Rho-dependent signaling pathways that regulate the expression of cell cycle regulatory proteins required for G1 phase progression and S phase entry.

Low-dose etoposide-treatment induces endoreplication and cell death accompanied by cytoskeletal alterations in A549 cells: Does the response involve senescence? The possible role of vimentin.

BACKGROUND: Senescence in the population of cells is often described as a program of restricted proliferative capacity, which is manifested by broad morphological and biochemical changes including a metabolic shift towards an autophagic-like response and a genotoxic-stress related induction of polyploidy. Concomitantly, the cell cycle progression of a senescent cell is believed to be irreversibly arrested. Recent reports suggest that this phenomenon may have an influence on the therapeutic outcome of anticancer treatment. The aim of this study was to verify the possible involvement of this program in the response to the treatment of the A549 cell population with low doses of etoposide, as well as to describe accompanying cytoskeletal alterations. METHODS: After treatment with etoposide, selected biochemical and morphological parameters were examined, including: the activity of senescence-associated ß-galactosidase, SAHF formation, cell cycle progression, the induction of p21Cip1/Waf1/Sdi1 and cyclin D1, DNA strand breaks, the disruption of cell membrane asymmetry/integrity and ultrastructural alterations. Vimentin and G-actin cytoskeleton was evaluated both cytometrically and microscopically. RESULTS AND CONCLUSIONS: Etoposide induced a senescence-like phenotype in the population of A549 cells. Morphological alterations were nevertheless not directly coupled with other senescence markers including a stable cell cycle arrest, SAHF formation or p21Cip1/Waf1/Sdi1 induction. Instead, a polyploid, TUNEL-positive fraction of cells visibly grew in number. Also upregulation of cyclin D1 was observed. Here we present preliminary evidence, based on microscopic analyses, that suggest a possible role of vimentin in nuclear alterations accompanying polyploidization-depolyploidization events following genotoxic insults.

Expression of cyclin A, B1 and D1 after induction of cell cycle arrest in the Jurkat cell line exposed to doxorubicin.

Jurkat human lymphoblastoid cells were incubated in increasing concentrations of doxorubicin (0.05, 0.1 and 0.15 µM) to induce cell death, and their expression of cyclin A, B1 and D1 was evaluated by flow cytometry (cell cycle progression, Annexin V assay, percentages and levels of each of the cyclins), transmission electron microscopy (ultrastructure) and confocal fluorescence microscopy (expression and intracellular localization of cyclins). After low-dose doxorubicin treatment, Jurkat cells responded mainly by G2/M arrest, which was related to increased cyclin B1, A and D1 levels, a low level of apoptosis and/or mitotic catastrophe. The influence of doxorubicin on levels and/or localization of selected cyclins was confirmed, which may in turn contribute to the G2/M arrest induced by the drug.

Phenethyl isothiocyanate-induced cytoskeletal changes and cell death in lung cancer cells.

Isothiocyanates are known for their anticarcinogenic and antitumor potential, however, the exact mechanism of their action has not been fully elucidated. The present study was designed to investigate and compare the effects of phenethyl isothiocyanate on cell morphology, the cytoskeleton and induction of cell death in human non-small cell lung cancer cell lines A549 and H1299 differing in p53 status. Cell viability tests (MTT assay, xCELLigence system) showed that PEITC exhibits lower cytotoxicity to A549 cells containing wild-type p53. The observed growth-inhibitory effect of PEITC was dose-dependent, but time-dependence was observed only at higher concentrations. The results of flow-cytometric and fluorescence-microscopic analyses indicate that PEITC induced disassembly of actin stress fibers and degradation of tubulin which, most likely, contributed to the induction of cell death. Although, 24-h incubation caused G2/M cell cycle arrest, the fraction of G2/M cells decreased in a dose- and time-dependent manner in favor of cells with sub-G1 DNA content. Further experiments (Annexin V staining, electron microscopic observations) confirmed that the apoptosis-inducing potency of PEITC is probably the main factor responsible for cell growth inhibition. However, PEITC treatment also resulted in the appearance of an increased proportion of H1299 cells exhibiting morphological features of mitotic catastrophe.

Expression of cyclin B1 after induction of senescence and cell death in non-small cell lung carcinoma A549 cells.

The purpose of this study was to evaluate the level of mitotic cyclin B1 in the context of senescence and cell death in A549 non-small cell lung carcinoma cells. This was performed through analysis of the cell cycle, the percentage of SA-ß-galactosidase-positive, as well as TUNEL-positive cells. Morphological alterations were studied using a transmission electron microscope. Changes in the intracellular level and the presence of cyclin B1 in the nucleus and cytoplasm areas were detected by flow cytometry and confocal fluorescence microscopy, respectively. In the cells exposed to various concentrations of doxorubicin, different kinds of cell death and senescent phenotype were observed. Alterations in the cell cycle and increased polyploidy may be indicative of mitotic catastrophe execution. Changes in cyclin B1 may also be strictly related to its different regulation at mitotic catastrophe and senescence programs.

[Cotinine--metabolism, application as a biomarker and the effects on the organism]. / Kotynina--metabolizm, zastosowanie jako biomarker i wplyw na organizm czlowieka.

This review presents the current state of knowledge on cotinine, the major metabolite of nicotine. Special attention is paid to the formation of this compound in the organism, its metabolism, application in diagnostic procedures and evaluation of its in vitro and in vivo activities. For many years, cotinine has been used as a biomarker of exposure to tobacco smoke. Currently, this compound is applied in many other studies including the use of cotinine in the treatment of various diseases. Several years ago, Scott et al. patented therapeutic applications of cotinine in chronic and acute inflammation. Cotinine is an interesting compound with a well-known metabolism; therefore there are suggestions for its application in the diagnosis and treatment of certain diseases. 

The influence of cotinine on the non-small-cell lung cancer line A549.

The aim of this investigation was to determine the influence of cotinine on the non-small-cell lung cancer line A549. The material for the study was the A549 cell line. The cells were subjected to 24-h incubation with cotinine at doses of 18 and 36 ng/ml. Control cells were incubated under analogous conditions without the addition of cotinine. Cell viability was determined and the cells were Mayer hematoxylin stained, embedded in epon, and observed under an electron microscope. A fluorescent method was used to evaluate F-actin. Cotinine's action resulted in alteration of the cytoskeleton, with changes in the organization of F-actin. Also observed was A549 cell death, presumably due to the activation of apoptotic and mitotic catastrophe pathways. Moreover, the results at the ultrastructural level suggest that cotinine influences not only the nucleus and cell shape by acting on the actin cytoskeleton, but also plays a crucial role in changes which include the remaining cellular organelles. Until now, research has been focused on determining the action of constituents of cigarette smoke, mainly nicotine. From this point of view, studies on cotinine seem justified. Results of the study allow us to suppose that cotinine, through F-actin, can influence the size and shape of non-small-cell lung cancer cells. There are some suggestions that cells of the A549 cell line can undergo death through apoptotic and mitotic catastrophe pathways as a result of cotinine's action.

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.