ß-Catenin Expression Regulates Cell Migration of Human Colonic Adenocarcinoma Cells Through Gelsolin.

BACKGROUND/AIM: ß-Catenin is one of the key players in colonic carcinogenesis. Being part of the E-cadherin complex, it regulates cell-cell adhesion and the migratory ability of cells. However, the role of nuclear ß-catenin in the cell migration process is poorly understood. Gelsolin is one of the most abundant actin-binding proteins, and is implicated in tumour cell motility and invasiveness. The aim of the present study was to evaluate the potential association between expression of ß-catenin and gelsolin, and their influence on the migration ability of colon adenocarcinoma LS180 cells. MATERIALS AND METHODS: The colonic adenocarcinoma cell line LS180, its more motile sublines (EB3, 3LNLN, 5W) and ß-catenin-knockdown LS180 cells were used to investigate the expression levels and subcellular localization of ß-catenin and gelsolin. RESULTS: Increased motility of colonic cancer cells was accompanied by a reduction of ß-catenin and up-regulation of gelsolin. CONCLUSION: ß-Catenin seems to be involved in the regulation of gelsolin expression, which in turn affects the migratory ability of colonic cancer cells. Our results could have important implications for the design of new anticancer therapies.

Gelsolin interacts with LamR, hnRNP U, nestin, Arp3 and ß-tubulin in human melanoma cells as revealed by immunoprecipitation and mass spectrometry.

Gelsolin, a multifunctional actin binding protein, plays a not yet fully understood role in tumorigenesis. Therefore the goal of this study was to identify additional molecular partners of gelsolin in human melanoma cells, separately in the cytoplasmic compartment and cell nuclei. For this purpose we performed immunoprecipitation experiments based on a modified protocol followed by mass spectrometry. The obtained results were confirmed by Western blot analysis, proximity ligation assays and confocal microscopy. As expected gelsolin interacted with actin, in particular we demonstrate its interaction with cytoplasmic ß and γ actins, and a newly discovered actin isoform, actbl2. As new gelsolin-interacting partners we identified the ribosomal protein Rpsa, also known as a non-integrin laminin receptor (LamR), and the heterogeneous nuclear ribonucleoprotein hnRNP U. Our data furthermore indicate that gelsolin interacts with particular components of the three cytoskeleton systems: nestin (intermediate filaments), Arp3 (actin cytoskeleton) and ß-tubulin (microtubules). We also report for the first time that gelsolin is a constituent of midbodies, a tubulin containing structure formed at the end of cytokinesis.

Active invadopodia of mesenchymally migrating cancer cells contain both ß and γ cytoplasmic actin isoforms.

Invadopodia are actin-rich protrusions formed by mesenchymally migrating cancer cells. They are mainly composed of actin, actin-associated proteins, integrins and proteins of signaling machineries. These protrusions display focalized proteolytic activity towards the extracellular matrix. It is well known that polymerized (F-)actin is present in these structures, but the nature of the actin isoform has not been studied before. We here show that both cytoplasmic actin isoforms, ß- and γ-actin, are present in the invadopodia of MDA-MB-231 breast cancer cells cultured on a 2D-surface, where they colocalize with the invadopodial marker cortactin. Invadopodial structures formed by the cells in a 3D-collagen matrix also contain ß- and γ-actin. We demonstrate this using isoform-specific antibodies and expression of fluorescently-tagged actin isoforms. Additionally, using simultaneous expression of differentially tagged ß- and γ-actin in cells, we show that the actin isoforms are present together in a single invadopodium. Cells with an increased level of ß- or γ-actin, display a similar increase in the number and size of invadopodia in comparison to control cells. Moreover, increasing the level of either actin isoforms also increases invasion velocity.

ß- and γ-Actins in the nucleus of human melanoma A375 cells.

Actin is a highly conserved protein that is expressed in all eukaryotic cells and has essential functions in the cytoplasm and the nucleus. Nuclear actin is involved in transcription by all three RNA polymerases, chromatin remodelling, RNA processing, intranuclear transport, nuclear export and in maintenance of the nuclear architecture. The nuclear actin level and polymerization state are important factors regulating nuclear processes such as transcription. Our study shows that, in contrast to the cytoplasm, the majority of endogenous nuclear actin is unpolymerized in human melanoma A375 cells. Most mammalian cells express the two non-muscle ß- and γ-actin isoforms that differ in only four amino acids. Despite their sequence similarity, studies analysing the cytoplasmic functions of these isoforms demonstrated that ß- and γ-actins show differences in localization and function. However, little is known about the involvement of the individual actin isoforms in nuclear processes. Here, we used the human melanoma A375 cell line to analyse actin isoforms in regard to their nuclear localization. We show that both ß- and γ-non-muscle actin isoforms are present in nuclei of these cells. Immunolocalization studies demonstrate that both isoforms co-localize with RNA polymerase II and hnRNP U. However, we observe differences in the ratio of cytoplasmic to nuclear actin distribution between the isoforms. We show that ß-actin has a significantly higher nucleus-to-cytoplasm ratio than γ-actin.

Ovocystatin affects actin cytoskeleton organization and induces proapoptotic activity.

Ovocystatin is a chicken egg white protein, generally known for its inhibitory activity against cysteine proteases. However, biological activity of ovocystatin does not seem to be well recognized in respect to other possible cellular effects. Our attention has been focused on ovocystatin cytotoxic effects in relation to its influence on actin cytoskeleton organization and apoptosis induction. In vitro studies with human melanoma A375, human cervix HeLa cancer cells and normal human fibroblasts - NHDF were done. Cytotoxic activity of ovocystatin was seen in respect to apoptosis induction - manifested by cell shape changes, phosphatydylserine translocation and actin cytoskeleton reorganization. Normal human fibroblasts have shown lower sensitivity to ovocystatin as compared with human melanoma A375 and human cervix HeLa cancer cells. In conclusion, ovocystatin affects actin cytoskeleton organization and displays proapoptotic activity towards applied cell lines. This implicates its application as a potential anticancer drug. However, its adverse effects on normal cells should be taken into consideration.

Effect of overexpression of ß- and γ-actin isoforms on actin cytoskeleton organization and migration of human colon cancer cells.

Actins are eukaryotic proteins, which are involved in diverse cellular functions including muscle contraction, cell motility, adhesion and maintenance of cell shape. Cytoplasmic actin isoforms ß and γ are ubiquitously expressed and essential for cell functioning. However, their unique contributions are not very well understood. The aim of this study was to determine the effect of ß- and γ-actin overexpression on the migration capacity and actin cytoskeleton organization of human colon adenocarcinoma BE cells. In cells overexpressing ß- or γ-actin, distinct cytoskeletal actin rearrangements were observed under the laser scanning confocal microscope. Overexpressed actins localized at the submembranous region of the cell body, especially near to the leading edge and on the tips of pseudopodia. The cells transfected with plasmids containing cDNA for ß- or γ-actin were characterized by increased migration and invasion capacities. However, the migration velocity was statistically significantly higher only in the case of γ-actin overexpressing cells. In conclusion, the increased level of ß- or γ-actin leads to actin cytoskeletal remodeling followed by an increase in migration and invasion capacities of human colon BE cells. These data suggest that expression of both actin isoforms has an impact on cancer cell motility, with the subtle predominance of γ-actin, and may influence invasiveness of human colon cancer.

[Functional diversification of cytoplasmic actin isoforms]. / Funkcjonalne zróznicowanie cytoplazmatycznych izoform aktyny.

The actin family consists of highly conservative proteins, abundant in all eukaryotic cells. Actin plays different roles in cell functioning including cell motility, maintenance of cell shape, signal transduction and transcription. The beta and y cytoplasmic actins are ubiquitously present in all cell types and are essential for cell survival. They differ only by four amino acids located at the N-terminus of the polypeptide chain. The proportion of cytoplasmic actins varies and depends on the cell type. In addition, it changes in pathological conditions. There is also some evidence that beta and gamma actins are located in different cytoplasmic areas, what suggests functional differences between them. Studies conducted in recent years, demonstrating the increase or reduction of cytoplasmic actin isoforms expression allow for better understanding of the role of these proteins in cell functioning. In this article, we present contemporary view on this subject.

Lumican - derived peptides inhibit melanoma cell growth and migration.

Lumican, a small leucine-rich proteoglycan of the extracellular matrix, presents potent anti-tumor properties. Previous works from our group showed that lumican inhibited melanoma cell migration and tumor growth in vitro and in vivo. Melanoma cells adhered to lumican, resulting in a remodeling of their actin cytoskeleton and preventing their migration. In addition, we identified a sequence of 17 amino acids within the lumican core protein, named lumcorin, which was able to inhibit cell chemotaxis and reproduce anti-migratory effect of lumican in vitro. The aim of the present study was to characterize the anti-tumor mechanism of action of lumcorin. Lumcorin significantly decreased the growth in monolayer and in soft agar of two melanoma cell lines - mice B16F1 and human SK-MEL-28 cells - in comparison to controls. Addition of lumcorin to serum free medium significantly inhibited spontaneous motility of these two melanoma cell lines. To characterize the mechanisms involved in the inhibition of cell migration by lumcorin, the status of the phosphorylation/dephosphorylation of proteins was examined. Inhibition of focal adhesion kinase phosphorylation was observed in presence of lumcorin. Since cancer cells have been shown to migrate and to invade by mechanisms that involve matrix metalloproteinases (MMPs), the expression and activity of MMPs were analyzed. Lumcorin induced an accumulation of an intermediate form of MMP-14 (~59kDa), and inhibited MMP-14 activity. Additionally, we identified a short, 10 amino acids peptide within lumcorin sequence, which was able to reproduce its anti-tumor effect on melanoma cells. This peptide may have potential pharmacological applications.

Overexpression of lumican affects the migration of human colon cancer cells through up-regulation of gelsolin and filamentous actin reorganization.

Cell migration is a multistep process initiated by extracellular matrix components that leads to cytoskeletal changes and formation of different protrusive structures at the cell periphery. Lumican, a small extracellular matrix leucine-rich proteoglycan, has been shown to inhibit human melanoma cell migration by binding to α2ß1 integrin and affecting actin cytoskeleton organization. The aim of this study was to determine the effect of lumican overexpression on the migration ability of human colon adenocarcinoma LS180 cells. The cells stably transfected with plasmid containing lumican cDNA were characterized by the increased chemotactic migration measured on Transwell filters. Lumican-overexpressing cells presented the elevated filamentous to monomeric actin ratio and gelsolin up-regulation. This was accompanied by a distinct cytoskeletal actin rearrangement and gelsolin subcellular relocation, as observed under laser scaning confocal microscope. Moreover, LS180 cells overexpressing lumican tend to form podosome-like structures as indicated by vinculin redistribution and its colocalization with gelsolin and actin at the submembrane region of the cells. In conclusion, the elevated level of lumican secretion to extracellular space leads to actin cytoskeletal remodeling followed by an increase in migration capacity of human colon LS180 cells. These data suggest that lumican expression and its presence in ECM has an impact on colon cancer cells motility and may modulate invasiveness of colon cancer.

Cofilin overexpression affects actin cytoskeleton organization and migration of human colon adenocarcinoma cells.

The dynamic reorganization of actin cytoskeleton is regulated by a large number of actin-binding proteins. Among them, the interaction of ADF/cofilin with monomeric and filamentous actin is very important, since it severs actin filaments. It also positively influences actin treadmilling. The activity of ADF/cofilin is reversibly regulated by phosphorylation and dephosphorylation at Ser-3, with the phosphorylated form (P-cofilin) being inactive. Here, we studied the effects of overexpression of cofilin and two cofilin variants in the human colon adenocarcinoma LS180 cell line. We have generated the LS180 cells expressing three different cofilin variants: WT (wild type), Ser 3 Ala (S3A) (constitutively active) or Ser 3 Asp (S3D) (constitutively inactive cofilin). The cells expressing WT cofilin were characterized by abundant cell spreading and colocalization of cofilin with the submembranous F-actin. Similar effects were observed in cells expressing S3A cofilin. In contrast, LS180 cells expressing S3D cofilin remained longitudinal in morphology and cofilin was equally distributed within the cell body. Furthermore, the migration ability of LS180 cells expressing different cofilin mutants was analyzed. In comparison to control cells, we have noticed a significant, approximately fourfold increase in the migration factor value of cells overexpressing WT type cofilin. The overexpression of S3D cofilin resulted in an almost complete inhibition of cell motility. The estimation of actin pool in the cytosol of LS180 cells expressing S3A cofilin has shown a significantly lower level of total actin in reference to control cells. The opposite effect was observed in LS180 cells overexpressing S3D cofilin. In summary, the results of our experiments indicate that phosphorylation "status" of cofilin is a factor affecting the actin cytoskeleton organization and migration abilities of colon adenocarcinoma LS180 cells.

Gelsolin affects the migratory ability of human colon adenocarcinoma and melanoma cells.

AIMS: Formation of different protrusive structures by migrating cells is driven by actin polymerization at the plasma membrane region. Gelsolin is an actin binding protein controlling the length of actin filaments by its severing and capping activity. The main goal of this study was to determine the effect of gelsolin expression on the migration of human colon adenocarcinoma LS180 and melanoma A375 cells. MAIN METHODS: Colon adenocarcinoma cell line LS180 was stably transfected with plasmid containing human cytoplasmic gelsolin cDNA tagged to enhanced green fluorescence protein (EGFP). Melanoma A375 cells were transfected with siRNAs directed against gelsolin. Real-time PCR and Western blotting were used to determine the level of gelsolin. The ability of actin to inhibit DNase I activity was used to quantify monomeric and total actin level and calculate the state of actin polymerization. Fluorescence confocal microscopy was applied to observe gelsolin and vinculin distribution along with actin cytoskeleton organization. KEY FINDINGS: Increased level of gelsolin expression leads to its accumulation at the submembranous region of the cell accompanied by distinct changes in the state of actin polymerization and an increase in the migration of LS180 cells. In addition, LS180 cells overexpressing gelsolin form podosome-like structures as indicated by vinculin redistribution and its colocalization with gelsolin and actin. Downregulation of gelsolin expression in melanoma A375 cells significantly reduces their migratory potential. SIGNIFICANCE: Our experimental data indicate that alterations in the expression level of gelsolin and its subcellular distribution may be directly responsible for determining migration capacity of human cancer cells.

Apoptotic effect of imatinib on human colon adenocarcinoma cells: influence on actin cytoskeleton organization and cell migration.

Imatinib mesylate (STI571) is the first member of a new class of agents that act by inhibiting specific tyrosine kinases, rather than killing all rapidly dividing cells. This drug is usually used in the treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors. It was recognized to inhibit activity of kinases such as Bcr/Abl, platelet-derived growth factor receptor, and c-kit. These proteins play important roles in cell growth, motility, and survival. Therefore, studies on the biological effects of imatinib on different cellular models are very important. Human colon adenocarcinoma LS180 cell line was used in the studies presented. Cells were exposed to 0.1-100 µM imatinib for 24 and 48 h. Dose-dependent decreases in cell viability and morphological changes were observed. Moreover, the apoptotic effect of imatinib (10 µM, 50 µM) after 24 h of exposure was demonstrated as evaluated by translocation of phosphatidylserine to external membrane leaflet and by increased activity of caspase-3. Special attention was focused on imatinib influence on actin cytoskeleton organization and migration ability of LS180 cells. Distinct alterations in actin cytoskeleton architecture occurred in response to drug treatment, accompanied by appearance of filamentous actin aggregates and decrease in actin polymerization state. These changes were correlated with remarkable decrease in cell migration capacity. In summary, our data clearly demonstrate that imatinib induces apoptosis and inhibits human colon adenocarcinoma cell migration. Therefore, this drug may have potential in colon cancer therapy in the future.

Gelsolin in human colon adenocarcinoma cells with different metastatic potential.

Gelsolin, one of a major actin-binding proteins, is involved in the regulation of actin cytoskeleton organization by its severing and capping activity towards actin filaments. Human colon adenocarcinoma cell line LS180 and its selected variants of different metastatic potential were used to check for a correlation between gelsolin level, its subcellular localization and the invasive capacity of cells. Based on immunoblotting experiments, a decreased level of gelsolin was detected in the most invasive 5W subline when compared to the parental cell line LS180. The intracellular distribution of actin filaments and gelsolin in colon adenocarcinoma cells was examined by confocal microscopy. In the 5W subline, unlike in the other examined cells, gelsolin was colocalized with filamentous actin at the cell periphery. In summary, in human colon adenocarcinoma cells, gelsolin level and its subcellular distribution seem to correlate with their metastatic potential.

[Types of tumor cells movement]. / Sposoby migracji komórek nowotworowych.

Problems in successful cancer therapy result from an adaptive character and high plasticity in tumor cells behaviour. Their accommodation to a differentiated environment is preceded by an alteration in expression profile of several proteins. Three types of tumor cell migration were characterized so far: mezenchymal, ameboid and collective. In mezechymal and ameboid types of tumor cell migration, cells move individually. Collective type of migration to a bigger extend presents characteristics of the mezenchymal one. Diverse types of tumor cell locomotion differ with cell protrutions and signaling pathways that control those processes. Mezenchymal type of movement is regulated by Cdc42 kinase. Cells that move in this manner present elongated shape with distinctly exposed lamellipodium and adhere to ECM proteins. Cellular membrane blebbing of pseudopodial character appear in ameboid type of movement. This one is under Rho/ROCK signal transduction cascade control. Our review focuses on description of different movement types and mechanisms of their regulation.

Methotrexate induces apoptosis in CaSki and NRK cells and influences the organization of their actin cytoskeleton.

Methotrexate is a widely used drug in treatments of various types of malignancies and in the therapy of rheumatoid arthritis. The goal of our study was to look at the effect of this dihydrofolate reductase inhibitor on the actin cytoskeleton, since actin plays an important role in cancer transformation and metastasis. For this reason we compared results obtained from experiments on CaSki (human uterine cervix cancer) and NRK (normal fibroblastic rat kidney) cells treated with methotrexate. It has been shown previously that methotrexate can induce apoptosis. Therefore we first examined whether methotrexate induces apoptosis in our model cells. For this aim we applied several assays like Caspase Glo 3/7, DNA fragmentation and binding of phosphatidylserine by annexin V-fluorescein. The data obtained indicated that methotrexate induces programmed cell death in CaSki and NRK cells. However, differences between CaSki and NRK cells were observed in the morphological alterations and dynamics of apoptosis induced by methotrexate. It seemed that cancer cells were more sensitive towards the cell death inducing activity at lower concentrations of methotrexate. Analysis by confocal microscopy of methotrexate-treated cells demonstrated that treatment with this folate antagonist affected the actin cytoskeleton, although the dis-organization of the actin cytoskeleton after treatment with methotrexate differed between cancer and normal cells.

Lumican core protein inhibits melanoma cell migration via alterations of focal adhesion complexes.

Lumican is a small leucine-rich proteoglycan (SLRP) of the extracellular matrix (ECM) with anti-tumor activity. We recently demonstrated that lumican inhibits the migration of melanoma cells and identified beta1 integrin as mediator of this effect [M.F. D'Onofrio, S. Brézillon, T. Baranek, C. Perreau, P.J. Roughley, F.X. Maquart, Y. Wegrowski, Identification of beta1 integrin as mediator of melanoma cell adhesion to lumican, Biochem. Biophys. Res. Commun. 365 (2008) 266-272]. The aim of the present work was to study beta1 integrin, focal adhesion complexes, actin distribution and expression in the presence of lumican substratum in comparison to type I collagen or fibronectin substrata in A375 human melanoma cells. The protein distribution was investigated by immunocytochemistry and confocal microscopy. In parallel, their expression was evaluated by Western immunoblotting and Real-time Reverse Transcription-PCR analyses. The interaction of melanoma cells with the lumican substratum resulted in heterogeneous distribution of beta1 integrin on cell membrane after 24h of seeding. Concomitantly, a reorganization of actin stress fibers and a significant decrease in vinculin immunostaining at focal adhesion complexes were observed. No alteration of the expression was detected at protein and mRNA levels. However, a cytosolic accumulation of vinculin focal adhesion protein was observed on lumican substratum by confocal microscopy. Moreover, vinculin expression was significantly increased in cytosolic fractions in comparison to cells seeded on type I collagen or fibronectin substrata. Our results suggest that lumican induces an alteration of the link between actin filaments and beta1 integrin, characterized by a cytosolic accumulation of vinculin focal adhesion protein, which could lead to a destabilization of focal adhesion complexes. In addition, focal adhesion kinase phosphorylated at tyrosine-397 (pFAK) was significantly decreased. Therefore, the cytoskeleton remodeling and the decreased pFAK phosphorylation induced by lumican in melanoma cells might explain, at least in part, the anti-invasive effect of this SLRP.

Lumican affects actin cytoskeletal organization in human melanoma A375 cells.

AIMS: Lumican, a small leucine-rich proteoglycan (SLRP), has attracted attention as a molecule of the extracellular matrix possibly involved in signalling pathways affecting cancer cell behaviour. The remodelling of the actin cytoskeleton, induced in response to external stimuli, is crucial for cell motility and intracellular signal transduction. The main goal of this study was to examine the effects of recombinant lumican on actin organization, the state of actin polymerization, actin isoform expression, and their sub-cellular distribution in the A375 human melanoma cell line. MAIN METHODS: Fluorescence and confocal microscopy were used to observe actin cytoskeletal organization and the sub-cellular distribution of cytoplasmic beta- and gamma-actins. The ability of actin to inhibit DNaseI activity was used to quantify actin. Western blotting and real-time PCR were used to determine the expression levels of the actin isoforms. KEY FINDINGS: A375 cells grown on lumican coatings changed in morphology and presented rearranged actin filament organization: from filaments evenly spread throughout the whole cell body to their condensed sub-membrane localization. In the presence of lumican, both actin isoforms were concentrated under the cellular membrane. A statistically significant increase in the total, filamentous, and monomeric actin pools was observed in A375 cells grown on lumican. SIGNIFICANCE: Novel biological effects of lumican, an extracellular matrix SLRP, on the actin pool and organization are identified, which may extend our understanding of the mechanism underlying the inhibitory effect of lumican on the migration of melanoma cells.

Liposomal formulation of DIMIQ, potential antitumor indolo[2,3-b]quinoline agent and its cytotoxicity on hepatoma Morris 5123 cells.

The cytotoxic and antitumor activity of DIMIQ (5,11-dimethyl-5H-indolo[2,3-b]quinoline), synthetic analog of neocryptolepine, makes this compound a potential antitumor agent. An attempt to obtain liposomal form of DIMIQ.HCl was undertaken in the present study. Standard experimental conditions were chosen and information on the physicochemical parameters of the liposome dispersion containing studied indoloquinoline agent was collected. The effective and efficient encapsulation of DIMIQ.HCl (66.6%) in conventional liposomes (FAT-MLV, DMPC:DMPG 7:3 w/w at pH 7.0), uniformity of the size of liposomal vesicles, and high stability at pH 6.5 were demonstrated. Hemolysis of sheep erythrocytes induced by free form of DIMIQ.HCl was dramatically decreased after addition of liposome-entrapped DIMIQ.HCl. Treatment of hepatoma Morris 5123 cells for 24 hr with different concentrations of both free and its liposomal formulation of DIMIQ.HCl resulted in significant changes in cell morphology accompanied by reduction of cell viability.

WITHDRAWN: PUBLISHED IN ERROR BY PUBLISHER: Lumican core protein increases melanoma cell adhesion through a beta 1-type integrin receptor.

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Beta-actin in human colon adenocarcinoma cell lines with different metastatic potential.

Human colon adenocarcinoma LS180 parental cell line and selected variants, characterized by different metastatic capacity were used to examine, whether a correlation exists between beta-actin expression, its subcellular distribution and metastatic potential of these cells. Cytosolic fraction (supernatant 105000 x g), isolated from the tumor cells was used as a source for actin quantification. The higher level of beta-actin was observed in the cytosol of three selected sublines to compare with LS180 parental line. Statistically significant increase of beta-actin level in highly motile EB3 cells variant should be underlined to compare with the other sublines. Distinct differences in the phenotype of adenocarcinoma cell variants were found, such as the changes in cells shape, cells spreading and ability to attach to the surface of culture dish. Actin cytoskeleton was visualized with fluorescence microscopy application and microfilaments rhodamine-conjugated phalloidin staining. beta-actin subcellular localization was done by immunofluorescence staining with monoclonal anti-beta actin antibodies. In the elongated cells (LS180, 3LNLN), this isoactin is dispersed in the whole cell body and concentrates in pseudopods and at the leading edges, when in the rounded variant (EB3) beta-actin dominates mainly in cortical ring under cellular membrane and it is also seen in the subtle protrusions. Summary of our former (Nowak et al., 2002, Acta Biochim. Polon., 49: 823) and current data lead to the conclusion that there is a distinct correlation between metastatic capacity of examined human colon adenocarcinoma cells, the state of actin polymerization, actin cytoskeleton organization and beta-actin expression.