Biological Properties of Melanoma and Endothelial Cells after Plasmid AMEP Gene Electrotransfer Depend on Integrin Quantity on Cells

The data on the biological responsiveness of melanoma and endothelial cells that are targeted by Antiangiogenic MEtargidin Peptide (AMEP) are limited; therefore, the antiproliferative, antimetastatic and antiangiogenic effects of AMEP were investigated in murine melanoma and human endothelial cells after plasmid AMEP gene electrotransfer into the cells in vitro. Plasmid AMEP, a plasmid coding for the disintegrin domain of metargidin targeting specific integrins, had cytotoxic and antiproliferative effects on murine melanoma and human endothelial cells. Among the metastatic properties of cells, migration, invasion and adhesion were investigated. Plasmid AMEP strongly affected the migration of murine melanoma and human endothelial cell lines and also affected the invasion of highly metastatic murine melanoma B16F10 and human endothelial cell lines. There was no effect on cell adhesion on Matrigel^TM or fibronectin in all cell lines. The antiangiogenic effect was shown with tube formation assay, where human microvascular endothelial cell line (HMEC-1) proved to be more sensitive to plasmid AMEP gene electrotransfer than the human umbilical vein endothelial cell line (HUVEC). The study indicates that antiproliferative and antimetastatic biological responses to gene electrotransfer of plasmid AMEP in murine melanoma cells were dependent on the integrin quantity on melanoma cells and not on the expression level of AMEP. The strong antiangiogenic effect expressed in human endothelial cell lines was only partly dependent on the quantity of integrins and seemed to be plasmid AMEP dose dependent.     

Metastatic potential of mouse Lewis lung cancer cells is regulated via ganglioside GM1 by modulating the matrix metalloprotease-9 localization in lipid rafts

To analyze mechanisms for cancer metastasis, we established high metastatic sublines from mouse Lewis lung cancer (P29) by repeated injection. Sublines established from the two subclones H7 and C4 commonly exhibited increased proliferation and invasion activity and reduced expression of ganglioside GM1, although they showed different preferences in their target organs of metastasis. The high metastatic sublines secreted higher levels of activated matrix metalloprotease (MMP)-9 as well as pro-MMP-9 in the culture medium than the parent lines. Furthermore, they contained MMP-9 at the glycolipid-enriched microdomain (GEM)/rafts fractionated by the sucrose density gradient ultracentrifugation of Triton X-100 extracts, whereas the parent cells showed faint bands at the fraction. When high metastatic sublines were treated with methyl-beta-cyclodextrin, their invasion activities were dramatically suppressed, and the MMP-9 secretion was also suppressed. All these results indicated that GEM/rafts play crucial roles in the increased invasion and high metastatic potential. To clarify the implication of reduced GM1 expression, low GM1-expressing cell lines were established using an RNA interference-expression vector of the GM1 synthase. Low GM1-expressing cell lines showed increased proliferation and invasion, enrichment in the GEM/rafts, and increased secretion of MMP-9. Among adhesion molecules, only integrin beta1 was detected in GEM/rafts with stronger intensity in high metastatic lines and low GM1-expressing cells. Taken together, integrins seemed to be enriched in the GEM/rafts by reduced GM1 levels, and subsequently MMP-9 was recruited to the GEM/rafts, resulting in its efficient secretion and activation, and eventually in the increased invasion and metastatic potentials.     

Metastasis-associated alterations in phospholipids and fatty acids of human prostatic adenocarcinoma cell lines.

Metastatic variants of human prostatic adenocarcinoma cell lines (DU-145, LNCaP, and ND-1) were studied by using soft agar colony forming efficiency, nude mice tumorigenicity, in vitro invasion assay, and type IV collagenase assay. The DU-145 and ND-1 cell line showed higher metastatic potential than LNCaP. Lipids from DU-145, ND-1, and LNCaP cells were extracted and analyzed by thin-layer chromatography and gas-liquid chromatography. The major lipids were phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, fatty acids, and cholesterol. The sphingomyelin level was significantly higher in highly metastatic cells (DU-145 and ND-1) compared with the lower metastatic variant (LNCaP). The increase in the synthetic pathway and decrease in degradation pathway of sphingomyelin in microsomal fractions was sufficient to account for the measured increase in sphingomyelin in DU-145 cells compared with LNCaP cells. The major fatty acids of these lipids were palmitic (16:0), stearic (18:0), oelic (18:1), and arachidonic acid (20:4). The arachidonic acid level was significantly decreased in DU-145 and ND-1 compared with LNCaP cells. Electron microscopic studies showed no significant changes in the morphology of DU-145, ND-1, and LNCaP cells. The results of these investigations demonstrate for the first time that sphingomyelin and arachidonic acid contents are different in high and low metastatic variants of human prostatic adenocarcinoma cell lines.     

Mutant EL-4 thymoma cells polyclonally activate murine and human B cells via direct cell interaction

In this report we show that three mutagenized sublines of (murine) EL-4 thymoma cells can constitutively activate human and/or murine B cells via an MHC-nonrestricted cell-cell interaction. The activation signal is not by itself mitogenic but renders B cells capable of proliferating in response to interleukin 2 (IL 2). In addition, one of the mutant EL-4 sublines can constitutively respond by release of IL 2 in the presence of IL 1-containing macrophage (P388D1) supernatant. The exact relationships between these functional properties of the mutant EL-4 thymoma cells and those associated with activated normal T helper-cells remain to be established. However, the EL-4 cells provide a unique system to study in parallel murine and human B cell responses. In particular, the following observations were made during the present study. First, anti-Ig antibodies (anti-Ig) were required for B cell activation in conjunction with two EL-4 sublines acting only on murine B cells, whereas with a third subline acting on both murine and human B cells, anti-Ig was not required. Anti-Ig by itself did not lead to significant B cell activation in the absence of mutant EL-4 (or normal T) cells. Second, the growth factor-stimulated proliferation of EL-4-activated B cells, following separation of the B cells from the EL-4 cells, lasted only 2 days. These results, thus, indicate that the requirement for a surface Ig-mediated B cell activation signal depends on the quality/intensity of a direct T cell signal and that cell-cell interactions may exert a more stringent control over the growth factor responsiveness of B cells as compared with T cells.     

An endothelial cell compatible biosensor fabricated using optically thin indium tin oxide silicon nitride electrodes

This study describes the fabrication and performance of an endothelial cell compatible, optically thin, indium tin oxide (ITO) microimpedance biosensor. The biosensor was constructed by sputtering a thin insulating layer of silicon nitride (Si(3)N(4)) onto a 100 nm thick ITO layer. Indium tin oxide electrodes were formed by chemically etching 250 or 500 microm diameter holes through the Si(3)N(4) insulating layer. The exposed ITO electrode was electrically connected to an ITO counter electrode, approximately 2 cm(2) in area, via a 400 microL well containing cell culture media. A lock-in amplifier circuit monitored the impedance of porcine pulmonary artery endothelial cells (PPAECs) cultivated on the electrodes as a function of frequency, between 10 and 100 kHz, and as a function of time, at 5.62 kHz. The ITO-Si(3)N(4) microelectrodes provided consistent and repeatable impedance measurements to the attachment and spreading of PPAECs. In addition, the ITO-Si(3)N(4) electrodes were recyclable, robust, resistant to ethanol sterilization, and had a high optical transmittance. Most importantly, the ITO-Si(3)N(4) electrodes allowed optical access for dynamic cellular attachment imaging. The 5.62 kHz time dependent cellular impedance response to the drug Cytochalasin D further demonstrated the feasibility of using this electrode configuration for dynamic cellular impedance studies.     

Gangliosides protect human melanoma cells from ionizing radiation-induced clonogenic cell death

With an experimental model of spontaneous lung metastases of melanoma developed in this laboratory, a range of sublines (variants and clones) with different metastatic potential and ganglioside expression was established from a single human melanoma cell line M4Be. Using anin vitro clonogenic assay and provided that cells were cultured for no more than five passages, variations in cellular radioresistance of M4Be and seven sublines derived from M4Be were detected. This study shows a positive correlation between the cell intrinsic radioresistance of M4Be and its seven sublines and their total ganglioside content. More precisely, the proportion of radioresistant cells in M4Be and the seven sublines correlated with the number of cells determined by flow cytometry that were positively labelled with a monoclonal antibody directed to GD3 disialoganglioside. Blocking the cellular biosynthesis of gangliosides with the inhibitor Fumonisin B1 or cleaving withVibrio cholerae neuraminidase the cell surface ganglioside-bound sialic acid in a radioresistant poorly metastatic subline increased its radiosensitivityin vitro. In contrast, enrichment of a radiosensitive metastatic subline with exogenous bovine brain GM1 increased its radioresistancein vitro. These results suggest that, in the radiation dose range important for radioprotection (0–1 Gy), membrane gangliosides radioprotect human melanoma cellsin vitro.Presented at the 43rd Annual Meeting of the Radiation Research Society, San Jose, USA, 1–6 April 1995 (Abstract).     

Nuclear DNA content and chromatin pattern of rat rhabdomyosarcoma cell sublines with different metastatic potentials.

There is a constant need of features able to characterize potentially metastatic cells among the heterogeneous cell subpopulations which constitute a tumor. Image cytometry of metastatic tumor cells give rise to variable results, partly because of a heterogeneous origin of cells, or potential drug effects. The aim of this work was to characterize nuclear changes observed in metastatic cell clones issued in vitro from the same parental cell population The nuclear phenotypes of 6 cell sublines isolated from a rat rhabdomyosarcoma cell line and differing in their metastatic ability were evaluated by image cytometry on Feulgen-stained preparations. Densitometric [5], geometric [3] and textural [9] features were computed from each nuclear image. For each cell subline, a metastatic score, ranging from 0 to 10, was calculated on the basis of in vivo invasivity data, by measuring the number of pulmonary metastases observed after s.c. graft of tumor cells in rats. Data obtained were compared to karyotype, growth characteristics, and oncogene expressions of cell lines. The nuclear DNA content, the chromosome numbers, the cell sublines doubling times, and the distribution of cells within the cell cycle appear unrelated with this score. On the contrary, increase in metastatic ability is accompanied by changes in chromatin pattern as assessed by textural features. Progressive increase in chromatin condensation can be observed in cell sublines with increasing metastatic score. These results were confirmed by an unsupervised multivariate partitioning of rhabdomyosarcoma cells which identified two separate subsets whose distributions within the analyzed cell lines correlate with their metastatic ability. These data suggest that, in rat rhabdomyosarcoma cell sublines, metastatic ability could be associated with nuclear morphological changes at the level of chromatin texture.     

Reproducible generation of autonomous malignant sublines from non-tumorogenic murine interleukin 3-dependent mast cell lines

Murine interleukin 3 (IL-3)-dependent permanent mast cell lines derived from normal mouse bone marrow were established using pokeweed mitogen-stimulated spleen cell conditioned medium (SCM) as a source of IL-3. When propagated continuously in media containing a high concentration of IL-3 (20% SCM or 20 U/ml murine recombinant IL-3 (rIL-3], all the cell lines remained strictly factor-dependent in vitro and non-tumorogenic in vivo. However, we were able to reproducibly generate autonomous sublines from cultures supplemented with low amounts of IL-3 (1% SCM or 2 U/ml rIL-3). Abrogation of exogeneous growth factor dependency was always associated with neoplastic transformation. In newly generated autonomous sublines an autocrine mechanism of growth regulation was evident in vitro.     

Ganglioside GM3 inhibits hepatoma cell motility via down‐regulating activity of EGFR and PI3K/AKT signaling pathway

Two related sublines derived from murine ascites hepatoma cell lines Hca‐F25, which were selected for their markedly different metastatic potential to lymph nodes, were found to be distinct in their ganglioside patterns. The low metastatic cell line (HcaP) contained a major ganglioside GM3, whereas the high metastatic cell line (HcaF) contained a major ganglioside GM2. Suppression of GM3 by P4 enhanced the mobility and migration of the low metastatic HcaP cells in vitro. Increase in GM3 content in high metastatic HcaF cells by addition of exogenous GM3 inhibited the mobility and migration. These results suggested that the differences in lymphatic metastasis potential between these two cell lines could be attributed to the differences in their ganglioside compositions, and GM3 could suppress the motility and migration of these cells. Further, we investigated the mechanism by which GM3 suppressed the cell mobility and migration. The results showed that suppression of GM3 synthesis by P4 in low metastatic HcaP cells promoted PKB/Akt phosphorylation at Ser473 and Thr308, and phosphorylation of EGFR at the Tyr1173. In contrast, increase in GM3 content in high metastatic HcaF cells by addition of exogenous GM3 into the culture medium suppressed phosphorylation of PKB/Akt and EGFR at the same residues. Taken together, these results suggested that the mechanism of GM3‐suppressed cell motility and migration may involve the inhibition of phosphorylation of EGFR and the activity of PI3K/AKT signaling pathway. J. Cell. Biochem. 114: 1616–1624, 2013. © 2013 Wiley Periodicals, Inc.     

The role of glycoconjugates in metastatic melanoma blood-borne arrest and cell surface properties

The role of glycoconjugates in cell surface and blood-borne implantation properties of murine metastatic melanoma sublines of low (B16-F1) or high (B 16-F10) potential to colonize lungs was investigated by treating melanoma cells with the antibiotic tunicamycin. This drug prevents glycosylation of glycoproteins by inhibiting the formation of lipid-linked oligosaccharide precursors. The degree of tunicamycin-mediated modifications in glycoproteins was assessed by monitoring the decrease in cell surface sialogalactoproteins by binding of ¹²⁵I-labeled Ricinus communis agglutinin I. Scanning electron microscopy of tunicamycin-treated B16-F1 and B16-F10 cells showed morphologic changes such as cell rounding and formation of numerous surface blebs. Tunicamycin-treated B16-F1 and B16-F10 cells lost their lung colonization abilities when injected intravenously into C57BL/6 mice, concomitant with lowered rates of adhesion to endothelial cell monolayers, endothelial extracellular matrix (basal lamina), and polyvinyl-immobilized fibronectin in vitro, suggesting that this drug inhibits experimental metastasis by modifying the surface glycoproteins involved in determining the adhesive properties of malignant cells.     

Expression of developmentally regulated endothelial cell locus 1 was induced by tumor-derived factors including VEGF

Developmentally regulated endothelial cell locus 1 (Del1) is a new angiogenic molecules expressed specifically in early embryonic endothelial cells. We investigated the relationship between Del1 and tumor cell-derived vascular endothelial growth factor (VEGF). Dunn osteosarcoma cells and high- and low-metastatic murine sarcoma cells did not express Del1. However, the expression of Del1 was observed in these primary tumor tissues and the pulmonary metastatic tissues after subcutaneous inoculation in vivo. Every tumor cell-conditioned medium containing VEGF induced the expression of Del1 in murine lung microvascular endothelial (MLE) cells, although control MLE cells did not express Del1. The anti-mouse VEGF monoclonal antibody inhibited the induction of the Del1 expression. In addition, mouse recombinant interleukin-1alpha and tumor necrosis factor-alpha also induced Del1 in MLE cells. Del1 may play an important role in tumor angiogenesis through the effects of tumor-derived factors including VEGF.     

T cell lines derived from the spinal cords of mice with experimental allergic encephalomyelitis are self reactive

Experimental allergic encephalomyelitis (EAE) is an animal model of T cell-mediated, central nervous system neuropathology that may be a relevant animal model for multiple sclerosis. EAE is usually induced by sensitization of animals with a xenogeneic myelin basic protein (MBP). Recently, MBP-reactive T cell lines and clones derived from lymphoid tissue of animals with EAE have proved very useful in elucidating certain aspects of the pathogenesis in EAE. However, questions relating to how T cells actually mediate the pathologic changes seen in EAE remain unresolved. We now report for the first time the derivation of long-term, interleukin 2-dependent T cell lines and sublines from a site of pathology in murine EAE--the spinal cord. All of the spinal cord-derived T cell lines and sublines were found to be "autoreactive" in that they responded to self (murine) MBP as well as to the xenogeneic immunogen, porcine MBP. The ability to derive T cell lines and sublines from the spinal cords of mice with EAE should now aid in the elucidation of pathogenetic mechanisms in EAE by allowing for a characterization of those T cells found at the site of pathology.     

The role of fibronectin in adhesion of metastatic melanoma cells to endothelial cells and their basal lamina

Vascular endothelial cells synthesize an extracellular matrix or basal lamina composed of collagens, proteoglycans and glycoproteins such as fibronectin (FN). Using affinity-purified anti-FN, we have examined the role of FN in adherence of metastatic B16 melanoma cells to endothelial cell monolayers which lack FN on apical cell surfaces and to their basal lamina which contains FN. B16 melanoma cells, which do not contain significant amounts of FN, attached at much higher rates to endothelial basal lamina and polyvinyl-immobilized FN compared with intact endothelial cell monolayers. Anti-FN failed to inhibit attachment of melanoma sublines of low (B16-F1) or high (B16-F10) metastatic potential to intact endothelial cell monolayers, inhibited slightly B16 cell attachment to basal lamina and completely abolished attachment of B16 cells to polyvinyl-immobilized FN. The antibiotic tunicamycin which inhibits glycosylation of B16 cell surface glycoproteins and blocks experimental metastasis [18] inhibited B16 attachment to endothelial cells, basal lamina and immobilized FN. The results suggest that FN mediates, only in part, the adhesion of B16 melanoma cells to basal lamina through glycoprotein receptors on B16 cells.     

The role of peroxiredoxin III on late stage of proerythrocyte differentiation

Peroxiredoxin III (Prdx III), the mitochondrial peroxidase, was preferentially expressed in murine erythroleukemia (MEL) cells. However, the mechanisms by which Prdx III regulates erythroid differentiation are unknown. In this study, K562 cells were differentiated by Ara-C treatment, and Prdx III was dramatically increased until day 5. We also investigated Prdx III expression pattern on in vitro erythropoiesis of human CD34(+) cells. When human CD34(+) cells became proerythrocyte on day 7, Prdx III was diminished, and then augmented on day 12. We established the stable sublines of Prdx III overexpression (O/E), and dominant-negative (D/N). The intracellular ROS level of Prdx III O/E cell line was lower than D/N stable cell lines. Moreover, Prdx III O/E cell line was placed in G1-arrest, but not D/N cell lines. Finally, the expression level of beta-globin and GATA-1 was dramatically increased in Prdx III O/E cell line.     

Transformation by v-H-ras does not restore proliferation of a set of temperature-sensitive cell-cycle mutants of rat 3Y1 fibroblasts

Three temperature-sensitive cell-cycle mutants of rat 3Y1 fibroblasts (3Y1tsD123, 3Y1tsG125, and 3Y1tsH203, each belonging to distinct complementation groups) were transformed with plasmid DNA carrying Harvey murine sarcoma virus cDNA. The criteria for transformation were increase in saturation cell density, capability to clone in soft agar, and alteration in the cellular morphology. At 39.8 degrees C (restrictive temperature of the parental cell lines), all the transformed sublines of each mutant ceased to proliferate and were arrested reversibly in the G1 phase of the cell cycle like the parental lines. At both 39.8 degrees C and 33.8 degrees C (permissive temperature for the parental lines), all the untransformed parental lines synthesized p21ras at low rate. At 33.8 degrees C, all the transformed sublines synthesized p21ras at much higher rate and expressed the morphological phenotype characteristic to v-H-ras-induced transformation. At 39.8 degrees C, the rate of p21ras synthesis was not changed in the transformed sublines of 3Y1tsD123 and 3Y1tsG125, and the morphology of transformed phenotype also remained intact. In the transformed subline of 3Y1tsH203, the rate of p21ras synthesis was lowered at 39.8 degrees C to that seen in the untransformed parental line, and the transformed phenotype in morphology disappeared. In all of the transformed sublines, the amount of v-H-ras mRNA markedly expressed at both 33.8 degrees C and 39.8 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Establishment of a pluripotent embryonal carcinoma cell line not expressing SSEA-1 and ECMA-7 phenotypes

A murine embryonal carcinoma (EC) cell line heterozygous for t0 recessive lethal mutation has been established from an embryo-derived transplantable teratocarcinoma TC1Ph of the genotype (129-T/t0 X C3H/Di)t0/+. The EC cell line, designated EC1Ph, and two cloned sublines, EC1Ph/a and EC1Ph/b, maintain the diploid karyotype (40, XY) and give rise to teratocarcinomas with differentiated derivatives of EC cells after inoculation into syngeneic recipients. The cloned sublines express low or zero amounts of SSEA-1 and ECMA-7 stage-specific antigens. At some passages, the EC1Ph line and the cloned subline EC1Ph/b express a significant quantity of class I H-2 antigens. This unusual EC phenotype resembles that of human teratocarcinoma cell lines.     

Junctional adhesion molecule-C promotes metastatic potential of HT1080 human fibrosarcoma

The junctional adhesion molecule (JAM) family is a key molecule in a process called transendothelial migration or diapedesis. Here, we report implications of JAM-C in cancer metastasis. We first determined the mRNA expression of JAMs in 19 kinds of cancer cell lines. JAM-C was expressed in most of tumors having potent metastatic properties. Especially in murine K-1735 melanoma cell lines, the highly metastatic sublines (M2 and X21) strongly expressed JAM-C when compared with the poorly metastatic ones (C-10 and C23). Next, we investigated the role of JAM-C in cancer metastasis by using human JAM-C (hJAM-C) gene-transfected HT1080 fibrosarcoma cells. In comparison with mock-transfected HT1080 cells, these cells showed a significant increase in the adhesion to various extracellular substrates and the invasion across a Matrigel-coated membrane. The knockdown of hJAM-C using small interfering RNA resulted in the suppression of both the adhesion and the invasion of HT1080 cells, suggesting that endogenous hJAM-C might be involved in tumor metastasis. Finally, we studied the role of hJAM-C in an in vivo experimental metastatic model. The results showed that the overexpression of hJAM-C in HT1080 cells significantly decreased the life spans of the tumorbearing mice. In contrast, the knockdown of hJAM-C in HT1080 cells suppressed the weight gain of the lungs with metastatic colonies. We conclude that the expression of JAM-C promotes metastasis by enhancing both the adhesion of cancer cells to extracellular matrices and the subsequent invasion.     

A self-renewing, bipotential erythroid/mast cell progenitor in continuous cultures of normal murine bone marrow

We have established permanent lines of nonadherent cells from fresh normal mouse bone marrow in media containing pokeweed mitogen-stimulated spleen cell conditioned medium (PWSCM). These lines continuously produced erythropoietic progenitor cells (detected by their ability to form erythroid bursts in semi-solid medium containing erythropoietin) together with cells having characteristics of the mast cell lineage (as demonstrated by metachromatic staining with toluidine blue, histamine content and membrane receptors for IgE). Sixteen such cell lines have been established in sixteen attempts. Cloning experiments were carried out to determine the nature of the progenitor cell(s) responsible for the permanence of these cultures. When cells were cultured in methylcellulose medium containing PWSCM, colonies were observed which reached macroscopic size after 4 weeks of incubation. Replating of individual primary colonies resulted in secondary colony formation, indicating the presence of progenitor cells with self-renewal potential. Forty-seven primary colonies were picked and their cells were suspended in liquid culture medium containing PWSCM. Of these, twenty-one could be expanded to establish permanently growing sublines. Sixteen of these sublines were found to be composed of both erythroid progenitors and mast cells. In five sublines only mast cells could be seen; none of the sublines appeared to be purely erythroid. Karyotypic analysis of mast cells and of erythroid cells of seven sublines derived from individual colonies which arose in cocultures of male and female cells revealed that the mast cells and erythroid cells were both of the same sex in each of the seven sublines; this demonstrates the single cell origin of each colony and of the two lineages derived from it. We conclude that these nonadherent, factor-dependent cell lines are maintained by self-renewal and differentiation of bipotential progenitor cells apparently restricted to the erythroid and mast cell lineages.     

Establishment and characterization of clonal lines with cancer stem- and progenitor-cell properties from monolayer Zajdela hepatoma

The aim of this study was to investigate the biology of cancer stem cells (CSC) from a metastatic tumor. Previously, we explanted the cells of rat ascites Zajdela hepatoma in vitro. We established a permanent monolayer cell line via selection of adhesive cells from multicellular floating islets. In the present work, we cloned these cells by a limiting-dilution method and established five novel clonal sublines of the hepatoma: three holoclonal sublines containing CSC and two meroclonal sublines. After a long-term cultivation (approximately 30 passages, freezing, and thawing), the cell of clonal sublines retained the features of CSC. They have a tumor-initiating potential and produce mainly holoclones upon recloning in the complete growth medium and large nonadhesive hepatospheres in the serum-free medium. Morphometric analysis showed that the cells of holoclonal and meroclonal sublines differed in the cell shape, area, nucleus size, and nuclear-cytoplasmic ratio. We have found for the first time that holoclonal cells of Zajdela hepatoma have a fibroblast-like morphology and form contacts with each other due to membrane protrusions. We suggest that the fibroblast-like morphology of CSC is an attribute of a metastatic tumor and demonstrates the capability of these cells for individual migration.