Attachment, spreading and growth in vitro of highly malignant and low malignant murine fibrosarcoma cells

Decreased adhesion to endothelial cells and matrix proteins of H-2Kb gene transfected tumour cells

Transfection of murine metastatic B78H1 cells (derived from B16 melanoma) with a syngeneic H-2Kb gene was used to study the effect of Major Histocompatibility Complex (MHC) gene products on tumour cell adhesion to endothelial cells and matrix proteins and the involvement in the metastatic process. H-2Kb-expressing transfectants showed a reduced adhesion to endothelial surfaces of different origin (four murine endotheliomas and human umbilical vein endothelial cells) when compared to parental B78H1 cells and to controls transfected with pSV2neo alone. On the average a 50-70% reduction in adhesion to endothelial cells was observed among H-2Kb transfectants. H-2Kb transfectants had a reduced expression of the alpha 4 integrin subunit, moreover the adhesion of Neo-transfected clones to endothelial cells was reduced to the levels of H-2Kb transfectants by antibodies directed against the beta 1 subunit and the endothelial VCAM-1 molecule, thus suggesting an impairment of the VLA-4/VCAM-1 interaction in H-2Kb transfectants. Adhesion to extracellular matrix components was also strongly decreased: in general the adhesion of H-2Kb cells showed a 50-75% inhibition with respect to Neo or parental controls. The highest difference was observed in adhesion to vitronectin and laminin, the lowest in adhesion to fibronectin. Reduction in adhesive properties of H-2Kb-expressing transfectants could be involved in the reduced metastatic ability, evaluated by means of intravenous injection of cells: H-2Kb transfectants yielded less than ten lung colonies, while all controls produced more than 100. Our data indicate that expression of a single class I MHC gene can significantly alter the metastatic phenotype of MHC-negative tumour cells and this could be related to a general alteration of tumour cell adhesive interactions.

Growth patterns of pulmonary metastases and primary tumours from five murine fibrosarcoma cell clones

The growth patterns, including the size, shape and regional preferences, of lung metastases from five murine fibrosarcoma cell clones were studied. Spontaneous metastases developed from tumours formed by subcutaneous inoculation of the cell clones. Lung colonies (experimental metastases) were established by i.v. injection of cells. The numbers of both spontaneously and experimentally formed subpleural lung metastases were counted through a stereomicroscope. The fraction of colonies that was located subpleurally was determined in histological sections of lungs. The growth kinetics of clonally derived primary tumours, and the number of spontaneous and experimental lung metastases, differed greatly between certain cell clones. The number of spontaneous lung metastases was correlated with the maximum size of primary tumours. No close correlation was observed between the size of the primary tumours and the size of experimental metastases. There were differences between the cell clones in the shape and regional preferences of their lung deposits. The subpleural colonies were generally larger than the intrapulmonary ones. Thus, both the regional distribution and the growth pattern of lung deposits differed between the clones.

Modulation of fibronectin synthesis and fibronectin binding during transformation and differentiation of mouse AKR fibroblasts

In previous studies it was shown that transformation of AKR fibroblasts with 3-methylcholanthrene was associated with a loss of surface fibronectin and that induction of differentiation of the transformed cells with N,N-dimethylformamide (DMF) was associated with reacquisition of surface fibronectin (Chakrabarty et al., J. Cell. Physiol. 133:415, 1987). It is shown in the present study that changes in surface fibronectin reflect altered fibronectin synthesis and altered fibronectin binding. Both the nontransformed cells (AKR-2B) and their transformed counterparts (AKR-MCA) bound 125I-fibronectin in a receptor-like fashion, but the AKR-MCA cells had only 20% of the receptors found on the AKR-2B cells. Whole cell extracts prepared from the AKR-2B cells and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions were examined for 125I-fibronectin binding. Under these conditions, the majority of binding occurred to moieties with molecular weights of 180 kD, 150 kD, and 97 kD. Binding to similar moieties on the AKR-MCA cells was virtually absent but occurred rapidly after treatment with DMF. The appearance of these moieties paralleled the acquisition of 125I-fibronectin binding activity by whole cells. Antibodies to the fibronectin receptor isolated from human placenta reacted with the DMF-sensitive moieties in immunoblot assays. Both the appearance of the fibronectin binding moieties and the acquisition of 125I-fibronectin binding activity by whole cells occurred within 6 hr of DMF treatment and increased over the subsequent 4 day period. The time course of these events paralleled closely the time course for induction of fibronectin biosynthesis by DMF. These changes in fibronectin binding and fibronectin production were associated with alterations in cell-substrate adhesion. The AKR-2B cells rapidly attached and spread on bovine serum albumin-coated dishes and on fibronectin-coated dishes, whereas the AKR-MCA cells were less adhesive on both substrates. Capacity to attach and spread was regained concomitantly with the induction of fibronectin binding and fibronectin production. Adhesion on both substrates was partially inhibited by antibodies to the fibronectin receptor and by RGDS. These studies suggest that fibronectin production and fibronectin binding are coregulated in AKR fibroblasts and that they function together to bring about changes in cell-substrate adhesion.

Microvascular endothelial cell heterogeneity: interactions with leukocytes and tumor cells

Endothelium constitutes a highly specialized organ that lines the vascular system and lymphatic channels. This organ is a complex network of arteries, veins, and microvessels that differ in size, structure, and function. The unique and strategic location imposes functional demands on the endothelium that are far greater than just being a passive barrier. Endothelial cells have the ability to differentiate both in structure and function in response to the needs of diverse tissue environments, making this organ extremely heterogeneous. Although vascular endothelial cells share certain common properties, they differ in regard to structure, antigenic and cell surface determinants, adhesion molecules, and metabolic function. The unique cell surface profiles expressed by endothelial cells in different tissue locations can be recognized by specific populations of circulating leukocytes or tumor cells, which contribute to their arrest and invasion patterns. This article attempts to review our current understanding of endothelial cell heterogeneity and its significance to patterns of leukocyte and tumor cell trafficking.

Fibronectin/laminin and their receptors in aberrant growth control in FR3T3 cells transformed by Ha-ras oncogene and epidermal growth factor gene

FR3T3 cells transfected with either the Ha-ras oncogene or the epidermal-growth-factor (EGF) gene demonstrate the transformed phenotype as indicated by in vitro and in vivo criteria. We have examined non-transformed FR3T3 cells as well as Ha-ras-oncogene-transformed and EGF-gene-transformed cells for expression of cell surface fibronectin and cell surface laminin. Fibronectin was absent from the surface of the Ha-ras-oncogene-transformed cells but present on both the EGF-gene-transformed cells and the non-transformed FR3T3 cells. Laminin was present on the cell surface in all 3 lines. The lack of surface fibronectin on the Ha-ras-oncogene-transformed cells was associated with reduced fibronectin production as indicated by immunoblotting of whole cell extracts and by ELISA. Concomitantly, there was a significant reduction of fibronectin binding by the Ha-ras-oncogene-transformed cells was compared to their EGF-gene-transformed and non-transformed counterparts. The Ha-ras-oncogene-transformed cells demonstrated reduced cell-substrate adhesiveness relative to the other two cell lines, as indicated by rates of attachment and spreading on plastic culture dishes in the presence of bovine serum albumin. They also demonstrated reduced adhesiveness in response to fibronectin but not laminin. Taken together, our results suggest that aberrant expression of fibronectin/fibronectin receptors is associated with Ha-ras-oncogene-induced transformation. In contrast, transformation by the EGF gene does not appear to involve aberrant expression of fibronectin/fibronectin receptors.

Isolation and characterization of low- and high-metastatic clones from murine RCT (Radiological, Chiba, and Toyama) sarcoma

We have established low- and high-metastatic clones, named RCT(-) and RCT(+) cells, respectively, from the RCT (Radiological, Chiba, and Toyama) sarcoma spontaneously developed in a C3H/He male mouse by the limiting-dilution method in vitro or by the combination of the lung passages and limiting-dilution methods. After 20 serial passages in vitro, the metastatic potential of each clone did not alter. Morphologically, both cells were spindle-shaped, but RCT(+) cells were slightly thicker and larger than RCT(-) cells. The organization of actin-containing filaments was slightly poorer in RCT(+) cells than that in RCT(-) cells. Marked differences were observed in their growth characteristics and adhesiveness to plastic or collagen-coated surfaces, that is, RCT(+) cells grew more slowly but could adhere more rapidly and firmly to the surfaces than RCT(-) cells. RCT(+) cells were agglutinated by all lectins used but several lectins could not agglutinate RCT(-) cells. These results could be a reflection of the difference in oligosaccharide residues on the surface of each cell and, in part, might reflect the difference in organization of the actin-containing filaments that regulate the mobility of lectin receptors. No significant difference between these cell clones was noted in their sensitivity to natural-killer-cell-mediated cytotoxicity in vitro. RCT(-) and RCT(+) cells are considered to be the most useful experimental model for the study of the certain sarcomas.

Normal nonmetastatic human trophoblast cells share in vitro invasive properties of malignant cells

First-trimester normal human trophoblast cells show some phenotypic similarities to malignant cells, e.g., rapid proliferation and ability to invade neighboring tissue, including basement membrane in situ, but do not have the ability for unlimited growth or metastasis. The present study examined whether the invasive ability of normal trophoblast cells is an intrinsic property of these cells, independent of the microenvironment provided by the pregnant uterus, and if so, whether they share some of the molecular mechanisms of invasion exercized by metastatic malignant cells. The ability of in vitro grown human trophoblast lines to invade an epithelium-free human amniotic membrane was measured from the temporal kinetics of retention of radioactivity within this membrane resulting from a penetration by 125I-iododeoxyuridine-labeled trophoblast cells. The magnitude of this invasion was compared to that of the highly metastatic human JAR-choriocarcinoma cell line and murine B16F10 melanoma line. Trophoblasts were found to share some of the same molecular mechanisms of invasion with the metastatic cell lines. Inhibitors of collagenase, plasmin, plasminogen, and plasminogen activators completely prevented invasion of the amnion by the trophoblast lines as well as by the metastatic JAR and B16F10 lines. Mersalyl, a compound known to activate collagenase, stimulated invasion by all cell lines tested, including under conditions in which plasmin activity was inhibited. In addition, trophoblasts produced significant levels of type IV collagenase and laminin, both of which appear to be important products of metastatic tumor cells required for basement membrane invasion. It may be concluded from these findings that the invasive property of first trimester human trophoblasts is genetically determined; that the magnitude of amnion invasion cannot differentiate between metastatic cell lines and invasive but nonmetastatic cell lines; and that invasiveness is not a sufficient prerequisite for metastatic ability.

Thrombospondin-induced adhesion of human keratinocytes

Human epidermal keratinocytes obtained from normal skin attached and spread on thrombospondin (TSP)-coated plastic dishes but failed to attach and spread on untreated plastic culture dishes or dishes coated with fibronectin or laminin. These cells produced minimal amounts of immunoreactive TSP. Keratinocytes established in culture on MCDB 153 medium and maintained for one to three passages in an undifferentiated state by continued cultivation in this low Ca2+-containing medium attached and spread on plastic dishes as well as on TSP-coated dishes. These cells also secreted significant amounts of TSP into the culture medium. When the keratinocytes were incubated for one day in MCDB 153 medium supplemented with high Ca2+ or in MEM (which also contains high Ca2+), there was decreased secretion of TSP into the culture medium concomitant with a reduction in attachment and spreading on plastic culture dishes. Proteolytic fragments of TSP were examined for stimulation of keratinocyte attachment and spreading. A 140-kd fragment produced by removal of the 25-kd heparin-binding domain had similar activity to the intact molecule while the 25-kd fragment was without effect. Further proteolytic treatment of the 140-kd fragment gave rise to a fragment consisting of 120 kd and 18-D moieties held together in disulphide linkage. This fragment did not support attachment or spreading. This study reveals that normal epidermal keratinocytes grown under conditions that maintain the undifferentiated state are able to produce TSP and utilize it as an attachment factor. When keratinocytes are grown under conditions that promote differentiation, ability to produce and utilize TSP is diminished. Since TSP is present at the dermal-epidermal junction and because TSP promotes keratinocyte attachment and spreading, this molecule may play an important role in maintaining normal growth of the basal cell layer and may also participate in reepithelialization during wound repair.

Marker polypeptide differences between spontaneous strongly and weakly metastatic cancer cells identified by 2-dimensional gel electrophoresis

A recent 2-dimensional gel electrophoresis study revealed several polypeptide differences between a strongly metastatic and a weakly metastatic clone from a single chemically induced murine fibrosarcoma (Jellum et al., 1984). To exclude the possibility that this was merely coincidental, the study is extended here to 2 other fibrosarcomas recently and similarly induced in mice of the same inbred strain. Metastatic potential was defined by the number of lung metastases spontaneously formed from a transplanted primary footpad tumor. One strongly (or moderately) metastatic cell line and I weakly metastatic line from each of the 3 fibrosarcomas were examined in the same experiments. In confirmation of our previous results, the same polypeptides consistently occurred in considerably greater amounts in the weakly metastatic than in the strongly metastatic cells. One of these marker polypeptides was absent from the strongly metastatic cell lines. In comparison with 2 of the 3 most metastatic lines, the third line was only moderately metastatic, and differed least strongly from the 3 weakly metastatic cell lines with regard to expression of th marker polypeptides. Marker polypeptide expression showed no consistent correlation with tumorigenicity. No other consistent polypeptide differences between strongly metastatic and weakly metastatic cells could be identified among the approximately 2,000 cellular polypeptides separated on the gels.

Thromboplastin release, but not content, correlates with spontaneous metastasis of cancer cells

No previous studies on the possible contribution of cancer-cell procoagulants to metastasis have fulfilled all the criteria for attaining biologically relevant and readily interpretable data (Grimstad et al., 1986), viz: (1) Spontaneous metastasis from primary tumors should be assessed in syngeneic animals; (2) cloned cell lines should be used to correlate cell properties, because heterogeneity within the cell lines employed is a source of serious error; (3) enough clones, derived from the same original tumor, should be used to identify only nonrandom correlations. Observing these criteria, we examined the procoagulant activities of 19 murine fibrosarcoma cell clones and 4 uncloned cell lines with high to moderate or low potential for lung metastases formation. The procoagulant activity found was exclusively of the thromboplastin (tissue factor, factor III) type. It occurred in all cell homogenates, but the quantities did not correlate with metastatic potential. In contrast, all highly to moderately metastatic cell clones and lines from 2 different fibrosarcomas shed thromboplastin activity into the culture medium, whereas no weakly metastatic cells did. Histological examination further supported these indications that release of thromboplastin from cancer cells can promote metastasis by initiating blood clotting and thereby facilitating arrest of the cancer cells in target organ vessels. Examination of a third fibrosarcoma showed that release of thromboplastin activity is not necessary for metastasis in all tumors.

Plasminogen activator production by human tumor cells: effect on tumor cell-extracellular matrix interactions

Cell lines derived from 3 different types of human tumor (e.g., squamous carcinomas, melanomas and gliomas) were examined for production of plasminogen activator activity and for attachment and spreading on various extracellular matrix components in the presence or absence of plasminogen. All of the squamous carcinoma and melanoma lines produced high levels of plasminogen activator activity. In contrast, 4 of 6 glioma lines had undetectable activity. Cells from all 3 tumor types attached and spread on fibrinogen-coated or fibrin-coated plastic dishes in the absence of plasminogen. In the presence of exogenous plasminogen, the attachment and spreading of the cells which produced high levels of plasminogen activator activity was inhibited. The plasminogen activator-deficient cells were much less sensitive to exogenous plasminogen. In the presence of plasminogen, attachment and spreading on fibronectin-coated dishes was also partially inhibited. In contrast, plasminogen had no effect on the attachment and spreading of the cells on type-I or -IV collagen, laminin or thrombospondin. Previous studies have shown that tumor-cell adhesion to the extracellular matrix depends on the synthesis of receptors for extracellular matrix components or on the synthesis of extracellular matrix components themselves. The present study shows that, in addition, the production of enzymes which are capable of degrading these components also influences tumor-cell adhesion to extracellular matrix moieties.

The application of lectins to the characterization and isolation of mammalian cell populations

Mammalian cells invariably contain a vast array of glycosylated moieties, both inside the cell and on the cell surface. There is an increasing awareness of the utility of these carbohydrates in delineating the phenotype or function of many populations of cells. To this end lectins are extremely useful reagents. Lectins are carbohydrate-binding proteins and glycoproteins of non-immune origin derived from numerous plants and animals. A wide variety of lectins with many distinct carbohydrate specificities have been isolated. Historically the most common laboratory techniques utilizing lectins have been agglutination, mitogen stimulation, and fluorescence techniques. Recent advances in the development and conjugation procedure for labels and matrices have led to the creation of numerous novel lectin-based assays. Lectins are currently used not only to identify cells with specified carbohydrate groups, but also to quantitate the carbohydrate groups or to isolate the carbohydrate-bearing cells or structures.

Direct evidence that cancer cell locomotion contributes importantly to invasion

This study was undertaken to clarify whether active locomotion of cancer cells is important for their ability to invade. The most rapidly moving cells were isolated from a cultured murine parent fibrosarcoma by successive cycles of migration through a micropore membrane. Cells were isolated by unstimulated locomotion and by haptotaxis to laminin, and the selected cells did indeed constitute rapidly locomoting subpopulations. These cells invaded biological tissues more efficiently than did the unselected parent cells. The cells selected by haptotaxis to laminin invaded most rapidly through amnion with basement membranes (containing laminin). Cancer cell haptotaxis to laminin in basement membranes thus promotes penetration of these tissue barriers. These results show in a direct manner that cancer cell locomotion is in fact important in invasion of biological tissues.

Cell-surface laminin-like molecules and alpha-D-galactopyranosyl end-groups of cloned strongly and weakly metastatic murine fibrosarcoma cells

Indications from previous work that cancer cell-surface laminin-like molecules and alpha-D-galactopyranosyl end-groups may contribute to spontaneous metastasis were further investigated. Both moieties are known to mediate cell attachment to various foreign surfaces. Five strongly metastatic and 5 weakly metastatic cell clones from a murine fibrosarcoma were examined for the occurrence of both cell-surface moieties by immunofluorescence flow cytometry and microscopy. None of these clones was rich in laminin-like molecules, which were least strongly expressed by the highly metastatic clones. The alpha-D-galactopyranosyl end-groups were strongly expressed by all strongly metastatic clones and by 2 weakly metastatic clones, but were only weakly expressed by the other weakly metastatic clones. These results indicate that the laminin-like cell-surface molecules are not necessary for spontaneous metastasis formation. However, the alpha-D-galactopyranosyl end-groups may be necessary, but are not sufficient for the cancer cells to form metastases. These carbohydrates are known to occur on the laminin-like molecules. The present results show that they must also exist on other cell-surface molecules.

Tumor type-specific differences in cell-substrate adhesion among human tumor cell lines

Cell lines derived from human tumors of 4 different histological types (squamous carcinomas, melanomas, gliomas and a fibrosarcoma) were examined for cell-substrate adhesion on plastic culture dishes and dishes coated with 50 micrograms of type-IV collagen. In the absence of exogenous adhesion factors, the squamous carcinoma cells attached and spread more rapidly than the other cells on both substrates. Once attached, the squamous carcinoma cells were also more difficult than the other cells to remove with proteolytic enzymes/EDTA. While the cell lines derived from melanomas, gliomas and the fibrosarcoma were less adhesive than the squamous carcinoma lines in the absence of exogenous adhesion factors, these cells were highly responsive to laminin. In contrast, laminin only slightly enhanced the attachment and spreading of squamous carcinoma cells on the plastic dishes and actually inhibited attachment and spreading on the collagen-coated dishes. These results indicate that there are tumor-type-specific differences in adhesiveness among human tumor cell lines and that cells from different tumor types may have distinct mechanisms for carrying out one of the functions critical to invasion.