Comparison of subpopulations of tumor cells with altered migratory activity, attachment characteristics, enzyme levels and in vivo behavior

Mouse colon carcinoma cells established for high incidence of experimental hepatic metastasis exhibit accelerated and anchorage-independent growth

Highly metastatic variants of mouse colon 38 colon carcinoma cells were established by repeated selection in vivo for liver metastasis and designated as SL4 cells. The SL4 cells formed colonies in the liver of 100% of syngenic mice when injected intrasplenically, while the incidence of liver metastasis was 27% of mice injected with parental cells. The weight of livers, which is an indicator of experimental hepatic metastasis formation, was significantly higher after intrasplenic injection and subsequent splenoctomy with SL4 cells than colon 38 cells. The incidence of hepatic metastasis after intracecal injection of SL4 cells was significantly higher than that of colon 38 cells. The SL4 cells were tested in vitro for their properties. Differences were not detected in the motility and invasive behavior between colon 38 cells and SL4 cells. SL4 cells showed a higher proliferation rate than colon 38 cells under adherent conditions. SL4 cells maintained a capacity to proliferate under non-adherent conditions whereas parental cells did not. SL4 cells should be a useful tool to study the mechanism of hepatic metastasis of colon carcinoma cells and to develop methods to prevent hepatic metastasis.

Differential expression of an alpha-galactosyl-containing trisaccharide on high- and low-malignant murine sarcoma cells: identification and regulation

Past studies have shown that carbohydrate residues reactive with the Griffonia simplicifolia isolectin B4 (GS I-B4) are present on the surface of highly-malignant murine sarcoma cells but are lacking or expressed in much lower amounts on the surface of low-malignant cells isolated from the same parent tumors (Am J Pathol 111: 27; J Nat Cancer Inst 71: 1281). In the present study it is shown that an antibody which recognizes the trisaccharide Galalpha1-3Galbeta1-4GlcNAc- is reactive with the highly-malignant cells but is non-reactive with the low-malignant cells. Further studies show that the high-malignant cells not only bind GS 1-B4 but also bind Evonymus europaea lectin (which like GS I-B4 recognizes terminal galactose in alpha1-3 linkage) and Erythina crystagalli lectin (which recognizes sub-terminal galactose in the beta1-4 linkage--e.g., Galbeta1-4GlcNAc). In contrast, the low malignant cells bind Erythina crystagalli lectin as efficiently as the high malignant cells but do not bind (or bind much smaller amounts of) either GS I-B4 or Evonymus europaea lectin. The present studies also show that there is no significant difference between high- and low-malignant cells in expression of alpha-galactosidase activity. In contrast, the high-malignant cells express high levels of alpha-galactosyl transferase activity while this enzyme is virtually undetectable in low-malignant cells. Taken together, these studies indicate that differential expression of a single monosaccharide residue distinguishes high- and low-malignant murine sarcoma cells. These studies also identify a mechanism to account for surface carbohydrate differences between the high- and low-malignant cells.

Simultaneous assessment of migration and proliferation of murine fibrosarcoma cells, as affected by hydroxyurea, vinblastine, cytochalasin B, Razoxane and interferon

Using porous cell culture chambers, we have simultaneously assessed growth and locomotion of cancer cells to investigate whether certain agents affect cell motility in addition to cell division. First, cells from a murine fibrosarcoma cell line, 1.0/L1, were grown in ordinary flask cultures to determine appropriate cell inocula. Doses of agents were selected to reduce the final 4 day culture cellularity to about 50%, when present during the last two days of culturing. Secondly, the effects of these agents on cell numbers in the porous chambers and on cell migration out of the chambers ('emigration fraction') were recorded. We also examined, using a similar type of porous chamber, whether the agents could affect leucocyte chemotaxis. Hydroxyurea (an inhibitor of DNA synthesis) reduced cancer cell emigration as well as cell growth, without interfering with leucocyte chemotaxis. Cytochalasin B (a microfilament disrupting agent) inhibited cancer cell motility and growth, as well as leucocyte chemotaxis. Vinblastine (a microtubule disrupting agent), at the very low dose chosen, reduced cancer cell growth, but did not consistently affect the migration of either cell type. The experimental anti-metastasis agent Razoxane reduced growth, but had no detectable effects on motility. High doses of natural murine interferon-alpha/beta weakly inhibited both cancer cell growth and locomotion. This motivates for further studies of these and other cytokines, as treatment with agents inhibiting cancer cell locomotion might possibly prevent peri-operative spread of cancer in patients.

Cell adhesion and migration of different human colon cell lines and primary tumors

Several cell lines derived from colon tumors (HT-29, WiDr, PT4, PT5) and from human liver metastases (LM3) and primary human colon tumor cells (PTR) were compared with regard to their ability to migrate and to attach to different substrates (collagen G, laminin, fibronectin). Cells from the WiDr cell lines migrated actively, whereas the other cell lines, and LM3 and the PTs showed almost no migratory activity. The attachment efficiency was best in all cell lines assayed when tested on collagen followed by laminin and fibronectin as substrates. The HT-29 cells showed the strongest adhesion to all substrates, while the adhesiveness of PT4, PT5, and LM3 was reduced. The WiDr cells which migrated best showed the lowest adhesion to the substrates.

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.

Mechanism of liver-specific metastatic tumor spread in a murine tumor model

Malignant tumors frequently show an organ-specific metastatic spread, the causes of which are still largely unknown. Using an experimental tumor model, a methylcholanthrene-induced pleomorphic myofibrosarcoma ER 15-P of the C57Bl6J mouse, we wanted to find out whether this phenomenon is due to an adaptation or to a selection of tumor cells. After i.v. injection of tumor cells from the primary ER 15-P into the tail vein of male mice, metastases were regularly found in the lungs, mediastinal lymph nodes, and brain, as well as in the liver and kidneys, and occasionally in the adrenals. The following experimental procedures were used to isolate a tumor cell line with a possible liver preference: (1) Tumor cells from the primary ER 15-P were injected into a mesenteric vein of male mice. Tumor cells from the resulting liver colonies were again injected into the portal system of one group of mice. In a second group, part of the same cell suspension was injected into the tail vein. This procedure was performed four times. (2) Tumor cells from the primary ER 15-P were applied into the tail vein of male mice. Tumor cells from the resulting liver metastases were reinjected directly into the tail vein. This experiment was repeated three times. (3) Tumor cells from the primary ER 15-P were injected into the tail vein of male mice. Tumor cells from liver metastases were then injected, first, into the portal system of one group of male mice, and thereafter into the tail vein of another group of animals. This experiment was repeated twice. The following results were obtained: (1) By a repeated adaptation of tumor cells from the primary ER 15-P to liver tissue, no tumor cell line could be isolated that would show a preferential metastatic spread to this organ after tail-vein injection. (2) Repeated i.v. passages of tumor cells from liver metastases into the tail vein led to the selection of a tumor cell line with a tendency to liver metastasis. (3) Tumor cells selected from liver metastases induced via tail-vein injection showed, after a prolonged stay in the liver and a successive i.v. passage into the tail vein, a marked specificity for this organ. These results indicate that the liver-specific spread of tumor cells in our model is based on the selection of a tumor cell line from the primary ER 15-P influenced by the hepatic microenvironment.

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.

Directional motility in strongly malignant murine tumor cells

Laminin, fibronectin and 12-O-tetradecanoyl phorbol acetate (TPA) were examined for their ability to induce biological responses (cell-to-substrate adherence and motility) in a series of strongly malignant and weakly malignant murine fibrosarcoma cells. All three agents caused increased cell-to-substrate attachment of the cell lines. Laminin and fibronectin induced a slow but sustained response, whereas with TPA the response was rapid and transient. The 3 agents also stimulated motility in the same cells. Random motility was seen with all of the cells but directional motility was observed primarily in the strongly malignant cells. With TPA, the response was chemotactic but laminin and fibronectin induced cell migration by haptotaxis. Since laminin and fibronectin are constituents of the extracellular matrix and since malignant tumor cells must cross the extracellular space during invasion, those properties of cells which allow for migration across a substrate containing these materials may contribute to the expression of malignancy.

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

Highly malignant cell lines and low-malignant cell lines isolated from three different methylcholanthrene-induced murine fibrosarcomas were examined for their ability to attach to plastic dishes and collagen-coated dishes under serum-free conditions and in the presence of serum. Most of the cells from the three highly malignant lines attached and spread under all conditions. By 72 h, there was a significant increase in the number of cells indicating that at least some of the cells had undergone division (even in the absence of serum). In contrast, fewer of the cells from the three low-malignant lines attached and spread on the plastic or collagen substrates in the absence of serum or in the presence of 0.1 per cent serum. However, when 15 micrograms laminin per dish was added along with the low-malignant cells, they then attached and spread on the plastic and collagen-coated dishes. Previous studies have indicated that the highly malignant lines express cell surface antigens that cross-react with laminin while the low-malignant cell lines do not. We speculate that the differences between the high- and low-malignant cells in the expression of cell surface laminin-like antigens contribute to the dissimilarities in attachment and spreading capacity. These differences may also contribute to the dissimilarity between these cells in malignant potential.

Contribution of alpha-D-galactopyranosyl end groups to attachment of highly and low metastatic murine fibrosarcoma cells to various substrates

There are much greater numbers of cell surface terminal, non-reducing alpha-D-galactorpyranosyl groups in highly malignant (metastatic) cells than are found in low malignant cells derived from the same murine fibrosarcoma. We have examined the contribution of these residues to attachment of the cells to various collagens and to plastic. Removal of these carbohydrate groups with alpha-galactosidase or blocking them with lectins from Griffonia simplicifolia seeds or with anti-blood group B antiserum all dramatically inhibited the attachment of both the highly malignant and the low malignant cells. Following removal with the enzyme, the alpha-D-galactopyranosyl end groups were rapidly resynthesized. This resynthesis was inhibited by tunicamycin, an inhibitor of de novo glycoprotein synthesis. This antibiotic also impaired cell attachment and, when used in addition to treatment with alpha-galactosidase, it inhibited cell attachment more than did treatment with the enzyme alone. The effects of all treatments on cell attachment were greater for the highly malignant than for the low malignant cells. With the latter cells, inhibition by lectin was seen only in the absence of serum, whereas the adhesion of highly malignant cells was affected in both the presence and the absence of serum. On their surface membrane the highly malignant cells express much more than do the low malignant cells of a glycoprotein that cross-reacts immunologically with laminin. The basement membrane glycoprotein laminin promotes cell attachment to collagen, and both glycoproteins contain terminal, non-reducing alpha-D-galactopyranosyl groups. Attachment of cells is a requirement for the formation of a metastasis, and thus the laminin-like molecule and the alpha-D-galactopyranosyl end groups (whether on the laminin-related moiety or on other cell surface molecules) may both be important for expression of the most malignant phenotype.

A model of tumor cell dormancy: effects of anesthesia and surgery

Three cloned populations of tumor cells obtained from a murine fibrosarcoma were able to remain viable for a long period of time in syngeneic mice which failed to exhibit clinically evident tumors following tumor cell inoculation. Viable tumor cells under such conditions can be considered to be in a dormant state. On the basis of past studies, two of the lines were shown to have low malignant potential, while the third line was shown to have a higher degree of malignant potential. The rates of spontaneous reactivation of tumor growth in animals carrying the low malignant cells were 3 and 4%, while a rate of 30% was observed in animals with the more malignant cells. Treatment of animals carrying the low malignant cells in a dormant state with anesthesia alone, (thiopental) or with anethesia and surgery, increased the rate of reactivation to 20-22%.