Sialoglycoproteins of murine RAW117 large cell lymphoma/lymphosarcoma sublines of various metastatic colonization properties

Lectins as versatile tools to explore cellular glycosylation

Lectins are naturally occurring carbohydrate-binding proteins that are ubiquitous in nature and highly selective for their, often incompletely characterised, binding partners. From their discovery in the late 1880s to the present day, they have provided a broad palette of versatile tools for exploring the glycosylation of cells and tissues and for uncovering the myriad functions of glycosylation in biological systems. The technique of lectin histochemistry, used to map the glycosylation of tissues, has been instrumental in revealing the changing profile of cellular glycosylation in development, health and disease. It has been especially enlightening in revealing fundamental alterations in cellular glycosylation that accompany cancer development and metastasis, and has facilitated the identification of glycosylated biomarkers that can predict prognosis and may have utility in development of early detection and screening, Moreover, it has led to insights into the functional role of glycosylation in healthy tissues and in the processes underlying disease. Recent advances in biotechnology mean that our understanding of the precise binding partners of lectins is improving and an ever-wider range of lectins are available, including recombinant human lectins and lectins with enhanced, engineered properties. Moreover, use of traditional histochemistry to support a broad range of cutting-edge technologies and the development of high throughout microarray platforms opens the way for ever more sophisticated mapping - and understanding - of the glycome.

The role of tumor cell adhesion as an important factor in formation of distant colorectal metastasis

PURPOSE

The interactions of blood-borne colorectal carcinoma cells with vascular endothelium are important during hematogenous formation of distant metastases. To adhere to the vessel wall, circulating carcinoma cells that come into contact with the microvasculature must resist the attractive forces of the flow of plasma and other circulating cells that tend to detach them from the wall.

METHODS

Hydrodynamic adhesion assays have been introduced to mimic the microcirculation and investigate cell adhesion under flow conditions. Different aspects of colorectal cancer cell adhesion during hematogenous formation of distant metastases are summarized and discussed in this review.

RESULTS

Adhesion of colorectal carcinoma cells to endothelial cells and extracellular matrix is influenced by the presence of fluid flow. Shear forces alone are able to induce signal transduction events in these cells that result in cell activation and modification of adhesive behavior.

CONCLUSIONS

Consideration of fluid dynamics of circulating colorectal cancer cell movement in the microcirculation leads to new knowledge of in vivo processes that are involved in tumor cell adhesion to the vessel wall in host organs. Shear forces have been found to influence adhesive properties of colorectal carcinoma cells to endothelial cells and underlying subendothelial extracellular matrix. Understanding the complex processes involved in tumor cell adhesion may result in the development of novel therapeutic strategies.

Phaseolus vulgaris leukoagglutinating lectin-binding reactivity in human diffuse large B-cell lymphoma and its relevance to the patient's clinical outcome: lectin histochemistry and lectin blot analysis

Many reports have suggested a strong correlation between certain lectin-binding patterns and biological behavior in various tumors. To clarify a relationship between lectin-binding reactivity and survival of patients with diffuse large B-cell lymphoma (B-DLCL), 57 cases with B-DLCL were analyzed by lectin histochemistry and lectin blot method with or without treatment of neuraminidase or acidic hydrolytic conditions. B-DLCL cases were grouped into three types based on the data on lectin-binding reactivity under neuraminidase-treated or untreated conditions: (i) Group A (non-reactive type); (ii) Group B (sialylated type); and (iii) Group C (non-sialylated type). Among various lectins, Phaseolus vulgaris-L (L-PHA) binding reactivity showed that the survival of patients with Group A + B or Group B was significantly shorter than that of patients with Group C. Lectin blot analysis revealed failure of L-PHA-binding to 32 kd and 29 kd glycoproteins, which may be attributable to the masking of L-PHA-binding sites by sialylation or the lack of L-PHA-binding sites, leading to the short survival of patients with B-DLCL. L-PHA-binding reactivity may be a useful marker for the evaluation of survival of patients with B-DLCL.

Analysis of lectin binding properties on human Burkitt's lymphoma cell lines that show high spontaneous metastasis to distant organs in SCID mice: the binding sites for soybean agglutinin lectin masked by sialylation are closely associated with metastatic lymphoma cells

Alterations in cell surface carbohydrates on human lymphoma cell lines with different spontaneous metastatic potential in the severe combined immunodeficiency (SCID) mouse model were analyzed. A difference in cell surface carbohydrates between high- (HBL-2, HBL-7 and HBL-8) and no- or low-(HBL-4, HBL-6, Daudi and Raji) spontaneous metastatic human lymphoma cell lines were analyzed on a FACScan using fluorescein-isothiocyanate (FITC)-conjugated lectins. The most consistent difference in lectin binding properties was found with soybean agglutinin (SBA) lectin. High-metastatic lymphoma cells (HBL-7 and HBL-8 cells) in vitro were found to bind the SBA lectin, but the cells in vivo (in primary tumors and metastatic tumors of SCID mice) showed considerably reduced SBA lectin binding. In addition, HBL-2 cells that almost did not bind SBA lectin in vitro and in vivo showed high spontaneous metastasis. Neuraminidase treatment revealed that SBA lectin binding sites were masked by sialic acid. On the other hand, no- or low-metastatic lymphoma cells in vitro and in vivo were found to bind SBA lectin. HBL-8 cell clones without SBA lectin binding showed high spontaneous metastasis to distant organs in SCID mice but HBL-8 cell clones with SBA lectin binding showed very low spontaneous metastasis. Sophora Japonica agglutinin (SJA) lectin is able to recognize the carbohydrates in common with SBA lectin, but it does not appear to be associated with metastatic capacity. These results suggest that the sialylation of particular carbohydrate residues on human lymphoma cells that are recognized by SBA lectin may be associated with the spontaneously metastatic capacity of human lymphoma cell lines in our SCID mouse model.

Selection for enhanced adhesion to microvessel endothelial cells or resistance to interferon-gamma modulates the metastatic potential of murine RAW117 large-cell lymphoma cells

Poorly liver metastatic large-cell lymphoma RAW117-P cells were sequentially selected in vitro for increased adhesion to murine hepatic sinusoidal endothelial cells. After three or four sequential selections, the selected sublines showed increased rates of adhesion to target hepatic microvessel endothelial cells and increased formation of experimental metastases in the liver. However, the endothelial cell adhesion-selected RAW117 sublines were generally unstable and gradually lost their enhanced adhesive and metastatic properties during passage in culture. Highly metastatic, liver-selected RAW117-H10 large-cell lymphoma cells were more resistant to the cytostatic effects of interferon-gamma (IFN-gamma) than poorly metastatic unselected parental RAW117-P cells. When tested for their sensitivity to IFN-gamma, the endothelial cell adhesion variants were significantly more resistant than the unselected RAW117-P cells, but after a 72-h treatment with IFN-gamma, the in vitro-selected cells lost their enhanced endothelial cell adhesion characteristics, their potential to colonize the liver, and their ability to grow when injected at subcutaneous or intramuscular sites. In contrast, the metastatic potential of similarly treated RAW117-P cells was unaffected by IFN-gamma during a 72-h treatment. Sequential selection of RAW117-P cells for increased resistance to IFN-gamma in vitro resulted in variant lines that were refractory to the growth-inhibiting effects of IFN-gamma, and these IFN-gamma-selected variants were also less adhesive to liver microvessel endothelial cells. The IFN-gamma-selected variants also lost their experimental metastatic potentials completely and their tumorigenicities at sites of subcutaneous or intramuscular injection. Cytofluorographic analysis indicated reduced cell surface expression of H-2Kd antigen and fibronectin receptor on the selected variant cells but no change in cell surface mu heavy chain immunoglobulin. The unselected and selected RAW117 lines had similar sensitivities to natural killer (NK) cell-mediated cytolysis, indicating that the in vivo differences were probably not due to differences in NK cell-mediated cytolysis. The results suggest that selection for adhesion to organ microvessel endothelial cells or sequential exposure to certain cytokines can affect the adhesive, growth and metastatic properties of RAW117 cells without modifying their responses to NK cells.

Use of Phaseolus vulgaris leukoagglutinating lectin in histochemical and blotting techniques: a comparison of digoxigenin- and biotin-labelled lectins

An increase in the number of beta 1,6 branches of the trimannosyl core of asparagine-linked oligosaccharides has been shown to be directly correlated with the metastatic potential of cultured tumour cells. The Phaseolus vulgaris leukoagglutinating lectin (PHA-L) binds to beta 1,6 branches of tri- and tetra-antennary oligosaccharides. We have applied digoxigenin- and biotin-conjugated PHA-L to establish a non-radioactive detection system for beta 1,6 branches, which can be used in lectin blotting as well as light and electron microscopic cytochemistry. For this purpose the HCT116 human colon carcinoma cell line and colon carcinoma tissue were investigated. Digoxigenin-conjugated PHA-L in conjunction with alkaline phosphatase-conjugated anti-digoxigenin antibodies was superior to biotin-conjugated PHA-L in lectin blotting with respect to sensitivity and specificity. Similarly, the digoxigenin conjugated PHA-L in conjunction with gold-labelled anti-digoxigenin antibodies resulted in more intense specific staining and lower background compared to biotin-conjugated PHA-L visualized with a streptavidin immunogold complex. The specificity of lectin binding in blotting and cytochemical studies was demonstrated by the absence of staining when the lectin was omitted or preabsorbed with glycoprotein, and following pretreatment of the cellular homogenates or tissue sections by N-glycosidase F. Our results demonstrate that digoxigenin-conjugated PHA-L provides high sensitivity and specificity for histochemical and blotting techniques and is amenable for quantification. The technique should have applications in tumour research.

Modulating the metastatic potential of murine RAW117 large-cell lymphoma cells by selection for resistance to interferon-gamma

Highly metastatic, in vivo-selected cells of RAW117-H10 large-cell lymphoma have been shown to be more resistant than poorly metastatic parental RAW117-P cells to the cytolytic and cytostatic activities of activated macrophages in co-culture experiments. Activated macrophages are known to produce soluble, cytostatic respiration-inhibiting factors, and such activities can be duplicated by interferon-gamma (IFN-gamma) or by combinations of IFN-gamma and Escherichia coli lipopolysaccharide (LPS). Highly metastatic RAW117-H10 cells are more resistant to the cytostatic effects of IFN-gamma and LPS than poorly metastatic RAW117-P cells, and short-term (up to 72 hr) treatment with IFN-gamma and LPS does not change the metastatic potentials of RAW117 cells. We have studied the effects of sequential selection of RAW117-P cells for increased resistance to IFN-gamma and LPS. After 7 to 13 sequential selections, the resulting variant lines were completely refractory to the growth-inhibitory effects of IFN-gamma and LPS and cross-tolerant to macrophage-conditioned medium. The selected variants also completely lost their experimental metastatic potentials and their tumorigenicities after s.c. or i.m. injection. Cytofluorographic analysis indicated reduced cell-surface expression of H-2Kd antigen and fibronectin receptor on the variant cells but no change in surface mu heavy-chain immunoglobulin. The IFN-gamma-selected lines were less adhesive to liver microvascular endothelial cells than the unselected RAW117 cell lines, but were equally sensitive to NK cytolysis by spleen cells. Our results suggest that exposure to certain cytokines can affect the growth and metastatic potential of RAW117 cells and result in the selection of resistant variants with altered biologic properties.

Separable growth and migration factors for large-cell lymphoma cells secreted by microvascular endothelial cells derived from target organs for metastasis

Metastatic variant sublines of the murine large-cell lymphoma cell line RAW117 were tested for their growth and migration properties in vitro in medium conditioned by soluble factors released from syngeneic mouse liver-, lung-, and brain-derived microvessel endothelial cells. Medium conditioned with hepatic sinusoidal endothelial cells stimulated the growth of highly liver-colonising (RAW117-H10) and highly liver- and lung-colonising (RAW117-L17) sublines at higher rates than the poorly metastatic parental line (RAW117-P) (H10 greater than L17 greater than P). Medium conditioned with lung microvessel endothelial cells selectively stimulated the growth of the lung-colonising RAW117-L17 subline. Medium conditioned with brain microvessel endothelial cells showed no growth selectivity, and equivalently stimulated the growth of various RAW117 cell sublines. Medium conditioned with hepatic sinusoidal endothelial cells preferentially promoted the migration of the liver-colonising H10 and L17 sublines, and medium conditioned with lung endothelial cells differentially stimulated the migration of the lung-colonising L17 subline; whereas medium conditioned with brain endothelial cells only slightly stimulated the migration of L17, but not H10 or P cells. Fractionation of medium conditioned with hepatic sinusoidal endothelial cells by DEAE Sephacel anion exchange chromatography revealed that the growth-stimulating activities were clearly separable from migration-stimulating activities. The growth- and migration-stimulating activities released from organ microvessel endothelial cells may be important in determining the ability of RAW117 cells to selectively form metastatic colonies in particular organs.

Butanol-extractable and detergent-solubilized cell surface components from murine large cell lymphoma cells associated with adhesion to organ microvessel endothelial cells

Metastatic variant cell lines of the murine RAW117 large cell lymphoma were used to study the cell surface components involved in syngeneic tumor cell/microvessel endothelial cell interactions. Poorly liver-metastatic parental RAW117-P cell line adhered to murine hepatic sinusoidal endothelial cell monolayers at significantly lower rates than the liver-selected, highly liver-metastatic RAW117-H10 line and both cell lines were poorly adherent to lung microvessel and bovine aorta endothelial cells. Viable, 2% 1-butanol-treated RAW117-H10 tumor cells formed fewer liver tumor nodules in experimental metastasis assays than untreated H10 cells and were significantly less adherent to murine hepatic sinusoidal endothelial cell monolayers. When 2% 1-butanol extracts of metabolically labeled or CHAPS detergent lysates of cell surface-labeled tumor cells were analyzed for their ability to bind to fixed microvessel endothelial cell monolayers, quantitative differences were found in the extractable tumor cell surface components that bound to the different organ-derived microvessel endothelial cells. Cell surface components (1-butanol extractable), of Mr approximately 85,000-90,000 and approximately 37,000-40,000 bound to hepatic sinusoidal endothelial cell monolayers to a greater extent than to murine lung microvessel endothelial or bovine aortic endothelial cell monolayers, whereas tumor cell surface components of Mr approximately 45,000, approximately 33,000, and approximately 25,000 bound similarly to endothelial cells regardless of origin. The results suggest but do not prove that tumor cell/endothelial cell adhesion involves multiple tumor cell surface components, some of which commonly bind to various endothelial cells and others for which binding may be dictated by the tissue origin and type of endothelial cell. Particular RAW117 butanol-extractable cell membrane components were associated with tumor cell-endothelial cell adhesion, and these components could be responsible, in part, for the preferential adhesion of RAW117 cells to liver sinusoidal endothelial cells and metastasis to liver.

Hyposialylation of high-molecular-weight membrane glycoproteins parallels the loss of metastatic potential in wheat-germ agglutinin-resistant Friend leukemia cells

From the highly metastatic in vivo-passaged Friend leukemia cells (FLC), WGA-resistant (WR) tumor cell variants were selected. These WR FLC had lost their capacity to metastasize when injected i.v. or s.c. into DBA/2 mice. We have characterized the plasma membrane glycoproteins of the different FLC types by: (i) metabolic labelling with (3H)-galactose; (ii) surface labelling with galactose oxidase-borohydride; (iii) direct binding of (125I)-lectins on glycoproteins separated by SDS-PAGE. The ensemble of these approaches showed that the 100- to 200-kDa glycoproteins of in vivo-passaged FLC and WR FLC exhibited a very similar distribution of the terminal galactose in their oligosaccharide moieties. In contrast, the expression of terminal sialic acid was reduced in WR FLC with respect to in vivo-passaged counterparts as appreciated by: (i) binding experiments with (125I)-WGA; (ii) cathodic shift of the 100- to 200-kDa glycoproteins in 2-dimensional electrophoresis studies, and (iii) thiobarbituric acid assay after FLC treatment with neuraminidase. Moreover, binding experiments with (125I)-LPHA, (125I)-ConA and (125I)-WGA (after Smith degradation) indicated that, in the 100- to 200-kDa region, virtually identical asparagine-linked tri- or tetra-antennary complex-type oligosaccharides were expressed in both cell types. We conclude that the sialylation of high-molecular-weight surface glycoproteins (particularly in the 150-kDa region) is strongly associated with the metastatic potential of FLC, especially to the liver.

Wheat germ agglutinin binding sites on human urothelial cells of different grades of transformation

125I-Wheat germ agglutinin (WGA) binding parameters of human urothelial cell lines of different grades of transformation (TGrII and TGrIII) were compared. The values of association constant (Ka) and the number of binding sites/cell for HCV29 (TGrII) cell line were about 3 x 10(6) M-1 and over 4 x 10(7), respectively. Two TGrIII cell lines, HCV29T and Hu549 revealed lower values for Ka, and considerably higher numbers of binding sites/cell (about 3 x 10(8) and 2 x 10(8), respectively). Binding of 125I-WGA to total cellular proteins resolved by SDS-PAGE and transferred to nitrocellulose showed multiple diffused bands in the range of 58-180 kDa. Some of these bands were characteristic for TGrII cells (124 kDa) or TGrIII cells (135 and 148 kDa).

Wheat germ agglutinin-binding protein changes in highly malignant Friend leukemia cells metastasizing to the liver

We have used binding of radioactive lectins (i.e. Concanavalin A (ConA), Wheat Germ Agglutinin (WGA) and Ricinus communis agglutinin I (RCAI)) to membrane glycoproteins separated in SDS gel electrophoresis, to detect specific carbohydrate changes in plasma membrane proteins of in vivo passaged Friend erythroleukemia cells (FLC). These cells are highly metastatic to the liver, whereas the original in vitro passaged tumor cells do not metastasize. Marked qualitative differences in the high molecular weight region of the gels (100-200 kD) were observed between the WGA binding glycoproteins of metastatic in vivo passaged FLC and nonmetastatic in vitro passaged FLC. Furthermore, the binding of WGA to plasma membrane proteins of in vivo passaged FLC was much greater than the binding of WGA to plasma membrane proteins of in vitro passaged FLC. Lectin binding experiments after sialic acid removal by in situ mild acid hydrolysis of FLC glycoproteins indicated that an increased sialylation of the 120 and 145 kD glycoproteins was responsible for the increased WGA reactivity of in vivo passaged FLC plasma membranes. Besides the increased sialylation, other changes in glycosylation of the 100-200 kD glycoproteins of in vivo passaged FLC were observed: (1) qualitative differences between the WGA binding patterns of the two cell types were restored after treatment of the gels with mild acid and subsequent Smith degradation; (2) after chemical removal of sialic acid residues from the gels, qualitative differences in the RCA binding patterns to the glycoproteins of the two cell types were apparent.

Organ specificity of tumor metastasis: role of preferential adhesion, invasion and growth of malignant cells at specific secondary sites

The locations of distant secondary tumors in many clinical cancers and animal tumors are nonrandom, and their distributions cannot be explained by simple anatomical or mechanical hypotheses based on the simple lodgment or trapping of tumor cell emboli in the first capillary bed encountered. Evidence from certain experimental tumor systems supports Paget's 'seed and soil' hypothesis on the nonrandom distributions of metastases, in which the unique properties of particular tumor cells ('seeds') and the different characteristics of each organ microenvironment ('soil') collectively determine the organ preference of metastasis. Experimentally, differential tumor cell adhesion to organ-derived microvessel endothelial cells and organ parenchymal cells, differential invasion of basement membranes and organ tissues, and differential responses to organ-derived growth-stimulatory and -inhibitory factors all appear to be important determinants in explaining the organ preference of metastasis. Each tumor system may achieve organ specificity because of its own unique set of multiple metastasis-associated properties and responses to host microenvironments. As neoplasms progress to more highly malignant states multisite metastases are more likely and organ-specific metastases may be masked or circumvented owing to stochastic events, tumor cell diversification, host selection processes, and increased production of tumor autocrine molecules that may modulate adhesion, invasion, growth, and other properties important in metastasis. The importance of each of these properties, however, appears to vary considerably among different metastatic tumor systems. These and other tumor cell and host properties may eventually be used to predict and explain the unique metastatic distributions of certain human malignancies.

Gene expression and tumor cell escape from host effector mechanisms in murine large cell lymphoma

Using in vivo selection methods, we obtained metastatic sublines of the murine RAW117 large cell lymphoma that form multiple liver metastases. The highly metastatic subline RAW117-H10 has a low number of gp70 molecules expressed at the cell surface and low cytostatic sensitivity to activated syngeneic macrophages. This subline was infected with endogenous RNA tumor virus isolated from a high virus-expressing RAW117-P subline of low metastatic potential. After superinfection the H10 subline gradually increased its expression of cell surface gp70 and showed enhanced sensitivity to macrophage-mediated cytostasis, suggesting that gp70 might be involved in host macrophage-mediated surveillance. Culture of RAW117-P and H10 cells in media conditioned by activated macrophages indicated that parental cells are severely growth inhibited in a dose dependent fashion while H10 cells showed almost no effect. Examination of differentially expressed genes in the highly metastatic RAW117-H10 cells by analysis of RNA blots indicated that a mitochondrial gene was expressed at a level that was approximately 10 times higher in H10 cells than in parental cells. This gene was identified as ND5, which codes for a subunit of NADH dehydrogenase (complex I of the mitochondrial electron transport chain); this complex is the target for an activated macrophage-released cytostatic factor. Among other possibilities, the results are consistent with the suggestion that highly metastatic RAW117 cells may escape macrophage surveillance by decreasing the synthesis of specific cell-surface receptors for cytostatic molecules and increasing the synthesis of specific cellular targets for such molecules.

Differential expression of endogenous sugar-binding proteins (lectins) in murine tumor model systems with metastatic capacity

In order to investigate possible differences in sugar binding activities of strongly versus weakly metastatic tumors, sugar-binding molecules (endogenous lectins) of murine tumor cells differing in metastatic capacity were analyzed by affinity chromatography on supports with immobilized sugars or glycoproteins and compared. After elution with specific sugar in the absence of Ca2+-ions, the proteins were separated by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis. In comparison to a weakly metastatic subline (Eb) spontaneous strongly metastatic variants (ESb) of a murine lymphoma contained additional sugar receptors for N-acetylglucosamine (Mr 30 kDa) and maltose (Mr 64 kDa, 62 kDa, 54 kDa and 32 kDa), and lacked one sugar receptor for myoinositol (Mr 85 kDa), N-acetylglucosamine (Mr 23 kDa) and maltose (Mr 22 kDa), respectively. The strongly metastatic variant ESb expressed the common beta-galactoside-specific lectin to a higher extent and receptors for myo-inositol, melibiose and mannan to a lower extent. In another model system derived from the murine mastocytoma cell line P 815 X 2A, biochemical analysis of the liver-metastasizing variant P 815 X 2B revealed additional characteristic N-acetylgalactosamine- and maltose-specific binding proteins. This variant had reduced amounts of receptors for beta-galactosides and fucose in comparison to the parental clone. In a third tumor system a similar qualitative difference was disclosed: a metastatic variant derived from spleen metastases displayed a sugar receptor profile with 5 additional beta-galactoside-binding proteins when compared to its parental clone 6-6#3 + F, which is a virally transformed fibroblast line. The results show that metastatic variants of 3 murine tumor models consisting of lymphomas, mastocytomas and sarcomas are characterized by qualitative and quantitative alterations in the profiles of sugar-binding proteins.

Differential growth properties of metastatic large-cell lymphoma cells in target organ-conditioned medium

Metastatic variant sublines of the murine RAW117-P large cell lymphoma have been sequentially selected in vivo for enhanced liver (RAW117-H10) or lung (RAW117-L17) colonization. Such cell sublines were tested for their survival and growth in vitro in medium conditioned by soluble factors released from mouse kidney, brain, liver, or lung tissues. Liver-colonizing H10 and L17 sublines were growth-stimulated by target liver tissue-derived factors at concentrations that inhibited the growth of the parental cells. Lung-colonizing L17 as well as liver-colonizing H10 cells were stimulated by lung tissue factors at concentrations that growth-inhibited the parental cells. In contrast, there was no significant growth stimulation by factors from kidney or brain tissues. In general, the metastatic patterns of RAW117 cells correlated with their abilities to be stimulated by medium from target organ tissues, but other factors, such as organ-specific adhesion mechanisms [10-12], must also be involved in the specificity of blood-borne metastatic organ colonization.