Carbohydrate-binding proteins in bovine kidney have consensus amino acid sequences of annexin family proteins

Ca(2+)-dependent carbohydrate-binding proteins were purified from bovine kidney extracts. Upon SDS-polyacrylamide gel electrophoresis under nonreducing conditions, the purified fraction gave doublet protein bands corresponding to 33 kDa (p33) and 41 kDa (p41). Under reducing conditions, a single protein band (p33) was observed. p33 and p41 were submitted to proteolytic digestion with endoproteinase Lys-C, the peptides produced were separated by reversed-phase high performance liquid chromatography, and their amino acid sequences were determined by an automated gas-phase protein sequenator. Most of the resulting partial amino acid sequences of these proteins were strikingly homologous to annexin IV, an annexin family protein, i.e. Ca2+/phospholipid-binding proteins, especially in the consensus sequences. In the presence of Ca2+, both proteins bound to vesicles composed of phosphatidylserine and phosphatidylethanolamine, but not phosphatidylcholine. These results indicated that p33 and p41 are members of annexin family proteins.

The primary structure of the Cytisus scoparius seed lectin and a carbohydrate-binding peptide

The complete amino acid sequence of 2-acetamido-2-deoxy-D-galactose-binding Cytisus scoparius seed lectin II (CSII) was determined using a protein sequencer. After digestion of CSII with endoproteinase Lys-C or Asp-N, the resulting peptides were purified by reversed-phase high performance liquid chromatography (HPLC) and then subjected to sequence analysis. Comparison of the complete amino acid sequence of CSII with the sequences of other leguminous seed lectins revealed regions of extensive homology. The amino acid residues of concanavalin A (Con A) involved in the metal binding site are highly conserved among those of CSII. A carbohydrate-binding peptide of CSII was obtained from the endoproteinase Asp-N digest of CSII by affinity chromatography on a column of GalNAc-Gel. This peptide was retained on the GalNAc-Gel column and was presumed to have affinity for the column. The amino acid sequence of the retarded peptide was determined using a protein sequencer. The retarded peptide was found to correspond to the putative metal-binding region of Con A. These results strongly suggest that this peptide represents the carbohydrate-binding and metal ion-binding sites of CSII.

Correlation between carbohydrate-binding specificity and amino acid sequence of carbohydrate-binding regions of Cytisus-type anti-H(O) lectins

A carbohydrate-binding peptide of the di-N-acetylchitobiose-binding Cytisus sessilifolius anti-H(O) lectin I (CSA-I) was isolated from the endoproteinase Asp-N digest of CSA-I by affinity chromatography on a column of N-acetyl-D-glucosamine oligomer-Sepharose (GlcNAc oligomer-Sepharose). The amino acid sequence of the carbohydrate-binding peptide of CSA-I was determined to be DTYFGKTYNPW using a gas-phase protein sequencer. This sequence corresponds to the sequence from Asp-129 to Trp-139 based on the primary structure of CSA-I, and shows a high degree of homology to those of the putative carbohydrate-binding peptide of the Laburnum alpinum lectin I (LAA-I) (DTYFGKAYNPW) and of the Ulex europaeus lectin II (UEA-II) (DSYFGKTYNPW). The binding of these three anti-H(O) lectins is known to be inhibited by di-N-acetylchitobiose but not by L-fucose. These results strongly suggest that there is a good correlation between the carbohydrate-binding specificity and the amino acid sequence of the carbohydrate-binding regions of di-N-acetylchitobiose-binding lectins.

A simple method for the release of asparagine-linked oligosaccharides from a glycoprotein purified by SDS-polyacrylamide gel electrophoresis

A simple method for the release of oligosaccharides from glycoproteins separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) has been developed. Asialo-alpha 1-acid glycoprotein, which was tritiated at the nonreducing terminal D-galactopyranosyl residue by reduction with sodium borotritide after incubation with D-galactose oxidase, was used as a model compound. After electrophoretic separation of the glycoprotein, oligosaccharides were released by the use of a gas-phase hydrazinolysis apparatus. In the first method, the gel was stained with Coomassie Blue and the glycoprotein together with the gel was directly subjected to gas-phase hydrazinolysis after removal of water in a P2O5 desiccator. The recovery of released oligosaccharides was 25.9 +/- 2.4%, based on the amount of the glycoprotein loaded on the gel within the range of 3.5-28.5 micrograms. In the second method, the glycoprotein was electroblotted onto an Immobilon transfer membrane and was visualized by staining with Coomassie Blue. A small piece of the membrane with the corresponding band was cut out, dried in a desiccator and subjected to gas-phase hydrazinolysis. In this case, the recovery of released oligosaccharides was 15.2 +/- 1.0%. These procedures, particularly the first one, should be widely applicable for the isolation of oligosaccharides from glycoproteins separated by SDS-PAGE.

Carbohydrate-binding peptides from several anti-H(O) lectins

Peptide fragments have been obtained from L-fucose-binding anti-H(O) lectins [Lotus tetragonolobus lectin (LTA) and Ulex europeus lectin I (UEA-I)] and di-N-acetylchitobiose-binding anti-H(O) lectins [Ulex europeus lectin II (UEA-II) and Laburnum alpinum lectin I (LAA-I)] by treatment with endoproteinase Asp-N or Lys-C. The peptide fragments were fractionated by affinity chromatography on a column of Fuc-Gel for LTA and UEA-I, and on a column of N-acetyl-D-glucosamine oligomer-Sepharose for UEA-II and LAA-I. The peptides with affinity for these columns were identified by peptide sequencing. All of these retarded peptides were found to be parts of the metal-binding regions of these lectins. It is strongly suggested that these peptides represent the carbohydrate-binding and metal ion-binding sites of legume lectins, respectively.

Alteration of the carbohydrate-binding specificity of the Bauhinia purpurea lectin through the preparation of a chimeric lectin

A chimeric lectin gene was constructed by using a cDNA clone coding the Bauhinia purpurea lectin (BPA) in which a part of the metal-binding region was replaced by the corresponding region of the mannose-binding Lens culinaris lectin (LCA). The chimeric lectin expressed in Escherichia coli was found to bind alpha mannosyl-bovine serum albumin (BSA) and this binding was inhibited by mannose.

Human colonic sulfomucin identified by a specific monoclonal antibody

Since the 1960s, the loss of sulfomucin from colonic epithelium has been considered to be an indicator of an early stage of carcinogenesis; yet, the biochemical basis for this phenomenon has never been elucidated. We recently prepared a monoclonal antibody (mAb) 91.9H that immunoprecipitates the normal colonic mucins metabolically incorporating [35S]-sulfate. This mouse IgG1 antibody did not cross-react with colon carcinoma mucins that lack sulfate groups. Using normal colonic epithelia unlabeled or radiolabeled with [35S]sulfate and [3H]glucosamine, we purified a high molecular weight glycoprotein that reacts with mAb 91.9H. This was achieved by a combination of DEAE-cellulose anion-exchange chromatography, consecutive treatments with chondroitinase ABC plus heparitinase and with sodium dodecyl sulfate plus 2-mercaptoethanol, and gel filtration on Sepharose CL-2B in the presence of 8 M urea. Antibody reactivity was found in acidic but not neutral high molecular weight glycoproteins. After Sepharose CL-2B fractionation, the mAb 91.9H-reactive fractions consisted of a component with an approximate molecular weight of 500,000-900,000. A purified sulfomucin contained protein, neutral sugar, amino sugar, sialic acid, and sulfate in an approximate ratio of 2.5:1.0:1.1:0.4:0.5. The polypeptide portion was rich in hydrophilic amino acids, particularly threonine. Binding of mAb 91.9H in solid-phase assays was inhibited to 50% by purified normal colon acidic mucin at doses of 5-50 micrograms/ml, depending on different preparations. Various glycosaminoglycans or sulfatides did not show inhibitory activity. Sulfomucin reactivity with mAb 91.9H, as determined by solid-phase-binding inhibition and by dot blot assays, was significantly reduced by chemical desulfation of sulfomucins with anhydrous hydrochloric acid, suggesting that sulfate groups served as a portion of the immunochemical determinant for this antibody. Sulfate residues were apparently linked to alkaline-sensitive carbohydrate chains, but alkaline-released carbohydrate chains did not react with mAb 91.9H. Immunohistochemical examinations showed that mAb 91.9H bound normal colonic epithelial cells, which also stained with high-iron diamine, more strongly than it bound colon carcinoma cells.

Human colon carcinoma cells with increased invasive capacity obtained by selection for sialyl-dimeric LeX antigen

Sialyl-dimeric LeX antigen (NeuAc alpha 2-3Gal beta 1-4[Fuc-alpha 1-3] GlcNAc beta 1-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc beta 1-R; SLX) is an oncodevelopmental carbohydrate antigen expressed both on glycolipids and on mucin-like glycoproteins in human colorectal carcinomas. The levels are higher in primary tumors at advanced stages than in tumors at early stages, and metastatic lesions contain a greater quantity of this antigen than corresponding primary tumors. To study whether this antigen influences the metastatic behavior of tumor cells, we selected SLX variant cells from the human colon carcinoma cell line KM12C using the specific monoclonal antibody FH6. We obtained two stable cell lines: a high expresser (KM12-HX) and a low expresser (KM12-LX) of this antigen. The growth rate of these cells are similar. A mucin-like glycoprotein reactive with monoclonal antibody FH6 was detected after electrophoretic separation of KM12-HX cell lysates but not of KM12-LX lysates. The degree of invasion was compared in assays in vitro using matrigel-coated filter membranes. The number of KM12-HX cells that invaded the membranes was significantly higher than KM12-LX cells.

Lactose-binding lectin expression in human colorectal carcinomas. Relation to tumor progression

Lactose-binding lectins having Mr values of approximately 14,000 (L-14.5) and approximately 35,000 Da have been found in a variety of vertebrate tissues, including normal intestine and colon, and in several types of tumors such as colon carcinomas. To determine the clinical relevance of such lectins in human colon cancer, specimens from 46 patients with colorectal carcinoma of identified Dukes' stages were selected and analyzed for the presence and amount of lactose-binding lectins by immunoblotting using a polyclonal, rabbit anti-lectin antibody followed by binding of 125I-labeled anti-rabbit IgG. The amount of a lectin having an Mr value of approximately 31,000 Da (L-31) varied among the specimens. The levels of L-31 lectin in colorectal cancer specimens from primary tumors of patients with distant metastases (Dukes' stage D) were significantly higher than were those from patients without detectable metastases (Dukes' stages B1 and B2). In contrast, among the various specimens the variation in the level of the L-14.5 lectin was smaller, and there was no correlation between the amount of this lectin and cancer stage. Immunohistochemical staining of thin sections of colorectal tumor specimens using antibodies specific for either L-31 or L-14.5 lectin revealed that the two were located at different places, the L-31 lectin primarily within the cytoplasm of carcinoma cells, and the L-14.5 lectin associated with secreted material. These results indicated that the relative amount of the L-31 lectin increases as the colorectal cancer progresses to a more malignant stage.

Metastatic behavior and cell surface properties of HT-29 human colon carcinoma variant cells selected for their differential expression of sialyl-dimeric Le(x)-antigen

Immunochemical studies of human colorectal carcinoma with various monoclonal antibodies against Le(X)-related carbohydrate antigens previously revealed that the amount of sialyl-dimeric Le(X) antigen (NeuAc alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-R: SLX) associated with metastatic lesions was greater than in the primary tumors. To assess whether an experimental model can be used to study the direct relationship between this carbohydrate antigen and the tumor cell's metastatic behavior, we selected variant cells with increased surface SLX from established human colon carcinoma cell line HT-29. The cells in the upper 5% or lower 5% population in fluorescence intensity after reacting with a monoclonal antibody, FH6, were retrieved separately by a fluorescence-activated cell sorter and propagated. After three- or four-times selection, we obtained stable cell lines with low and high cell surface SLX antigens (HT-29 M1 and HT-29 M2, respectively). Binding of monoclonal antibody FH6 was detected to glycolipids extracted from HT-29 M2 cells but not from HT-29 M1 cells. Glycoprotein components having reactivity with monoclonal antibody FH6 were below the detectable level. HT-29 M2 cells injected intrasplenically into nude mice showed a slightly reduced incidence of metastasis to lung, liver and lymph nodes than did HT-29 M1 cells. Subsequently we found that SLX antigen was not detectable by immunohistochemical examination of these tumor cells grown in nude mice. Re-established cell line from nude mice xenografts expressed SLX antigen in vitro.

Ectopic expression of mucins in colorectal cancer metastasis

Cancer metastasis is an ectopic growth of malignant cells. In human colorectal cancer, it is hypothesized that, during the progression of the disease to an advanced stage, highly malignant and metastatic tumor cells arise within primary tumors and become predominant. Based on this hypothesis, molecules associated with metastatic cells have been sought by the comparison of surgical specimens from patients at various clinical stages. Colorectal carcinomas with increased metastatic potential and with poor prognosis have been characterized by a loss of an organ-specific mucin determinant (sulfomucin), by an increased expression of non-intestinal sialomucins, and by an ectopic expression of adhesion ligands (sialyl-dimeric Lex antigens) on mucins.

Increased content of an endogenous lactose-binding lectin in human colorectal carcinoma progressed to metastatic stages

The quantity and localization of two lactose-binding lectins with molecular weights of 31,000 and 14,500 in human colorectal carcinoma tissue specimens obtained by surgical resection have been studied using specific polyclonal antibodies. Electrophoretic separation and blotting of detergent extracts of tumor tissues (48 specimens), followed by the binding of an antibody that recognizes both of these lectins, demonstrated that the contents of Mr 31,000 and 14,500 lectins vary from one specimen to another. The Mr 31,000 lectin content was higher in tumor specimens classified as Dukes' stage D than in those from other stages. A significant correlation was found between Mr 31,000 lectin levels and the levels of carcinoembryonic antigen in the patients' sera at the time of surgery. Immunohistochemical staining with antibodies specific for each lectin was performed with 20 colon carcinoma tissues and 5 colonic adenoma tissues. The results showed that the Mr 31,000 lectin localizes in the cytoplasm of colorectal carcinoma cells and normal epithelial cells, whereas antibody binding to Mr 14,500 lectin is observed in a limited number of carcinoma specimens and is mainly associated with luminal surfaces and secretory products. Adenoma cells were reactive with Mr 14,500 anti-lectin antibody at their luminal surfaces or cytoplasms, but they did not stain with Mr 31,000 anti-lectin antibody. These results suggest that a correlation exists among the level of the Mr 31,000 lectin, the serum level of carcinoembryonic antigen, and the stage of progression of colorectal carcinomas.

Relationships between heparanase activity and increasing metastatic potential of fibroblasts transfected with various oncogenes

We have examined the effects of transformation by activated H-ras and other transforming oncogenes on the activity of the enzyme, heparanase. Degradation of 3H-N-acetylated-partially N-desulfated heparan sulfate by cellular extracts of the transformants was assessed by gel permation chromatography. More extensive degradation was observed with 10T1/2 mouse embryo fibroblasts transfected with an activated H-ras oncogene. The cells having the highest metastatic potential (CIRAS-3) were shown to contain the greatest heparanase activity, giving 49% higher levels of activity than parental cells (P less than 0.0002). Furthermore, the enzyme activity produced by a series of H-ras transformed cell lines increased progressively with metastatic potential (non-parametric rank correlation coefficient r = 0.96). Transfection of NIH 3T3 fibroblasts with activated H-ras, v-src or v-fes oncogenes, which induced the metastatic phenotype, did not lead to large increases in heparanase activities. Also, inhibition of ras-induced malignancy by cotransfection of rat REF cells with the Ad2 E1a oncogene did not produce significant declines in heparanase activities. These results are consistent with the view that modifications in heparanase activity can play a role in the complex process of metastasis in some, but not all situations.

Soluble factor in normal tissues that stimulates high-molecular-weight sialoglycoprotein production by human colon carcinoma cells

The stimulation of high molecular weight sialoglycoprotein synthesis by a soluble factor derived from normal colon tissues was studied in vitro with human colon carcinoma cell lines, HT-29 P and a metastatic variant HT-29 LMM. The synthesis of all three high-molecular-weight sialoglycoproteins (approximate Mr 900,000, 740,000, and 450,000) by HT-29 P cells or HT-29 LMM cells growing in vitro was enhanced by supplementing the culture medium with a conditioned medium of fresh human colon organ culture. Changes were detected by polyacrylamide gel electrophoresis of lysates from [3H]glucosamine-labeled cells on 3% gels followed by fluorography, or by electrophoresis of lysates from unlabeled cells followed by incubation with 125I-labeled wheat germ agglutinin and autoradiography. No changes were detected in the major protein components or in glycoproteins at Mr less than 200,000 as revealed by polyacrylamide gel electrophoresis. The treated cells did not change their growth rate or morphology. The connective tissue portions of the colon tissues were apparently responsible for the production of this stimulatory substance. The stimulatory activity was preserved at 56 degrees C but was inactivated by heating at 100 degrees C. The substance was eluted from a Sephacryl S-200 column at a position between the elution positions of ovalbumin and trypsinogen. The colon carcinoma cells treated with the conditioned medium and producing increased amounts of high-molecular-weight sialoglycoproteins were less sensitive to the cytolytic effects of recombinant interleukin 2-activated human peripheral blood lymphocytes than untreated cells were. The treated colon carcinoma cells induced stronger platelet aggregation than their untreated counterparts did. Therefore, this substance may represent one of the normal host tissue factors that can influence and modulate malignant behavior of carcinoma cells growing in vivo.

Metastatic potential of colon carcinoma. Expression of ABO/Lewis-related antigens

Four monoclonal antibodies specific to various Lewisx-related antigens were tested for binding to monolayers and detergent extracts of the human colon carcinoma cell line HT-29 P and its metastatic variant HT-29 LMM. Only monoclonal antibody FH6 (antisialyl-dimeric Lex) bound more to the metastatic variant compared with HT-29 P. Detergent extracts of human tissues were then assayed for their FH6-binding activity. Normal colonic mucosa displayed less FH6 binding than either Dukes stage B or D primary colon carcinomas. Liver metastases from colorectal carcinoma demonstrated greater binding than stage B and stage D primary tumors, and more than normal liver. Expression of sialyl-dimeric Lex increases as the metastatic potential of colorectal carcinomas increases, and is related to the progression of colorectal cancer.

Increased expression of sialyl-dimeric LeX antigen in liver metastases of human colorectal carcinoma

We collected a total of 78 tissue specimens, including primary colorectal carcinoma, normal colonic mucosa, and liver metastases of colon carcinoma, to examine whether the extracts of these tissues inhibited the binding of a monoclonal antibody FH6, specific for sialyl-dimeric LeX antigen. The results of inhibition assays demonstrated that: (a) contents of FH6-reactive molecules were greater in carcinoma tissues than in normal colonic mucosa; (b) metastatic foci in livers contained more FH6-reactive molecules than primary tumors; (c) primary tumors from Dukes' stage B1 patients contained less FH6-reactive molecules than primary tumors from Dukes' stage D patients. The inhibitory activity of these tumor tissue extracts against the binding of a monoclonal antibody FH6 to cultured colon carcinoma cells was eliminated by prior treatment of the extracts with sialidase, confirming that the FH6-reactive materials were sialyl-dimeric LeX antigen. Electrophoretic separation of tumor tissue extracts on 3% polyacrylamide gels followed by direct staining with monoclonal antibody FH6 revealed that very high molecular weight glycoproteins, presumably mucins, contained sialyl-dimeric LeX antigen.

Monoclonal antibody against human colonic sulfomucin: immunochemical detection of its binding sites in colonic mucosa, colorectal primary carcinoma, and metastases

Previous studies using metabolic labeling of fresh colonic mucosa and colorectal carcinoma with [35S]sulfate followed by biochemical analysis demonstrated that the amount of a sulfated high-molecular-weight glycoprotein expressed in primary colorectal carcinoma was lower than that in normal mucosa, and that the amount further decreased in liver metastases. This suggested that this sulfated molecule represented a sulfomucin previously defined by histochemical reactivity with a cationic dye. We have extracted and partially purified this high-molecular-weight sulfated glycoprotein from normal human colonic mucosa. We immunized mice with the partially purified sulfomucin and generated hybridomas. One cloned hybridoma, designated as 91.9H, produced a monoclonal antibody strongly reactive with a component which migrated at an identical position as the metabolically [35S]sulfate-labeled high-molecular-weight glycoprotein after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The reactive molecules appeared to have a polydisperse nature with a molecular weight ranging between 400,000 and 900,000. The [35S]sulfate-labeled high-molecular-weight glycoprotein was bound to Staphylococcus Protein A-agarose coated with this monoclonal antibody but did not bind to unconjugated Protein A-agarose. The immunoprecipitated substance also migrated at an apparent molecular weight range of 400,000 to 900,000. The reactivity of monoclonal antibody 91.9H with the extracts of normal mucosa, colorectal primary carcinoma, and metastasis was compared by dot blot assay on a nitrocellulose membrane. This antibody was more reactive with the extracts of mucosa adjacent to carcinoma tissues than with the carcinoma extracts. Primary tumors showed higher reactivity than metastases in most of the cases. These results strongly suggest that this antibody is specific to colonic sulfomucins or at least to mucins closely related to colonic mucins previously identified by metabolic labeling with [35S]sulfate.

Electrophoretic analysis of four high molecular weight sialoglycoproteins produced by metastatic human colon carcinoma cells

We have found that polyacrylamide gel electrophoresis in 3% gels in the presence of sodium dodecyl sulfate is suitable for the separation of cellular glycoproteins having molecular weights ranging from 200,000 to 1,000,000. The gels secured on a rigid support (Gelbond) allow blotting techniques with lectins and antibodies for the detection of glycoproteins. Using these methods we have separated lysates of HT-29 human colon carcinoma cells and detected at least four distinct high molecular weight sialoglycoproteins having molecular weights of 900,000, 740,000, 560,000, and 450,000. The expression of the 900,000 component, as revealed by wheat germ agglutinin binding, was much higher in a subline of HT-29 cells established from liver metastases in a nude mouse than it was in the parental cells. The relative intensity of wheat germ agglutinin binding to these four sialoglycoprotein components differs depending upon their growth phase in vitro. These glycoproteins were also detectable by the binding of peanut agglutinin, provided the glycoproteins were previously treated in the gels with mild acid to remove the sialic acid from their carbohydrate chains, suggesting that mucin-type carbohydrate chains are present on these glycoproteins. The same set of glycoproteins can be detected by metabolic labeling of the cells with [3H]glucosamine in tissue culture. Very similar glycoprotein profiles are revealed by metabolic labeling of fresh colon carcinoma tissues with [3H]glucosamine in vitro.

Differential expression of a sialoglycoprotein with an approximate molecular weight of 900,000 on metastatic human colon carcinoma cells growing in culture and in tumor tissues

Wheat germ agglutinin (WGA)-binding cellular glycoproteins produced by HT-29 human colon carcinoma and its variant cells established from liver metastases in nude mice after intrasplenic injection were analyzed by polyacrylamide gel electrophoresis. On 5.5% polyacrylamide gels five major sialoglycoproteins (approximate Mr 115,000, 145,000, 190,000, 450,000, and 740,000) reactive with WGA were common to the parental and metastatic sublines. There was an additional component of Mr approximately 900,000 that was prominent in cells established from liver metastases. Specific removal of sialic acid from the glycoproteins eliminated WGA binding, indicating that all the WGA-binding glycoproteins including the Mr 900,000 component were sialoglycoproteins. Smith degradation following mild acid hydrolysis resulted in formation of WGA-binding carbohydrate chains on Mr 115,000, 145,000, 190,000, and 900,000 components, but not on Mr 450,000 and 740,000 components, which indicated that these two sialoglycoproteins bore different oligosaccharides from the other sialoglycoproteins. The Mr 900,000 component was more prominent with HT-29 cells growing in nude mice than those growing in vitro. WGA binding to the Mr 900,000 component of metastasis-derived HT-29 cells growing in a nude mouse was higher than that of parental cells growing in nude mice. The expression in liver metastases derived from parental as well as metastatic cells was higher than the primary tumor growing in the spleen of the same mouse, indicating that the levels of Mr 900,000 sialoglycoprotein (SGP = 900) were regulated by intrinsic and environmental factors. The influence of organ microenvironmental factors was confirmed by analyzing sialoglycoproteins of HT-29 cells growing in the liver of a nude mouse following intrahepatic injection. Analyses of human colorectal carcinoma tissues and liver metastases revealed a polydisperse WGA-reactive high-molecular-weight component similar to that seen in tumors growing in nude mice. The mean value of WGA binding to high-molecular-weight glycoproteins in the primary tumors of stage B1 patients was smaller than that of all other primary tumors. Comparison of primary tumors with liver metastases from the same patients indicated that the level of SGP-900-like high-molecular-weight glycoproteins in metastases was not always higher than those in primary tumors.

Increased content of chondroitin sulfate proteoglycan in human colorectal carcinoma metastases compared with the primary tumor as determined by an anti-chondroitin-sulfate monoclonal antibody

To determine if the amount of chondroitin sulfate proteoglycan (CSPG) in human colorectal tumor tissue correlates with the tumor's aggressiveness we immunochemically determined the CSPG levels in colorectal carcinomas at different stages. A total of 50 specimens--4 polyps, 15 stage B tumors, 9 stage C tumors, 12 stage D tumors, 7 liver metastases, and 3 lymph node metastases--were examined. Tumor tissues were extracted with 4 M guanidine hydrochloride containing protease inhibitors. The extracts were serially diluted and blotted onto nitrocellulose membranes. Reactivity of a chondroitin sulfate-specific mouse monoclonal antibody (CS-56) was determined by biotinylated goat antimouse Ig and avidin-biotin-peroxidase complex. After comparing tissues from tumors at different stages (classified by the presence or absence of metastasis), we could not find a positive or negative correlation between the amount of CSPG in primary colorectal carcinoma tissues and the tumor's metastatic potential. However, the metastatic foci in the liver or lymph node contained higher amounts of CSPG than the primary tumors did. Immunohistochemical staining of colon carcinoma tissue with CS-56 revealed that CSPG is predominantly localized in fibrotic portions in the tumor tissues. Two-year follow-up studies indicated that a high level of CSPG in primary tumors was not predictive of recurrence.

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.

Heparanases and tumor metastasis

The successful penetration of endothelial basement membranes is an important process in the formation of hematogenous tumor metastases. Heparan sulfate (HS) proteoglycan is a major constituent of endothelial basement membranes, and we have found that HS-degradative activities of metastatic B16 melanoma sublines correlate with their lung-colonizing potentials. The melanoma HS-degrading enzyme is a unique endo-beta-D-glucuronidase (heparanase) that cleaves HS at specific intrachain sites and is detectable in a variety of cultured human malignant melanomas. The treatment of B16 melanoma cells with heparanase inhibitors that have few other biological activities, such as N-acetylated N-desulfated heparin, results in significant reductions in the numbers of experimental lung metastases in syngeneic mice, indicating that heparanase plays an important role in melanoma metastasis. HS-degrading endoglycosidases are not tumor-specific and have been found in several normal tissues and cells. There are at least three types of endo-beta-D-glucuronidases based on their substrate specificities. Melanoma heparanase, an Mr approximately 96,000 enzyme with specificity for beta-D-glucuronosyl-N-acetylglucosaminyl linkages in HS, is different from platelet and mastocytoma endoglucuronidases. Elevated levels of heparanase have been detected in sera from metastatic tumor-bearing animals and malignant melanoma patients, and a correlation exists between serum heparanase activity and extent of metastases. The results suggest that heparanase is potentially a useful marker for tumor metastasis.