Proposed molecular basis of murine tumor cell-hepatocyte interaction

Naturally occurring antibodies directed against carbohydrate tumor antigens

Healthy persons carry within their pool of circulating antibodies immunoglobulins preferentially of IgM isotype, which are directed against a variety of tumor-associated antigens. In closer scrutiny of their nature, some of these antibodies could be defined as naturally occurring antibodies due to the germline configuration of the variable immunoglobulin region. The majority of these immunoglobulins recognize carbohydrate antigens which can be classified as oncofetal antigens. Many of these IgM antibodies present in the peripheral blood circulation can bind to tumor cells and of these a minor portion are also able to destroy tumor cells by several mechanisms, as for instance complement-mediated cytolysis or apoptosis. It was postulated that anti-carbohydrate antibodies are part of an anti-tumor immune response, while their presence in the peripheral blood of healthy donors is still waiting for a plausible explanation. It may be that recognition of defined epitopes, including carbohydrate sequences, by naturally occurring antibodies constitutes the humoral arm of an anti-tumor immune response as part of the often postulated tumor surveillance. The cytotoxic capacity of these antibodies inspired several research groups and pharmaceutical companies to design novel strategies of immunoglobulin-based anti-tumor immunotherapy.

Inhibition of spontaneous breast cancer metastasis by anti-Thomsen-Friedenreich antigen monoclonal antibody JAA-F11

Thomsen-Friedenreich antigen (TF-Ag) is expressed in many carcinomas, including those of the breast, colon, bladder, and prostate. TF-Ag is important in adhesion and metastasis and as a potential immunotherapy target. We hypothesized that passive transfer of JAA-F11, an anti-TF-Ag monoclonal antibody, may create a survival advantage for patients with TF-Ag-expressing tumors by cytotoxicity, blocking of tumor cell adhesion, and inhibition of metastasis. This was tested using in vitro models of tumor cell growth; cytotoxicity assays; in vitro, ex vivo, and in vivo models of cancer metastasis; and, finally, in vivo effects in mice with metastatic breast cancer. Unlike some anti-TF-Ag antibodies, JAA-F11 did not enhance breast carcinoma cell growth. JAA-F11 did not induce the killing of 4T1 tumor cells through complement-dependent cytotoxicity or apoptotic mechanisms. However, JAA-F11 blocked the stages of metastasis that involve the adhesion of human breast carcinoma cells to human endothelial cells (human umbilical vein endothelial cells and human bone marrow endothelial cells 60) in in vitro static adhesion models, in a perfused ex vivo model, and in murine lung vasculature in an in vivo metastatic deposit formation assay. JAA-F11 significantly extended the median survival time of animals bearing metastatic 4T1 breast tumors and caused a > 50% inhibition of lung metastasis.

Prognostic impact of Thomsen-Friedenreich tumor antigen and disseminated tumor cells in the bone marrow of breast cancer patients

PURPOSE

The Thomsen-Friedenreich antigen (TF, CD176) is a specific oncofetal carbohydrate epitope (Gal beta1-3GalNAc alpha-O-Ser/Thr) expressed on the surface of various carcinomas. It mediates endothelium adhesion and formation of metastases. As it also causes immune response, its prognostic impact is indeterminate. The presence of disseminated tumor cells in the bone marrow of breast cancer patients (DTC-BM) indicates worse prognosis. We examined the expression of TF in primary breast cancer tissue of 265 patients with known BM status at the time of first diagnosis.

METHODS

BM aspiration, cytospin preparation and immunocytochemical staining with the anti-Cytokeratin antibody A45 B/B3 was done following a standardised protocol. TF expression was examined immunohistochemically on Tissue Micro Arrays (TMA) with the anti-TF antibody A78-G/A7. Evaluation was done using the immunoreactive score (IRS).

RESULTS

Median IRS for TF expression was 2 (0-12). 68 of 265 patients (25.7%) showed DTC-BM with a median of 2/2 x 10(6) cells (1-1500). There was no correlation between TF expression and DTC-BM. After a median follow up of 60.1 months (7-119), the detection of DTC-BM showed prognostic significance for overall survival (OS, p = 0.034), whereas TF positivity (IRS > 2) indicated prolonged disease-free (p = 0.01), distant disease-free (p = 0.005), and overall survival (p = 0.005).

DISCUSSION

Patients with TF-positive tumors had a significantly better prognosis. Dissemination routes, TF-mediated metastasis formation, and the immunogeneity of TF might determine the prognostic impact of TF expression in different tumor entities. Further characterisation of primary tumors and DTC-BM could help to improve the biological understanding of metastases and develop targeted therapies.

Thomsen-Friedenreich and Tn Antigens in Nipple Fluid: Carbohydrate Biomarkers for Breast Cancer Detection

PURPOSE

Novel biomarkers would facilitate early and accurate diagnosis of breast cancer. The Thomsen-Freidenreich (TF) and Tn antigens are aberrantly glycosylated carbohydrate cancer-associated antigens found in approximately 80% of adenocarcinomas. Both TF and Tn are expressed on cell-surface glycoproteins and glycolipids. Nipple aspirate fluid (NAF) is concentrated in secreted proteins and lipids from cells that give rise to cancer. The objective of this study was to determine if NAF from breasts with cancer contains elevated levels of TF and Tn compared with NAF from normal breasts. A sensitive and specific antigen capture immunoassay for TF and Tn detection in NAF was developed for this purpose.

EXPERIMENTAL DESIGN

Fifty NAF samples, 25 from breasts with cancer and 25 from normal breasts, were examined. Antigen capture immunoassays were done on the samples using monoclonal antibodies that specifically recognized either TF or Tn antigen in NAF. These antibodies captured serially diluted NAF samples, and the concentration of TF or Tn was determined by comparing absorbance values against a standard curve generated from standard sources of TF or Tn.

RESULTS

TF and Tn were detected in 19 of 25 and 20 of 25 NAF samples from breasts with cancer, respectively, compared with 0 of 25 and 1 of 25 NAF samples from breasts without cancer (P < 0.001 for both TF and Tn). In 92% of the cancerous breast NAF samples tested, either TF or Tn was found.

CONCLUSIONS

Simultaneous measurement of TF and Tn in NAF may facilitate the noninvasive detection of breast cancer and warrants further study.

Thomsen-Friedenreich (T) antigen expression increases sensitivity of natural killer cell lysis of cancer cells

In this study, we demonstrate a correlation between T antigen expression on a panel of human carcinoma cell lines and their sensitivity to porcine NK cell lysis. Specifically, the more T antigen is expressed, the more sensitive the cancer cells are to porcine NK cell lysis. Furthermore, this correlation also exists for these cells and their ability to induce tumors in vivo. In this porcine animal model, the less T antigen is expressed, the more prolific the tumor growth in vivo and vice versa. Using the human colorectal adenocarcinoma cell line SW-48, we used limiting dilution to clone 2 populations of cells, one expressing high and the other low levels of T antigen, clones 143 and 111, respectively. In these cloned cells, the clone that expressed more T antigen was more NK-sensitive in vitro and weakly induced tumor growth in vivo. Inversely, the clone that expressed less T antigen clone was more NK-resistant in vitro and grew more prolific tumors in vivo. Using soluble T antigen in a competitive inhibition assay, there was a decrease in porcine NK cell killing of the T antigen+ human cell line Colo 320HSR. Taken together, these findings suggest a novel role for T antigen in the NK cell recognition of cancer cells, specifically as markers for NK sensitivity in carcinoma cell lines. The significance of T antigens as targets for NK cell-mediated lysis is novel and identifies NK cell-T antigen interactions as potentially significant in the immunotherapy of cancer and its associated metastases.

O-glycosylation in Echinococcus granulosus: identification and characterization of the carcinoma-associated Tn antigen

In the present work we demonstrate that the cancer-associated O-glycosylated Tn antigen (GalNAc-O-Ser/Thr) is expressed by the cestode Echinococcus granulosus. This antigen was detected in both larval and adult worm extracts, with the highest specific activity observed in the adult excretion/secretion preparation. Histochemical analysis showed that Tn is preferentially expressed in the parenchyma in both parasite stages and the external part of tegument in adult worms. A similar pattern was observed for sialyl-Tn, a related O-linked antigen. Tn glycoproteins from protoscoleces were resolved by SDS-PAGE in two main components of 43 and 49 kDa. After purification, this material was reactive with lectins which bind GlcNAc/sialic acid, GalNAc, and T antigen. In a preliminary evaluation, high levels of Tn antigen were detected in serum samples from patients with hydatid cyst, suggesting that the measure of Tn in serum could be a biomarker of this disease, although extensive work is necessary in order to determine the clinical usefulness of this assay. The results reported here, the first evidence of O-glycosylation pathways in E. granulosus and the presence of Tn antigen in cestodes, suggest that the evaluation of O-glycosylated antigens might give new insights in the host-parasite relationship.

Grading dysplasia in colorectal adenomas by means of the quantitative binding pattern determination of Arachis hypogaea, Dolichos biflorus, Amaranthus caudatus, Maackia amurensis, and Sambucus nigra agglutinins

The current study deals with the setting up of a new tool that enables the benign versus the malignant nature of colorectal adenomas to be determined accurately. The 2 objectives are to determine (1) whether adenomas should, or should not, be included in a 2- or a 3-tier grading system, and (2) whether severe dysplasias and carcinomas in situ share common or different biological characteristics. The levels of expression of different types of glycoconjugates were characterized in a series of 166 colorectal specimens, including 14 normal, 90 dysplastic, and 62 cancerous cases. The glycoconjugate expressions were demonstrated for 5 lectins, namely, Arachis hypogaea (PNA), Dolichos biflorus (DBA), Amaranthus caudatus (ACA), Maackia amurensis (MAA) and Sambucus nigra (SNA). The glycoconjugates demonstrated by these 5 lectins belong to the family of the Thomsen-Friedenreich antigens. The binding patterns of the 5 lectins were quantitatively determined by means of computer-assisted microscopy. The quantitative data were submitted to discriminant analyses. Our results show that the specific glycochemical staining patterns could be identified unambiguously and without misclassification between benign (normal and low dysplasia) and malignant (ie, either as moderate/severe dysplasia, carcinoma in situ, or cancer) cases. The data also strongly suggested that (1) dysplasias seem to be distinguishable in 2 instead of 3 groups, that is, low versus moderate/severe (high); and (2) moderate/severe dysplasias are biologically distinct from carcinomas in situ. The methodology developed can be applied directly in routine diagnosis to identify moderate/severe dysplasia specimens already exhibiting features common to carcinomas, and which therefore should be treated consistently in view of the fact that our data strongly suggest that most moderate/severe dysplasias are still benign, whereas carcinomas in situ are real carcinomatous lesions.

Specific role of T and Tn tumor-associated antigens in adhesion between a human breast carcinoma cell line and a normal human breast epithelial cell line

The possibility that tumor-associated antigens T and Tn act as adhesion molecules between normal and malignant breast epithelial cells at the early stages of recognition in the metastatic pathway was examined in vitro. The adhesive specificity of the antigens was assessed by means of in vitro adhesion tests between a carcinomatous breast cancer cell line (ZR75-30) and a normal epithelial breast cell line (HLB100) using both monoclonal antibodies and lectins specific as well as nonspecific for each antigen. Adhesion assay was performed using monolayers of the normal cell line prepared on plastic culture plates and the tumor cell line labeled with a fluorescent dye as a probe. The adhesion between the two cell types occurred with significant specificity via T and Tn antigens (P<0.001), and was temperature-dependent. The results suggest that at the early stages of recognition by tumor cells in the metastatic process, T and Tn antigens play a role as adhesion molecules between the tumor cells and adjacent normal cells.

Development and characterization of monoclonal antibody to T-antigen: (gal beta1-3GalNAc-alpha-O)

The saccharide antigen, Gal beta1-3GalNAc or T antigen, is of biologic importance in many systems. It is a tumor-associated carbohydrate antigen, a temporally expressed antigen in germinal center B cells and cortical T cells, a parasite-associated antigen, a spermatozoa vitality marker and an antigen on aged red blood cells. It may play a role in normal cellular adhesion and in tumor cell metastasis. Well characterized monoclonal antibodies (MAb) to Gal beta1-3GalNAc will be useful for further studies in these areas. We developed an IgG3 MAb to Gal beta1-3GalNAc by immunizing the mice with a synthetic Gal beta1-3GalNAc-BSA conjugate. The MAb was analyzed using inhibition enzyme immunoassays with related synthetically prepared sugars to determine the restrictions involved in the antibody binding. Use of synthetic sugars as competitors enabled us to delineate the epitope restrictions on the binding activity of this monoclonal and will enable use of this MAb in studies concerning the biologic importance of this disaccharide.

Quantitative computerized image analysis of Tn and T (Thomsen-Friedenreich) epitopes in prognostication of human breast carcinoma

The precursors of the blood group N and M-immunodominant structures, Tn and T (Thomsen-Friedenreich) epitopes (EPs) occur in approximately 90% of carcinomas (CAs) but are masked in benign-diseased and healthy tissues. We determined quantitatively on 55 primary invasive ductal breast CAs, stages I to IV, the prognostic value of extent of Tn and T EP expression over an observation period exceeding 5 years postoperatively. Classical, established pathological and histological prognostic characteristic indicators associated with survival were subdivided by standard criteria into favorable and unfavorable categories. Tissue sections were reacted with monoclonal anti-Tn and -T antibodies, followed by the streptavidin-biotin-peroxidase-DAB procedure; counterstain was methyl green. Tn and T EPs were then quantitated by computerized image analysis. Of the 55 CAs, 51 clearly expressed Tn and T, and four had traces. Strong Tn EP expression was statistically significantly associated with shortened 5-year disease-free interval, increasing pTNM stages, positive lymph node status, and increasing combined histological grades. T EPs were usually well expressed but showed no significant association with prognostic factors. Our results suggest that quantitative immunohistochemistry-image analysis of Tn EPs of primary breast CAs may add new parameters to prognostication.

Characterization of peptides that bind the tumor-associated Thomsen-Friedenreich antigen selected from bacteriophage display libraries

Peptides with high affinities and specificities for numerous proteins and nucleic acids have been previously identified from random peptide bacteriophage display libraries. Here, random peptide bacteriophage display libraries were used to identify sequences that bound the cancer-associated Thomsen-Friedenreich glycoantigen (T antigen). The T antigen, present on most malignant cells, contains an immunodominant Gal beta1 --> 3GalNAc alpha disaccharide unmasked on the surfaces of most carcinomas. This antigen has been postulated to be involved in tumor cell aggregation and metastasis. Two 15 amino acid random peptide bacteriophage display libraries were affinity selected with glycoproteins displaying T antigen on their surfaces. Sequence analysis revealed that many of the peptides shared homology with sugar recognition sites in several carbohydrate-binding proteins. A comparison of affinity selected sequences from both libraries yielded a common motif (W-Y-A-W/F-S-P) rich in aromatic amino acids. Four peptides, corresponding to the affinity selected sequences, were chemically synthesized and characterized for their carbohydrate recognition properties. The synthetic peptides exhibited high specificities and affinities to T antigen displayed on asialofetuin or conjugated to bovine serum albumin (Kd = 5 nM for MAP-P30 binding to asialofetuin) as well as free T-antigen disaccharide in solution (Kd = 10 microM for MAP-P30, 20 microM for P10). Two peptides, P30 and P10, demonstrated high affinities and specificities for both asialofetuin and T antigen in solution. Iodination of a lone tyrosine residue in each sequence dramatically reduced their abilities to bind T antigen, suggesting that the tyrosine residue plays an important role in carbohydrate recognition. That these peptides are of functional significance is evidenced by the ability of both P30 and P10 to inhibit asialofetuin-mediated melanoma cell aggregation in vitro and to compete with peanut lectin for binding to T antigen displayed on the surface of MDA-MB-435 breast carcinoma cells in situ.

The synthesis of galactopyranosyl derivatives with beta-galactosidases of different origins

beta-Galactosidases from four different sources were used to catalyze the transfer of beta-D-galactopyranosyl from 4-nitrophenyl-beta-D-galactopyranoside to a hydroxyl group of 2-acetamido-2-deoxy-galactopyranose in the synthesis of Gal beta (1-3)GalNAc (1), Gal beta (1-4)GalNAc (2) and Gal beta (1-6)GalNAc (3), in triethyl phosphate buffered solutions (20-60%). When beta-galactosidases from Penicillium multicolor and Aspergillus oryzae were used as the catalysts, the beta (1-6)-linked disaccharide was produced as the major product. However, with beta-galactosidase from Bifidobacterium bifidum, the major products were the beta (1-4) and beta (1-6)-linked disaccharides. On the other hand, with beta-galactosidase from Streptococcus 6646K, beta (1-3)-linked disaccharide was predominant together with beta (1-4)-linked isomer. Gal beta (1-3)GlcNAc (4), Gal beta (1-4)GlcNAc (5) and Gal beta (1-6)GlcNAc (6) were also synthesized with beta-galactosidase from S. 6646K and B. bifidum with 2-acetamido-2-deoxy-glucopyranose as the acceptor and PNPGal as the donor. In both cases, the beta (1-4)-linked disaccharide was predominantly produced. In addition, a comparative study was carried out to determine the regioselectivity of the transglycosylation reaction as well as the hydrolytic specificity toward the same linked disaccharides.

Identification of peptide sequences that bind the Thomsen-Friedenreich cancer-associated glycoantigen from bacteriophage peptide display libraries

The goal of this study was to determine if polypeptides that bind specifically to the carcinoma-associated Thomsen-Friedenreich (T) antigen could be isolated from a random peptide bacteriophage display library. T antigen is a carbohydrate antigen that is exposed and immunoreactive on the surfaces of most primary carcinomas and their metastases, while it is masked on normal cells. Tumor-specific surface carbohydrates are often used as markers of cell differentiation and play a role in cell aggregation, which is an important step in the metastatic process. Therefore, peptides that bind and mask T antigen may yield useful carbohydrate-specific probes and provide insight into carbohydrate-mediated tumor-cell aggregation. A 15-amino acid random peptide bacteriophage display library was screened for polypeptides that exhibited high specificity to two glycoproteins which display T antigen on their surfaces. The results suggest that synthetic peptides identified from the bacteriophage display library have high affinities (Kd approximately 1 microM) and specificities for proteins and human tumor cells which present T antigen. Thus, random bacteriophage peptide display libraries may be a rich source of sequences that bind to carbohydrate antigen structures.

Tumor marker disaccharide D-Gal-beta 1, 3-GalNAc complexed to heat-labile enterotoxin from Escherichia coli

Heat-labile enterotoxin (LT) is part of the cholera toxin (CT) family and consists of a catalytic A subunit and a B pentamer that serves to recognize the oligosaccharide part of the GM1 ganglioside receptor. We report here the crystal structure of heat-labile enterotoxin in complex with the disaccharide portion of the Thomsen-Friedenreich (T-antigen) tumor marker. The toxin:carbohydrate complex is determined to 2.13 A resolution, yielding an R-factor of 18.5%. The T-antigen disaccharide, D-Gal-beta 1,3-GalNAc-Ser/Thr, is present in more than 85% of human carcinomas and monitoring its autoimmune response is used for the early detection of tumors. Insight into the molecular recognition of this tumor antigen by sugar binding proteins can benefit the development of a diagnostic tool for human carcinomas as well as a T-antigen directed anticancer drug delivery system.

Flow cytometric analysis of T and Tn epitopes on chronic lymphocytic leukemia cells

Immunophenotyping of peripheral blood lymphocytes from six patients with B-cell chronic lymphocytic leukemia (B-CLL) and five normal volunteers was done and their T and Tn epitopes analyzed using specific monoclonal antibodies and flow cytometry. Lymphocytes from all patients showed strong Tn expression as compared to normal control lymphocytes. By contrast, T antigen was not expressed, The TN expression may be a useful diagnostic and prognostic marker for B-CLL.

Expression of Thomsen-Friedenreich-related antigens in primary and metastatic colorectal carcinomas. A reevaluation

BACKGROUND

Expression of the pancarcinoma Thomsen-Friedenreich (TF) carbohydrate antigen or, more correctly, hapten, in colorectal carcinomas is not generally agreed on. Furthermore, its suggested role in liver metastasis so far has not been substantiated by direct immunohistochemical evidence.

METHODS

Cryostat sections from 52 primary tumors (20 with adjacent transitional mucosa), 22 liver metastases of colorectal carcinomas, and 17 samples of normal mucosae were examined immunohistologically with a panel of at least two monoclonal antibodies (mAbs) each to TF, to its precursor, Tn, and to sialosyl-Tn, among them two newly developed anti-TF mAbs.

RESULTS

Of the primary colorectal carcinomas, 60% expressed TF. Staining was more intense with TF-alpha/beta-reactive than with exclusively TF-alpha- or TF-beta-reactive mAbs. Normal and transitional mucosae were negative. Liver metastases were positive for TF in a significantly higher percentage of cases (91%) than primary carcinomas. Patients with TF-positive primary tumors had a significantly higher risk to develop liver metastases compared with patients with TF-negative tumors (57% vs. 14%, respectively). Tn and sialosyl-Tn were expressed concomitantly in most primary (85%) and metastatic (95%) colorectal carcinomas. These antigens also were detected in transitional mucosae (Tn in 25%, sialosyl-Tn in 55% of cases). Normal mucosae were negative.

CONCLUSIONS

These results prove unequivocally the presence of exposed TF epitopes in a majority of colorectal carcinomas in which both anomers of TF are expressed. These data further suggest that TF favors liver metastasis and that its expression in primary colorectal carcinomas is a significant risk factor for the development of liver metastasis.

Blood group antigens as tumor markers, parasitic/bacterial/viral receptors, and their association with immunologically important proteins

Blood group antigens (BGAs) are chemical moieties on the red blood cell (RBC) membrane. Some BGAs (e.g., A, B, H, Lewis, P, I) are widely distributed throughout the body and may not be primarily erythroid antigens. Statistical correlations with ABO blood groups and disease have been made for years and have been highly controversial. It is not known if BGAs have a biological function. There are increasing reports of BGAs [e.g., Le(x) (an isomer of Le(a)), Le(y) (an isomer of Le(b)), T, Tn, "A-like"] appearing as "new" antigens on malignant tissue. Their presence and membrane density appears to correlate with the metastatic potential of the tumor. This often parallels loss of normal BGAs (e.g., ABH) from the tissue. Some of these antigens have been shown to influence the humoral and cellular response and have been used in assays to determine preclinical cancer, and in tumor immunotherapy. Interactions of some parasites and bacteria with human cells have been shown to depend on the presence of certain BGAs. P. vivax malarial parasites only enter human RBCs when the Fy6 Duffy blood group protein is present on the RBCs. Certain E. coli will only attach to the epithelial cells of the urinary tract if P or Dr BGAs are present in the epithelial cells. The P antigen is also the RBC receptor for Parvovirus B19. Leb has recently been found to be the receptor for H. pylori in the gastric tissue. The high frequency BGA, AnWj, is the RBC receptor for H. influenzae. BGAs have been shown to be associated closely with some important complement proteins. Ch/Rg BGAs have been found not to be true BGAs but are RBC-bound C4 (C4d). Knops/McCoy/York BGAs have been located on the C3b/C4b receptor (CR1). The high frequency BGAs of the Cromer (Cr) system are located on decay accelerating factor (DAF or CD55). Cartwright (Yt) BGAs are located on RBC acetylcholinesterase molecules. DAF and acetylcholinesterase are on phosphatidylinositol-glycan (PIG) linked proteins. When the PIG anchor is missing from RBCs, as in paroxysmal nocturnal hemoglobinuria, the affected RBCs lack all Cr, Yt, JMH, Hy/Gy, Do and Emm BGAs. The most important ligand for P, E and L selectins is sialyl-Le(x). This interaction is the tethering stage that start the leukocytes' journey from the circulation into the tissue. It appears that malignant cells may move through tissue in a similar way and may explain the close association of Le(x) with metastasis. Thus, there are increasing data suggesting a biological role for BGAs unrelated to the RBC.

Analysis of a heterogeneous group of human breast carcinoma associated glycoproteins bearing the Tn determinant

The Tn determinant (GalNAc alpha-O-Ser/Thr) is expressed by about 90% of human carcinomas, but is cryptic in most normal human tissues. A murine monoclonal antibody (MAb) 83D4, developed following immunization with human breast carcinoma cells, reacts with a Tn-related epitope. In the present study we characterized the glycoprotein antigen identified by 83D4 in the human breast carcinoma cell line MCF-7. We further showed that the 83D4 antigenic determinant is masked in human milk fat globule membranes (HMFGM), and can be exposed upon mild m-periodate treatment after desialylation. Western-blot analysis resolved the 83D4 antigen from MCF-7 into two main components of 120-190 kD and > 500 kD respectively. Non equilibrium pH gradient electrophoresis/SDS PAGE revealed the acidic nature of the reactive glycoproteins (pI 4.43-4.70). 83D4 antigenic activity resolved by CsCl gradient ultracentrifugation layered on a wide range of densities (1.30-1.46 g/ml) including typical densities of mucin-like glycoproteins but also lower densities. The amino acid composition of the antigen, relatively rich in serine but poor in threonine and proline, confirmed the divergence from other mucin-like carcinoma-associated glycoproteins. Dicarboxylic amino acids were abundant, accounting in part for the acidic nature of the molecules. ELISA and Western-blot analysis of the subcellular fractions from MCF-7 cells revealed that the 83D4 antigen is mainly contained in plasma membranes (85%) from which it may be resolved into two broad bands (slow and fast migrating components). These results provide information on a group of breast carcinoma associated glycoproteins related to but different from typical mucins, and provide data on alteration of O-glycosylation in tumor cells.

A successful liver metastasis model in mice with neuraminidase treated colon 26

The aim of this study was to establish a reproducible and quantitative liver metastasis model in mice. The in vitro colon 26 (C-26) cultured cell line was initially taken from an in vivo transplantable C-26 adenocarcinoma tumor mass using the standard enzymatic treatments, collagenase and DNAse. In vitro cultured cells x 10(4) were introduced into the portal vein of syngeneic BALB/c mice to induce liver metastases and, 3 weeks later metastatic foci were found in approximately 50% to 70% of the mice. In contrast, C-26 cells desialylated by neuraminidase (Nase) treatment greatly increased the incidence of hepatic metastases with countable hepatic colonies being found in all mice (100%). This result seems to be related to the liver-characteristic D-galactose receptors, since pre-injection with an excess amount of galactocerebroside completely prevented tumor colonization in the liver. Thus, although we cannot disregard the involvement of other adhesion molecules in this system as yet, our experimental model may become a useful tool for the analysis of hepatic metastases from colon cancer in the future.

Differences in antigen-binding affinity caused by a single amino acid substitution in the variable region of the heavy chain

Site-directed mutagenesis has been used to examine the importance of histidine-99 in the VH CDR3 region of a mouse/human chimeric anti-TAG72 antibody, cB72.3-1-3. The expression vectors mpSV2neo-EP1-V-m4-10C gamma 1, containing seven different mutant VH region fragments (Vm4-10) in association with the immunoglobulin enhancer (E), promoter (P1) and human genomic C gamma 1 region fragments, were transfected into a heavy chain loss mutant cell line B72.3 Mut(K), respectively. Mutant chimeric antibodies cB72.3m4-10 were purified from the transfectant supernates, and their binding affinities for the TAG72 antigen relative to that of the original cB72.3-1-3 antibody were compared. Substitution of histidine-99 by glutamine resulted in a higher affinity antibody (cB72.3m4) whereas substitution by isoleucine resulted in a lower affinity antibody (cB72.3m9). The binding affinity of these mutant antibodies varied nearly eight-fold. It was concluded that the residue at position 99 in the VH CDR3 region is in a 'contact' position in the B72.3/TAG72 antibody-combining site. The polar side-chains of glutamine and asparagine or the ionized side-chains of histidine, arginine or glutamic acid contribute to higher binding affinity, whereas the hydrophobic side-chains of isoleucine, leucine or phenylalanine resulted in a lower binding affinity for the TAG72 antigen.

Tn antigen, a marker of potential for metastasis of uterine cervix cancer cells

BACKGROUND

The expressions of Thomsen-Friedenreich antigen (T-Ag) and Tn antigen (Tn-Ag), precursors of MN blood group antigens, were examined in the tissues of squamous cell carcinoma of the uterine cervix from 111 patients to determine their clinicopathologic significance with regard to the biologic behaviors of cancer cells and the clinical course of the patients.

METHODS

T-Ag and Tn-Ag were measured by the avidin-biotin-peroxidase (ABC) method with peanut (Arachis hypogaea) lectin (PNA) and Vicia villosa agglutinin (VVA), respectively.

RESULTS

Unlike expression of T-Ag, that of Tn-Ag was correlated closely with vascular permeation of cancer cells, their parametrial spread and metastasis to the pelvic lymph nodes, and also with a low 5-year survival rate. No correlation was found between expression of Tn-Ag and other parameters, such as the clinical stage or histologic type. Furthermore, Tn-Ag expression was independent of the degree of cancer involvement in the fibromuscular stroma of the cervix, which seems to be a marker of the aggressiveness of cancer cell proliferation.

CONCLUSIONS

These results indicate that Tn-Ag expression is a useful indicator of the potential for metastatic potential of cancer cells. Thus, a combination of estimations of the degree of cancer involvement in the cervical stroma and Tn-Ag expression seems the most useful for predicting the prognosis of patients with cervical cancer.

The blood group antigen-related glycoepitopes: key structural determinants in immunogenesis and AIDS pathogenesis

This overview will focus on the functional and pathophysiological aspects of blood group antigen (BGA)-related glycodeterminants with regard to immunogenesis and AIDS pathogenesis. It has been postulated that in a broad range of histogenetically different tissues and organs, BGA-related glycoepitopes are expressed on the cell surface at definite stages of cell differentiation. These glycoepitopes are expressed during embryogenesis, organogenesis, tissue repair, regeneration, remodelling and maturation when 'sorting-out' of one homotypic cell population from a heterotypic assemblage of cells occurs (1). In this event, the BGA-related glycoepitopes, if being expressed on the cell surface, play roles of key structural determinants in cell-cell recognition, association and aggregation. This mechanism will be discussed in relation to immunogenesis with regard to antigen presentation, self-non-self discrimination, and positive and negative selection during thymic education. It is postulated that the appearance of BGA-related glycoepitopes on the cell membrane is a consequence of the association of major histocompatibility complex antigens (MHC) and peptides, with the subsequent elimination of cells carrying a high density of BGA-related glycoepitopes on their surface. After human immunodeficiency virus (HIV) glycoproteins are glycosylated by host cell glycosyltransferases, the virus may use the BGA-related glycodeterminants as ligands and/or receptors for expansion to a spectrum of target cells during AIDS development and generalization of the infection throughout the body. We will review the experimental evidence that supports the concept that HIV uses an alternative to the gp120/CD4 ligand/receptor system, and that the alternative mechanism is probably carbohydrate-mediated in nature.

The blood group antigens (BGA)-related glycoepitopes. A key structural determinant in immunogenesis and cancer pathogenesis

This overview has been focused on the functional and pathophysiological aspects of blood group antigens (BGA)-related glycodeterminants. It has been postulated that in a broad range of histogenetically different tissues and organs BGA-related glycoepitopes are expressed on the cell surface at definite stages of cell differentiation during embryogenesis, organogenesis, tissue repair, regeneration, remodeling and maturation when 'sorting-out' behaviour of one homotypic cell population from heterotypic assemblage of cells occurs. In this event the BGA-related glycoepitopes, if being expressed on the cell surface, play a role of key structural determinants in cell-cell recognition, association and aggregation. This mechanisms has been discussed in relation to immunogenesis regarding of antigen presentation, self-non-self discrimination, positive and negative selection during thymic education. It is postulated that the appearance of the BGA-related glycoepitopes on the cell membrane is a consequence of the association of MHC and peptides, with subsequent elimination of cells carring high density of BGA-related glycoepitopes on their surface. In cancer it has been considered as a key mechanism of phenotypic divergence of tumor cells, immunoselection, tumor progression and metastasis.

Simple mucin-type carbohydrates in oral stratified squamous and salivary gland epithelia

Simple mucin-type carbohydrate antigens, T, Tn, and sialosyl-Tn, have been found to be good markers of malignant transformation in several epithelial tissues as a result of incomplete synthesis with precursor accumulation. The T, Tn, and sialosyl-Tn antigens represent the initial, most immature glycosylation of serine and threonine amino acids of proteins. In normal adult cells these structures are generally masked by addition of further saccharides to form more complex structures. We analyzed simple mucin-type carbohydrates in human labial stratified squamous and minor salivary gland epithelia in order to define the glycosylation pattern in normal cells in relation to epithelial differentiation and maturation. A panel of monoclonal antibodies with well-characterized specificity for T, Tn, sialosyl-Tn and the histo-blood group H and A variants hereof were used in immunohistology of sections from 30 individuals with known ABO, Lewis, and secretor status. In stratified epithelium the sialylated T structure was confined to cell membranes of immature basal cells, whereas the H and A variants were observed on cell membranes of more mature parabasal and spinous cell layers. Furthermore, superficial spinous cells produced a fine granular cytoplasmic staining for Tn and sialosyl-Tn antigens. In minor salivary glands mucous cells expressed Tn and sialosyl-Tn as well as the H and A variants in the area of the nucleus, whereas T and the H variant were found in duct cells and unsubstituted T antigen in myoepithelial cells. These results indicate that incomplete synthesis, i.e., deletion of sialyltransferases and/or histo-blood group ABH transferases, may result in accumulation of T, Tn, and sialosyl-Tn antigens in oral epithelia, thus offering a baseline for further studies of changes in premalignant and malignant oral epithelia.

Lectin reactivity of murine fibrosarcoma lines with a different metastatic potential

Lectins are suitable tools for investigating the glycoconjugate characteristics of metastatic cells. In the present study, we investigated whether there were differences between high metastatic T3 cells and a low metastatic isolate in their reactivities to several lectins specific for galactosyl and sialyl groups. Analysis of reactivity of the two cell lines to wheat germ agglutinin revealed a complex pattern. In fact, T3 cells had high-affinity, neuraminidase-resistant as well as low-affinity, neuraminidase-sensitive receptors. Instead, the low metastatic isolate showed only high-affinity receptors, both neuraminidase-resistant and neuraminidase-sensitive The two cell lines reacted similarly to galactose-specific lectins. These findings indicate that sialyl groups, rather than galactosyl groups, affect the metastatic behavior of our cell system.

Carcinoma autoantigens T and Tn and their cleavage products interact with Gal/GalNAc-specific receptors on rat Kupffer cells and hepatocytes

We studied interactions of isolated Thomsen-Friedenreich (T)- and Tn-specific glycoproteins with the Gal/GalNAc-specific receptors on rat Kupffer cells and compared them to those with rat hepatocytes. Immunoreactive T and Tn are specific pancarcinoma epitopes. Electron microscopy of gold-labelled T and Tn antigens revealed their specific binding to Kupffer cells, followed by their uptake via the coated pit/vesicle pathway of receptor-mediated endocytosis. Preincubation of Kupffer cells with GalNAc and GalNAc-BSA, but not GlcNAc or GlcNAc-BSA specifically inhibited binding of the T and Tn glycoproteins. Desialylated, isologous erythrocytes (T RBC) are known to bind to the Gal/GalNAc receptors of rat Kupffer cells and hepatocytes. This attachment was specifically inhibited by T and Tn in a concentration-dependent manner: 50% T RBC-Kupffer cell contacts were inhibited at 8.5.10(-6) mM T and 8.5.10(-5) mM Tn antigen concentrations, respectively. The corresponding figures for hepatocytes were 6.10(-6) mM T and 1.2.10(-6) mM Tn antigen. Amino-terminal cleavage products of the T glycoprotein, possessing clusters terminating in non-reducing Gal/GalNAc, inhibited T RBC binding to Kupffer cells and hepatocytes usually at 10(-2) to 10(-5) mM concentrations, whereas GalNAc, galactose and galactose glycosides inhibited at millimolar concentrations. Galactose-unrelated carbohydrates were inactive at concentrations greater than or equal to 50 mM.

Are pancarcinoma T and Tn differentiation antigens?

Human fetal tissues were studied for presence of immunoreactive Thomsen-Friedenreich (T) and Tn epitopes (EPs) using well-defined anti-T and anti-Tn rodent monoclonal antibodies. T and Tn are universal (pan) carcinoma (CA) markers that are occluded in normal postfetal tissues except in some immunoprivileged enclaves. Immunohistochemical methods using avidin-biotin immunoperoxidase for staining were employed. Tissues between 45 and 117 days after ovulation were studied. In most instances, anti-T and anti-Tn antibodies showed similar immunoreactivity as demonstrated by positive immunohistochemical staining. The most intense staining was in epithelial and mesothelial components; the mesenchyme stained more faintly. All human sera have anti-T and anti-Tn antibodies, stimulated largely by intestinal flora. The presence of immunoreactive T and Tn during an early phase of fetal development, as shown here, and their known absence in noncarcinomatous postfetal tissues suggests that T and Tn, in addition to their association with CA, are stage-specific oncofetal antigens in pretolerogenic differentiation phases.

Tn epitope (N-acetyl-D-galactosamine alpha-O-serine/threonine) density in primary breast carcinoma: a functional predictor of aggressiveness

This interpretive review attempts to dovetail advanced work by different groups of investigators on blood group and carcinoma (CA) glycoconjugates that have terminal, immunoreactive Tn epitopes (GalNAc alpha-O-Ser/Thr), and on the interaction of those structures with complementary antibodies and lectins. Fenlon et al. (1987) and Leathem and Brooks (1987) found a positive correlation between primary breast CA aggressiveness and its affinity for Helix pomatia (HPA) lectin. This phenomenon was used successfully to accurately predict, in studies on 305 breast CA patients, early or late CA recurrence and patient survival time. The innate specificity of the large HPA combining groove (aside from its avid reactivity with appropriately spaced GalNAc alpha-O-) remains obscure, despite careful investigation for more than a decade (Baker et al., 1983). Leathem and Brooks presumed that HPA recognizes a hitherto "undefined biological marker" that indicates a breast CA's aggressiveness. Our own work has shown that the chemically fully defined Tn epitope, as measured with human polyclonal and murine monoclonal anti-Tn antibodies, occurs in immunoreactive form in approximately 90% of all breast and lung adenoCAs studied. Tn is occluded and non-reactive in healthy and non-CA-diseased tissues. We found that CA-associated Tn is an adhesion molecule in attachment to healthy cells; an increase in its density on breast CA cell membranes parallels greater aggressiveness of breast tumors in both humans and mice (the only species studied). Thus, Tn may be all or a major part of the postulated "as yet undefined biological marker" associated with high breast CA aggressiveness. Besides being helpful in the elucidation of some aspects of breast CA pathogenesis, these findings on primary breast CA have clinical implications in that they should facilitate stratification of breast CA patients for adjuvant treatment.

Comparison by leukocyte adherence inhibition of human immune response to cancer-associated immunogens, Thomsen-Friedenreich (T) and Tn, myelin basic protein, and organ-specific cancer neoantigens

Peripheral blood leukocytes from cancer patients exhibit nonadherence to glass as an index of antigen recognition when incubated individually with four distinct, soluble tumor-related substances. Crude cancer extracts, purified antigens, T and Tn, myelin basic protein (MBP), and organ-specific cancer neoantigens (OSN), all elicited narrow dose-dependent leukocyte adherence inhibition (LAI) response curves. The present study focused on the reasons for the narrow antigen dose-LAI response relationship. Between 9 and 20 pmol of antigens elicited the maximum number of nonadherent leukocytes; cleavage products of T antigen and the nonapeptide (T18) of MBP required about a 10-fold increase in molar concentration for the same LAI response. When crude cancer extracts were combined with pure antigen or the pure antigens were combined at concentrations shown to give maximum LAI responses, the positive LAI responses were negated. The chemoattractant LTB4 at 10(-11) M triggered maximum LAI. But when MBP was added with the LTB4 at progressively increasing concentrations, there was dose-dependent negation of LAI. The magnitude of LAI depended on the total amount of mediator released rather than the rate of release. When leukocytes from cancer patients were incubated with optimum to high concentrations of MBP, the supernatants contained a mediator that gave similar bell-shaped dose-LAI responses on control leukocytes indicating that leukocytes from cancer patients react to a much broader range of antigen concentration than indicated by the LAI assay alone. High antigen dose negated LAI because of excess mediator production. Antigen-generated mediators had a biphasic effect inducing nonadherence and then adherence of leukocytes.

Blood group Tn-active macromolecules from human carcinomas and erythrocytes: characterization of and specific reactivity with mono- and poly-clonal anti-Tn antibodies induced by various immunogens

In contrast to healthy and noncarcinoma-diseased tissues, greater than 80% of all carcinomas (CAs) tested express immunoreactive O-(2-acetamido-2-deoxy-alpha-D-galacto-pyranosyl)-(1----3)-serine/threon ine [alpha-D-GalpNAc-(1----3)-Ser/Thr] in their glycoproteins. CA cells shed, into the tumor's environment, Tn, which is involved in cancer pathogenesis as adhesion molecule and as autoimmunogen. An increase in density of Tn on primary CA frequently parallels augmented CA aggressiveness. Tn-Active glycoproteins of culture-grown human breast CA DU 4475 cells were isolated from cytoplasm and from spent growth medium, and erythrocyte (RBC) Tn antigen was prepared by (1----3)-beta-D-galactosidase treatment of isolated human O RBC MN glycoprotein-derived Thomsen-Friedenreich (T) antigen. Immunochemical, serological, physical, and chemical analyses showed close resemblance of CA- and RBC-derived Tn antigens. The preponderant carbohydrate in both Tn glycoproteins is the alpha-D-GalpNAc residue, and the antigens have a qualitatively and quantitatively similar amino acid composition. Highly specific rodent monoclonal (Mo) anti-Tn antibodies (Abs) were elicited with Tn RBC and normal O RBC-derived Tn antigen, and compared with CA-anti-Tn MoAbs unwittingly evoked by others. A sensitive enzyme immunoassay (EIA) with Tn antigen as solid phase was developed. In this system, highly purified, "naturally occurring" anti-Tn antibodies, which all humans possess, were more sensitive in quantitating breast CA Tn structures than the anti-Tn MoAbs induced by Tn RBCs, and by RBC- and CA-derived Tn-active antigens. The sensitivity of anti-Tn MoAbs was higher in detecting RBC-Tn.

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.

Identification and characterization of a murine receptor for galactose-terminated glycoproteins

The asialoglycoprotein receptor, the hepatic binding lectin for galactose-terminated glycoproteins, has been isolated and characterized from human, rabbit and rat liver. Several recent studies have shown the existence of the same receptor in murine liver. However, the biochemical structure of the receptor in murine liver has not been resolved. In this paper, we describe the identification and purification of the receptor for asialoglycoproteins from murine liver. The purified receptor has three polypeptides with apparent molecular weights of 42,000, 45,000 and 51,000, respectively, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Furthermore, our studies suggest that the receptor from murine liver is very similar to its counterpart in rat liver, although some potential interesting differences have also been observed. Initial studies indicate that this receptor is well conserved in different mouse strains.

Inhibition of liver tumor cell colonization in two animal tumor models by lectin blocking with D-galactose or arabinogalactan

Repeated administration of the hepatic lectin blocking agents D-galactose or arabinogalactan completely prevented the settling of metastatic cells of sarcoma L-1 tumor in the liver of Balb/c mice and greatly reduced the colonization process of highly metastatic ESb lymphoma cells of the liver of DBA/2 mice. Therefore, when hepatic lectins were blocked with competitive glycoconjugates, tumor cell colonization of the liver could be prevented in two different model systems.

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.

Endogenous galactoside-binding lectins: a new class of functional tumor cell surface molecules related to metastasis

The formation of secondary tumors by circulating cancer cells (blood-borne metastasis) correlates with an increased tendency of the cells to form emboli by aggregation with other tumor cells or with host cells. Although it is evident that cell-cell recognition and adhesion are mediated by cell surface components, the identity of these molecules is only now being unraveled. Over the last decade an increasing number of studies have demonstrated the presence of endogenous carbohydrate-binding proteins on the surface of various normal cells, and it has been proposed that such lectin-like molecules might be involved in intercellular adhesion. We have shown that various tumor cell lines contain endogenous galactose-specific lectins. Lectin activity was detected at the cell surface by the binding of asialofetuin. This glycoprotein also enhanced the aggregation of the tumor cells. After purification by affinity chromatography on immobilized asialofetuin the lectin activity was associated with two proteins of Mr 14,500 and 34,000. By using polyclonal and monoclonal antilectin antibodies in conjunction with various immunologic techniques we have demonstrated that the endogenous lectins are present on the surface of different tumor cells. Quantitation of cell surface lectins by flow cytometric analyses of antilectin antibody binding revealed that among related tumor cells those exhibiting a higher metastatic potential expressed more lectin on their surface. The binding of monoclonal antilectin antibodies to metastatic cells decreased asialofetuin-induced homotypic aggregation in vitro and suppressed the ability of the cells to form lung metastases after intravenous injection in the tail vein of syngeneic mice. These results strongly implicate the tumor cell surface lectins in cell adhesion and metastasis. We propose that such lectins can increase the ability of tumor cells that enter the blood stream to form aggregates with other tumor cells, or to adhere to host cells or the extracellular matrix and thereby increase their metastatic potential. Other contributing components to tumor cell-host cell interactions are cell surface carbohydrate-binding proteins that have been detected on lymphocytes, platelets, macrophages, hepatocytes, and endothelial cells. These lectin-like molecules might recognize and bind carbohydrates expressed on the surface of tumor cells and enhance emboli formation and organ colonization.

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.