The use of lectins in histopathology

Neuroprotective effects of vitamin C and garlic on glycoconjugates changes of cerebellar cortex in lead-exposed rat offspring

The deteriorating effects of Lead (Pb) on central nervous system (CNS) such as cerebellum has been demonstrated in previous studies. Glycoconjugates with the important role in CNS development may be affected by Pb-exposure. Utilization of antioxidant agents and herbal plants has attracted a great deal of attention on attenuating neurotoxicants-induced damage. Thus, in this study the neuroprotective effects of vitamin C and garlic on content of glycoconjugates of cerebellar cortex in Pb-exposed animals were investigated. Wistar pregnant rats were divided into: control (C), Pb-exposed (Pb) (1500 ppm lead acetate in drinking water), Pb plus vitamin C (Pb + Vit C) (500 mg/kg) intraperitoneally, Pb plus garlic (Pb + G) (1 mL /100 g body weight fresh garlic juice via gavage), Pb plus vitamin C and garlic (Pb + Vit C + G), and sham groups (Sh). Finally, levels of Pb in blood were measured in both rats and offspring on postnatal day 50 (PND50). Also, the cerebellums were removed for measuring Pb-levels and performing lectin histochemistry. Blood and cerebellar Pb-levels were increased in Pb-exposed group compared to control group (P < 0.001), whereas they were decreased significantly in Pb + Vit C, Pb + G, and Pb + Vit C + G groups (P < 0.01). By using MPA, UEA-1, and WGA lectin histochemistry, Pb-exposed group showed weak staining intensity compared to other groups. Besides, significant decrease was observed in the density of lectin-positive neurons of Pb-exposed group compared to the control group (P < 0.001). Moreover, strong staining intensity and high lectin-positive neurons were found in Pb + Vit C, Pb + G and Pb + Vit C + G groups than Pb-exposed group (P < 0.001). The present study revealed that Pb-exposure can result in alteration in the cerebellar glycoconjugates contents and co-administration of vitamin C and garlic could attenuate the adverse effects of Pb. The findings of this study revealed the ameliorating effects of vitamin C and garlic against Pb, suggesting the potential use of vitamin C and garlic as preventive agents in Pb poisoning.

A Descriptive Study of Lectin Histochemistry of the Placenta in Cattle following Inoculation of Neospora caninum

The aim of this study was to describe the lectin-binding pattern in the placentas of cows infected experimentally with Neospora caninum. Four cows were inoculated intravenously with 1 × 10⁸ tachyzoites of the NC-1 strain of N. caninum at 150 ± 7 days of pregnancy. Two control cows were administered a placebo. An indirect fluorescence antibody test (IFAT) was performed on serum samples obtained before and after the inoculation. The cows were killed at 30 and 37 days post inoculation. Samples of placenta were taken for histopathology and lectin histochemistry. Fetal tissues and fluids were collected for histopathology and IFAT, respectively. All infected cows had high antibody titres. All fetuses had characteristic histopathological lesions, including non-suppurative meningoencephalitis, myocarditis, hepatitis and myositis, suggesting N. caninum infection. Only two infected fetuses developed specific antibodies. Mild non-suppurative inflammatory infiltrates were recorded in the placentae. Differences in the lectin-binding pattern were observed between infected animals and controls in the glycocalyx (CON-A and WGA) and apical cytoplasm (RCA-I and CON-A) of the trophoblastic cells; giant trophoblastic cells (CON-A and DBA); glycocalyx (PNA, WGA) and apical cytoplasm (CON-A, WGA, PNA, DBA and RCA-I) of endometrial cells; trophoblast of the interplacentomal region (WGA); endothelium (CON-A, SBA, RCA-1 and WGA); and finally, mesenchyme (CON-A, RCA-1, SBA, PNA and DBA). These findings indicate that there is a distinctive pattern of lectin binding in the placenta of cattle infected with N. caninum. The direct effect of the presence of the protozoa as well as the altered expression of cytokines could explain these changes in the maternofetal interface.

Lectin binding patterns and immunohistochemical antigen detection in placenta and lungs of Brucella abortus-bovine infected fetuses

Lectin binding relies on the affinity of these substances for specific terminal sugars. The method facilitates the identification of complex structures to which the terminal sugar attaches and may reveal physiological or pathological changes in cells, intracellular interactions or extracellular transport pathways. This study was carried out to investigate the effect of infection with Brucella abortus on the pattern of lectin binding in bovine fetal lungs (n=6) and bovine placentas (n=5). Fetal lungs and placenta from heifers experimentally inoculated with B. abortus, strain 2308 were examined by histological, lectin-histochemical, immunohistochemical and cultural techniques. B. abortus antigens were immunohistochemically detected in fetal lungs and placenta. An increase in the labeling with UEA-1, DBA, PNA, RCA-1 and SBA was found in the lungs and an increase in the labeling with UEA-1, ConA, PNA, DBA was found in the placentas. The present lectin histochemical study revealed a distinctive pattern of oligosaccharide distribution in the lungs and placenta of B. abortus-infected fetuses.

Endothelial-like cells derived directly from human tumor xenografts

Tumor-associated endothelial cells (TAECs) harboring various genomic abnormalities have been described in human cancers although their origins remain obscure. We generated 4 human cancer cell lines tagged with multiple markers, grew them as xenografts, and characterized their TAECs. Depending on their tumor of origin, 5-40% of TAECs reproducibly expressed all tags. Tagged TAECs (tTAECS) were morphologically, immunologically and functionally similar, although not identical, to normal endothelial cells (ECs) and contained only human chromosomes. tTAECs underwent a senescent-like proliferative arrest after several in vitro passages, but could be immortalized by telomerase, thus allowing us to show that the retention of the EC phenotype was of long-term duration. In contrast, nonimmortalized tTAECs could be propagated in vivo where they incorporated into the tumor neo-vasculature. Although consistent with previous reports that some tumor cells may undergo "vasculogenic mimicry" (VM), the tumor-derived endothelial-like cells described here appear distinctly different. Moreover, their properties and behaviors are more durable than expected for cells undergoing VM, are not the result of fusions between ECs and tumor cells, and are cell autonomous. These findings could have significant implications for therapies that target tumor angiogenesis.

Lectins from the Red Marine Algal Species Bryothamnion seaforthii and Bryothamnion triquetrum as Tools to Differentiate Human Colon Carcinoma Cells

The carbohydrate-binding activity of the algal lectins from the closely related red marine algal species Bryothamnion triquetrum (BTL) and Bryothamnion seaforthii (BSL) was used to differentiate human colon carcinoma cell variants with respect to their cell membrane glyco-receptors. These lectins interacted with the cells tested in a dose-dependent manner. Moreover, the fluorescence spectra of both lectins clearly differentiated the cells used as shown by FACS profiles. Furthermore, as observed by confocal microscopy, BTL and BSL bound to cell surface glycoproteins underwent intense internalization, which makes them possible tools in targeting strategies.

Significance of a galactose specific plant lectin for the differential diagnosis of adenocarcinoma cells in effusion

Background:

Distinguishing adenocarcinoma cells from reactively proliferated mesothelial cells and macrophages is one of the greatest challenges in the cytodiagnosis of effusions. Aberrant glycosylation of cell surface glycoconjugates is emblematic to malignancy, and lectins being an important class of probes to demonstrate these aberrations, lectin cytochemistry is of great interest to differentiate adenocarcinoma cells from reactive mesothelial cells.

Aim:

The present study analyzed the potential of a plant lectin to distinguish malignant cells from reactive mesothelial cells and macrophages.

Materials and Methods:

Snake gourd lectin (SGL) was isolated, purified and conjugated to horse radish peroxidase (HRP) and incubated with the cells of benign (46) as well as malignant (39) effusions using the standard immunocytochemical method with diaminobenzidine as the chromogen. The lectin-bound areas were quantitatively assessed as mild, moderate and intense binding.

Statistical Analysis:

The mean score for benign and malignant effusions were statistically analyzed. Student's ‘t’-test was performed to assess the significance.

Results:

The lectin HRP complex bind to the cytoplasm of benign and malignant cells as well as macrophages. A significantly higher score for intense binding (P = 0.001) was found to differentiate malignant cells from reactive mesothelial cells. Macrophages showed intense irregular binding.

Conclusions:

SGL binding assay can play a role in the differential diagnosis of metastatic adenocarcinoma in effusions.

Expression pattern of glycoconjugates in the integument of Bufo ictericus (Anuran, Bufonidae): Biochemical and histochemical (lectin) profiles

Mucous consists of glycoproteins and proteoglycans produced by specific secretory cells (mucocytes). In anurans the cutaneous mucous is produced by intradermal glands and displays both mechanical and chemical protection functions. Indeed, mucous maintains the integument moist and facilitates gas exchange (cutaneous respiration). In this work, the carbohydrate moiety distribution was investigated in the integument of Bufo ictericus using conventional and lectin histochemistry to describe the pattern of cutaneous glycoconjugate expression, including both secretory and structural proteoglycans. As a preliminary step, the descendent chromatography in Whatmann 1MM paper was undertaken to prepare the histochemical trials involving the lectins. In B. ictericus, the integument exhibits the basic morphological structure found in lower terrestrial vertebrates: the epidermis is a keratinized squamous stratified epithelium supported by spongious and compact layers. The spongy dermis contain secretory portion of both mucous and serous (or poison) glands. The paper chromatography identified galactose, fucose and mannose as characteristic sugar residues. The secretory cells of the mucous gland in the dermis, as well as the interstice between the stratum corneum and the subjacent stratum spinosum in the epidermis exhibit alpha-l-fucose and alpha-galactose residues. The serous glands give no reaction. The alpha-mannose residue was detected in the extracellular matrix of spongious dermis, but not in the dermal glands. The different glycoconjugate location reflects in two glycoconjugates categories: the secretory which participate in the water flow regulation, and the structural which is involved in the dermal maintenance.

Pattern expression of glycan residues in AZT-treated K562 cells analyzed by lectin cytochemistry

The present paper shows that human chronic myeloid (K562) cells exposed 3 h to 20 microM 3'-azido-3'-deoxythymidine (AZT) exhibit marked variations of the oligosaccharide moiety of glycoconjugates. These changes were analyzed by confocal fluorescence microscopy, upon incubation of control and AZT-treated cells with biotin-lectin conjugates to visualize cell surface glycans or total glycans after cells permeabilization. In addition, cell fluorescence distribution of the biotinylated lectins, localized with streptavidin conjugates labeled with Alexa Fluor 488, was analyzed by flow cytometry. The results obtained show significant variations on the expression/distribution of membrane surface glycans as detected by both WGA and SNA, two lectins that recognize primarily cellular internal membrane glycolipids. A further interesting result was the significant increase of N-acetylglucosamine linked glycans localized either at the cell surface or intracellularly but only in K562 cells exposed to AZT. On the whole, our data demonstrate that AZT alters both lipid and N-linked glycosylations thus confirming previous observations, from our laboratory and from other Authors, that the drug impair the nucleotide-sugar import in the Golgi's lumen. AZT does also alter the O-linked glycosylations that occur in the Golgi complex since these reactions require the incorporation of sialic acid, GlcNAc and GalNAc all of which are sensitive to the drug.

Expression pattern of glycoconjugates in the Bidderian and ovarian follicles of the Brazilian toad Bufo ictericus analyzed by lectin histochemistry

The Bidder's organ and ovary of the Brazilian toad Bufo ictericus were studied by light microscopy, using hematoxylin-eosin (HE) and periodic acid Schiff (PAS) staining. The expression and distribution of carbohydrate moieties was analyzed by lectin histochemistry, using 8 lectins with different carbohydrate specificities: Ulex europaeus (UEA I), Lens culinaris (LCA), Erythrina cristagalli (ECA), Arachis hypogaea (PNA), Ricinus communis (RCA I), Aleuria aurantia (AAA), Triticum vulgaris (WGA), and Glycine maximum (SBA). The results showed that the Bidderian zona pellucida presented alpha-mannose, alpha-L-fucose, beta-D-galactose, N-acetyl-D-glucosamine, and alpha/beta-N-acetyl-galactosamine residues. The Bidderian follicular cells showed the presence of beta-D-galactose and N-acetyl-D-glucosamine. In the extracellular matrix, alpha-mannose and alpha/beta-N-acetyl-galactosamine residues were detected. The ovarian zona pellucida showed alpha-L-fucose, N-acetyl-D-glucosamine, alpha/beta-N-acetyl-galactosamine residues, and alpha-mannose and N-acetyl-D-glucosamine residues were detected in the follicular cells. Thus, the zona pellucida in both organs contains N-acetyl-D-glucosamine, and alpha/beta-N-acetyl-galactosamine residues. alpha-L-fucose residues were detected in the zona pellucida of both organs, using different lectins. Considering that beta-D-galactose residue was absent from ovary but present in the Bidder's organ, this sugar residue may play an important role in follicle development, blocking the Bidderian follicles and preventing further development of the Bidder's organ into a functional ovary.

Tumor galectinology: insights into the complex network of a family of endogenous lectins

Beta-Galactosides of cell surface glycoconjugates are docking sites for endogenous lectins of the galectin family. In cancer cells, primarily galectins-1 and -3 have been studied to date. With the emergence of insights into their role in growth control, resistance to or induction of apoptosis and invasive behavior the notion is supported that they can be considered as functional tumor markers. In principle, the same might hold true for the other members of the galectin family. But their expression in tumors has hitherto been a subject of attention only to a very limited extent. Pursuing our concept to define the complexity of the galectin network in cancer cells and the degree of functional overlap/divergence with diagnostic/therapeutic implications, we have introduced comprehensive RT-PCR monitoring to map their galectin gene expression. The data on so far less appreciated galectins in this context such as galectins-4 and -8 vindicate this approach. They, too, attach value to extend the immunohistochemical panel accordingly. Our initial histopathological and cell biological studies, for example on colon cancer progression, prove the merit of this procedure. Aside from the detection of gene expression profiles by RT-PCR, the detailed molecular biological monitoring yielded further important information. We describe different levels of regulation of galectin production in colon cancer cells in the cases of the tandem-repeat-type galectins-8 and -9. Isoforms for them are present with insertions into the peptide linker sequence attributed to alternative splicing. Furthermore, variants with distinct amino acid substitutions (galectin-8, Po66-CBP, PCTA-1, CocaI/II and galectin-9/ecalectin) and generation of multiple mRNA species, notably those coding for truncated galectin-8 and -9 versions with only one lectin site, justify to portray these two family members not as distinct individuals but as groups. In aggregate, the ongoing work to thoroughly chart the galectin network and to disentangle the individual functional contributions is expected to make its mark on our understanding of the malignant phenotype in certain tumor types.

Plant lectins: occurrence, biochemistry, functions and applications

Growing insights into the many roles of glycoconjugates in biorecognition as ligands for lectins indicates a need to compare plant and animal lectins. Furthermore, the popularity of plant lectins as laboratory tools for glycan detection and characterization is an incentive to start this review with a brief introduction to landmarks in the history of lectinology. Based on carbohydrate recognition by lectins, initially described for concanavalin A in 1936, the chemical nature of the ABH-blood group system was unraveled, which was a key factor in introducing the term lectin in 1954. How these versatile probes are produced in plants and how they are swiftly and efficiently purified are outlined, and insights into the diversity of plant lectin structures are also given. The current status of understanding their functions calls for dividing them into external activities, such as harmful effects on aggressors, and internal roles, for example in the transport and assembly of appropriate ligands, or in the targeting of enzymatic activities. As stated above, attention is given to intriguing parallels in structural/functional aspects of plant and animal lectins as well as to explaining caveats and concerns regarding their application in crop protection or in tumor therapy by immunomodulation. Integrating the research from these two lectin superfamilies, the concepts are discussed on the role of information-bearing glycan epitopes and functional consequences of lectin binding as translation of the sugar code (functional glycomics).

Glycohistochemistry: the why and how of detection and localization of endogenous lectins

The central dogma of molecular biology limits the downstream flow of genetic information to proteins. Progress from the last two decades of research on cellular glycoconjugates justifies adding the enzymatic production of glycan antennae with information-bearing determinants to this famous and basic pathway. An impressive variety of regulatory processes including cell growth and apoptosis, folding and routing of glycoproteins and cell adhesion/migration have been unravelled and found to be mediated or modulated by specific protein (lectin)-carbohydrate interactions. The conclusion has emerged that it would have meant missing manifold opportunities not to recruit the sugar code to cellular information transfer. Currently, the potential for medical applications in anti-adhesion therapy or drug targeting is one of the major driving forces fuelling progress in glycosciences. In histochemistry, this concept has prompted the introduction of carrier-immobilized carbohydrate ligands (neoglycoconjugates) to visualize the cells' capacity to be engaged in oligosaccharide recognition. After their isolation these tissue lectins will be tested for ligand analysis. Since fine specificities of different lectins can differ despite identical monosaccharide binding, the tissue lectins will eventually replace plant agglutinins to move from glycan profiling and localization to functional considerations. Namely, these two marker types, i.e. neoglycoconjugates and tissue lectins, track down accessible binding sites with relevance for involvement in interactions in situ. The documented interplay of synthetic organic chemistry and biochemistry with cyto- and histochemistry nourishes the optimism that the application of this set of innovative custom-prepared tools will provide important insights into the ways in which glycans can act as hardware in transmitting information during normal tissue development and pathological situations.

Cepaea hortensis agglutinin-I, specific for O-glycosidically linked sialic acids, selectively labels endothelial cells of distinct vascular beds

The lectin Cepaea hortensis agglutinin-I (CHA-I) binds to O-glycosidically linked sialic acids with previously characterized specificity. Employing histochemistry, we demonstrate that CHA-I is a useful probe for detecting sialic acids in formalin-fixed human tissues in a specific manner. It stains the endothelium of arteries and veins in all tissues examined, and labels the capillaries in distinct vascular beds including the brain, colon, thyroid, pituitary, and adrenal. By contrast, the endothelial sinusoids in the liver, spleen, and bone marrow remained unstained. The staining pattern of CHA-I overlaps with the distribution of the sialomucin and L-selectin ligand podocalyxin, which includes positivity of podocytes and interstitial but not glomerular capillaries. CHA-I-positive epithelial structures were found in the lung, liver and kidney. Colon carcinoma cells were labelled with CHA-I but not haemangiosarcomas. In summary, CHA-I is a useful tool for detecting O-glycosidically linked sialic acids in formalin-fixed tissues, and a potentially powerful tool for the isolation and characterization of unknown sialomucins in normal and eventually in diseased tissues.

Lectin histochemistry of laryngeal squamous cell carcinomas

A panel of five biotinylated lectins was applied to study the presence and distribution of membrane carbohydrate residues in the normal laryngeal epithelium and in laryngeal squamous cell carcinomas (SCCs) of 86 patients with the avidin-biotin peroxidase complex technique. The lectin-binding pattern of well-differentiated SCCs was comparable to that of the spinous cells of the normal laryngeal epithelium. In the less differentiated SCCs, staining of the keratinocyte plasma membrane with lectins was either reduced or absent, indicating a decline in the glycosylation of cell surface glycoconjugates. The lectins applied here could be used in the rapid assessment of less-differentiated areas within a laryngeal SCC, but they cannot be regarded as reliable markers of laryngeal keratinocytes undergoing malignant transformation.

An IgG monoclonal antibody against Dictyostelium discoideum glycoproteins specifically recognizes Fucalpha1,6GlcNAcbeta in the core of N-linked glycans. Localized expression of core-fucosylated glycoconjugates in human tissues

Core fucosylation of N-linked oligosaccharides (GlcNAcbeta1, 4(Fucalpha1,6)GlcNAcbeta1-Asn) is a common modification in animal glycans, but little is known about the distribution of core-fucosylated glycoproteins in mammalian tissues. Two monoclonal antibodies, CAB2 and CAB4, previously raised against carbohydrate epitopes of Dictyostelium discoideum glycoproteins (Crandall, I. E. and Newell, P. C. (1989) Development 107, 87-94), specifically recognize fucose residues in alpha1,6-linkage to the asparagine-bound GlcNAc of N-linked oligosaccharides. These IgG3 antibodies do not cross-react with glycoproteins containing alpha-fucoses in other linkages commonly seen in N- or O-linked sugar chains. CAB4 recognizes core alpha1,6 fucose regardless of terminal sugars, branching pattern, sialic acid linkage, or polylactosamine substitution. This contrasts to lentil and pea lectins that recognize a similar epitope in only a subset of these structures. Additional GlcNAc residues found in the core of N-glycans from dominant Chinese hamster ovary cell mutants LEC14 and LEC18 progressively decrease binding. These antibodies show that many proteins in human tissues are core-fucosylated, but their expression is localized to skin keratinocytes, vascular and visceral smooth muscle cells, epithelia, and some extracellular matrix-like material surrounding subpopulations of lymphocytes. The availability of these antibodies now allows for an extended investigation of core fucose epitope expression in development and malignancy and in genetically manipulated mice.

Is the binding of the lectin Helix pomatia agglutinin (HPA) of prognostic relevance in tumours of the upper aerodigestive tract?

The lectin Helix pomatia agglutinin (HPA) has been used as a prognostic indicator in a number of clinical studies including those of breast, colorectal and gastric cancer. Binding of HPA to tissue sections was associated with a bad prognosis indicating that the carbohydrate residue recognized by this lectin is linked to metastasis. In order to investigate whether HPA binding is also of prognostic relevance in squamous cell carcinomas of the upper aerodigestive tract, 53 tumours of this region were stained with HPA. Almost all tumours (95%) bound HPA to various degrees and hence HPA binding is of no prognostic relevance in this group of tumours. These findings indicate a fundamental difference in the role of carbohydrate residues in metastasis between squamous cell carcinoma (as in our study) and in tumours derived from glandular tissues such as breast, colon and stomach.

Ulex Europeus Agglutinin (UEA-I) lectin binding in breast carcinoma and its relationship to prognostic factors

In this study, lectin binding was compared with pathological prognostic factors and clinical follow-up details. Formalin-fixed, paraffin-embedded tissues from 43 cases of breast carcinoma were studied for binding with Ulex Europeus Agglutinin (UEA-I) lectin. Staining results were compared with tumor size, histologic and nuclear grade, lymph node status (number, capsular and pericapsular invasion), blood and lymphatic vessel invasion, ER and PR status, clinical stage and the patients' short-term follow-up details. Analysis of staining with UEA-I showed a significant relationship with blood vessel invasion (P < 0.01) and lymphatic vessel invasion (P < 0.05). Furthermore, PR showed a significant inverse correlation with lectin binding (P < 0.05). Staining with UEA-I related significantly with axilliary lymph node metastases (P < 0.05). UEA-I was positive in four (66.6%) out of six cases with distant organ mestastasis. This study confirms that, in breast cancer, lectin binding to the cancer cells can be a reliable indicator for axilliary metastases, and the need for additional therapeutic interventions.

Characterization of the binding specificity of Anguilla anguilla agglutinin (AAA) in comparison to Ulex europaeus agglutinin I (UEA-I)

Using immunochemical and immunohistochemical methods, the binding site of Anguilla anguilla agglutinin (AAA) was characterized and compared with the related fucose-specific lectin from Ulex europaeus (UEA-I). In solid-phase enzyme-linked immunoassays, the two lectins recognized Fuc alpha 1-2Gal beta-HSA. AAA additionally cross-reacted with neoglycolipids bearing lacto-N-fucopentaose (LNFP) I [H type 1] and II [Le(a)] and lactodifucotetraose (LDFT) as glycan moieties. UEA-I, on the other hand, bound to a LDFT-derived neoglycolipid but not to the other neoglycolipids tested. Binding of AAA to gastric mucin was competitively neutralized by Le(a)-specific monoclonal antibodies. UEA-I binding, on the other hand, was reduced after co-incubation with H type 2- and Le(y)-specific monoclonal antibodies. According to our results, AAA reacts with fucosylated type 1 chain antigens, whereas UEA-I binds only to the alpha 1-2-fucosylated LDFT-derived neoglycolipid. In immunohistochemical studies, the reactivity of AAA and UEA-I in normal pyloric mucosa from individuals with known Lewis and secretor status was analysed. AAA showed a broad reaction in the superficial pyloric mucosa from secretors and non-secretors, but AAA reactivity was more pronounced in Le(a+b-) individuals. On the other hand, UEA-I stained the superficial pyloric mucosa only from secretor individuals. A staining of deep mucous glands by the lectins was found in all specimens. Both reacted with most human carcinomas of different origin. Slight differences in their binding pattern were observed and may be explained by the different fine-specificities of the lectins.

Differential expression of jackfruit-lectin-specific glycoconjugates in metastatic adenocarcinoma and reactive mesothelial cells-a diagnostic aid in effusion cytology

Distinguishing reactive mesothelial cells from adenocarcinoma cells in serous effusions on the basis of morphological criteria alone is often difficult. Interest has therefore been focused on identifying reliable methods to supplement the conventional cytological techniques. Plant lectins have been reported as diagnostic markers for malignant cells. We studied 51 aspirated samples of benign and malignant effusions using horseradish-peroxidase-conjugated jackfruit lectin. No significant difference was observed between the cells of pleural and peritoneal fluids. The reactively proliferated mesothelial cells of benign effusions showed a predominance of mild staining while moderate and intense staining was predominant in malignant effusions. Intense and irregular lectin binding was observed in macrophages irrespective of the cause of effusion. The lectin staining method therefore appears to have some clinical significance as an additional diagnostic aid for use in effusion cytology.

Use of lectins as diagnostic and therapeutic tools for cancer

Within the past few years, lectins have become a well-established means for understanding varied aspects of cancer and metastasis. Evidence is now emerging that lectins are dynamic contributors to tumor cell recognition (surface markers), cell adhesion and localization, signal transduction across membranes, mitogenic stimulation, augmentation of host immune defense, cytotoxicity, and apoptosis. To advance understanding of these lectin-dependent processes, attempts are being made to discover new lectins that have one or more of these functions and to develop lectin- (or glycoconjugate-) based tools that could be used to home in on tumor cells. This review will summarize current research on the lectins and recent advances in the development of lectin-based diagnostic and therapeutic tools for cancer. Additionally, the future potential of lectin-based diagnosis and therapy is discussed.

Lectin binding pattern in normal human labial mucosa

The pattern of lectin binding in normal human labial mucosa was examined by light and electron microscopy using eight different lectins (ConA, LCA, WGA, UEA-1, RCA-1, SBA, DBA and PNA) and compared with the patterns in normal human skin and oesophageal mucosa. As seen by light microscopy, ConA, LCA, and WGA stained cell membranes in all layers of the mucosae. RCA-1 stained the plasma membrane of cells in the basal and middle layers, whereas cells in the superficial layers showed little positive staining. UEA-1, SBA, and PNA stained the cells in the middle layers weakly in some cases. No positive staining for DBA was seen. By electron microscopy, reaction product indicating ConA-binding sites was observed in the plasma membrane, cisternae of the endoplasmic reticulum, nuclear envelope and the Golgi apparatus. Binding of LCA, WGA, and RCA-1 was observed in the plasma membrane. These results show that the binding pattern of PNA, SBA, and RCA-1 in labial mucosa is different from that in the normal skin or oesophageal mucosa, although the labial mucosal epithelium, epidermis, and oesophageal epithelium are all stratified squamous epithelia. These differences in the cell-surface sugar residues are likely to be related to the possible functional differences in these tissues.

Bauhinia purpurea (BPA) binding to normal and neoplastic thyroid glands

Biotinylated bauhinia purpurea agglutinin (BPA) was studied, using the ABC method, in different thyroid gland conditions (26 follicular adenomas, 39 papillary carcinomas, 15 follicular carcinomas, and 10 normal thyroids), to determine whether specific lectin binding patterns were developed during malignant transformation that could enable the distinction of carcinoma from adenoma. In normal thyroids, BPA was very rarely and faintly reactive with follicular cells. In neoplastic conditions, BPA binding profiles for follicular adenoma were essentially identical to those of normal follicles, whereas BPA unequivocally reacted with follicular carcinoma and papillary carcinoma. BPA reacted more strongly with cells of papillary structures than with those forming solid nests and follicles. In papillary carcinoma, BPA binding was observed mostly in the apical surface and cytoplasm of carcinoma cells, whereas a diffuse cytoplasmic binding pattern was predominant in follicular carcinoma. Neuraminidase treatment had little or no effect on either normal or adenomatous follicular epithelium, whereas in follicular carcinoma, the number of positive cells and the staining intensity was increased. These findings suggest that BPA would be useful for the differential diagnosis of papillary and follicular carcinomas, and less consistently so, for differentiating follicular carcinoma from follicular adenoma. Peanut agglutinin with similar sugar specificity was not reactive with follicular cells either in normal or neoplastic glands.

Expression of galactoside-specific endogenous lectins and their ligands in human oral squamous cell carcinoma

Human endogenous lectins have a wide spectrum of biological functions. The present study analyses the expression of beta-galactoside specific and N-acetyl-D-galactosamine specific endogenous lectins in oral squamous cell carcinomas using biotinylated neoglycoproteins. The expression pattern of beta-galactosyl-containing glycoconjugates or ligands of beta-galactoside specific lectins in these tissues was also studied using an endogenous biotinylated lectin, the human 14-kDa lectin. For comparison a galactoside specific plant lectin from mistletoe, Viscum album was also employed. The results demonstrate that oral squamous cell carcinomas mainly express accessible binding sites for lactosylated neoglycoprotein (90%) while few carcinomas expressed mild amount of N-acetyl-D-galactosamine specific binding sites (40%). There was no difference in the binding patterns of these probes between well and less differentiated carcinomas. Expression of these neoglycoprotein binding sites were mostly concentrated in immature basaloid cells, indicating a possible association with cell proliferation. The binding pattern of D-galactosyl specific lectins (human 14-kDa and mistletoe lectins) showed conspicuous differences. This feature emphasizes the caution that needs to be exercised in interpreting the biological significance of results attained using plant lectins on human tissue.

Distribution patterns in glycoconjugate expression during the development of the rat palate

The distribution of complex carbohydrate structures during the embryonic development of the rat palate was analysed by examining lectin-binding patterns in serial paraffin and cryostat sections. With few exceptions, the binding patterns showed a general increase in lectin receptors in the more developed stages of palatogenesis. High mannose oligosaccharides were especially amplified during development. Terminal fucose molecules were not expressed. In contrast, terminal sialic acid molecules were ubiquitously distributed in epithelial and mesenchymal tissues. Non-sialylated terminal N-acetylglucosamine was specifically restricted to evolving bone matrix. Before palatal fusion, quantitative but not qualitative differences were detected between oral, nasal, and medial-edge epithelial surfaces. The only exception was LCA, which specifically marked epithelial cells at the tip of palatal shelves. A very selective affinity for Jacalin was demonstrated in the oral epithelium of the palate after day 16, suggesting the presence of sialylated terminal galactose-(beta-1,3)-N-acetylgalactosamine. PNA specifically marked the basal lamina of the oral side of palatal processes. The binding patterns of DBA, GSL IA, SBA, and VVA indicated that the epithelium of the tongue is characterized by terminal alpha- and beta-galactose residues, whereas palatine cells possess only molecules with beta-anomery. During palatogenesis, glycosaminoglycans patterns were significantly modified. Our data suggest that alteration of complex carbohydrate structures may play a central role in modulating cell-cell and cell-matrix interactions. The significance of these findings, however, remains to be elucidated.

Cell type-dependent alterations of binding of synthetic blood group antigen-related oligosaccharides in lung cancer

Blood group antigen-related oligosaccharides have been implicated in growth regulation, cell mobility control and adhesion; we are therefore interested in the localization of receptors for these oligosaccharides in tumour cells. Labelled neoglycoconjugates that carry synthetic sugar structures are suitable tools to determine: whether such binding sites are present in human lung cancer; whether structural alterations of the glycoligand part will affect extent of binding; and whether cell type-associated alterations can be detected. Sections from 121 cases of lung cancer, representing small cell and non-small cell lung carcinoma, mesothelioma and metastases from extrapulmonary primary carcinomas were used to study the binding of nine synthetic AH- and Le-related oligosaccharides. Probes with fucose-alpha 1-3/4-N-acetylglucosamine-beta 1-R, an A-like disaccharide and 3'-sulfated galactose as ligand appear to bind less well to small cell than to non-small cell lung cancer cases, whereas Lec-disaccharide distinguishes mesothelioma from metastatic carcinoma. The latter ligand, A-like disaccharide and H (type III)-like trisaccharide exhibit evident cell type-associated differences in extent of binding. Thus, tailor-made neoglycoconjugates constitute a promising class of histopathological tools that warrants further study.

Jack fruit lectin-specific glycoconjugate expression during the progression of cervical intraepithelial neoplasia: a study on exfoliated cells

The expression of glycoconjugates specific to Jack fruit lectin (JFL) was studied in the exfoliated squamous cells of different grades of intraepithelial and invasive neoplasia of the uterine cervix. It was observed that while normal cells showed almost negative binding, the lectin binding percentage of squamous cells significantly increased with increasing atypia of the epithelium. Correlation analysis between different groups revealed that mild lectin binding in cells had a negative correlation and intense binding had a positive correlation with various stages of tumor progression. These results indicate that the number of cells with aberrant expression of glycoconjugates increases as neoplastic transformation advances. The percentage of labeled and unlabeled cells also shows a continuous transition from low to severe grades of cervical intraepithelial neoplasia and invasive carcinomas. The present study therefore shows that JFL may be used as a probe for further elaboration of detection and grading of precancerous and cancerous lesions of the uterine cervix.

Purification and characterization of a sialic acid-specific lectin from Tritrichomonas mobilensis

New sialic acid-specific lectin has been isolated from culture supernatant of the protozoan Tritrichomonas mobilensis. It was purified by adsorption by erythrocytes or bovine submaxillary gland mucin (BSM)-Sepharose affinity chromatography. The T. mobilensis lectin (TML) does not require bivalent cations for activity and agglutinates all human erythrocytes. The lectin forms multimeric complexes with molecular mass 556 and 491 kDa as determined by size-exclusion chromatography. SDS/PAGE under reducing conditions disclosed a large band of 343 kDa and three bands of 246, 265 and 286 kDa which, after denaturation with urea, were split into three subunits of 56, 61 and 66 kDa; under non-reducing conditions there were two bands, of 360 and 260 kDa. Western blots performed with anti-TML monoclonal antibodies revealed bands identical with those in the silver-stained gels, suggesting homogeneity of the BSM -Sepharose-purified lectin. TML is a highly glycosylated protein with approx. 8% of N-linked glycosides found by protein-N-glycanase F treatment; the total amount of saccharides revealed by chemical deglycosylation was 20%. Haemagglutination-inhibition studies documented exclusive specificity for sialic acid (NeuAc). Both (alpha 2-->6)- and (alpha 2-->3)-linked and free NeuAc were eight times more potent inhibitors than N-glycolylneuraminic acid. The lectin does not require O-acetyl groups on NeuAc for recognition. A spectrum of mono- and oligo-saccharides other than sialic acid had no inhibitory effect at 200 mM. Anti-TML monoclonal antibodies strongly inhibited the lectin activity. TML was stable at temperatures below 4 degrees C and lyophilized with 3% (w/w) glycerol.

Expression of lectin-specific cellular glycoconjugates during oral carcinogenesis

The binding pattern of two lectins, concanavalin A (ConA) and peanut agglutin (PNA), in various phases of tumour progression in the oral epithelium was studied. These included non-dysplastic, dysplastic and neoplastic lesions as well as normal tissue. ConA and PNA showed intense staining in the basement membrane of all types of lesions. Little difference was observed in the staining patterns between different stages of oral carcinogenesis, either with ConA or PNA. ConA showed mild cytoplasmic and membrane staining in all types of lesions while PNA showed moderate to intense staining in both the cytoplasm and membrane of lower-layer cells in all histological groups. The present study therefore shows that these lectins have limited value in the elucidation of oral carcinogenesis and are of insignificant diagnostic value.

Analysis of lectin binding sites in the gut of hooded Lister rats with special emphasis on recently detected lectins

Seven recently isolated lectins were tested for their ability to bind to tissue sections of rat gut. Binding sites for N-Acetylgalactosamine specific lectins were found in mucins, in the brush border membrane and in goblet cells. Non-reducing terminal mannose residues were absent from cell surface membranes but were detected in the supranuclear region of goblet cells and enterocytes. The results of lectin binding obtained in this study were generally similar to lectin-gut interactions observed in vivo.

Laryngeal hyperplastic lesions, follow-up study and application of lectins and anticytokeratins for their evaluation

A retrospective study of 878 biopsy specimens from 692 patients with laryngeal hyperplastic aberrations was performed according to the Kambic-Lenart classification. Special attention was focused on 88 patients with persistent or recurring disease. In these carcinoma developed in 17 (2.4%) patients, 12 (1.7%) of whom had had atypical hyperplasia. We therefore propose that the term precancerosis, which so definitely implies cancer, should be replaced with the expression risky epithelium where nothing is determined in advance, but a careful follow-up of the patients is imperative. In particular cases of laryngeal hyperplastic lesions, mainly in abnormal and in atypical hyperplasias when the tissue specimens are cut tangentially, the exact identification and position of individual epithelial cells is essential. In such cases histochemical and immunohistochemical methods yield more precise evaluation. Lectins and cytokeratins provide good markers of epithelial maturation. These results contribute to a more useful evaluation of laryngeal hyperplastic lesions, crucial for the choice of adequate therapy.

Lectin-binding profiles for normal skin appendages and their tumors

A histochemical investigation of lectin-binding sites was carried out on formalin-fixed paraffin-embedded sections of 60 skin appendage tumors and adjacent normal skin appendages, using four different biotinylated lectins, peanut agglutinin (PNA), Dolichos biflorus agglutinin (DBA), soybean agglutinin (SBA), and Ulex europaeus agglutinin-1 (UEA-1), and avidin-biotin-horseradish peroxidase labeling. In the secretory segments of eccrine sweat glands, the superficial dark cells showed strong cytoplasmic staining with UEA-1, whereas DBA and SBA strongly stained the plasma membranes of basal clear cells. The acinar cells of apocrine sweat glands revealed sporadic apical membrane staining with all four lectins. In some cases, the luminal membranes of sweat gland ducts showed apical membranous staining with all four lectins. In the hair follicles, the inner root sheath was positive for all four lectins, and the outer root sheath was stained by PNA. The sebaceous ducts, as well as the outer root sheath at the level of sebaceous duct insertion, were also labeled by all four lectins. Sebaceous lobules showed cytoplasmic and membrane staining of mature sebocytes with PNA and SBA. Although sweat gland tumors revealed differences in lectin binding when compared to their corresponding normal tissues, the lectin-binding pattern of pilosebaceous tumors was analogous to the pilosebaceous apparatus.

Mucoid cytoplasmic inclusions in urothelial carcinomas

To date, mucoid cytoplasmic inclusions in urothelial carcinomas have rarely been noted. However, we were impressed by the fact that these corpuscles are readily detectable in numerous urothelial neoplasms. Therefore, a histologic analysis of 100 cases of urothelial carcinomas was performed. Overall, 37 cases revealed periodic acid-Schiff-positive cytoplasmic inclusions. These were observed in 14% of grade 1, 49% of grade 2, and 63% of grade 3 carcinomas. The inclusions were histochemically, immunohistochemically, and ultrastructurally identified as cytoplasmic deposits of mucoid materials. Two types of deposits, condensed and noncondensed, could be distinguished. The demonstration of mucoid deposits in otherwise poorly differentiated metastatic carcinomas may be of some differential diagnostic importance insofar as urothelial carcinoma has to be considered as the possible primary tumor.

Lectin-binding carbohydrates in sexual differentiation of rat male and female gonads

Development and sexual differentiation of the mammalian gonad involve changes in the type and distribution of different proteins and glycoproteins in and around the epithelial gonadal cords, the future seminiferous tubules in the testis, and follicles in the ovary. To study changes in cellular carbohydrate-containing compounds in the sex-specific morphogenesis of rat gonads, sections from embryonic, fetal and early postnatal gonads were labelled with seven different fluorescein isothiocyanate (FITC)-conjugated plant lectins of various carbohydrate-binding specificities. Double labelling of laminin with tetramethylrhodamine isothiocyanate (TRITC)-conjugated antibodies was used to outline the epithelial tissues. From the results we conclude that the abundance and similar distribution of carbohydrates in the early gonads of both sexes supports their sexually indifferent nature. Furthermore, the basement membranes of the differentiating gonadal cords in both sexes have common features, which differ, however, from those of the other developing urogenital organs. Changes in carbohydrate composition appear with the sexual differentiation of the gonads; the similarity of the changes in lectin binding to the gonadal cords of embryonic and fetal male, and to postnatal female, suggests similar mechanisms of cell-cell interactions in both sexes although activated at different developmental stages. These carbohydrate specificities at the tissue level should be taken into account together with cell-type specific changes, e.g. in the formation of the zona pellucida, when the phenomenon of polymorphic expression of different compounds is integrated into theories of epithelial differentiation.

Five types of pyloric cells in the antral mucosa of the stomach

Only one type of pyloric cells in the exocrine antral glands is usually described in the literature. The review of 100 gastrectomy specimens revealed 5 types of pyloric cells: one composed of "ordinary" pyloric cells (i.e. cuboidal cells with ill-defined borders, pale, bubbly cytoplasm with an inconspicuous cytoplasmic network). The second type was characterized by pyloric cells with a small, regular vacuole, usually in a subnuclear position. The vacuole in such cells was negative for mucous stains. The third type of pyloric cells had a large intracytoplasmatic vacuole. Cells with this characteristic were found in cystically dilated pyloric glands. The vacuoles in such cells were usually negative for mucous stains although a rim of PAS or alcian blue positive substance was found in some vacuoles. The fourth type of pyloric cells had eosinophilic granules in the cytoplasm. These granules were proven to contain lysozyme. The fifth type had a non-vacuolated, homogeneous ("glassy") cytoplasm which was weakly positive for PAS but negative for acid mucins or mannosides. While the significance of the various types of pyloric cells herein described remains unclear, their easy identification in H & E stained preparations would permit more elaborated studies with histochemistry, immunohistochemistry and/or transmission electron microscopy in the future.

Localization of endogenous beta-galactoside-specific lectins by neoglycoproteins, lectin-binding tissue glycoproteins and antibodies and of accessible lectin-specific ligands by mammalian lectin in human breast carcinomas

Protein-carbohydrate interactions constitute a system of molecular interaction with relevance to pathologic conditions. Carrier-immobilized carbohydrate structures enable the histochemical investigation of the protein part of this recognitive system. However, thorough systematic studies are inevitably required for standardized application of this relatively novel class of markers. Consequently, serial sections of 21 cases of malignant breast lesion were comparatively analyzed with three different types of probe, specific for beta-galactoside-binding lectins. In addition to the chemically lactosylated neoglycoprotein, human lectin-binding glycoproteins, purified by affinity chromatography on resins with an immobilized beta-galactoside-specific lectin, and a lectin-specific antibody were employed to answer the question whether differences occur in their capacity for lectin localization. The patterns of staining were qualitatively similar, the lectin-binding glycoproteins yielding the most intense reaction. Having assured the reliable applicability of the neoglycoprotein, structural alterations of the subterminal carbohydrate residue on the labelled carrier addressed the issue, whether selectivity of binding can be inferred histochemically, allowing rational synthetic tailoring. An N-acetylglucosamine residue in beta-1,3-linkage proved to be a less favorable extension than this type of sugar in beta-1,4-linkage or an N-acetylgalactosamine moiety in beta-1,3-linkage. Binding was clearly reduced in cells of normal breast tissue with this probe. In order to gain evidence on the expression of potential carbohydrate ligands for the glyco- and immunohistochemically localized binding activity, a labelled mammalian beta-galactoside-specific lectin was similarly used as histochemical tool. It effectively bound to accessible sites in the sections. The binding pattern was different to that of plant lectins with specificity to beta-galactosides. This result underscores that caution is necessary in the functional interpretation of results of studies with plant, not mammalian lectins.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycopeptide-albumin derivative: it preparation and histochemical ligand properties

Carrier-immobilized mono- or disaccharides and other carbohydrate structures, derived by custom-made chemical synthesis, have already proven to be valuable ligands for localizing carbohydrate-binding proteins in tissue sections. Defined purified glycopeptides, as components of neoglycoproteins, offer the possibility of increasing their structural complexity and, thereby, their receptor selectivity. To test the feasibility of this approach, the glycopeptide man6-glcNAc2-asparagine derived from ovalbumin was purified after pronase digestion. It was coupled to bovine serum albumin as carrier protein with the homobifunctional linking agent bis-(sulphosuccinimidyl)suberate to yield the diglycosylated concanavalin A-reactive product. Following biotinylation, it was used to detect mannose-specific binding sites in fixed cells of seven human leukemia or lymphoma lines and in fixed, paraffin-embedded sections of human breast cancer. In comparison to chemically mannosylated bovine serum albumin with ten sites of glycosylation or to ovalbumin, this derivative produced a similar pattern of reaction with a quantitatively lower extent of staining in most cases. Remarkably, the presence of potential endogenous ligands for the detected receptor sites was ascertained using the plant lectin concanavalin A. Thus, the conjugation of a purified, deliberately selected glycopeptide to a suitable carrier produces a histochemical tool for detecting glycopeptide-specific binding sites.

Neoglycoprotein binding to colorectal tumour cells: comparison between primary and secondary lesions

Biotinylated neoglycoproteins are useful to determine the expression of sugar receptors (lectins) histochemically in routinely processed tissue sections. Assessment of the presence of distinct receptor classes with specificity to beta-galactosides and to alpha- or beta-N-acetylgalactosamine, selected on the basis of their potential relevance for recognition processes within the metastatic cascade in murine model systems, was performed for a common human tumour type, colorectal cancer. The four different types of neoglycoproteins, derived from covalent attachment of commercially available derivatives of beta-N-acetylgalactosamine, differed only quantitatively in their capacity to detect specific binding on cultured cells and tissue sections, thus posing no major restriction on the choice of synthetic process for histochemical efficiency of the product. Glycocytological application revealed specific probe binding and a regulation of level of receptor expression for a human colon carcinoma cell line primarily for N-acetylgalactosamine-specific receptors upon retinoic acid-induced differentiation. Monitoring of sections of the 12 cases of primary and secondary colorectal lesions invariably disclosed the presence of the respective receptors, the extent of cell labelling in primary tumours and metastases being similar. Establishment of metastases, even in different target organs, is apparently not followed by a major phenotypic variation in this feature.

Lectin binding pattern in the embryonal and early fetal human vertebral column

Paraffin sections from vertebral columns of ten human embryos and fetuses ranging from stage 16 to the 12th week were stained with the FITC-coupled lectins PNA, RCA I, Con A and WGA in order to investigate changes in carbohydrate-binding sites during vertebral development. PNA revealed a specific binding site in the vertebral body blastema in the precartilaginous stage of development. Beginning with the 25-mm CRL embryo, PNA-binding sites occurred in the developing fibrous annulus and the inner zone of the intervertebral discs. The first binding sites for RCA I were seen in the extracellular matrix of vertebral bodies during the cartilaginous stage of vertebral development. During early ossification of the vertebrae, staining for RCA I-binding sites in the cytoplasm of the chondrocytes and the area around the future cartilaginous end-plates was observed. Con A bound to the chondrocyte cytoplasm, and also very strongly to notochordal cells in all developmental stages examined. WGA-binding sites appeared simultaneously with cartilage formation. Connective tissue components, e.g. ligaments, were diffusely stained by WGA. Also this lectin showed an affinity for vertebral body chondrocytes. We discuss the biochemical aspects of these lectin-binding sites, and their possible roles in the differentiation process of the human vertebral column. The results of this first lectin histochemical study on human vertebral development are compared with related results in other species.

[Tumor lectinology--status and perspectives of clinical application]

A detailed knowledge of the mechanisms of molecular recognition is a prerequisite to rationally improved diagnostic and therapeutic procedures in diseases. In addition to sequences of amino acids, carbohydrate structures apparently store biological information that is thought to be relevant for physiologically important processes. Such ligands, namely the carbohydrate part of cellular glycoconjugates, can be recognized by specific endogenous binding proteins like lectins. If their presence can be reliably ascertained and correlated to the clinical course of the disease, e.g. in oncology, lectinology may help to define a yet undisclosed role for this class of proteins in tumor progression and spread.