Prognostic significance of Helix pomatia lectin and c-erbB-2 oncoprotein in human breast cancer

Lectins as a promising therapeutic agent for breast cancer: A review

Efficient treatment of cancer has been a subject of research by scientists for many years. Current treatments for cancer, such as radiotherapy, chemotherapy and surgery have been used in traditional combination therapy, but they have major setbacks like non-specificity, non-responsiveness in certain cancer types towards treatment, tumor recurrence, etc. Epidemiological data has shown that breast cancer accounts for 14% of cancer cases occurring in Indian women. In recent years, scientists have started to focus on the use of natural compounds like lectins obtained from various sources to counter the side effects of traditional therapy. Lectins like Sambucus nigra Agglutinin, Maackia amurensis lectin, Okra lectins, Haliclona caerulea lectin, Sclerotium rolfsii lectin, etc., have been discovered to have both diagnostic and therapeutic potential for breast cancer patients. Lectins have been found to have inhibitory effects on various cancer cell activities such as neo-angiogenesis, causing cell cycle arrest at the G1 phase, and inducing apoptosis. The major idea behind the use of lectins in cancer diagnostics and therapeutics is their capability to bind to glycosylated proteins that are expressed on the cell surface. This review focuses on an exploration of the roles of post-translational modification in cancer cells, especially glycosylation, and the potential of lectins in cancer diagnosis and therapeutics.

N-acetylgalactosamine glycans function in cancer cell adhesion to endothelial cells: A role for truncated O-glycans in metastatic mechanisms

Failure in O-glycan chain extension exposing Tn antigen (GalNAc-O-Ser/Thr) is clinically associated with cancer metastasis. This study provides evidence of a functional role for aberrant GalNAc-glycans in cancer cell capture from blood flow and/or adhesion to endothelium. Adhesion of breast cancer cells to human umbilical vein endothelial cell monolayers was modelled under sweeping flow. Adhesion of metastatic, GalNAc glycan-rich, MCF7 and ZR 75 1 cells to endothelium increased over timepoints up to 1.5 hour, after which it plateaued. Adhesion was significantly inhibited (p < 0.001) when cell surface GalNAc-glycans were masked, an effect not seen in GalNAc glycan-poor, non-metastatic BT 474 cells. Masking irrelevant galactose- and mannose-glycans had no inhibitory effect. Imaging of cells post-adhesion over a 24 hour time course using confocal and scanning electron microscopy revealed that up to 6 hours post-adhesion, motile, rounded cancer cells featuring lamellipodia-like processes crawled on an intact endothelial monolayer. From 6-12 hours post-adhesion, cancer cells became stationary, adopted a smooth, circular flattened morphology, and endothelial cells retracted from around them leaving cleared zones in which the cancer cells proceeded to form colonies through cell division.

Relevance of βGal-βGalNAc-containing glycans and the enzymes involved in their synthesis for invasion and survival in breast cancer patients

To study the influence of glycosylation on breast cancer progression by analyses on glycan, mRNA, and protein level. For detection of glycan structures, we performed lectin histochemistry with five lectins of different specificity (UEA-1, HPA, GNA, PNA, and PHA-L) on a tissue microarray with >400 breast cancer samples. For comparison, mRNA expression of glycosylation enzymes involved in the synthesis of HPA and PNA binding glycostructures (GALNT family members and C1GALT1) was analyzed in microarray data of 194 carcinomas. Additionally, C1GALT1 protein expression was analyzed by Western blot analysis in 106 tumors. Correlations with clinical and histological parameters including recurrence-free (RFS) and overall survival (OAS) were calculated. Positive binding of four lectins (HPA, GNA, PNA, and PHA-L) correlated significantly with parameters involved in tumor metastasis, namely lymphangiosis, vascular invasion, lymph node involvement, and presence of disseminated tumor cells in bone marrow. HPA and PNA binding also showed a negative prognostic impact in our cohort. Correspondingly, high expression of C1GALT1, GALNT1, GALNT8, or GALNT14 mRNA and C1GALT1 protein correlated significantly with shorter OAS. Notably, combined overexpression of C1GALT1/GALNT1 or C1GALT1/GALNT8 mRNA was associated with a significantly reduced OAS (HR 3.15 and 2.73) and RFS (HR 2.01 and 1.94), pointing to an additive influence of these enzymes. This prognostic impact retained significance in multivariate analysis including classical prognostic markers. Our data indicate that glycan structures containing βGal-βGalNAc residues and the enzymes involved in their synthesis play a role in breast cancer progression, at least partly by their promoting influence on haematogenic and lymphatic spread.

Selectin-deficiency reduces the number of spontaneous metastases in a xenograft model of human breast cancer

Metastasis formation is a complex process still poorly understood. Previous work in a colon cancer xenograft model showed that E(ndothelial) and P(latelet) selectins mediate spontaneous metastasis to the lungs. To investigate the functional role of selectins in breast cancer, human DU4475 breast cancer cells were injected subcutaneously into pfp-/-rag2-/- mice and in all their selectin-deficient variants (EP-/-, E-/- and P-/-). Pfp-/-rag2-/- mice as well as all their selectin-deficient variants developed primary tumours and spontaneous metastases. Compared with the wild-type mice, disseminated tumours cells were significantly lower (74% reduction, P=0.046) in the bone marrow of selectin-deficient mice. Pfp-/-rag2-/- mice developed significantly higher numbers of lung metastases (6644.83±741.77) than the E-/- (4053.33±112.58; P=0.002) and the EP-/- pfp-/-rag2-/- mice (4665.65±754.50; P<0.001). The results indicate that E- and P-selectins play a role in spontaneous metastasis formation both into bone marrow and lungs. However, spontaneous metastasis was not completely abrogated, hence additional cell adhesion molecules must be involved in the metastatic spread.

A new murine IgG1 anti-Tn monoclonal antibody with in vivo anti-tumor activity

The Tn antigen (GalNAc α-O-Ser/Thr) is heterogeneously synthesized by a variety of tumors and contains an epitope defined by lectins and antibodies as a cluster of αGalNAc carbohydrates synthesized within a peptide sequence, which is rich in serine and/or threonine. The Tn antigen has been utilized as a target in vaccine experiments and also used as a biomarker for prognosis of different cancer forms. In this paper, we present a new monoclonal antibody, GOD3-2C4, with the clear hallmarks of an anti-Tn antibody. It was generated through somatic cell hybridization after immunization of a mouse with a tumor cell line and a Tn carrying mucin. The antibody recognizes synthetic Tn antigen and binds breast, colon, lung, ovarian and pancreas cancer. The GOD3-2C4 antibody has antibody-dependent cellular cytotoxicity activity against Jurkat cells in vitro, and for the first time, it can be shown that an anti-Tn antibody has a significant in vivo effect on a human cancer cell line grown as a xenograft in severe combined immunodeficiency mice.

Cytotoxic effect of achatinin(H) (lectin) from Achatina fulica against a human mammary carcinoma cell line (MCF7)

The hemolymph-derived achatinin(H) (lectin) from Achatina fulica showed a marked cytotoxic effect on MCF7, a human mammary carcinoma cell line. IC(50) values as measured by the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide assay for achatinin(H) ranged from 6 to 10 microg/ml in the MCF7 cells. MCF7 cells showed significant morphological changes leading to cell death. The above cell death was observed after 48 h of treatment with 8 microg/ml when compared to untreated cells. Alterations in the tumor marker enzymes, as well as in antioxidant enzymes, were observed after achatinin(H) treatment. The specificity and purity of the achatinin(H) was confirmed by the Western blot assay. Achatinin(H) binding to MCF7 cells was detected by anti-achatinin(H), and visualization of the achatinin(H) binding sites on confluent MCF7 cells was confirmed by flourescein isothiocyanate conjugated secondary antibody. MCF7-treated cells fluoresced, indicating the presence of achatinin(H) binding sites. Fluorescence-activated cell sorting analysis of the cell cycle showed a significant increase in S-phase in MCF7 cells after 48 h of achatinin(H) treatment. The cells were arrested in G(2)/M phase of the cell cycle after 48 h with significant changes in cell viability. Cellular damage was confirmed by agarose gel electrophoresis with the characteristic appearance of a DNA streak in treated MCF7 cells indicating the ongoing apoptosis.

HPA binding and metastasis formation of human breast cancer cell lines transplanted into severe combined immunodeficient (scid) mice

Six human breast cancer cell lines were injected subcutaneously into scid mice and their in vivo growth behaviour and HPA binding pattern were analysed. Furthermore, the role of HPA binding glycoconjugates concerning the adhesion to endothelial cells in vitro was investigated. Four of the tested cell lines engrafted in the scid mouse model but they showed considerable variations concerning their growth behaviour, their metastatic potential and their HPA binding pattern. HPA inhibited adhesive interactions between cell lines derived from metatstatic sources and tumour necrosis factor (TNF)alpha stimulated endothelial cells. The transplantation of HPA defined breast cancer cell lines into scid mice is a useful animal model for the research of breast cancer and its metastasis. The HPA binding glycoconjugates appear to be associated with adhesive interactions between metastasising tumour cells and endothelial cells.

Characterization of lectins and their specificity in carcinomas-An appraisal

Lectins, a group of specific glycoproteins present in animal as well as plant cells, are used as differentiating markers to study cancers and metastatic cell lines. This property of lectins depends on the process of cellular glycosylation. Glycosylation of some of the extracellular membrane proteins and lipids maintains the cell/cell and cell/matrix interactions. Chemical alterations in glycosylation play an important role in the metastatic behavior of tumor cells. Carbohydrate residues of the membrane glycoproteins can be detected using lectins due to their binding specificity to carbohydrates. Lectins, therefore have gained an importance in the field of cancer research. Galectins, a specialized group of lectin like proteins that are Ca+ independent and galactoside binding, are also considered as differentiation markers in some specific cancers like the carcinomas of thyroid.Thus the use of lectins and galectins to identify specific carbohydrates present on cell surface help in invasion and metastasis processes.

Validation of a simple avidin-biotin detection method for Helix pomatia lectin (HPA) binding as a prognostic marker in cancer

Helix pomatia lectin (HPA) binding is a marker of metastatic competence in several human cancers. The altered cellular glycosylation detected by HPA is of clinical interest and functional significance, but research has been hampered by uncertainty over appropriate and accessible histochemical methods. Most studies have employed a complex multi-layered detection system localising binding of unconjugated HPA by layering with a polyclonal antibody to HPA, a biotinylated secondary antibody against the first antibody and streptavidin peroxidase. This detection system is sensitive and yields accurate prognostic information, but is lengthy and requires antibodies against HPA that are not widely available. A simpler technique, that uses peroxidase-labelled HPA is inappropriate as the carbohydrate-combining characteristics of the lectin are altered, and the prognostic significance of lectin binding is lost. Therefore a valid alternative, simple and accessible technique is required. In the present study, we compare the results of labelling of HPA binding using the complex multi-layered detection system with a simple avidin-biotin method. In a series of 101 breast cancers, both methods gave comparable results. Therefore, the avidin-biotin method appears to be appropriate for studies on HPA binding to detect altered glycoforms in cancer. It is hoped that its adoption may encourage research into this clinically significant alteration in cellular glycosylation.

GalNAc glycoprotein expression by breast cell lines, primary breast cancer and normal breast epithelial membrane

Over-expression of N-acetylgalactosamine glycoproteins as detected by binding of the lectin from Helix pomatia (HPA), is associated with metastatic competence and poor patient prognosis in a range of human adenocarcinomas. These glycoproteins remain poorly characterised, and their functional role has yet to be elucidated. This study describes characterisation of a range of human breast/breast cancer cell lines for the expression of the N-acetylgalactosaminylated glycoproteins of interest, and their comparison with normal breast epithelium and a range of clinical breast carcinoma samples. Confocal and light microscopy studies revealed cytochemical HPA-binding patterns consistent with a fundamental disruption in normal glycobiosynthetic pathways attending increasing metastatic potential. We report the most complete comparative analysis of HPA-binding ligands from cultured breast cells, clinical breast carcinoma samples and normal breast epithelium to date. Lectin blotting identified 11 major HPA-binding glycoprotein bands common to both clinical tumour samples and breast cell lines and 6 of these bands were also expressed by samples of normal breast epithelium, albeit at much lower levels. Moreover, very marked quantitative but not qualitative differences in levels of expression consistent with metastatic capability were noted.

Helix pomatia agglutinin lectin-binding oligosaccharides of aggressive breast cancer

Predicting long-term outcome after breast-cancer diagnosis remains problematic, particularly for patients with clinically small, axillary lymph node- negative tumours. Evidence suggests that the lectin Helix pomatia agglutinin (HPA) identifies oligosaccharides associated with poor-prognosis cancer. Our aim was to identify oligosaccharides that bind HPA in aggressive breast cancers. Breast-cancer cell lines (MCF-7, BT-549 and BT-20) and a cell line from human milk (HBL-100), which showed a range of HPA-binding intensities, were used to extract HPA-binding glycoproteins. Oligosaccharides were released using anhydrous hydrazine and separated on a range of HPLC matrices. We investigated whether HPA-binding oligosaccharides from cell lines were present in human breast-cancer tissues, using 69 breast-cancer specimens from patients with between 5 and 10 years' follow-up. A monosialylated oligosaccharide was over-expressed in the cell line that bound HPA strongly. Further analysis by normal-phase HPLC showed that the 2-aminobenzamide-conjugated oligosaccharide had a hydrodynamic volume of 4.58 glucose units (HPAgly1). Increased expression of HPAgly1 was associated with HPA staining of breast-cancer specimens (Student's t-test p = 0.025). Analysis of oligosaccharide levels and disease-free survival after treatment for breast cancer indicated a shorter disease-free interval for patients with elevated levels of HPAgly1. This is the first time that histochemical lectin staining has been correlated with biochemical mapping of oligosaccharides. Using this approach, we have identified a monosialylated HPA lectin-binding oligosaccharide present in breast-cancer cells grown in vitro which is elevated in breast-cancer specimens that bind the lectin.

N-acetylgalactosamine, N-acetylglucosamine and sialic acid expression in primary breast cancers

Binding of the lectin from Helix pomatia (HPA), which recognises N-acetylgalactosamine and N-acetylglucosamine glycans, is a predictor of metastasis and poor prognosis in a number of human adenocarcinomas, including breast cancer. The glycoproteins to which it binds in these tumours have been only partially characterised, and the mechanisms underlying their biosynthesis remain unknown. In this study, 111 primary breast cancers were assessed for binding of HPA and labelling characteristics were compared directly with those of Dolichos biflorus agglutinin and soybean agglutinin, both of which also recognise N-acetylgalactosamine, Griffonia simplicifolia agglutinin II, which recognises N-acetylglucosamine, and Limax flavus agglutinin, Sambucus nigra agglutinin and Maackia amurensis lectin I, all of which recognise sialic acids. Results indicate that the HPA-binding partners expressed by cancer cells are predominantly N-acetylgalactosamine glycans, but some recognition of N-acetylglucosamine species is also likely. There was no evidence to support the hypothesis that overexpression of these moieties results from failure in sialylation. Alternative mechanisms, for example alterations in levels of activity of appropriate glycosyl transferases or disruption in transport and processing mechanisms leading to failure of normal chain extension of glycans may be responsible, and these are areas that warrant further investigation.

ERBB2 oncogene in human breast cancer and its clinical significance

We reveiwed the relationships between ERBB2 amplification and/or overexpression in human breast cancer and the clinicopathological parameters described in the literature (97 studies involving 22,616 patients) in order to draw conclusions regarding its clinical interest. The mean of ERBB2 positivity (26%, ranging from 5 to 55%) is not dependent on the method used to evaluate ERBB2 amplification or overexpression. Despite the discrepancies observed between the different studies, several associations between ERBB2 positivity and the classical clinicopathological parameters were noted. There are clear relationships between ERBB2 positivity and the lack of steroid receptors, the histological subtypes of mammary tumours (ductal invasive and in situ), worse histological and nuclear grades, aneuploidy and high rate of proliferation. In univariate analyses, ERBB2 is strongly associated with poor prognosis. All these data indicate that ERBB2 is a marker of aggressiveness of the tumour. However, ERBB2 does not retain a clinical prognostic significance in multivariate analyses, since it is associated with several strong prognostic parameters. When considering the prognostic value of ERBB2 in relation to treatment, a significantly worse survival of the treated patients is noted in ERBB2 positive patients. This suggest that ERBB2 could be a marker of reduced response to chemotherapy and hormonal treatment. With respect to the tumour response to treatment, the results, provided as yet by pilot studies, remain controversial and further investigations are necessary to evaluate the predictive value of ERBB2. Finally, new therapeutic approaches targeting the cells overexpressing ERBB2 have been developed.

Lectin histochemical HPA-binding pattern of human breast and colon cancers is associated with metastases formation in severe combined immunodeficient mice

Metastasis formation is a major clinical problem in cancer treatment, and no significant progress in the treatment of metastatic spread has been made. This apparent lack of progress is partly caused by the absence of clinically relevant animal models of metastases. The binding of the lectin Helix pomatia agglutinin (HPA) has been associated with a poor prognosis in breast and colon cancer patients. HPA-positive and -negative human breast and colon cancer cell lines were transplanted into severe combined immunodeficient (SCID) mice. HPA-positive breast cancer cell lines (MCF-7 and T47D) metastasized in SCID mice, whereas the HPA-negative ones (BT20, HS578T and HBL100) did not. The HPA-positive colon cancer cell line HT29 metastasized, while the HPA-negative ones (COLO320DM, SW480 and SW620) did not. However, in two of eight SCID mice inoculated with the HPA-negative colon cancer cell line, CACO2 metastatic deposits were found. Despite this exception, HPA binding is a good indicator of the metastasis of human breast and colon cancer cells in SCID mice: 23 out of 26 HPA-positive cancers metastasized, as opposed to only two out of 38 HPA-negative cancers. This experimental model is well suited for investigating the functional role of carbohydrate residues recognized by HPA in breast and colon cancer metastasis.

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.

Does the lectin Helix pomatia agglutinin bind to hyaluronic acid in breast and colon cancer?

The lectin Helix pomatia agglutinin (HPA) has been successfully used as an indicator of metastatic spread in a number of epithelial neoplasms including breast, colorectal, gastric, prostate and oesophageal cancers. Despite its use, the binding partners of HPA in tissue sections have not been defined at the molecular level. HPA has two main binding specificities: 1) N-acetylgalactosamine (GalNac) and 2) N-acetylglucosamine (GlucNac). In order to determine whether HPA binds to hyaluronic acid (a GlucNac-containing glycosaminoglycan) a dot blot assay was performed which confirmed hyaluronic acid as a binding partner for HPA. In the next step, experiments were performed using hyaluronate lyase predigestion before HPA application on clinical and experimental human tumours grown in severe combined immunodeficient (SCID) mice to assess whether the HPA binding in the dot blot system also occurred in tissue sections. The results from all samples indicate that hyaluronate lyase pretreatment does not alter HPA binding to tumour cells both in the patients' samples and in the human cancer cell lines grown in SCID mice. This also indicates that HPA binds to similar carbohydrate residues in patients' samples and in SCID mouse-grown human tumour cells. It seems, therefore, unlikely that HPA recognises hyaluronic acid as a binding partner in tissue sections of human tumours, and hence GalNac-containing glycoproteins seem to be the more likely ligands for HPA in cancer cells.

Localization of binding sites of Ulex europaeus I, Helix pomatia and Griffonia simplicifolia I-B4 lectins and analysis of their backbone structures by several glycosidases and poly-N-acetyllactosamine-specific lectins in human breast carcinomas

Several studies have shown the deletion of blood group A or B antigens and the accumulation of H antigens in human breast carcinomas. Other studies have independently demonstrated that the binding sites of lectins such as Helix pomatia agglutinin (HPA) and Griffonia simplicifolia agglutinin I-B4 (GSAI-B4) are highly expressed in these cells. In order to clarify the molecular mechanisms of malignant transformation and metastasis of carcinoma cells, it is important to understand the relationship between such phenotypically distinct events. For this purpose, we examined whether the binding sites of these lectins and Ulex europaeus agglutinin I (UEA-I) are expressed concomitantly in the same carcinoma cells and analyzed their backbone structures. The expression of the binding sites of these lectins was observed independently of the blood group (ABO) of the patients and was not affected by the histological type of the carcinomas. Observation of serial sections stained with these lectins revealed that the distribution of HPA binding sites was almost identical to that of GSAI-B4 in most cases. Furthermore, in some cases, UEA-I binding patterns were similar to those of HPA and GSAI-B4 but in other cases, mosaic staining patterns with these lectins were also observed, i.e., some cell clusters were stained with both HPA and GSAI-B4 but not with UEA-I and adjacent cell clusters were stained only with UEA-I. Digestion with endo-beta-galactosidase or N-glycosidase F markedly reduced the staining intensity of these lectins. Together with the reduction of staining by these lectins, reactivity with Griffonia simplicifolia agglutinin II appeared in carcinoma cells following endo-beta-galactosidase digestion. Among the lectins specific to poly-N-acetyllactosamine, Lycopersicon esculentum agglutinin (LEA) most vividly and consistently stained the cancer cells. Next to LEA, pokeweed mitogen agglutinin was also effective in staining these cells. Carcinoma cells reactive with these lectins corresponded well to those stained with both HPA and GSAI-B4, and in some cases, with UEA-I. These results demonstrate that the binding sites of UEA-I, HPA, and GSAI-B4 are expressed concomitantly in the same carcinoma cells and all carry linear and branched poly-N-acetyllactosamine on N-glycans, suggesting that the synthesis of this complex carbohydrate is one of the most important and basic processes leading to the malignant transformation of cells, invasion, and metastasis of carcinoma cells.

A tumour-associated cell-surface glycoprotein accompanying p53 overexpression and higher growth potential for gastric cancer

Tumour-associated cell-surface glycoprotein is associated with tumour progression in gastric cancer. We investigated the biological significance of tumour-associated cell-surface glycoprotein, determined by the binding of Helix pomatia agglutinin (HPA), with regard to survival time and to the malignant potential of cancer cells in serosally invasive gastric cancer in 119 patients. HPA was positively stained in 75 of 119 patients (63.0%) with gastric cancer with serosal invasion. In patients with HPA-positive tissue, the tumour was larger than in HPA-negative cases and was frequently located in the middle third of the stomach. The incidence of lymph node metastasis was higher than in patients with HPA-negative tissue. There were no differences between the cases staining negatively and positively with HPA with respect to the other factors examined. Gastric cancer tissues with HPA-positive staining revealed a higher positive rate of abnormal p53 staining and a higher concentration of proliferating cell nuclear antigen (PCNA) labelling. The survival time of the patients with HPA positive staining was shorter than for those whose tissues were HPA negative. Thus, tumour-associated cell-surface glycoprotein is apparently closely related to the malignant potential of serosally invasive gastric cancer.