Suborganellar resolution imaging for the localisation of human glycosylation enzymes in tobacco Golgi bodies.

Plant cells are a capable system for producing economically and therapeutically important proteins for a variety of applications, and are considered a safer production system than some existing hosts such as bacteria or yeasts. However, plants do not perform protein modifications in the same manner as mammalian cells do. This can impact on protein functionality for plant-produced human therapeutics. This obstacle can be overcome by creating a plant-based system capable of 'humanising' proteins of interest resulting in a glycosylation profile of synthetic plant-produced proteins as it would occur in mammalian systems. For this, the human glycosylation enzymes (HuGEs) involved in N-linked glycosylation N-acetylglucosaminyltransferase IV and V (GNTIV and GNTV), ß-1,4-galactosyltransferase (B4GALT1), and α-2,6-sialyltransferase (ST6GAL) were expressed in plant cells. For these enzymes to carry out the stepwise glycosylation functions, they need to localise to late Golgi body cisternae. This was achieved by a protein targeting strategy of replacing the mammalian Golgi targeting domains (Cytoplasmic-Transmembrane-Stem (CTS) regions) with plant-specific ones. Using high-resolution and dynamic confocal microscopy, we show that GNTIV and GNTV were successfully targeted to the medial-Golgi cisternae while ST6GAL and B4GALT1 were targeted to trans-Golgi cisternae. Plant cells are a promising system to produce human therapeutics for example proteins used in enzyme replacement therapies. Plants can provide safer and cheaper alternatives to existing expression systems such as mammalian cell culture, bacteria or yeast. An important factor for the functionality of therapeutic proteins though are protein modifications specific to human cells. However, plants do not perform protein modifications in the same manner as human cells do. Therefore, plant cells need to be genetically modified to mimic human protein modifications patterns. The modification of importance here, is called N-linked glycosylation and adds specific sugar molecules onto the proteins. Here we show the expression of four human glycosylation enzymes, which are required for N-linked glycosylation, in plant cells. In addition, as these protein modifications are carried out in cells resembling a factory production line, it is important that the human glycosylation enzymes be placed in the correct cellular compartments and in the correct order. This is carried out in Golgi bodies. Golgi bodies are composed of several defined stacks termed cis-, medial and trans-Golgi body stacks. For correct protein function, two of these human glycosylation enzymes need to be placed in the medial-Golgi attacks and the other two in the trans-Golgi stacks. Using high-resolution laser microscopy in live plant cells, we show here that the human glycosylation enzymes are sent within the cells to the correct Golgi body stacks. These are first steps to modify plant cells in order to produce human therapeutics.

Therapeutic Fractional Doses of Ionizing Radiation Promote Epithelial-Mesenchymal Transition, Enhanced Invasiveness, and Altered Glycosylation in MCF-7 Breast Cancer Cells.

The clinical outcome of radiation therapy is restricted due to the acquired radio-resistance of a subpopulation of tumour cells that may cause tumour relapse and distant metastasis. While the effects of ionizing radiation (IR) such as DNA damage and cell stress are well-documented, the potential role of IR in inducing invasive potential in cancer cells has not been broadly studied, therefore we aimed to investigate it in this study. MCF-7 cells irradiated with 0 Gy (control) or 2 Gy X-ray therapeutic doses of IR were assessed for cell viability, percentage of apoptotic cells, and reactive oxygen species (ROS) levels, DNA fragmentation, Matrigel invasion, assessment of epithelial-mesenchymal transition (EMT) markers and Helix pomatia agglutinin (HPA) binding at 30 min, 4- or 24-h post-IR. Reduction in cell viability, increase in apoptotic cells, ROS positive cells, and DNA fragmentation were observed, while functional invasiveness and EMT were exacerbated together with altered glycosylation in MCF-7 cells irradiated with 2 Gy X-ray compared to control cells. These findings indicate that despite the detrimental effects of 2 Gy X-ray IR on MCF-7 cells, a subpopulation of cells may have gained increased invasive potential. The exacerbated invasive potential may be attributed to enhanced EMT and altered glycosylation. Moreover, deregulation of transforming growth factor-beta (TGF-ß) following IR may be one of the elements responsible for these changes, as it lies in the intersection of these invasion-promoting cell processes.

GALNTs: master regulators of metastasis-associated epithelial-mesenchymal transition (EMT)?

In humans, the UDP-N-α-D galactosamine:polypeptide N-acetylgalactosaminyltransferases family (ppGalNAc-Ts, GalNAc-Ts or GALNTs) comprises 20 isoenzymes. They are responsible for the initial synthesis of α-GalNAc1,3-O-Ser/Thr, or Tn antigen, at initiation of mucin type O-linked glycosylation. This structure is normally extended by the further sequential action of glycosytransferases to build more complex linear or branched O-linked structures, but in cancers it is frequently left unelaborated, and its presence is often associated with poor patient prognosis. Altered levels of GALNT expression or distribution have also been extensively reported in a wide range of cancers. These changes would be predicted to result in marked alterations in GalNAc O-linked glycosylation, including altered levels of site specific O-linked glycosylation and changes in the glycan structures formed, including, potentially, exposure of truncated O-glycans such as Tn antigen. Many reports have demonstrated that altered levels of specific GALNTs have prognostic significance in cancers, or shown that they are associated with changes in cell behaviour, including proliferation, migration, invasion or growth and metastasis in animal models. We have previously reviewed how deregulation of GALNTs in several epithelial cancers is a feature of different stages metastasis. Here we consider evidence that changes in GALNT expression, and therefore consequent alterations in GalNAc O-linked glycosylation, may directly influence molecules implicated in aspects of epithelial-mesenchymal transition (EMT), a fundamental aspect of cancer metastasis, during which epithelial cancer cells lose their cell-cell junctions, apical-basal polarity and adhesive interactions with basement membrane and become mesenchymal, with a spindle-shaped morphology and increased migratory capacity.

Ionising Radiation Promotes Invasive Potential of Breast Cancer Cells: The Role of Exosomes in the Process.

Along with the cells that are exposed to radiation, non-irradiated cells can unveil radiation effects as a result of intercellular communication, which are collectively defined as radiation induced bystander effects (RIBE). Exosome-mediated signalling is one of the core mechanisms responsible for multidirectional communication of tumor cells and their associated microenvironment, which may result in enhancement of malignant tumor phenotypes. Recent studies show that exosomes and exosome-mediated signalling also play a dynamic role in RIBE in cancer cell lines, many of which focused on altered exosome cargo or their effects on DNA damage. However, there is a lack of knowledge regarding how these changes in exosome cargo are reflected in other functional characteristics of cancer cells from the aspects of invasiveness and metastasis. Therefore, in the current study, we aimed to investigate exosome-mediated bystander effects of 2 Gy X-ray therapeutic dose of ionizing radiation on the invasive potential of MCF-7 breast cancer cells in vitro via assessing Matrigel invasion potential, epithelial mesenchymal transition (EMT) characteristics and the extent of glycosylation, as well as underlying plausible molecular mechanisms. The findings show that exosomes derived from irradiated MCF-7 cells enhance invasiveness of bystander MCF-7 cells, possibly through altered miRNA and protein content carried in exosomes.

Does Direct and Indirect Exposure to Ionising Radiation Influence the Metastatic Potential of Breast Cancer Cells.

Ionising radiation (IR) is commonly used for cancer therapy; however, its potential influence on the metastatic ability of surviving cancer cells exposed directly or indirectly to IR remains controversial. Metastasis is a multistep process by which the cancer cells dissociate from the initial site, invade, travel through the blood stream or lymphatic system, and colonise distant sites. This complex process has been reported to require cancer cells to undergo epithelial-mesenchymal transition (EMT) by which the cancer cells convert from an adhesive, epithelial to motile, mesenchymal form and is also associated with changes in glycosylation of cell surface proteins, which may be functionally involved in metastasis. In this paper, we give an overview of metastatic mechanisms and of the fundamentals of cancer-associated glycosylation changes. While not attempting a comprehensive review of this wide and fast moving field, we highlight some of the accumulating evidence from in vitro and in vivo models for increased metastatic potential in cancer cells that survive IR, focusing on angiogenesis, cancer cell motility, invasion, and EMT and glycosylation. We also explore the indirect effects in cells exposed to exosomes released from irradiated cells. The results of such studies need to be interpreted with caution and there remains limited evidence that radiotherapy enhances the metastatic capacity of cancers in a clinical setting and undoubtedly has a very positive clinical benefit. However, there is potential that this therapeutic benefit may ultimately be enhanced through a better understanding of the direct and indirect effects of IR on cancer cell behaviour.

Lectin Histochemistry: Historical Perspectives, State of the Art, and the Future.

Lectins, discovered more than 100 years ago and defined by their ability to selectively recognize specific carbohydrate structures, are ubiquitous in living organisms. Their precise functions are as yet under-explored and incompletely understood but they are clearly involved, through recognition of their binding partners, in a myriad of biological mechanisms involved in cell identity, adhesion, signaling, growth regulation, in health and disease. Understanding the complex "sugar code" represented by the glycome is a major challenge and at the forefront of current biological research. Lectins have been widely employed in histochemical studies to map glycosylation in cells and tissues. Here, a brief history of the discovery of lectins and early developments in their use is presented along with a selection of some of the most interesting and significant discoveries to emerge from use of lectin histochemistry. Further, an evaluation of the next generation of lectin-based technologies is presented, including the potential for designing recombinant lectins with more precisely defined binding characteristics, linking lectin-based studies with other technologies to answer fundamental questions in glycobiology, and approaches to exploring the interactions of lectins with their binding partners in more detail.

Isolation of Viable Glycosylation-Specific Cell Populations for Further In Vitro or In Vivo Analysis Using Lectin-Coated Magnetic Beads.

The glycans displayed on the cell surface are highly heterogeneous and their function in cell recognition, identity, signaling, adhesion, and behavior is increasingly recognized. Moreover, as it is yet incompletely understood, it is a topic of significant current interest. Lectins (naturally occurring carbohydrate-binding proteins) are very useful tools for exploring cellular glycosylation. Cell populations, within or between different tissues or species, and in development, health and disease, exhibit different glycosylation and thus distinct lectin-binding characteristics. Even monoclonal cell populations of established cell lines feature subpopulations with strikingly different glycosylation characteristics, and these differences may reflect differences in behavior or function. By separating cell populations on the basis of their cell surface glycosylation, the functional significance of glycosylation can be investigated in in vitro or in vivo models. Also, factors affecting glycosylation, which are also incompletely understood, can be explored or manipulated. In the protocol given here, cells can be separated into subpopulations on the basis of their recognition by a specific biotinylated lectin of choice immobilized on avidin-coated magnetic beads. Importantly, the protocol has been optimized such that lectin-binding and non-binding cells remain viable such that they can be further cultured, if necessary, for subsequent investigations.

Breast cancer osteomimicry and its role in bone specific metastasis; an integrative, systematic review of preclinical evidence.

Metastasis accounts for most of the deaths from breast cancer and the preference of invasive breast cancer metastasising to bone has been widely reported. However, the biological basis of breast cancer osteotropism is not fully understood. This paper provides, for the first time, an integrative, systematic review of evidence of molecular factors that have functional roles in the homing of metastatic breast cancer to the bone. Pubmed, Web of Science and EBSCOhost were searched using keywords and synonyms for molecular, metastasis, breast cancer and bone to identify articles published between January 2004 and August 2016. 4491 potentially relevant citations were retrieved. 63 articles met the inclusion criteria, which were primary studies reporting evidence of molecular factors that have functional roles in predisposing breast cancer bone metastasis in vivo. 12 of those 63 articles that additionally met quality criteria were included in the review. Extracted data were tabulated and key findings that indicated biological mechanisms involved in breast cancer metastasis to bone were synthesised. 15 proteins expressed by breast cancer cells were identified as factors that mediate breast cancer bone metastasis: ICAM-1, cadherin-11, osteoactivin, bone sialoprotein, CCN3, IL-11, CCL2, CITED2, CXCR4, CTGF, OPN, CX3CR1, TWIST1, adrenomedullin and Enpp1. Upregulation or overexpression of one or more of them by breast cancer cells resulted in increased breast cancer metastasis to bone in vivo, except for CCL2 where bone-metastatic cells showed a reduced expression of this factor. All factors identified, here expressed by breast cancer cells, are proteins that are normally expressed in the bone microenvironment and linked to physiologic bone functions. All have a functional role in one of more of the following: cell proliferation and differentiation, bone mineralization and remodelling, cell adhesion and/or chemokine signalling. Six of them (cadherin-11, ICAM-1, OPN, CX3CR1, CCN3 and osteoactivin) have a reported function in cell adhesion and another eight (CCN3, osteoactivin, Enpp1, IL-11, CTGF, TWIST1, adrenomedullin and CITED2) are reported to be involved in cell proliferation and differentiation. This review collates and synthesises published evidence to increase our understanding of the biology of breast cancer osteomimicry in the development of bone metastasis. Findings of this review suggest that changes in expression of proteins in breast cancer cells that confer osteomimicry facilitate homing to bone to enable the development of bone metastasis.

The extended ppGalNAc-T family and their functional involvement in the metastatic cascade.

O-linked glycosylation of proteins begins with the attachment of a single N-acetylgalactosamine (GalNAc) residue to a serine or threonine residue of the polypeptide and glycosylation of proteins can dramatically change their properties, interactions and activities. This initial attachment is catalysed by members of a family of 20 isoenzymes, the UDP-N-α-D-galactosamine: polypeptide N-acetylgalactosaminyltransferases or ppGalNAc-Ts. Why such a large family of isoenzymes are required to perform, apparently, a single function has been the subject of intense interest. The ppGalNAc-Ts, in fact, have overlapping, but distinct, substrate specificities and are differentially expressed in different cells and tissues and under different conditions of differentiation and development, allowing subtle and complex control of cellular glycosylation. Intriguingly, there is a growing body of evidence showing that altered expression of members of this transferase family are a common feature of many types of cancer and, crucially, that the resulting aberrant glycosylation has functional effects. Here, we review what is known of the expression and distribution of these intriguing transferases in health and in malignancy and, for the first time, bring together what is known of the functional and molecular effects of their disregulation in each step of the complex cascade of cancer metastasis.

In vitro invasion assay using matrigel™: a reconstituted basement membrane preparation.

Basement membranes, specialized extracellular matrices composed of collagens, laminins, and proteoglycans, form thin, continuous sheetlike structures that separate epithelial tissues from adjacent connective tissues. The crossing of basement membranes by cancer cells is a crucial aspect of metastasis-it must occur in order that cancer cells can invade lymphatic or blood vessels during dissemination and also when they penetrate into the target organ tissue where they will eventually colonize to form secondary tumors. The assay system described in this chapter utilizes the solubilized basement membrane preparation Matrigel™ and measures the ability of cells to attach to the matrix, invade into and through the matrix, and migrate towards a chemoattractant. It is technically straightforward and requires no specialist equipment and provides a useful tool for assessing the invasive ability of cancer cells, exploring the functional role of specific cell surface molecules/receptors in this process and screening for inhibitors of invasive ability, thus contributing to current knowledge of the molecular events occurring during the invasive process.

Rocking adhesion assay system to study adhesion and transendothelial migration of cancer cells.

Adhesion of metastatic cancer cells to the vascular endothelium of the target organs and their subsequent transendothelial migration is one of the critical, yet poorly understood, steps of the metastatic cascade. Conventionally, the mechanisms of this complex process have been studied using static adhesion systems or flow assay systems. Static assay systems are easy to set up and perform but do not mimic the physiological conditions of blood flow. Flow assays closely mimic physiological conditions of flow but are time consuming and require specialist equipment. In this chapter we describe the rocking adhesion system which incorporates the key advantages of both the static and flow assay systems and not only is easy to set up and perform but also mimics conditions of blood flow.

Basic immunocytochemistry for light microscopy.

Immunocytochemistry, the identification of cell- or tissue-bound antigens in situ, by means of a specific antibody-antigen reaction, tagged microscopically by a visible label, has a remarkably wide range of applications. The basic techniques are straightforward and can be adapted to explore the localisation of virtually any molecule of interest to the researcher in samples of normal and/or malignant cells. Heterogeneity can be mapped and loss or gain of immunoreactivity with tumour progression can be visualised. In this chapter, methodologies are given for appropriate preparation of cells and tissues, including cells cultured on coverslips (which can be used for live cell imaging), cell smears, frozen (cryostat) and fixed, paraffin wax-embedded tissue sections. Heat- and enzyme-based antigen retrieval methods are covered. Basic detection methods, which can be readily adapted, are given for direct (labelled primary antibody), simple indirect (labelled secondary antibody), avidin-biotin (biotinylated primary antibody), avidin-biotin complex (ABC), peroxidase-anti-peroxidase or alkaline phosphatase-anti-alkaline phosphatase (PAP or APAAP), and polymer-based methods. The use of enzyme labels including horseradish peroxidase and alkaline phosphatase, and fluorescent labels, are considered.

Lectin histochemistry to detect altered glycosylation in cells and tissues.

Lectins are naturally occurring carbohydrate-binding molecules. A very wide range of purified lectins are commercially available which exhibit a diversity of carbohydrate-binding preferences. They can be used in the laboratory to detect carbohydrate structures on, or in, cells and tissues in much the same way that purified antibodies can be employed to detect cell- or tissue-bound antigens using immunocytochemistry. As lectins can distinguish subtle alterations in cellular glycosylation, they are helpful in exploring the glycosylation changes that attend both transformation to malignancy and tumour progression. In this chapter, methodologies are given for appropriate preparation of many types of cell and tissue preparations, including cells cultured on coverslips (which can be used for live-cell imaging), cell smears, and frozen (cryostat) and fixed, paraffin wax-embedded tissue sections. Heat- and enzyme-based carbohydrate retrieval methods are covered. Basic detection methods, which can be readily adapted to the researcher's needs, are given for direct (labelled lectin), simple indirect (labelled secondary antibody directed against the lectin), and avidin-biotin (biotinylated lectin) and avidin-biotin complex. The use of both the enzyme label, horseradish peroxidase, and fluorescent labels is considered.

Measurement of circulating cell-derived microparticles by flow cytometry: sources of variability within the assay.

INTRODUCTION: Circulating cell-derived microparticles (MPs) have been implicated in several disease processes and elevated levels are found in many pathological conditions. The detection and accurate measurement of MPs, although attracting widespread interest, is hampered by a lack of standardisation. The aim of this study was to establish a reliable flow cytometric assay to measure distinct subtypes of MPs in disease and to identify any significant causes of variability in MP quantification. MATERIALS AND METHODS: Circulating MPs within plasma were identified by their phenotype (platelet, endothelial, leukocyte and annexin-V positivity (AnnV+). The influence of key variables (i.e. time between venepuncture and centrifugation, washing steps, the number of centrifugation steps, freezing/long-term storage and temperature of thawing) on MP measurement were investigated. RESULTS: Increasing time between venepuncture and centrifugation leads to increased MP levels. Washing samples results in decreased AnnV+MPs (P=0.002) and platelet-derived MPs (PMPs) (P=0.002). Double centrifugation of MPs prior to freezing decreases numbers of AnnV+MPs (P=0.0004) and PMPs (P=0.0004). A single freeze thaw cycle of samples led to an increase in AnnV+MPs (P=0.0020) and PMPs (P=0.0039). Long-term storage of MP samples at -80° resulted in decreased MP levels. CONCLUSIONS: This study found that minor protocol changes significantly affected MP levels. This is one of the first studies attempting to standardise a method for obtaining and measuring circulating MPs. Standardisation will be essential for successful development of MP technologies, allowing direct comparison of results between studies and leading to a greater understanding of MPs in disease.

Molecular interactions in cancer cell metastasis.

Metastasis, the process by which cancer cells leave the primary tumour, disseminate and form secondary tumours at anatomically distant sites, is a serious clinical problem as it is disseminated disease, which is often impossible to eradicate successfully, that causes the death of most cancer patients. Metastasis results from a complex molecular cascade comprising many steps, all of which are interconnected through a series of adhesive interactions and invasive processes as well as responses to chemotactic stimuli. In spite of its clinical significance, it remains incompletely understood. This review provides an overview of some of the molecular interactions that are critical to metastasis. It summarises the principle molecular players in the major steps of the metastatic cascade. These are: (1) tumour angiogenesis, (2) disaggregation of tumour cells from the primary tumour mass, mediated by cadherins and catenins, (3) invasion of, and migration through, the basement membrane (BM) and extracellular matrix (ECM) surrounding the tumour epithelium, and subsequent invasion of the BM of the endothelium of local blood vessels. This is mediated through integrins and proteases, including urokinase form of plasminogen activator (uPA), matrix metalloproteinases (MMPs) and cathepsins, (4) intravasation of the tumour cells into the blood vessels prior to hematogeneous dissemination to distant sites, (5) adhesion of the circulating tumour cells to the endothelial cell lining at the capillary bed of the target organ site. This occurs through adhesive interactions between cancer cells and endothelial cells involving selectins, integrins and members of the immunoglobulin superfamily (IgSF), (6) invasion of the tumour cells through the endothelial cell layer and surrounding BM (extravasation) and target organ tissue and (7) the development of secondary tumour foci at the target organ site.

Strategies for analysis of the glycosylation of proteins: current status and future perspectives.

More than half of human proteins are glycosylated by a bewildering array of complex and heterogeneous N- and O-linked glycans. They function in myriad biological processes, including cell adhesion and signalling and influence the physical characteristics, stability, function, activity and immunogenicity of soluble glycoproteins. A single protein may be glycosylated differently to yield heterogenous glycoforms. Glycosylation analysis is of increasing interest in biomedical and biological research, the pharmaceutical and healthcare industry and biotechnology. This is because it is increasingly apparent that glycosylation changes in diseases, such as cancer, making it a promising target for development of clinically useful biomarkers and therapeutics. Furthermore, as the non-human cells employed in expression systems glycosylate their proteins very differently to human cells, and as glycosylation changes unpredictably under changing environmental conditions, glycans analysis for quality control, optimum efficacy and safety of recombinant glycoproteins destined for human therapeutic use is paramount. The complexities of carbohydrate chemistry make analysis challenging and while there are a variety of robust methodologies available for glycan analysis, there is currently a pressing need for the development of new, streamlined, high throughput approaches accessible to non-specialist laboratories.

Immunolocalisation of members of the polypeptide N-acetylgalactosaminyl transferase (ppGalNAc-T) family is consistent with biologically relevant altered cell surface glycosylation in breast cancer.

An extensive family of UDP-N-alpha-d-galactosamine: polypeptide N-acetylgalactosaminyltransferases (polypeptide N-acetylgalactosaminyltransferases, ppGalNAc-T's) catalyse the attachment of the first N-acetylgalactosamine (GalNAc) monosaccharide to the polypeptide at the initiation of O-linked glycosylation of proteins. Some members of the family are broadly expressed while others are more restricted in their distribution, their expression and activity being confined to certain cells or tissues, being associated with physiological states or differentiation. Their careful regulation, which is not well understood, may mediate the synthesis of varied glycoforms of cellular proteins with different biological activities. Disruptions in glycosylation are a common feature of cancer and may have functional significance. Immunocytochemistry with confocal scanning laser microscopy was employed to detect members of the ppGalNAc-T family, ppGalNAc-T1, -T2, -T3, -T4 and -T6 in a range of breast cell lines. The cells were chosen to represent a range of phenotypes from 'normal'/benign (HMT 3,522), primary, non-metastatic breast cancer (BT 474), to aggressive, metastatic breast cancer (ZR75-1, T47D, MCF-7, DU 4,475). They stably synthesise varying levels, consistent with origin and phenotype, of aberrantly glycosylated glycoproteins featuring exposed, terminal GalNAc residues, including the cancer-associated Tn antigen, which, in numerous studies, have been associated with metastatic competence and poor cancer prognosis. GalNAc-T1 and -T2 were detectable at low levels in all cell lines studied. ppGalNAc-T4, which has never been described in breast, was very weakly detectable in BT 474, MCF7 and T47D. ppGalNAc-T3 and -T6 were weakly detectable or undetectable, respectively, in the cell line HMT 3,522 derived from 'normal'/benign breast epithelium, but were readily detectable in all malignant cell lines. Thus, a broader range of ppGalNAc-T's were detectable in the malignant cell lines in comparison to the 'normal'/benign cells, where only the 'housekeeping' ppGalNAc-T1 and -T2 were present. Expression of normally tightly restricted ppGalNAc-T's may result in initiation of O-linked glycosylation at normally unoccupied potential glycosylation sites leading to altered glycoforms of proteins with changed biological activity which may contribute to the pathogenesis of cancer.

Protein glycosylation in diverse cell systems: implications for modification and analysis of recombinant proteins.

A major challenge for the biotechnology industry is to engineer the glycosylation pathways of expression systems to synthesize recombinant proteins with human glycosylation. Inappropriate glycosylation can result in reduced activity, limited half-life in circulation and unwanted immunogenicity. In this review, the complexities of glycosylation in human cells are explained and compared with glycosylation in bacteria, yeasts, fungi, insects, plants and nonhuman mammalian species. Key advances in the engineering of the glycosylation of expression systems are highlighted. Advances in the challenging and technically complex field of glycan analysis are also described. The emergence of a new generation of expression systems with sophisticated engineering for humanized glycosylation of glycoproteins appears to be on the horizon.

Detection of aberrant glycosylation in breast cancer using lectin histochemistry.

Lectins are naturally occurring, carbohydrate-binding molecules that can be isolated from diverse biological sources and used in the laboratory to investigate the presence of carbohydrate structures in or on cells, in much the same way as antibodies can be used to probe cells and tissues for the presence of specific antigens. As it is becoming increasingly apparent that subtle alterations in the glycosylation of cancer cells can profoundly influence their biological behavior (with consequent implications for patient outcome and prognosis), lectin histochemistry is a potentially useful modification of the more widely used technique of immunohistochemistry. This chapter provides an introductory background to lectins and their use in breast cancer research, and provides basic protocols for lectin histochemistry that highlight the important technical differences between this approach and immunohistochemistry. The methods given here are broadly applicable and can be modified to investigate virtually any glycosylation change of potential interest in breast cancer research.

SDS-PAGE and Western blotting to detect proteins and glycoproteins of interest in breast cancer research.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting to detect proteins and glycoproteins is one of the most widely used and broadly useful techniques in cancer research, allowing the proteins in a complex sample--such as a blood sample, aspirate, or solid tumor homogenate--to be separated according to molecular weight and visualized within a gel matrix and/or, once separated, transferred onto a supporting membrane, where they may be probed for the binding of antibodies or lectins. In this chapter, the theory and principles of SDS-PAGE and Western blotting are briefly outlined, and basic methods are given that can be applied to investigate virtually any (glyco)protein of interest in breast cancer research.