Immune recognition of tumor-associated mucin MUC1 is achieved by a fully synthetic aberrantly glycosylated MUC1 tripartite vaccine. Proc Natl Acad Sci U S A. 2012;109:261-266. [PMID: 22171012 DOI: 10.1073/pnas.1115166109]

Linear synthesis and immunological properties of a fully synthetic vaccine candidate containing a sialylated MUC1 glycopeptide

A strategy for the linear synthesis of a sialylated glycolipopeptide cancer vaccine candidate has been developed using a strategically designed sialyl-Tn building block and microwave-assisted solid-phase peptide synthesis. The glycolipopeptide elicited potent humoral and cellular immune responses. T-cells primed by such a vaccine candidate could be restimulated by tumor-associated MUC1.

A conjugate of octamer-binding transcription factor 4 and toll-like receptor 7 agonist prevents the growth and metastasis of testis embryonic carcinoma

Background

The immune non-recognition is often the underlying cause of failure in tumor immunotherapeutic. This is because most tumor-related antigens are poorly immunogenic, and fail to arouse an efficient immune response against cancers. Here we synthesized a novel TLR7 agonist, and developed a safe and effective immunotherapeutic vaccine by conjugating this TLR7 agonist with the pluripotency antigen OCT4.

Methods

Purified recombinant OCT4 protein was covalently linked with a novel TLR7 agonist to form a TLR7-OCT4 conjugate (T7-OCT4). After conjugation, the in vitro release of IL-12 and IFN-γ was observed in spleen lymphocytes. Mice were immunized with TLR7-OCT4, and the release of IFN-γ, the percentages of CD3+/CD8+ T cells and the OCT4-specific cytotoxicity rates were measured. The immunized mice were challenged with mouse embryonic carcinoma (EC), and the tumor volume and tumor weight were determined. Blood routine examination was performed to evaluate the biosafety of TLR7 agonist and TLR7-OCT4 conjugate in mice.

Results

T7-OCT4 conjugate significantly increased the in vitro release of IL-12 and IFN-γ by mouse spleen lymphocytes. In addition, the release of IFN-γ, the percentages of CD3+/CD8+ T cells and the tumor-specific cytotoxicity rates in immunized mice were significantly higher. Importantly, in EC xenografted mice, immunization with T7-OCT4 conjugate decreased the growth of the tumor dramatically up to 90 %, as compared to mice immunized with OCT4 protein or TLR7 agonist alone. Furthermore, blood routine examination demonstrated that no abnormalities of the blood cells and components in the blood fluids were detected by T7-OCT4 and TLR7 agonist injections.

Conclusions

Our results showed that conjugating OCT4 protein to the novel TLR7 agonist produced a vaccine which is effective and safe in preventing tumor growth in mice. Our results suggest that this type of vaccine formulation has great potentiality in preventive vaccines against OCT4 expressing tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0524-y) contains supplementary material, which is available to authorized users.

Stereoselective Synthesis of Natural and Non-natural Thomsen-nouveau Antigens and Hydrazide Derivatives

A selective glycosylation strategy enabling access to all stereochemical combinations of tumor associated Thomsen-nouveau (Tn) antigen, D-GalNAc-O-Ser/Thr, has been developed. The key component for selectivity is the phthalimide-protected D- or L-amino acid acceptors which allow access to α- or β-anomers in excellent yields (72-96%) and selectivity (∼100%) when appropriate C-2 substitution is installed. The glycoamino acid intermediates were divergently converted to Tn-based carboxylates or to hydrazides by tandem Pd-C debenzylation followed by treatment with hydrazine hydrate or hydrazine hydrate treatment alone.

Glycans in Medicinal Chemistry: An Underexploited Resource

The biological relevance of glycans as mediators of key physiological processes, including disease-related mechanisms, makes them attractive targets for a wide range of medical applications. Despite their important biological roles, especially as molecular recognition elements, carbohydrates have not been fully exploited as therapeutics mainly due to the scarcity of structure-activity correlations and their non-drug-like properties. A more detailed understanding of the complex carbohydrate structures and their associated functions should contribute to the development of new glycan-based pharmaceuticals. Recent significant progress in oligosaccharide synthesis and chemical glycobiology has renewed the interest of the medicinal chemistry community in carbohydrates. This promises to increase our possibilities to harness them in drug discovery efforts for the development of new and more effective, synthetic glycan-based therapeutics and vaccines.

Immunotherapeutic approaches to ovarian cancer treatment

Despite advances in combinatorial chemotherapy regimens and the advent of intraperitoneal chemotherapy administration, current therapeutic options for ovarian cancer patients are inadequate. Immunotherapy offers a novel and promising therapeutic strategy for treating ovarian tumors. Following the demonstration of the immunogenicity of ovarian tumors, multiple immunotherapeutic modalities have been developed. Antibody-based therapies, immune checkpoint blockade, cancer vaccines, and chimeric antigen receptor-modified T cells have demonstrated preclinical success and entered clinical testing. In this review, we discuss these promising immunotherapeutic approaches and emphasize the importance of combinatorial treatment strategies and biomarker discovery.

Detection of tumor-associated glycopeptides by lectins: the peptide context modulates carbohydrate recognition

Tn antigen (α-O-GalNAc-Ser/Thr) is a convenient cancer biomarker that is recognized by antibodies and lectins. This work yields remarkable results for two plant lectins in terms of epitope recognition and reveals that these receptors show higher affinity for Tn antigen when it is incorporated in the Pro-Asp-Thr-Arg (PDTR) peptide region of mucin MUC1. In contrast, a significant affinity loss is observed when Tn antigen is located in the Ala-His-Gly-Val-Thr-Ser-Ala (AHGVTSA) or Ala-Pro-Gly-Ser-Thr-Ala-Pro (APGSTAP) fragments. Our data indicate that the charged residues, Arg and Asp, present in the PDTR sequence establish noteworthy fundamental interactions with the lectin surface as well as fix the conformation of the peptide backbone, favoring the presentation of the sugar moiety toward the lectin. These results may help to better understand glycopeptide-lectin interactions and may contribute to engineer new binding sites, allowing novel glycosensors for Tn antigen detection to be designed.

MUC1 as a potential target in anticancer therapies

MUC1 is a glycoprotein that is overexpressed in tumor cells. In normal cells it forms a protective layer against microbes and toxic chemicals, besides providing lubrication on ductal surfaces. Oversecretion of MUC1 provide cancer cells with invasiveness, metastasis, and resistance to death induced by reactive oxygen species. MUC1 is made up of 2 heterodimers, MUC1-N and MUC1-C. MUC1-N is heavily glycosylated at 5 regions of the variable N-tandem repeats. MUC1-C is divisible into extracellular, intracellular, and cytoplasmic domain (MUC1-C/CD). The extracellular domain serves as a docking site for epidermal growth factor receptors and other receptor kinases; the transmembrane domain serves to relay messages from extracellular to MUC1-C/CD. The MUC1-C/CD has 5 phosphorylating sites that on interacting with the SH2 domain of specific proteins can stimulate tumor growth. Therapies targeting MUC1 consists of monoclonal antibodies (MAb), vaccines, or small molecules (aptamers). MAb therapies are mainly aimed at MUC1-N with little success, however, new generation of MAb are being developed for MUC1-C. Vaccines (peptide, carbohydrate, glycopeptide, DNA, and dendritic cell) have been developed that recognizes the aberrant glycosylated region of the variable N-tandem repeats in MUC1-N, whereas new generation vaccines are aimed at the cytoplasmic region of MUC1-C. Aptamers (peptides that resemble DNA, RNA) have been used for blocking the dimerization of CQC region and the 5 phosphorylating region of MUC1-C. In addition, aptamers have been used as cytotoxic drug carriers. However, none of the therapies for MUC1 are currently in clinical application, as they need further refinement and evaluation.

CpG-loaded multifunctional cationic nanohydrogel particles as self-adjuvanting glycopeptide antitumor vaccines

Self-adjuvanting antitumor vaccines by multifunctional cationic nanohydrogels loaded with CpG. A conjugate consisting of tumor-associated MUC1-glycopeptide B-cell epitope and tetanus toxin T-cell epitope P2 is linked to cationic nanogels. Oligonucleotide CpG complexation enhances toll-like receptor (TLR) stimulated T-cell proliferation and rapid immune activation. This co-delivery promotes induction of specific MUC1-antibodies binding to human breast tumor cells without external adjuvant.

Antibody induction directed against the tumor-associated MUC4 glycoprotein

Mucin glycoproteins are important diagnostic and therapeutic targets for cancer treatment. Although several strategies have been developed to explore anti-tumor vaccines based on MUC1 glycopeptides, only few studies have focused on vaccines directed against the tumor-associated MUC4 glycoprotein. MUC4 is an important tumor marker overexpressed in lung cancer and uniquely expressed in pancreatic ductual adenocarcinoma. The aberrant glycosylation of MUC4 in tumor cells results in an exposure of its peptide backbone and the formation of tumor-associated glycopeptide antigens. Due to the low immunogenicity of these endogenous structures, their conjugation with immune stimulating peptide or protein carriers are required. In this study, MUC4 tandem-repeat glycopeptides were conjugated to the tetanus toxoid and used for vaccination of mice. Immunological evaluations showed that our MUC4-based vaccines induced very strong antigen-specific immune responses. In addition, antibody binding epitope analysis on glycopeptide microarrays, were demonstrating a clear glycosylation site dependence of the induced antibodies.

Synthesis and biological evaluation of a novel MUC1 glycopeptide conjugate vaccine candidate comprising a 4'-deoxy-4'-fluoro-Thomsen-Friedenreich epitope

The development of selective anticancer vaccines that provide enhanced protection against tumor recurrence and metastasis has been the subject of intense research in the scientific community. The tumor-associated glycoprotein MUC1 represents a well-established target for cancer immunotherapy and has been used for the construction of various synthetic vaccine candidates. However, many of these vaccine prototypes suffer from an inherent low immunogenicity and are susceptible to rapid in vivo degradation. To overcome these drawbacks, novel fluorinated MUC1 glycopeptide-BSA/TTox conjugate vaccines have been prepared. Immunization of mice with the 4’F-TF-MUC1-TTox conjugate resulted in strong immune responses overriding the natural tolerance against MUC1 and producing selective IgG antibodies that are cross-reactive with native MUC1 epitopes on MCF-7 human cancer cells.

The Cosmc connection to the Tn antigen in cancer

The Tn antigen is a tumor-associated carbohydrate antigen that is not normally expressed in peripheral tissues or blood cells. Expression of this antigen, which is found in a majority of human carcinomas of all types, arises from a blockage in the normal O-glycosylation pathway in which glycans are extended from the common precursor GalNAcα1-O-Ser/Thr (Tn antigen). This precursor is generated in the Golgi apparatus on newly synthesized glycoproteins by a family of polypeptide α-N-acetylgalactosaminyltransferases (ppGalNAcTs) and then extended to the common core 1 O-glycan Galβ1-3GalNAcα1-O-Ser/Thr (T antigen) by a single enzyme termed the T-synthase (core 1 β3-galactosyltransferase or C1GalT). Formation of the active form of the T-synthase requires a unique molecular chaperone termed Cosmc, encoded by Cosmc on the X-chromosome (Xq24 in humans, Xc3 in mice). Cosmc resides in the endoplasmic reticulum (ER) and prevents misfolding, aggregation, and proteasome-dependent degradation of newly synthesized T-synthase. Loss of expression of active T-synthase or Cosmc can lead to expression of the Tn antigen, along with its sialylated version Sialyl Tn antigen as observed in several cancers. Both genetic and epigenetic pathways, in addition to potential metabolic regulation, can result in abnormal expression of the Tn antigen. Engineered expression of the Tn antigen by disruption of either C1GalT (T-syn) or Cosmc in mice is associated with a tremendous range of pathologies and engineered expression of the Tn antigen in mouse embryos leads to embryonic death. Studies indicate that many membrane glycoproteins expressing the Tn antigen and/or truncated O-glycans may be dysfunctional, due to degradation and/or misfolding. Thus, expression of normal O-glycans is associated with health and homeostasis whereas truncation of O-glycans, e.g. the Tn and/or Sialyl Tn antigens is associated with cancer and other pathologies.

Functional impact of tumor-specific N-linked glycan changes in breast and ovarian cancers

Changes in glycosylation have been implicated in various human diseases, including cancer. Research over the past few decades has produced significant findings that illustrate the importance of cancer-specific alterations in glycosylation in the regulation of tumor formation and metastasis. The identification of glycan-based biomarkers and strategies targeting specific glycan epitopes on the tumor cell surface has become one of the widely pursued research areas. In this chapter, we will summarize and provide perspective on available knowledge about the functional roles that glycan structures play in the development and progression of the gynecological cancers, breast and ovarian, with a specific focus on N-linked glycans. A better understanding of the functional roles for glycans in cancer will drive future innovations for diagnostics and therapeutics.

Total synthesis of glycosylated proteins

Glycoproteins are an important class of naturally occurring biomolecules which play a pivotal role in many biological processes. They are biosynthesized as complex mixtures of glycoforms through post-translational protein glycosylation. This fact, together with the challenges associated with producing them in homogeneous form, has hampered detailed structure-function studies of glycoproteins as well as their full exploitation as potential therapeutic agents. By contrast, chemical synthesis offers the unique opportunity to gain access to homogeneous glycoprotein samples for rigorous biological evaluation. Herein, we review recent methods for the assembly of complex glycopeptides and glycoproteins and present several examples from our laboratory towards the total chemical synthesis of clinically relevant glycosylated proteins that have enabled synthetic access to full-length homogeneous glycoproteins.

Single molecule study of heterotypic interactions between mucins possessing the Tn cancer antigen

Mucins are linear, heavily O-glycosylated proteins with physiological roles that include cell signaling, cell adhesion, inflammation, immune response and tumorgenesis. Cancer-associated mucins often differ from normal mucins by presenting truncated carbohydrate chains. Characterization of the binding properties of mucins with truncated carbohydrate side chains could thus prove relevant for understanding their role in cancer mechanisms such as metastasis and recognition by the immune system. In this work, heterotypic interactions of model mucins that possess the Tn (GalNAcαThr/Ser) and T (Galβ1-3GalNAcαThr/Ser) cancer antigens derived from porcine submaxillary mucin (PSM) were studied using atomic force microscopy. PSM possessing only the Tn antigen (Tn-PSM) was found to bind to PSM analogs possessing a combination of T, Tn and STn antigens as well as biosynthetic analogs of the core 1 blood group A tetrasaccharide (GalNAcα1-3[Fucα1-2] Galβ1-3GalNAcαSer/Thr). The rupture forces for the heterotypic interactions ranged from 18- to 31 pN at a force-loading rate of ∼0.5 nN/s. The thermally averaged distance from the bound complex to the transition state (xβ) was estimated to be in the range 0.37-0.87 nm for the first barrier of the Bell Evans analysis and within 0.34-0.64 nm based on a lifetime analysis. These findings reveal that the binding strength and energy landscape for heterotypic interactions of Tn-PSM with the above mucins, resemble homotypic interactions of Tn-PSM. This suggests common carbohydrate epitope interactions for the Tn cancer antigen with the above mucin analogs, a finding that may be important to the role of the Tn antigen in cancer cells.

Aberrant glycosylation promotes lung cancer metastasis through adhesion to galectins in the metastatic niche

Metastasis is the leading cause of cancer-associated deaths. Although dissemination of tumor cells likely occurs early in tumorigenesis, the constituents of the microenvironment play essential rate-limiting roles in determining whether these cells will form clinically relevant tumors. Recent studies have uncovered many molecular factors that contribute to the establishment of a protumorigenic metastatic niche. Here, we demonstrate that galectin-3, whose expression has clinical associations with advanced malignancy and poor outcome, contributes to metastatic niche formation by binding to carbohydrates on metastatic cells. We show that galectin-3 is expressed early during tumorigenesis by both CD11b(+)Gr-1(+) and CD11b(+)Ly-6C(hi) leukocytes. Tumors mobilize these myeloid populations through secretion of soluble factors, including IL6. We find that metastatic cancer cells exhibit elevated presentation of the oncofetal galectin-3 carbohydrate ligand, the Thomsen-Friedenreich antigen, on their surfaces as a result of altered C2GnT2 and St6GalNAc4 glycosyltransferase activity that inhibits further glycosylation of this carbohydrate motif and promotes metastasis.

SIGNIFICANCE

Although clinical observations of elevated serum galectin-3 levels and altered glycosylation have been associated with malignancy, we identify novel roles for glycosyltransferases in promoting adhesion to galectins in the metastatic niche. This identification of a cytokine-leukocyte-glycosylation axis in metastasis provides mechanistic explanations for clinical associations between malignancy and aberrant glycosylation.

Recent progress in antitumoral synthetic vaccines

Antitumoral synthetic vaccines offer a promising alternative to overcome problems associated with traditional treatments. Numerous vaccine prototypes have been described in the last two decades; however, none of them have been revealed satisfactory in clinical trials due to side effects, low bioavailability, uncertain molecular composition, and/or reproducibility. Here we highlight major advances in carbohydrate-based vaccines, which open new perspectives in cancer immunotherapy.

Liposomes as vaccine delivery systems: a review of the recent advances

Liposomes and liposome-derived nanovesicles such as archaeosomes and virosomes have become important carrier systems in vaccine development and the interest for liposome-based vaccines has markedly increased. A key advantage of liposomes, archaeosomes and virosomes in general, and liposome-based vaccine delivery systems in particular, is their versatility and plasticity. Liposome composition and preparation can be chosen to achieve desired features such as selection of lipid, charge, size, size distribution, entrapment and location of antigens or adjuvants. Depending on the chemical properties, water-soluble antigens (proteins, peptides, nucleic acids, carbohydrates, haptens) are entrapped within the aqueous inner space of liposomes, whereas lipophilic compounds (lipopeptides, antigens, adjuvants, linker molecules) are intercalated into the lipid bilayer and antigens or adjuvants can be attached to the liposome surface either by adsorption or stable chemical linking. Coformulations containing different types of antigens or adjuvants can be combined with the parameters mentioned to tailor liposomal vaccines for individual applications. Special emphasis is given in this review to cationic adjuvant liposome vaccine formulations. Examples of vaccines made with CAF01, an adjuvant composed of the synthetic immune-stimulating mycobacterial cordfactor glycolipid trehalose dibehenate as immunomodulator and the cationic membrane forming molecule dimethyl dioctadecylammonium are presented. Other vaccines such as cationic liposome-DNA complexes (CLDCs) and other adjuvants like muramyl dipeptide, monophosphoryl lipid A and listeriolysin O are mentioned as well. The field of liposomes and liposome-based vaccines is vast. Therefore, this review concentrates on recent and relevant studies emphasizing current reports dealing with the most studied antigens and adjuvants, and pertinent examples of vaccines. Studies on liposome-based veterinary vaccines and experimental therapeutic cancer vaccines are also summarized.

Glycan-mediated modification of the immune response

Aberrantly glycosylated tumor antigens represent promising targets for the development of anti-cancer vaccines, yet how glycans influence immune responses is poorly understood. Recent studies have demonstrated that GalNAc-glycosylation enhances antigen uptake by dendritic cells as well as CD4⁺ T-cell and humoral responses, but prevents CD8⁺ T-cell activation. Here, we briefly discuss the relevance of glycans as candidate targets for anti-cancer vaccines.

Emerging immunotherapy strategies in breast cancer

Although immunogenicity is typically associated with renal cell carcinomas and melanoma, there are several compelling reasons why immune-based therapies should be explored in breast cancer. First, breast cancers express multiple putative tumor-associated antigens, such as HER-2 and MUC-1, which have been the successful focus of vaccine development over the past decade, translating into tumor-specific immune responses and, in some cases, clinical benefit. Second, passive immune strategies with anti-HER-2 antibodies, such as trastuzumab and pertuzumab, have led to survival benefits in breast cancer. Finally, the successes observed with novel immunotherapeutic strategies, such as immune checkpoint blockade and adoptive T-cell therapies in other malignancies, combined with a growing body of literature that supports an interplay between solid tumors and the immune system, indicate that these strategies have the potential to revolutionize the treatment of breast cancer.

Protecting-group-free one-pot synthesis of glycoconjugates directly from reducing sugars

The conversion of sugars into glycomimetics typically involves multiple protecting-group manipulations. The development of methodology allowing the direct aqueous conversion of free sugars into glycosides, and mimics of oligosaccharides and glycoconjugates in a high-yielding and stereoselective process is highly desirable. The combined use of 2-azido-1,3-dimethylimidazolinium hexafluorophosphate and the Cu-catalyzed Huisgen cycloaddition allowed the synthesis of a range of glycoconjugates in a one-step reaction directly from reducing sugars under aqueous conditions. The reaction, which is completely stereoselective, may be applied to the convergent synthesis of triazole-linked glycosides, oligosaccharides, and glycopeptides. The procedure provides a method for the one-pot aqueous ligation of oligosaccharides and peptides bearing alkyne side chains.

MUC1 expression in papillary thyroid carcinoma is associated with BRAF mutation and lymph node metastasis; the latter is the most important risk factor of relapse

BACKGROUND

The incidence of papillary thyroid carcinoma (PTC) has increased over the past 30 years in Western countries. PTC is usually associated with a good prognosis, but there is a wide range of aggressiveness, and some patients develop distant metastasis and/or resistance to standard treatment. Early identification of these high-risk tumors is a current challenge for appropriate patient management. MUC1 expression has been studied previously in thyroid cancer, but its prognostic value remains controversial. Here, we correlated MUC1 expression in PTC with clinical and pathological features and with the presence of the BRAF(V600E) mutation.

METHODS

We performed a clinical and morphological analysis of 190 thyroid tumors (95 PTCs and 95 adenomas). MUC1 immunohistochemistry was carried out on a tissue microarray using different antibodies. The presence of the BRAF(V600E) mutation was investigated by pyrosequencing. MUC1 mRNA levels were assessed by quantitative reverse transcription polymerase chain reaction on a subset of PTC.

RESULTS

MUC1 expression was observed in 49% of PTCs and was found to correlate with the presence of papillary architecture, a stromal lymphoid infiltrate, aggressive histological subtypes, extrathyroidal extension, lymph node metastasis, nuclear pseudoinclusions, lymphovascular invasion, and the presence of the BRAF(V600E) mutation (p<0.0001). MUC1 was abundant in nuclear pseudoinclusions. Multivariate analysis showed a strong association of MUC1 expression with the presence of the BRAF(V600E) mutation and lymph node metastasis (p<0.0001). Lymph node metastasis was the most important risk factor of relapse.

CONCLUSIONS

Our study shows an association between MUC1 expression and the presence of the BRAF(V600E) mutation in PTC. Analysis of MUC1 expression could improve the risk stratification of PTCs.

Covalent bond or noncovalent bond: a supramolecular strategy for the construction of chemically synthesized vaccines

A novel noncovalent strategy to construct chemically synthesized vaccines has been designed to trigger a robust immune response and to dramatically improve the efficiency of vaccine preparation. Glycosylated MUC1 tripartite vaccines were constructed through host-guest interactions with cucurbit[8]uril. These vaccines elicited high levels of IgG antibodies that were recognized by transformed cells and induced the secretion of cytokines. The antisera also mediated complement-dependent cytotoxicity. This noncovalent strategy with good suitability, scalability, and feasibility can be applied as a universal strategy for the construction of chemically synthesized vaccines.

Strategy for Designing a Synthetic Tumor Vaccine: Multi-Component, Multivalency and Antigen Modification

Synthetic tumor vaccines have been proven to be promising for cancer immunotherapy. However, the limitation of the specificity and efficiency of the synthetic tumor vaccines need further improvements. To overcome these difficulties, additional tumor-associated targets need to be identified, and optimized structural designs of vaccines need to be elaborated. In this review, we summarized the main strategies pursued in the design of synthetic tumor vaccines, such as multi-component, multivalency, antigen modification and other possible ways to improve the efficiency of synthetic tumor vaccines.

Immune and anticancer responses elicited by fully synthetic aberrantly glycosylated MUC1 tripartite vaccines modified by a TLR2 or TLR9 agonist

The mucin MUC1 is overexpressed and aberrantly glycosylated by many epithelial cancer cells manifested by truncated O-linked saccharides. Although tumor-associated MUC1 has generated considerable attention because of its potential for the development of a therapeutic cancer vaccine, it has been difficult to design constructs that consistently induce cytotoxic T-lymphocytes (CTLs) and ADCC-mediating antibodies specific for the tumor form of MUC1. We have designed, chemically synthesized, and immunologically examined vaccine candidates each composed of a glycopeptide derived from MUC1, a promiscuous Thelper peptide, and a TLR2 (Pam3 CysSK4 ) or TLR9 (CpG-ODN 1826) agonist. It was found that the Pam3 CysSK4 -containing compound elicits more potent antigenic and cellular immune responses, resulting in a therapeutic effect in a mouse model of mammary cancer. It is thus shown, for the first time, that the nature of an inbuilt adjuvant of a tripartite vaccine can significantly impact the quality of immune responses elicited against a tumor-associated glycopeptide. The unique adjuvant properties of Pam3 CysSK4 , which can reduce the suppressive function of regulatory T cells and enhance the cytotoxicity of tumor-specific CTLs, are likely responsible for the superior properties of the vaccine candidate 1.

Synthesis and evaluation of monophosphoryl lipid A derivatives as fully synthetic self-adjuvanting glycoconjugate cancer vaccine carriers

A fully synthetic carbohydrate-based cancer vaccine is an attractive concept, but an important topic in the area is to develop proper vaccine carriers that can improve the immunogenicity and other immunological properties of tumor-associated carbohydrate antigens (TACAs). In this context, four monophosphoryl derivatives of Neisseria meningitidis lipid A were synthesized via a highly convergent and effective strategy and evaluated as vaccine carriers and adjuvants. The conjugates of these monophosphoryl lipid A (MPLA) derivatives with a modified form of the sTn antigen were found to elicit high titers of antigen-specific IgG antibodies, indicating a T cell-dependent immune response, in the absence of an external adjuvant. It was concluded that MPLAs could be utilized as potent vaccine carriers and built-in adjuvants to create fully synthetic self-adjuvanting carbohydrate-based cancer vaccines. The lipid composition and structure of MPLA were shown to have a significant influence on its immunological activity, and among the MPLAs examined, natural N. meningitidis MPLA exhibited the most promising properties. Moreover, Titermax Gold, a conventional vaccine adjuvant, was shown to inhibit, rather than promote, the immunological activity of MPLA conjugates, maybe via interacting with MPLA.

Mucins and tumor resistance to chemotherapeutic drugs

Epithelial cancer patients not considered eligible for surgical resection frequently benefit from chemotherapy. Chemotherapy is the treatment of cancer with one or combination of cytotoxic or cytostatic drugs. Recent advances in chemotherapy allowed a great number of cancer patients to receive treatment with significant results. Unfortunately, resistance to chemotherapeutic drug treatment is a major challenge for clinicians in the majority of epithelial cancers because it is responsible for the inefficiency of therapies. Mucins belong to a heterogeneous group of large O-glycoproteins that can be either secreted or membrane-bound. Implications of mucins have been described in relation to cancer cell behavior and cell signaling pathways associated with epithelial tumorigenesis. Because of the frequent alteration of the pattern of mucin expression in cancers as well as their structural and functional characteristics, mucins are thought to also be involved in response to therapies. In this report, we review the roles of mucins in chemoresistance and the associated underlying molecular mechanisms (physical barrier, resistance to apoptosis, drug metabolism, cell stemness, epithelial-mesenchymal transition) and discuss the therapeutic tools/strategies and/or prognosis biomarkers for personalized chemotherapy that could be proposed from these studies.

MUC1: a multifaceted oncoprotein with a key role in cancer progression

The transmembrane glycoprotein Mucin 1 (MUC1) is aberrantly glycosylated and overexpressed in a variety of epithelial cancers, and plays a crucial role in progression of the disease. Tumor-associated MUC1 differs from the MUC1 expressed in normal cells with regard to its biochemical features, cellular distribution, and function. In cancer cells, MUC1 participates in intracellular signal transduction pathways and regulates the expression of its target genes at both the transcriptional and post-transcriptional levels. This review highlights the structural and functional differences that exist between normal and tumor-associated MUC1. We also discuss the recent advances made in the use of MUC1 as a biomarker and therapeutic target for cancer.

Oligosaccharides and peptide displayed on an amphiphilic polymer enable solid phase assay of hapten specific antibodies

Copovidone, a copolymer of vinyl acetate and N-vinyl-2-pyrrolidone, was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, and after deacetylation the polymer was functionalized by introduction of amino, azide, and alkyne pendant groups to allow attachment of glycans and peptide. Candida albicans β-mannan trisaccharides 1 and 2 and M. tuberculosis arabinan hexasaccharide 3 with appropriate tethers were conjugated to the polymers by squarate or click chemistry. C. albicans T-cell peptide 4 bearing a C-terminal ε-azidolysine was also conjugated to copovidone by click chemistry. The resulting conjugates provide convenient non-protein-based antigens that are readily adsorbed on ELISA plates, and display excellent characteristics for assay of antibody binding to the haptenic group of interest. Copovidone and BSA glycoconjugates exhibited similar adsorption characteristics when used to coat ELISA plates, and both conjugates were optimal when used as coating solutions at low nanogram/mL concentrations. Provided that the copovidone conjugated glycan is stable to acid, assay plates can be easily processed for reuse at least three times without detectable variation or degradation in ELISA readout.

Sialyl Tn-expressing bladder cancer cells induce a tolerogenic phenotype in innate and adaptive immune cells

Despite the wide acceptance that glycans are centrally implicated in immunity, exactly how they contribute to the tilt immune response remains poorly defined. In this study, we sought to evaluate the impact of the malignant phenotype-associated glycan, sialyl-Tn (STn) in the function of the key orchestrators of the immune response, the dendritic cells (DCs). In high grade bladder cancer tissue, the STn antigen is significantly overexpressed and correlated with the increased expression of ST6GALNAC1 sialyltransferase. Bladder cancer tissue presenting elevated expression of ST6GALNAC1 showed a correlation with increased expression of CD1a, a marker for bladder immature DCs and showed concomitant low levels of Th1-inducing cytokines IL-12 and TNF-α. In vitro, human DCs co-incubated with STn(+) bladder cancer cells, had an immature phenotype (MHC-II(low), CD80(low) and CD86(low)) and were unresponsive to further maturation stimuli. When contacting with STn(+) cancer cells, DCs expressed significantly less IL-12 and TNF-α. Consistent with a tolerogenic DC profile, T cells that were primed by DCs pulsed with antigens derived from STn(+) cancer cells were not activated and showed a FoxP3(high) IFN-γ(low) phenotype. Blockade of STn antigens and of STn(+) glycoprotein, CD44 and MUC1, in STn(+) cancer cells was able to lower the induction of tolerance and DCs become more mature. Overall, our data suggest that STn-expressing cancer cells impair DC maturation and endow DCs with a tolerogenic function, limiting their capacity to trigger protective anti-tumour T cell responses. STn antigens and, in particular, STn(+) glycoproteins are potential targets for circumventing tumour-induced tolerogenic mechanisms.

Emerging principles for the therapeutic exploitation of glycosylation

Glycosylation plays a key role in a wide range of biological processes. Specific modification to a glycan's structure can directly modulate its biological function. Glycans are not only essential to glycoprotein folding, cellular homeostasis, and immune regulation but are involved in multiple disease conditions. An increased molecular and structural understanding of the mechanistic role that glycans play in these pathological processes has driven the development of therapeutics and illuminated novel targets for drug design. This knowledge has enabled the treatment of metabolic disorders and the development of antivirals and shaped cancer and viral vaccine strategies. Furthermore, an understanding of glycosylation has led to the development of specific drug glycoforms, for example, monoclonal antibodies, with enhanced potency.

Adaptive immune activation: glycosylation does matter

Major histocompatibility complex (MHC) class I and II are glycoproteins that can present antigenic peptides at the cell surface for recognition and activation of circulating T lymphocytes. Here, the importance of the modification of protein antigens by glycans on cellular uptake, proteolytic processing, presentation by MHC and subsequent T-cell priming is reviewed. Antigen glycosylation is important for a number of diseases and vaccine design. All of the key proteins involved in antigen recognition and the orchestration of downstream effector functions are glycosylated. The influence of protein glycosylation on immune function and disease is covered.

Glycotherapy: new advances inspire a reemergence of glycans in medicine

The beginning of the 20(th) century marked the dawn of modern medicine with glycan-based therapies at the forefront. However, glycans quickly became overshadowed as DNA- and protein-focused treatments became readily accessible. The recent development of new tools and techniques to study and produce structurally defined carbohydrates has spurred renewed interest in the therapeutic applications of glycans. This review focuses on advances within the past decade that are bringing glycan-based treatments back to the forefront of medicine and the technologies that are driving these efforts. These include the use of glycans themselves as therapeutic molecules as well as engineering protein and cell surface glycans to suit clinical applications. Glycan therapeutics offer a rich and promising frontier for developments in the academic, biopharmaceutical, and medical fields.

The challenge and promise of glycomics

Glycomics is a broad and emerging scientific discipline focused on defining the structures and functional roles of glycans in biological systems. The staggering complexity of the glycome, minimally defined as the repertoire of glycans expressed in a cell or organism, has resulted in many challenges that must be overcome; these are being addressed by new advances in mass spectrometry as well as by the expansion of genetic and cell biology studies. Conversely, identifying the specific glycan recognition determinants of glycan-binding proteins by employing the new technology of glycan microarrays is providing insights into how glycans function in recognition and signaling within an organism and with microbes and pathogens. The promises of a more complete knowledge of glycomes are immense in that glycan modifications of intracellular and extracellular proteins have critical functions in almost all biological pathways.

S-Michael additions to chiral dehydroalanines as an entry to glycosylated cysteines and a sulfa-Tn antigen mimic

Stereoselective sulfa-Michael addition of appropriately protected thiocarbohydrates to chiral dehydroalanines has been developed as a key step in the synthesis of biologically important cysteine derivatives, such as S-(β-D-glucopyranosyl)-D-cysteine, which has not been synthesized to date, and S-(2-acetamido-2-deoxy-α-D-galactopyranosyl)-L-cysteine, which could be considered as a mimic of Tn antigen. The corresponding diamide derivative was also synthesized and analyzed from a conformational viewpoint, and its bound state with a lectin was studied.

Carbohydrate antigen delivery by water soluble copolymers as potential anti-cancer vaccines

Tumor associated carbohydrate antigens (TACAs) are overexpressed on tumor cells, which renders them attractive targets for anti-cancer vaccines. To overcome the poor immunogenicity of TACAs, we designed a polymer platform for antigen presentation by co-delivering TACA and helper T (Th) cell epitope on the same chain. The block copolymer was synthesized by cyanoxyl-mediated free radical polymerization followed by conjugation with a TACA Tn antigen and a mouse Th-cell peptide epitope derived from polio virus (PV) to afford the vaccine construct. The glycopolymer vaccine elicited an anti-Tn immune response with significant titers of IgG antibodies, which recognized Tn-expressing tumor cells.

Genetically engineered mice as experimental tools to dissect the critical events in breast cancer

Elucidating the mechanism of pathogenesis of breast cancer has greatly benefited from breakthrough advances in both genetically engineered mouse (GEM) models and xenograft transplantation technologies. The vast array of breast cancer mouse models currently available is testimony to the complexity of mammary tumorigenesis and attempts by investigators to accurately portray the heterogeneity and intricacies of this disease. Distinct molecular changes that drive various aspects of tumorigenesis, such as alterations in tumor cell proliferation and apoptosis, invasion and metastasis, angiogenesis, and drug resistance have been evaluated using the currently available GEM breast cancer models. GEM breast cancer models are also being exploited to evaluate and validate the efficacy of novel therapeutics, vaccines, and imaging modalities for potential use in the clinic. This review provides a synopsis of the various GEM models that are expanding our knowledge of the nuances of breast cancer development and progression and can be instrumental in the development of novel prevention and therapeutic approaches for this disease.

Synthesis and immunological evaluation of self-adjuvanting MUC1-macrophage activating lipopeptide 2 conjugate vaccine candidates

The synthesis and immunological evaluation of self-adjuvanting cancer vaccine candidates comprising of mucin 1 (MUC1) (glyco)peptides linked to macrophage activating lipopeptide 2 (MALP2) is described.

A straightforward protocol for the preparation of high performance microarray displaying synthetic MUC1 glycopeptides

BACKGROUND

Human serum MUC1 peptide fragments bearing aberrant O-glycans are secreted from columnar epithelial cell surfaces and known as clinically important serum biomarkers for the epithelial carcinoma when a specific monoclonal antibody can probe disease-relevant epitopes. Despite the growing importance of MUC1 glycopeptides as biomarkers, the precise epitopes of most anti-MUC1 monoclonal antibodies remains unclear.

METHODS

A novel protocol for the fabrication of versatile microarray displaying peptide/glycopeptide library was investigated for the construction of highly sensitive and accurate epitope mapping assay of various anti-MUC1 antibodies.

RESULTS

Selective imine-coupling between aminooxy-functionalized methacrylic copolymer with phosphorylcholine unit and synthetic MUC1 glycopeptides-capped by a ketone linker at N-terminus provided a facile and seamless protocol for the preparation of glycopeptides microarray platform. It was demonstrated that anti-KL-6 monoclonal antibody shows an extremely specific and strong binding affinity toward MUC1 fragments carrying sialyl T antigen (Neu5Acα2,3Galβ1,3GalNAcα1→) at Pro-Asp-Thr-Arg motif when compared with other seven anti-MUC1 monoclonal antibodies such as VU-3D1, VU-12E1, VU-11E2, Ma552, VU-3C6, SM3, and DF3. The present microarray also uncovered the occurrence of IgG autoantibodies in healthy human sera that bind specifically with sialyl T antigen attached at five potential O-glycosylation sites of MUC1 tandem repeats.

CONCLUSION

We established a straightforward strategy toward the standardized microarray platform allowing highly sensitive and accurate epitope mapping analysis by reducing the background noise due to nonspecific protein adsorption.

GENERAL SIGNIFICANCE

The present approach would greatly accelerate the discovery research of new class autoantibodies as well as the development of therapeutic mAbs reacting specifically with disease-relevant epitopes.

Glycan elongation beyond the mucin associated Tn antigen protects tumor cells from immune-mediated killing

Membrane bound mucins are up-regulated and aberrantly glycosylated during malignant transformation in many cancer cells. This results in a negatively charged glycoprotein coat which may protect cancer cells from immune surveillance. However, only limited data have so far demonstrated the critical steps in glycan elongation that make aberrantly glycosylated mucins affect the interaction between cancer cells and cytotoxic effector cells of the immune system. Tn (GalNAc-Ser/Thr), STn (NeuAcα2-6GalNAc-Ser/Thr), T (Galβ1–3GalNAc-Ser/Thr), and ST (NeuAcα2-6Galβ1–3GalNAc-Ser/Thr) antigens are recognized as cancer associated truncated glycans, and are expressed in many adenocarcinomas, e.g. breast- and pancreatic cancer cells. To investigate the role of the cancer associated glycan truncations in immune-mediated killing we created glyco-engineered breast- and pancreatic cancer cells expressing only the shortest possible mucin-like glycans (Tn and STn). Glyco-engineering was performed by zinc finger nuclease (ZFN) knockout (KO) of the Core 1 enzyme chaperone COSMC, thereby preventing glycan elongation beyond the initial GalNAc residue in O-linked glycans. We find that COSMC KO in the breast and pancreatic cancer cell lines T47D and Capan-1 increases sensitivity to both NK cell mediated antibody-dependent cellular-cytotoxicity (ADCC) and cytotoxic T lymphocyte (CTL)-mediated killing. In addition, we investigated the association between total cell surface expression of MUC1/MUC16 and NK or CTL mediated killing, and observed an inverse correlation between MUC16/MUC1 expression and the sensitivity to ADCC and CTL-mediated killing. Together, these data suggest that up-regulation of membrane bound mucins protects cells from immune mediated killing, and that particular glycosylation steps, as demonstrated for glycan elongation beyond Tn and STn, can be important for fine tuning of the immune escape mechanisms in cancer cells.