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]

Toll like receptors TLR1/2, TLR6 and MUC5B as binding interaction partners with cytostatic proline rich polypeptide 1 in human chondrosarcoma

Metastatic chondrosarcoma is a bone malignancy not responsive to conventional therapies; new approaches and therapies are urgently needed. We have previously reported that mTORC1 inhibitor, antitumorigenic cytostatic proline rich polypeptide 1 (PRP-1), galarmin caused a significant upregulation of tumor suppressors including TET1/2 and SOCS3 (known to be involved in inflammatory processes), downregulation of oncoproteins and embryonic stem cell marker miR-302C and its targets Nanog, c-Myc and Bmi-1 in human chondrosarcoma. To understand better the mechanism of PRP-1 action it was very important to identify the receptor it binds to. Nuclear pathway receptor and GPCR assays indicated that PRP-1 receptors are not G protein coupled, neither do they belong to family of nuclear or orphan receptors. In the present study, we have demonstrated that PRP-1 binding interacting partners belong to innate immunity pattern recognition toll like receptors TLR1/2 and TLR6 and gel forming secreted mucin MUC5B. MUC5B was identified as PRP-1 receptor in human chondrosarcoma JJ012 cell line using Ligand-receptor capture technology. Toll like receptors TLR1/2 and TLR6 were identified as binding interaction partners with PRP-1 by western blot analysis in human chondrosarcoma JJ012 cell line lysates. Immunocytochemistry experiments confirmed the finding and indicated the localization of PRP-1 receptors in the tumor nucleus predominantly. TLR1/2, TLR6 and MUC5B were downregulated in human chondrosarcoma and upregulated in dose-response manner upon PRP-1 treatment. Experimental data indicated that in this cellular context the mentioned receptors had tumor suppressive function.

Synthetic Three-Component HIV-1 V3 Glycopeptide Immunogens Induce Glycan-Dependent Antibody Responses

Eliciting broadly neutralizing antibody (bNAb) responses against HIV-1 is a major goal for a prophylactic HIV-1 vaccine. One approach is to design immunogens based on known broadly neutralizing epitopes. Here we report the design and synthesis of an HIV-1 glycopeptide immunogen derived from the V3 domain. We performed glycopeptide epitope mapping to determine the minimal glycopeptide sequence as the epitope of V3-glycan-specific bNAbs PGT128 and 10-1074. We further constructed a self-adjuvant three-component immunogen that consists of a 33-mer V3 glycopeptide epitope, a universal T helper epitope P30, and a lipopeptide (Pam₃CSK₄) that serves as a ligand of Toll-like receptor 2. Rabbit immunization revealed that the synthetic self-adjuvant glycopeptide could elicit substantial glycan-dependent antibodies that exhibited broader recognition of HIV-1 gp120s than the non-glycosylated V3 peptide. These results suggest that the self-adjuvant synthetic glycopeptides can serve as an important component to elicit glycan-specific antibodies in HIV vaccine design.

Targeted antigen delivery by an anti-class II MHC VHH elicits focused αMUC1(Tn) immunity

Unusual patterns of glycosylation on the surface of transformed cells contribute to immune modulation and metastasis of malignant tumors. Active immunization against them requires effective antigen presentation, which is complicated by a lack of access to tumor-specific posttranslational modifications through standard genetic approaches and by the low efficiency of passive antigen sampling. We found that antigen targeted to antigen presenting cells via class II MHC products can elicit a robust immune response against MUC1(Tn) bearing a defined tumor-associated glycoform, Tn. The two-component vaccine construct was prepared by sortase-mediated protein ligation of a synthetic MUC1(Tn) fragment to a class II MHC-binding single-domain antibody fragment (VHH7) as targeting moiety. We show that VHH7 targets antigen presenting cells in vivo, and when conjugated to MUC1(Tn) can elicit a strong αMUC1(Tn) immune response in mice. The resulting sera preferentially recognized the MUC1 epitope with the tumor-associated carbohydrate antigen Tn and were capable of killing cancer cells in a complement-mediated cytotoxicity assay. Immunoglobulin isotype analysis and cytokine release assays suggested a favorable Th1 response. A single boost 12 months after primary immunization triggered a recall response of the same quality, suggesting that long-term αMUC1(Tn) memory had been achieved.

Chitosan nanoparticles based nanovaccines for cancer immunotherapy

Cancer immunotherapy based on tumor vaccine is very promising and intriguing for carcinoma treatment. Herein, antitumor nanovaccines consisting of self-assembled chitosan (CS) nanoparticles and two-component mucin1 (MUC1) glycopeptide antigens were reported. Two different kinds of polyanionic electrolyte [sodium tripolyphosphate (TPP) and γ-poly-L-glutamic acid (γ-PGA)] were combined with chitosan polymers to fabricate the diameter of nearly 400–500 nm CS nanoparticles by electrostatic interactions. The nanovaccines were constructed by physically mixing MUC1 glycopeptide antigens with CS nanoparticles, which reduced vaccine constructing complexity compared with traditional chemical total synthetic vaccines. Immunological studies revealed that the CS/γ-PGA nanoparticle could dramatically enhance the immunogenicity of peptide epitope and produce significantly high titers of IgG antibody which was even better than Freund’s adjuvant-containing vaccines.

Self-Assembled Nano-Immunostimulant for Synergistic Immune Activation

Immunotherapy has become one of the most promising therapies for the treatment of diseases. Synthetic immunostimulants and nanomaterial immunostimulant systems are indispensable for the activation of the immune system in cancer immunotherapy. Herein, a strategy for preparing self-assembled nano-immunostimulants (SANIs) for synergistic immune activation is reported. Three immunostimulants self-assemble into nanoparticles through electrostatic interactions. SANIs showed strong synergistic immunostimulation in macrophages. SANIs could also induce a strong antitumor immune response to inhibit tumor growth in mice and act as an efficient adjuvant of antitumor vaccines. Therefore, SANIs may be generally applied in cancer immunotherapy. This novel SANI strategy provides a new way for the development of both immunostimulants and -suppressants.

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

Glycosylation is an immensely important biological process and one that is highly controlled and very efficient in nature. However, in a chemical laboratory the process is much more challenging and usually requires the extensive use of protecting groups to squelch reactivity at undesired reactive moieties. Nonetheless, by taking advantage of the differential reactivity of the anomeric center, a selective activation at this position is possible. As a result, protecting group-free strategies to effect glycosylations are available thanks to the tremendous efforts of many research groups. In this review, we showcase the methods available for the selective activation of the anomeric center on the glycosyl donor and the mechanisms by which the glycosylation reactions take place to illustrate the power these techniques.

Immunogenicity of a Fully Synthetic MUC1 Glycopeptide Antitumor Vaccine Enhanced by Poly(I:C) as a TLR3-Activating Adjuvant

Fully synthetic MUC1 glycopeptide antitumor vaccines have a precisely specified structure and induce a targeted immune response without suppression of the immune response when using an immunogenic carrier protein. However, tumor-associated aberrantly glycosylated MUC1 glycopeptides are endogenous structures, "self-antigens", that exhibit only low immunogenicity. To overcome this obstacle, a fully synthetic MUC1 glycopeptide antitumor vaccine was combined with poly(inosinic acid:cytidylic acid), poly(I:C), as a structurally defined Toll-like receptor 3 (TLR3)-activating adjuvant. This vaccine preparation elicited extraordinary titers of IgG antibodies which strongly bound human breast cancer cells expressing tumor-associated MUC1. Beside the humoral response, the poly(I:C) glycopeptide vaccine induced a pro-inflammatory environment, very important to overcome the immune-suppressive mechanisms, and elicited a strong cellular immune response crucial for tumor elimination.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

Harnessing cancer cell metabolism for theranostic applications using metabolic glycoengineering of sialic acid in breast cancer as a pioneering example

Abnormal cell surface display of sialic acids - a family of unusual 9-carbon sugars - is widely recognized as distinguishing feature of many types of cancer. Sialoglycans, however, typically cannot be identified with sufficiently high reproducibility and sensitivity to serve as clinically accepted biomarkers and similarly, almost all efforts to exploit cancer-specific differences in sialylation signatures for therapy remain in early stage development. In this report we provide an overview of important facets of glycosylation that contribute to cancer in general with a focus on breast cancer as an example of malignant disease characterized by aberrant sialylation. We then describe how cancer cells experience nutrient deprivation during oncogenesis and discuss how the resulting metabolic reprogramming, which endows breast cancer cells with the ability to obtain nutrients during scarcity, constitutes an "Achilles' heel" that we believe can be exploited by metabolic glycoengineering (MGE) strategies to develop new diagnostic methods and therapeutic approaches. In particular, we hypothesize that adaptations made by breast cancer cells that allow them to efficiently scavenge sialic acid during times of nutrient deprivation renders them vulnerable to MGE, which refers to the use of exogenously-supplied, non-natural monosaccharide analogues to modulate targeted aspects of glycosylation in living cells and animals. In specific, once non-natural sialosides are incorporated into the cancer "sialome" they can be exploited as epitopes for immunotherapy or as chemical tags for targeted delivery of imaging or therapeutic agents selectively to tumors.

Microarray Analysis of Antibodies Induced with Synthetic Antitumor Vaccines: Specificity against Diverse Mucin Core Structures

Glycoprotein research is pivotal for vaccine development and biomarker discovery. Many successful methodologies for reliably increasing the antigenicity toward tumor-associated glycopeptide structures have been reported. Deeper insights into the quality and specificity of the raised polyclonal, humoral reactions are often not addressed, despite the fact that an immunological memory, which produces antibodies with cross-reactivity to epitopes exposed on healthy cells, may cause autoimmune diseases. In the current work, three MUC1 antitumor vaccine candidates conjugated with different immune stimulants are evaluated immunologically. For assessment of the influence of the immune stimulant on antibody recognition, a comprehensive library of mucin 1 glycopeptides (>100 entries) is synthesized and employed in antibody microarray profiling; these range from small tumor-associated glycans (T_N , ST_N , and T-antigen structures) to heavily extended O-glycan core structures (type-1 and type-2 elongated core 1-3 tri-, tetra-, and hexasaccharides) glycosylated in variable density at the five different sites of the MUC1 tandem repeat. This is one of the most extensive glycopeptide libraries ever made through total synthesis. On tumor cells, the core 2 β-1,6-N-acetylglucosaminyltransferase-1 (C2GlcNAcT-1) is down-regulated, resulting in lower amounts of the branched core 2 structures, which favor formation of linear core 1 or core 3 structures, and in particular, truncated tumor-associated antigen structures. The core 2 structures are commonly found on healthy cells and the elucidation of antibody cross-reactivity to such epitopes may predict the tumor-selectivity and safety of synthetic vaccines. With the extended mucin core structures in hand, antibody cross-reactivity toward the branched core 2 glycopeptide epitopes is explored. It is observed that the induced antibodies recognize MUC1 peptides with very high glycosylation site specificity. The nature of the antibody response is characteristically different for antibodies directed to glycosylation sites in either the immune-dominant PDTR or the GSTA domain. All antibody sera show high reactivity to the tumor-associated saccharide structures on MUC1. Extensive glycosylation with branched core 2 structures, typically found on healthy cells, abolishes antibody recognition of the antisera and suggests that all vaccine conjugates preferentially induce a tumor-specific humoral immune response.

Large-scale synthesis and structural analysis of a synthetic glycopeptide dendrimer as an anti-cancer vaccine candidate

A complex glycopeptide was obtained in multigram as a fully synthetic anti-cancer vaccine for human use.

Genetically engineered mucin mouse models for inflammation and cancer

Mucins are heavily O-glycosylated proteins primarily produced by glandular and ductal epithelial cells, either in membrane-tethered or secretory forms, for providing lubrication and protection from various exogenous and endogenous insults. However, recent studies have linked their aberrant overexpression with infection, inflammation, and cancer that underscores their importance in tissue homeostasis. In this review, we present current status of the existing mouse models that have been developed to gain insights into the functional role(s) of mucins under physiological and pathological conditions. Knockout mouse models for membrane-associated (Muc1 and Muc16) and secretory mucins (Muc2) have helped us to elucidate the role of mucins in providing effective and protective barrier functions against pathological threats, participation in disease progression, and improved our understanding of mucin interaction with biotic and abiotic environmental components. Emphasis is also given to available transgenic mouse models (MUC1 and MUC7), which has been exploited to understand the context-dependent regulation and therapeutic potential of human mucins during inflammation and cancer.

Novel Immunotherapeutic Approaches for Head and Neck Squamous Cell Carcinoma

The immune system plays a key role in preventing tumor formation by recognizing and destroying malignant cells. For over a century, researchers have attempted to harness the immune response as a cancer treatment, although this approach has only recently achieved clinical success. Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide and is associated with cigarette smoking, alcohol consumption, betel nut use, and human papillomavirus infection. Unfortunately, worldwide mortality from HNSCC remains high, partially due to limits on therapy secondary to the significant morbidity associated with current treatments. Therefore, immunotherapeutic approaches to HNSCC treatment are attractive for their potential to reduce morbidity while improving survival. However, the application of immunotherapies to this disease has been challenging because HNSCC is profoundly immunosuppressive, resulting in decreased absolute lymphocyte counts, impaired natural killer cell function, reduced antigen-presenting cell function, and a tumor-permissive cytokine profile. Despite these challenges, numerous clinical trials testing the safety and efficacy of immunotherapeutic approaches to HNSCC treatment are currently underway, many of which have produced promising results. This review will summarize immunotherapeutic approaches to HNSCC that are currently undergoing clinical trials.

Presentation of underglycosylated mucin 1 in pancreatic adenocarcinoma (PDAC) at early stages

Underglycosylated mucin 1 antigen (uMUC1) is a proven biomarker of cancer progression relevant to many malignancies including pancreatic ductal adenocarcinoma (PDAC). However, while ample evidence exists of the expression of total MUC1, little is known about the abundance of the underglycolsylated form of the antigen and its significance in disease progression. Such knowledge is important because the underglycosylated form of MUC1 is intimately linked to metastatic potential. Here, we investigated the expression uMUC1 at various stages of PDAC including pancreatic intraepithelial neoplasia (PanIN). Immunohistochemical analysis was performed on human tissue microarrays (TMAs) containing PDAC and PanIN using monoclonal antibody specific to uMUC1. uMUC1 expression was analyzed by a traditional pathological scoring system and using automatic imaging analysis software. Our results demonstrated low uMUC1 abundance in PanIN lesions and a transient increase in antigen availability in stage I PDAC, followed by decreased expression in later stages of the disease. An additional finding was that there was intermediate expression of uMUC1 in adjacent normal tissues from PDAC irrespective of the stage. These studies suggest the intriguing possibility that a pro-metastatic uMUC1 expression signature may appear at early stages of PDAC, providing an additional clue about the aggressive nature of pancreatic cancer.

Cytotoxic T cell responses are enhanced by antigen design involving the presentation of MUC1 peptide on cholera toxin B subunit

Induction of cytotoxic T lymphocytes (CTL) is critical to cancer vaccine based immunotherapy. Efforts to elicit CTLs against tumor MUC1 with peptide based vaccine have not been successful in clinical application. We have design a MUC1 vaccine by replacing B cell epitope of CTB with MUC1 VNTR peptide. Immunization with hybrid CTB-MUC1 plus aluminum hydroxide and CpG adujuvant (CTB-MUC1-Alum-CpG) induce MUC1-specific CTLs in mice. Moreover, this vaccination can prevent tumor growth and reduce tumor burden in MUC1⁺B16 mice model. Meanwhile, CTB-MUC1-Alum-CpG vaccination can promote Th1 cells and CD8+ T cells inflate to tumor tissue. Our approach might be applicable to other cancer vaccine design.

Lipopeptides: a novel antigen repertoire presented by major histocompatibility complex class I molecules

Post-translationally modified peptides, such as those containing either phosphorylated or O-glycosylated serine/threonine residues, may be presented to cytotoxic T lymphocytes (CTLs) by MHC class I molecules. Most of these modified peptides are captured in the MHC class I groove in a similar manner to that for unmodified peptides. N-Myristoylated 5-mer lipopeptides have recently been identified as a novel chemical class of MHC class I-presented antigens. The rhesus classical MHC class I allele, Mamu-B*098, was found to be capable of binding N-myristoylated lipopeptides and presenting them to CTLs. A high-resolution X-ray crystallographic analysis of the Mamu-B*098:lipopeptide complex revealed that the myristic group as well as conserved C-terminal serine residue of the lipopeptide ligand functioned as anchors, whereas the short stretch of three amino acid residues located in the middle of the lipopeptides was only exposed externally with the potential to interact directly with specific T-cell receptors. Therefore, the modes of lipopeptide-ligand interactions with MHC class I and with T-cell receptors are novel and fundamentally distinct from that for MHC class I-presented peptides. Another lipopeptide-presenting MHC class I allele has now been identified, leading us to the prediction that MHC class I molecules may be separated on a functional basis into two groups: one presenting long peptides and the other presenting short lipopeptides. Since the N-myristoylation of viral proteins is often linked to pathogenesis, CTLs capable of sensing N-myristoylation may serve to control pathogenic viruses, raising the possibility for the development of a new type of lipopeptide vaccine.

Delivery of therapeutics with nanoparticles: what's new in cancer immunotherapy?

The application of nanotechnology to the treatment of cancer or other diseases has been boosted during the last decades due to the possibility to precise deliver drugs where needed, enabling a decrease in the drug's side effects. Nanocarriers are particularly valuable for potentiating the simultaneous co-delivery of multiple drugs in the same particle for the treatment of heavily burdening diseases like cancer. Immunotherapy represents a new concept in the treatment of cancer and has shown outstanding results in patients treated with check-point inhibitors. Thereby, researchers are applying nanotechnology to cancer immunotherapy toward the development of nanocarriers for delivery of cancer vaccines and chemo-immunotherapies. Cancer nanovaccines can be envisioned as nanocarriers co-delivering antigens and adjuvants, molecules often presenting different physicochemical properties, in cancer therapy. A wide range of nanocarriers (e.g., polymeric, lipid-based and inorganic) allow the co-formulation of these molecules, or the delivery of chemo- and immune-therapeutics in the same system. Finally, there is a trend toward the use of biologically inspired and derived nanocarriers. In this review, we present the recent developments in the field of immunotherapy, describing the different systems proposed by categories: polymeric nanoparticles, lipid-based nanosystems, metallic and inorganic nanosystems and, finally, biologically inspired and derived nanovaccines. WIREs Nanomed Nanobiotechnol 2017, 9:e1421. doi: 10.1002/wnan.1421 For further resources related to this article, please visit the WIREs website.

Immunological Evaluation of Recent MUC1 Glycopeptide Cancer Vaccines

Aberrantly glycosylated mucin 1 (MUC1) is a recognized tumor-specific antigen on epithelial cell tumors. A wide variety of MUC1 glycopeptide anti-cancer vaccines have been formulated by many research groups. Some researchers have used MUC1 alone as an immunogen whereas other groups used different antigenic carrier proteins such as bovine serum albumin or keyhole limpet hemocyanin for conjugation with MUC1 glycopeptide. A variety of adjuvants have been used with MUC1 glycopeptides to improve their immunogenicity. Fully synthetic multicomponent vaccines have been synthesized by incorporating different T helper cell epitopes and Toll-like receptor agonists. Some vaccine formulations utilized liposomes or nanoparticles as vaccine delivery systems. In this review, we discuss the immunological evaluation of different conjugate or synthetic MUC1 glycopeptide vaccines in different tumor or mouse models that have been published since 2012.

Novel targets for paclitaxel nano formulations: Hopes and hypes in triple negative breast cancer

Triple negative breast cancer is defined as one of the utmost prevailing breast cancers worldwide, possessing an inadequate prognosis and treatment option limited to chemotherapy and radiotherapy, creating a challenge for researchers as far as developing a specific targeted therapy is concerned. The past research era has shown several promising outcomes for TNBC such as nano-formulations of the chemotherapeutic agents already used for the management of the malignant tumor. Taking a glance at paclitaxel nano formulations, it has been proven beneficial in several researches in the past decade; nevertheless its solubility is often a challenge to scientists in achieving success. We have henceforth discussed the basic heterogeneity of triple negative breast cancer along with the current management options as well as a brief outlook on pros and cons of paclitaxel, known as the most widely used chemotherapeutic agent for the treatment of the disease. We further analyzed the need of nanotechnology pertaining to the problems encountered with the current paclitaxel formulations available discussing the strategic progress in various nano-formulations till date taking into account the basic research strategies required in terms of solubility, permeability, physicochemical properties, active and passive targeting. A thorough review in recent advances in active targeting for TNBC was carried out whereby the various ligands which are at present finding its way into TNBC research such as hyaluronic acid, folic acid, transferrin, etc. were discussed. These ligands have specific receptor affinity to TNBC tumor cells hence can be beneficial for novel drug targeting approaches. Conversely, there are currently several novel strategies in the research pipeline whose targeting ligands have not yet been studied. Therefore, we reviewed upon the numerous novel receptor targets along with the respective nano-formulation aspects which have not yet been fully researched upon and could be exemplified as outstanding target strategies for TNBC which is currently an urgent requirement.

Aberrant Glycosylation of Anchor-Optimized MUC1 Peptides Can Enhance Antigen Binding Affinity and Reverse Tolerance to Cytotoxic T Lymphocytes

Cancer vaccines have often failed to live up to their promise, although recent results with checkpoint inhibitors are reviving hopes that they will soon fulfill their promise. Although mutation-specific vaccines are under development, there is still high interest in an off-the-shelf vaccine to a ubiquitous antigen, such as MUC1, which is aberrantly expressed on most solid and many hematological tumors, including more than 90% of breast carcinomas. Clinical trials for MUC1 have shown variable success, likely because of immunological tolerance to a self-antigen and to poor immunogenicity of tandem repeat peptides. We hypothesized that MUC1 peptides could be optimized, relying on heteroclitic optimizations of potential anchor amino acids with and without tumor-specific glycosylation of the peptides. We have identified novel MUC1 class I peptides that bind to HLA-A*0201 molecules with significantly higher affinity and function than the native MUC1 peptides. These peptides elicited CTLs from normal donors, as well as breast cancer patients, which were highly effective in killing MUC1-expressing MCF-7 breast cancer cells. Each peptide elicited lytic responses in greater than 6/8 of normal individuals and 3/3 breast cancer patients. The CTLs generated against the glycosylated-anchor modified peptides cross reacted with the native MUC1 peptide, STAPPVHNV, suggesting these analog peptides may offer substantial improvement in the design of epitope-based vaccines.

Interactions of mucins with the Tn or Sialyl Tn cancer antigens including MUC1 are due to GalNAc-GalNAc interactions

The molecular mechanism(s) underlying the enhanced self-interactions of mucins possessing the Tn (GalNAcα1-Ser/Thr) or STn (NeuNAcα2-6GalNAcα1-Ser/Thr) cancer markers were investigated using optical tweezers (OT). The mucins examined included modified porcine submaxillary mucin containing the Tn epitope (Tn-PSM), ovine submaxillary mucin with the STn epitope (STn-OSM), and recombinant MUC1 analogs with either the Tn and STn epitope. OT experiments in which the mucins were immobilized onto polystyrene beads revealed identical self-interaction characteristics for all mucins. Identical binding strength and energy landscape characteristics were also observed for synthetic polymers displaying multiple GalNAc decorations. Polystyrene beads without immobilized mucins showed no self-interactions and also no interactions with mucin-decorated polystyrene beads. Taken together, the experimental data suggest that in these molecules, the GalNAc residue mediates interactions independent of the anchoring polymer backbone. Furthermore, GalNAc-GalNAc interactions appear to be responsible for self-interactions of mucins decorated with the STn epitope. Hence, Tn-MUC1 and STn-MUC1 undergo self-interactions mediated by the GalNAc residue in both epitopes, suggesting a possible molecular role in cancer. MUC1 possessing the T (Galβ1-3GalNAcα1-Ser/Thr) or ST antigen (NeuNAcα2-3Galβ1-3GalNAcα1-Ser/Thr) failed to show self-interactions. However, in the case of ST-MUC1, self-interactions were observed after subsequent treatment with neuraminidase and β-galactosidase. This enzymatic treatment is expected to introduce Tn-epitopes and these observations thus further strengthen the conclusion that the observed interactions are mediated by the GalNAc groups.

Entirely Carbohydrate-Based Vaccines: An Emerging Field for Specific and Selective Immune Responses

Carbohydrates are regarded as promising targets for vaccine development against infectious disease because cell surface glycans on many infectious agents are attributed to playing an important role in pathogenesis. In addition, oncogenic transformation of normal cells, in many cases, is associated with aberrant glycosylation of the cell surface glycan generating tumor associated carbohydrate antigens (TACAs). Technological advances in glycobiology have added a new dimension to immunotherapy when considering carbohydrates as key targets in developing safe and effective vaccines to combat cancer, bacterial infections, viral infections, etc. Many consider effective vaccines induce T-cell dependent immunity with satisfactory levels of immunological memory that preclude recurrence. Unfortunately, carbohydrates alone are poorly immunogenic as they do not bind strongly to the MHCII complex and thus fail to elicit T-cell immunity. To increase immunogenicity, carbohydrates have been conjugated to carrier proteins, which sometimes can impede carbohydrate specific immunity as peptide-based immune responses can negate antibodies directed at the targeted carbohydrate antigens. To overcome many challenges in using carbohydrate-based vaccine design and development approaches targeting cancer and other diseases, zwitterionic polysaccharides (ZPSs), isolated from the capsule of commensal anaerobic bacteria, will be discussed as promising carriers of carbohydrate antigens to achieve desired immunological responses.

Preparation and evaluation of the tumor-specific antigen-derived synthetic mucin 1 peptide: A potential candidate for the targeting of breast carcinoma

PURPOSE

The goal of this study was to prepare a synthetic peptide derived from breast tumor associated antigen and to evaluate its potential as a breast cancer imaging agent.

METHODS

A mucin 1 derived peptide was synthesized by solid-phase peptide synthesis and examined for its radiochemical and metabolic stability. The tumor cell binding affinity of (99m)Tc-MUC1 peptide was investigated on MUC1-positive T47D and MCF7 breast cancer cell lines. In vivo biodistribution was studied in normal Balb/c mice and in vivo tumor targeting and imaging in MCF7 and T47D tumor-bearing nude mice.

RESULTS

The synthesized MUC1-derived peptide displayed high radiochemical and metabolic stability. In vitro tumor cell-binding on T47D and MCF7 cell lines demonstrated high affinity of (99m)Tc-MUC1 peptide towards human breast cancer cells (binding affinities in nanomolar range). Pharmacokinetic studies performed on Balb/c mice are characterized by an efficient clearance from the blood and excretion predominantly through the urinary system. In vivo tumor uptake in nude mice with MCF7 tumor xenografts was 2.77±0.63% ID/g as early as 1h p.i. whereas in nude mice with T47D human ductal breast epithelial cancer cells, the accumulation in the tumor was found to be 2.65±0.54% ID/g at 1h p.i. Also tumor lesion was detectable in γ-camera imaging. The tumor uptake values were always higher than the blood and muscle uptake, with good tumor retention and good tumor-to-blood and tumor-to-muscle ratios. A low to moderate (<5% ID/g) accumulation and retention of (99m)Tc-MUC1 was found in the major organs (i.e., lungs, stomach, liver, intestines, kidneys, etc.) in both normal and tumor-bearing mice.

CONCLUSION

This study suggests that (99m)Tc-MUC1 tumor-antigen peptide may be a potential candidate for the targeted imaging of MUC1-positive human tumors and warrants further investigation.

Mucin architecture behind the immune response: design, evaluation and conformational analysis of an antitumor vaccine derived from an unnatural MUC1 fragment

A tripartite cancer vaccine candidate, containing a quaternary amino acid (α-methylserine) in the most immunogenic domain of MUC1, has been synthesized and examined for antigenic properties in transgenic mice. The vaccine which is glycosylated with GalNAc at the unnatural amino acid, was capable of eliciting potent antibody responses recognizing both glycosylated and unglycosylated tumour-associated MUC1 peptides and native MUC1 antigen present on cancer cells. The peptide backbone of the novel vaccine presents the bioactive conformation in solution and is more resistant to enzymatic degradation than the natural counter part. In spite of these features, the immune response elicited by the unnatural vaccine was not improved compared to a vaccine candidate containing natural threonine. These observations were rationalized by conformational studies, indicating that the presentation and dynamics of the sugar moiety displayed by the MUC1 derivative play a critical role in immune recognition. It is clear that engineered MUC1-based vaccines bearing unnatural amino acids have to be able to emulate the conformational properties of the glycosidic linkage between the GalNAc and the threonine residues. The results described here will be helpful to the rational design of efficacious cancer vaccines.

Up-regulation of C1GALT1 promotes breast cancer cell growth through MUC1-C signaling pathway

Aberrant glycosylation is frequently observed in cancers. Core 1 β1,3-galactosyltransferase (C1GALT1) is an exclusive enzyme in humans that catalyzes the biosynthesis of core 1 O-glycan structure, Gal-GalNAc-O-Ser/Thr, whose expression is commonly up-regulated during tumorigenesis. Little is known about the function of C1GALT1 in breast cancer. This study aims to determine the correlation between C1GALT1 expression and breast cancer clinicopathological features and roles of C1GALT1 in breast cancer malignant phenotypes. Public databases and our data showed that C1GALT1 mRNA and C1GALT1 protein are frequently up-regulated in breast cancer; and increased C1GALT1 expression correlates with higher histological grade and advanced tumor stage. Overexpression of C1GALT1 enhanced breast cancer cell growth, migration, and invasion in vitro as well as tumor growth in vivo. Conversely, C1GALT1 knockdown suppressed these malignant phenotypes. Furthermore, C1GALT1 modulates O-glycan structures on Mucin (MUC) 1 and promotes MUC1-C/β-catenin signaling in breast cancer cells. These findings suggest that C1GALT1 enhances breast cancer malignant progression through promoting MUC1-C/β-catenin signaling pathway. Unveiling the function of C1GALT1 in breast cancer opens new insights to the roles of C1GALT1 and O-glycosylation in tumorigenesis and renders the potential of C1GALT1 as a target of novel therapeutic agent development.

MUC1 Vaccines, Comprised of Glycosylated or Non-Glycosylated Peptides or Tumor-Derived MUC1, Can Circumvent Immunoediting to Control Tumor Growth in MUC1 Transgenic Mice

It remains challenging to produce decisive vaccines against MUC1, a tumor-associated antigen widely expressed by pancreas, breast and other tumors. Employing clinically relevant mouse models, we ruled out such causes as irreversible T-cell tolerance, inadequate avidity, and failure of T-cells to recognize aberrantly glycosylated tumor MUC1. Instead, every tested MUC1 preparation, even non-glycosylated synthetic 9mer peptides, induced interferon gamma-producing CD4⁺ and CD8⁺ T-cells that recognized glycosylated variants including tumor-associated MUC1. Vaccination with synthetic peptides conferred protection as long as vaccination was repeated post tumor challenge. Failure to revaccinate post challenge was associated with down-regulated tumor MUC1 and MHC molecules. Surprisingly, direct admixture of MUC1-expressing tumor with MUC1-hyperimmune T-cells could not prevent tumor outgrowth or MUC1 immunoediting, whereas ex vivo activation of the hyperimmune T-cells prior to tumor admixture rendered them curative. Therefore, surrogate T-cell preactivation outside the tumor bed, either in culture or by repetitive vaccination, can overcome tumor escape.

Synthesis of a Liposomal MUC1 Glycopeptide-Based Immunotherapeutic and Evaluation of the Effect of l-Rhamnose Targeting on Cellular Immune Responses

Generation of a CD8(+) response to extracellular antigen requires processing of the antigen by antigen presenting cells (APC) and cross-presentation to CD8(+) T cell receptors via MHC class I molecules. Cross-presentation is facilitated by efficient antigen uptake followed by immune-complex-mediated maturation of the APCs. We hypothesize that improved antigen uptake of a glycopeptide sequence containing a CD8(+) T cell epitope could be achieved by delivering it on a liposome surface decorated with an immune complex-targeting ligand, an l-Rhamnose (Rha) epitope. We synthesized a 20-amino-acid glycopeptide TSAPDT(GalNAc)RPAPGSTAPPAHGV from the variable number tandem repeat region of the tumor marker MUC1 containing an N-terminal azido moiety and a tumor-associated α-N-acetyl galactosamine (GalNAc) at the immunogenic DTR motif. The MUC1 antigen was attached to Pam3Cys, a Toll-like receptor-2 ligand via copper(I)-catalyzed azido-alkyne cycloaddition (CuAAc) chemistry. The Rha-decorated liposomal Pam3Cys-MUC1-Tn 4 vaccine was evaluated in groups of C57BL/6 mice. Some groups were previously immunized to generate anti-Rha antibodies. Anti-Rha antibody expressing mice that received the Rha liposomal vaccine showed higher cellular immunogenicity compared to the control group while maintaining a strong humoral response.

Synthesis and immunological evaluation of N-acyl modified Tn analogues as anticancer vaccine candidates

Tumor-associated carbohydrate antigens (TACAs), which are aberrantly expressed on the surface of tumor cells, are important targets for anticancer vaccine development. Herein, several N-acyl modified Tn analogues were synthesized and conjugated with carrier protein CRM197. The immunological results of these glycoconjugates indicated that 6-CRM197 elicited higher titers of antibodies which cross-reacted with native Tn antigen than the unmodified 2-CRM197 did. The IFN-γ-producing frequency of lymphocytes in mice treated with 6-CRM197 was obviously increased, compared to that of mice vaccinated with 2-CRM197 (p=0.016), which was typically associated with the Th1 response. Moreover, the elicited antisera against antigen 6-CRM197 reacted strongly with the Tn-positive tumor cells, implying the potential of this glycoconjugate as an anticancer vaccine.

Synthesis and immunological evaluation of MUC1 glycopeptide conjugates bearing N-acetyl modified STn derivatives as anticancer vaccines

Unnatural STn disaccharides with N-acetyl modifications were incorporated into a 20-amino acid MUC1 tandem repeat sequence. The modified STn-MUC1 glycopeptide–protein conjugates showed high immunogenicity.

Fully synthetic self-adjuvanting MUC1-fibroblast stimulating lipopeptide 1 conjugates as potential cancer vaccines

We have designed and synthesized MUC1-fibroblast stimulating lipopeptide 1 conjugates as potential self-adjuvanting cancer vaccines using a linear solid phase peptide synthesis strategy.

Effects of the multiple O-glycosylation states on antibody recognition of the immunodominant motif in MUC1 extracellular tandem repeats

The conformational impact of the clusteredO-glycans strongly influences recognition by antibodies of the cancer-relevant epitope in the MUC1 extracellular tandem repeat domain.

Multi-component self-assembled anti-tumor nano-vaccines based on MUC1 glycopeptides

Novel multi-component self-assembled nano-vaccines containing both Pam₃CSK₄ and CpG were developed based on the strategy of electrostatic interaction.

Glycomaterials for immunomodulation, immunotherapy, and infection prophylaxis

Synthetic carbohydrate-modified materials that can engage the innate and adaptive immune systems are receiving increasing interest to confer protection against onset of future disease, such as pathogen infection, as well as to treat established diseases, such as autoimmunity and cancer.

Molecular basis of antibody binding to mucin glycopeptides in lung cancer

Glycopeptides bearing Tn epitopes are emerging targets for cancer diagnosis and immunotherapy. In this study, we analyzed membrane proteins containing O-glycosylated tandem repeat (TR) sequences in lung cancer patients of different types and stages, using gene microarray data in public domain. The expression of Tn and glycopeptide epitopes on the surface of lung cancer cell lines were studied by monoclonal IgG antibodies 14A, 16A, and B72.3. The binding of mAbs to synthetic glycopeptides were studied by surface plasmon resonance. Nine mucin mRNAs were found to be expressed in lung cancer patients but at similar level to healthy individuals. At protein level, a glycopeptide epitope on cancer cell surface is preferably recognized by mAb 16A, as compared to peptide-alone (14A) or sugar-alone epitopes (B72.3). 14A and 16A favor clustered TR containing more than three TR sequences, with 10-fold lower Kd than two consecutive TR. B72.3 preferrably recognized clustered sialyl-Tn displayed on MUC1 but not other O-glycoproteins, with 100-fold stronger binding when MUC1 is transfected as a sugar carrier, while the total sugar epitopes remain unchanged. These findings indicate that clusters of both TR backbones and sugars are essential for mAb binding to mucin glycopeptides. Three rules of antibody binding to mucin glycopeptides at molecular level are presented here: first, the peptide backbone of a glycopeptide is preferentially recognized by B cells through mutations in complementarity determining regions (CDRs) of B cell receptor, and the sugar-binding specificity is acquired through mutations in frame work of heavy chain; secondly, consecutive tandem repeats (TR) of peptides and glycopeptides are preferentially recognized by B cells, which favor clustered TR containing more than three TR sequences; thirdly, certain sugar-specific B cells recognize and accommodate clustered Tn and sialyl-Tn displayed on the surface of a mucin but not other membrane proteins.

Preparation and evaluation of polyethylenimine-functionalized carbon nanotubes tagged with 5TR1 aptamer for targeted delivery of Bcl-xL shRNA into breast cancer cells

In this study, single-walled carbon nanotubes (SWCNTs) were covalently attached to poly(ethylene glycol) (PEG) and polyethylenimine (PEI) 10 kDa, or its derivatives, to fabricate efficient carriers for gene delivery. PEI 10 kDa was modified by alkylcarboxylation of its primary amines with a series of ω-bromo-alkylcarboxylic acids to provide a range of vectors with increased lipophilicity. PEI 10 kDa or its alkylcarboxylate derivatives were conjugated to SWCNT-PEG to develop vectors possessing effective DNA condensation ability which can interact with cell membrane via both nano-needle mechanism and electrostatic interactions produced by SWCNT and PEI, respectively. The results demonstrated that SWCNT-PEG-PEI and SWCNT-PEG-derivatives of PEI could condense DNA into particle size less than 150 nm with positive surface charges between 6.3-30.8 mV. To improve the antitumor efficacy, we developed a targeted gene delivery system using a 5 TR1 aptamer. The most efficient vector, which was prepared by attachment of SWCNT-PEG to modified PEI 10 kDa with 10-bromodecanoic acid (10%), showed 8.5-10 folds enhancement in transfection activity at C/P ratio 6 as compared to the gold standard PEI 25 kDa at C/P ratio of 0.8. We also showed that the selected polyplex could efficiently and selectively transfer plasmid shRNA to MUC1 positive cells.

A Fully Synthetic Self-Adjuvanting Globo H-Based Vaccine Elicited Strong T Cell-Mediated Antitumor Immunity

Therapeutic cancer vaccines based on the abnormal glycans expressed on cancer cells, such as the globo H antigen, have witnessed great progress in recent years. For example, the keyhole limpet hemocyanin (KLH) conjugate of globo H has been on clinical trials as a cancer vaccine. However, such vaccines have intrinsic problems, such as inconsistence in eliciting T cell-mediated immunity in cancer patients and difficult quality control. To address the issue, a structurally defined fully synthetic glycoconjugate vaccine composed of globo H and monophosphoryl lipid A (MPLA) was developed. The new vaccine was shown to elicit robust IgG1 antibody responses and T cell-dependent immunity, which is desired for anticancer vaccine, and induce significantly faster and stronger immune responses than the globo H-KLH conjugate. Moreover, it was self-adjuvanting, namely, inducing immune responses without the use of an external adjuvant, thus MPLA was not only a vaccine carrier but also a build-in adjuvant. It was also found that antibodies induced by the new vaccine could selectively bind to and mediate strong complement-dependent cytotoxicity to globo H-expressing MCF-7 cancer cell. All of the results have demonstrated that the globo H-MPLA conjugate is a better cancer vaccine than the globo H-KLH conjugate under experimental conditions and is worth further investigation and development.