Expression of underglycosylated MUC1 antigen in cancerous and adjacent normal breast tissues

Research progress of MUC1 in genitourinary cancers

MUC1 is a highly glycosylated transmembrane protein with a high molecular weight. It plays a role in lubricating and protecting mucosal epithelium, participates in epithelial cell renewal and differentiation, and regulates cell adhesion, signal transduction, and immune response. MUC1 is expressed in both normal and malignant epithelial cells, and plays an important role in the diagnosis, prognosis prediction and clinical monitoring of a variety of tumors and is expected to be a new therapeutic target. This article reviews the structural features, expression regulation mechanism, and research progress of MUC1 in the development of genitourinary cancers and its clinical applications.

Tumor-associated carbohydrate antigens of MUC1 - Implication in cancer development

Glycosylation of cancerous epithelial MUC1 protein is specifically altered in comparison to that which is presented by healthy cells. One of such changes is appearing tumor-associated carbohydrate antigens (TACAs) which are rare in normal tissues and are highly correlated with poor clinical outcomes and cancer progression. This review summarizes and describes the role of Tn, T antigens, their sialylated forms as well as fucosylated Lewis epitopes in different aspects of tumor development, progression, and metastasis. Finally, applications of MUC1 glycan epitopes as potential targets for therapeutic strategy of cancers are notified. One of the novelties of this review is presentation of TACAs as inherently connected with MUC1 mucin.

Deep Learning-based structure modelling illuminates structure and function in uncharted regions of β-solenoid fold space

Repeat proteins are common in all domains of life and exhibit a wide range of functions. One class of repeat protein contains solenoid folds where the repeating unit consists of β-strands separated by tight turns. β-solenoids have distinguishing structural features such as handedness, twist, oligomerisation state, coil shape and size which give rise to their diversity. Characterised β-solenoid repeat proteins are known to form regions in bacterial and viral virulence factors, antifreeze proteins and functional amyloids. For many of these proteins, the experimental structure has not been solved, as they are difficult to crystallise or model. Here we use various deep learning-based structure-modelling methods to discover novel predicted β-solenoids, perform structural database searches to mine further structural neighbours and relate their predicted structure to possible functions. We find both eukaryotic and prokaryotic adhesins, confirming a known functional linkage between adhesin function and the β-solenoid fold. We further identify exceptionally long, flat β-solenoid folds as possible structures of mucin tandem repeat regions and unprecedentedly small β-solenoid structures. Additionally, we characterise a novel β-solenoid coil shape, the FapC Greek key β-solenoid as well as plausible complexes between it and other proteins involved in Pseudomonas functional amyloid fibres.

Anti-PD1 antibody enhances the anti-tumor efficacy of MUC1-MBP fusion protein vaccine via increasing Th1, Tc1 activity and decreasing the proportion of MDSC in the B16-MUC1 melanoma mouse model

In previous studies, we have obtained a notable anti-tumor efficacy of the recombinant MUC1-MBP vaccine in the process of mouse B16-MUC1 melanoma treatment. However, the tumor cannot be eliminated completely. We found that the tumor inhibition rate decreased from 81.67% (five immunizations) to 43.67% (eight immunizations) after more than five immunizations, indicating persistent vaccine stimulation may activate immunosuppressive factors. In the present study, we revealed that programmed cell death 1 (PD1), an inhibitory molecule suppressing T cell function, expressed on splenic and tumor-infiltrating T cells were up-regulated by the vaccine. Therefore, to optimize the anti-tumor efficacy of the vaccine, we employed combination immunotherapy with MUC1-MBP vaccine and αPD1 (anti-PD1 antibody). Results showed that combination immunotherapy induced a more remarkable anti-tumor efficacy, the tumor clearance being increased to 80% from 20% which obtain by MUC1-MBP vaccine immunizations. To investigate the possible underlying mechanism, IFN-γ secretion and cytotoxic T lymphocyte (CTL) cytotoxicity were measured by enzyme-linked immunosorbent assay (ELISA) and xCELLigence real-time cell analyzer (RTCA) respectively. T cell subsets and immunosuppressive cells in the mouse spleen and tumor microenvironment were analyzed by FACS. Results showed that the proportion of splenic CD8⁺T cells and tumor infiltration was increased and the activity of CTL killing, T helper 1 (Th1), Type 1 CD8⁺T (Tc1) was enhanced, indicating that the anti-tumor efficacy enhanced by combination immunotherapy was mainly through boosting CD8⁺T cells mediated anti-tumor cellular immunity. Additionally, combination immunotherapy significantly decreased the splenic and tumor-infiltrating myeloid derived suppressor cells (MDSCs). These results demonstrated that combination immunotherapy with MUC1-MBP vaccine and αPD1 was capable to invoke a more potent anti-tumor immune response and provide a foundation for further research.

MUC1-Targeted Radiopharmaceuticals in Cancer Imaging and Therapy

Mucin 1 (MUC1) is a large, transmembrane mucin glycoprotein overexpressed in most adenocarcinomas and plays an important role in tumor progression. Regarding its cellular distribution, biochemical features, and function, tumor-related MUC1 varies from the MUC1 expressed in normal cells. Therefore, targeting MUC1 for cancer immunotherapy and imaging can exploit the difference between cancerous and normal cells. Radiopharmaceuticals have a potential use as carriers for the delivery of radionuclides to tumors for a diagnostic imaging and radiotherapy. Several radiolabeled targeting molecules like peptides, antibodies, and aptamers have been efficiently demonstrated in detecting and treating cancer by targeting MUC1. This review provides a brief overview of the current status of developments and applications of MUC1-targeted radiopharmaceuticals in cancer imaging and therapy.

Potential of Anti-MUC1 Antibodies as a Targeted Therapy for Gastrointestinal Cancers

Gastrointestinal cancers (GI) account for 26% of cancer incidences globally and 35% of all cancer-related deaths. The main challenge is to target cancer specific antigens. Mucins are heavily O-glycosylated proteins overexpressed in different cancers. The transmembrane glycoprotein MUC1 is the most likeable target for antibodies, owing to its specific overexpression and aberrant glycosylation in many types of cancers. For the past 30 years, MUC1 has remained a possible diagnostic marker and therapeutic target. Despite initiation of numerous clinical trials, a comprehensively effective therapy with clinical benefit is yet to be achieved. However, the interest in MUC1 as a therapeutic target remains unaltered. For all translational studies, it is important to incorporate updated relevant research findings into therapeutic strategies. In this review we present an overview of the antibodies targeting MUC1 in GI cancers, their potential role in immunotherapy (i.e., antibody-drug and radioimmunoconjugates, CAR-T cells), and other novel therapeutic strategies. We also present our perspectives on how the mechanisms of action of different anti-MUC1 antibodies can target specific hallmarks of cancer and therefore be utilized as a combination therapy for better clinical outcomes.

Breast cancer cutaneous metastases are associated to uMUC1 and sialyl Lewis x and to highly malignant primary tumors

Breast cancer spreading to different organs have been related to different molecules and mechanisms, but cutaneous metastasis remains unexplored. Increasing evidence showed that MUC1 and some of its carbohydrate associated antigens may be implicated in breast cancer metastasis. In this study we analyzed these tumor markers in order to identify breast cancer cutaneous metastatic profiles. A cohort of 26 primary tumors from breast cancer patients with cutaneous metastases were included; also, cutaneous and lymphatic node metastatic samples and primary tumors from breast cancer patients without metastases were analysed. Immunohistochemical (IHC) studies demonstrated that both underglycosylated MUC1 (uMUC1) and sialyl Lewis x (sLex) to be positively associated with cutaneous metastatic primary tumors (p < 0.05). Notably, a high percentage of tumors with cutaneous metastases were characterized as triple negative and Her2+ tumors (37.5 % and 29 %, respectively). Some discordant results were found between primary tumors and their matched cutaneous metastases. To determine if MUC1 variants may be carriers of carbohydrate antigens, subcellular fractions from a cutaneous metastatic lesion were obtained, immunoprecipitated and analyzed by Western blot. We found that the isolated uMUC1 with a molecular weight of>200 kDa was also the site for binding of anti-sLex MAb; in coincidence, a high correlation of positive IHC expression of both markers was observed. Our findings confirm that breast cancer cutaneous metastases were associated to highly malignant primary tumors and sustain the hypothesis that u-MUC1 and sLe x may drive breast cancer cutaneous metastases.

Indomethacin enhances anti-tumor efficacy of a MUC1 peptide vaccine against breast cancer in MUC1 transgenic mice

In recent years, vaccines against tumor antigens have shown potential for combating invasive cancers, including primary tumors and metastatic lesions. This is particularly pertinent for breast cancer, which is the second-leading cause of cancer-related death in women. MUC1 is a glycoprotein that is normally expressed on glandular epithelium, but is overexpressed and under-glycosylated in most human cancers, including the majority of breast cancers. This under-glycosylation exposes the MUC1 protein core on the tumor-associated form of the protein. We have previously shown that a vaccine consisting of MUC1 core peptides stimulates a tumor-specific immune response. However, this immune response is dampened by the immunosuppressive microenvironment within breast tumors. Thus, in the present study, we investigated the effectiveness of MUC1 vaccination in combination with four different drugs that inhibit different components of the COX pathway: indomethacin (COX-1 and COX-2 inhibitor), celecoxib (COX-2 inhibitor), 1-methyl tryptophan (indoleamine 2,3 dioxygenase inhibitor), and AH6809 (prostaglandin E₂ receptor antagonist). These treatment regimens were explored for the treatment of orthotopic MUC1-expressing breast tumors in mice transgenic for human MUC1. We found that the combination of vaccine and indomethacin resulted in a significant reduction in tumor burden. Indomethacin did not increase tumor-specific immune responses over vaccine alone, but rather appeared to reduce the proliferation and increase apoptosis of tumor cells, thus rendering them susceptible to immune cell killing.

Glycosylation Changes in Brain Cancer

Protein glycosylation is a posttranslational modification that affects more than half of all known proteins. Glycans covalently bound to biomolecules modulate their functions by both direct interactions, such as the recognition of glycan structures by binding partners, and indirect mechanisms that contribute to the control of protein conformation, stability, and turnover. The focus of this Review is the discussion of aberrant glycosylation related to brain cancer. Altered sialylation and fucosylation of N- and O-glycans play a role in the development and progression of brain cancer. Additionally, aberrant O-glycan expression has been implicated in brain cancer. This Review also addresses the clinical potential and applications of aberrant glycosylation for the detection and treatment of brain cancer. The viable roles glycans may play in the development of brain cancer therapeutics are addressed as well as cancer-glycoproteomics and personalized medicine. Glycoprotein alterations are considered as a hallmark of cancer while high expression in body fluids represents an opportunity for cancer assessment.

Restoring anti-oncodriver Th1 responses with dendritic cell vaccines in HER2/neu-positive breast cancer: progress and potential

HER2/neu is expressed in the majority of in situ breast cancers, but maintained in 20-30% of invasive breast cancer (IBC). During breast tumorigenesis, there is a progressive loss of anti-HER2 CD4(pos) Th1 (anti-HER2Th1) from benign to ductal carcinoma in situ, with almost complete loss in IBC. This anti-HER2Th1 response can predict response to neoadjuvant therapy, risk of recurrence and disease-free survival. Vaccines consisting of HER2-pulsed type I polarized dendritic cells (DC1) administered during ductal carcinoma in situ and early IBC can efficiently correct anti-HER2Th1 response and have clinical impact on the disease. In this review, we will discuss the role of anti-HER2Th1 response in the three phases of immunoediting during HER2 breast cancer development and opportunities for reversing these processes using DC1 vaccines alone or in combination with standard therapies. Correcting the anti-HER2Th1 response may represent an opportunity for improving outcomes and providing a path to eliminate escape variants.

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.

CA27.29 as a tumour marker for risk evaluation and therapy monitoring in primary breast cancer patients

Several trials showed that tumour markers are associated with an impaired prognosis for breast cancer. Whether earlier treatment can improve the course of the disease remains controversial. The SUCCESS Trial compares FEC (500/100/500)-docetaxel (100) vs. FEC (500/100/500)-docetaxel/gemcitabine (75/2000) as well as 2 vs. 5 years of zoledronate in high-risk primary breast cancer patients. In 2669 patients, CA27.29 was measured before and after chemotherapy with the ST AIA-PACK CA27.29 reagent for the AIA-600II automated enzyme immunoassay (Tosoh Bioscience, Belgium). Values above 31 U/ml were considered positive. Of the patients, 7.6 % (n = 202, mean 19, range 3-410) and 19.1 % (n = 511, mean 21, range 3-331) had elevated marker levels before and after chemotherapy, respectively. Of the patients, 4.9 and 78 % showed elevated and low CA27.29, respectively, at both time points. After treatment, 35 % of the pre-therapy positive patients were negative, and 15 % of the initially negative patients became positive. The correlation between both time points was significant (p < 0.0001). No correlations among nodal status, grading, hormonal status, HER2 status and CA27.29 levels were found. However, tumour size (p = 0.02), older age (p < 0.001) and post-menopausal status (p = 0.006) were significantly associated with higher CA27.29 levels. Before treatment, the prevalence of elevated CA27.29 was equally distributed between both treatment arms, whereas after chemotherapy, 13.7 % of the patients in the FEC-doc arm showed an increased level vs. 25.4 % of the patients in the FEC-doc/gemcitabine arm (p < 0.0001). However, we could not show a significant association between the G-CSF application (yes vs. no) and CA27.29 status before/after chemotherapy (p = 0.75). These results indicate a close relationship between CA27.29 levels and tumour mass. Increased values after the completion of chemotherapy might be attributed to treatment effects and should be considered with caution.

Functional Consequences of Differential O-glycosylation of MUC1, MUC4, and MUC16 (Downstream Effects on Signaling)

Glycosylation is one of the most abundant post-translational modifications that occur within the cell. Under normal physiological conditions, O-linked glycosylation of extracellular proteins is critical for both structure and function. During the progression of cancer, however, the expression of aberrant and truncated glycans is commonly observed. Mucins are high molecular weight glycoproteins that contain numerous sites of O-glycosylation within their extracellular domains. Transmembrane mucins also play a functional role in monitoring the surrounding microenvironment and transducing these signals into the cell. In cancer, these mucins often take on an oncogenic role and promote a number of pro-tumorigenic effects, including pro-survival, migratory, and invasive behaviors. Within this review, we highlight both the processes involved in the expression of aberrant glycan structures on mucins, as well as the potential downstream impacts on cellular signaling.

Molecular Portrait of the Normal Human Breast Tissue and Its Influence on Breast Carcinogenesis

Normal human breast tissue consists of epithelial and nonepithelial cells with different molecular profiles and differentiation grades. This molecular heterogeneity is known to yield abnormal clones that may contribute to the development of breast carcinomas. Stem cells that are found in developing and mature breast tissue are either positive or negative for cytokeratin 19 depending on their subtype. These cells are able to generate carcinogenesis along with mature cells. However, scientific data remains controversial regarding the monoclonal or polyclonal origin of breast carcinomas. The majority of breast carcinomas originate from epithelial cells that normally express BRCA1. The consecutive loss of the BRCA1 gene leads to various abnormalities in epithelial cells. Normal breast epithelial cells also express hypoxia inducible factor (HIF) 1α and HIF-2α that are associated with a high metastatic rate and a poor prognosis for malignant lesions. The nuclear expression of estrogen receptor (ER) and progesterone receptor (PR) in normal human breast tissue is maintained in malignant tissue as well. Several controversies regarding the ability of ER and PR status to predict breast cancer outcome remain. Both ER and PR act as modulators of cell activity in normal human breast tissue. Ki-67 positivity is strongly correlated with tumor grade although its specific role in applied therapy requires further studies. Human epidermal growth factor receptor 2 (HER2) oncoprotein is less expressed in normal human breast specimens but is highly expressed in certain malignant lesions of the breast. Unlike HER2, epidermal growth factor receptor expression is similar in both normal and malignant tissues. Molecular heterogeneity is not only found in breast carcinomas but also in normal breast tissue. Therefore, the molecular mapping of normal human breast tissue might represent a key research area to fully elucidate the mechanisms of breast carcinogenesis.

Common Genetic Variants of PSCA, MUC1 and PLCE1 Genes are not Associated with Colorectal Cancer

BACKGROUND

Polymorphisms of genes encoding PSCA, PLCE1 and MUC1 have been associated with the risk of different cancers in genome wide association studies (GWAS). Up to date there are limited data on the role of these genetic alterations in colorectal cancer (CRC) development. The aim of this study was to evaluate potential associations between single nucleotide polymorphisms (SNPs) of genes encoding PSCA, PLCE1 and MUC1 and the presence of CRC in European populations.

MATERIALS AND METHODS

Gene polymorphisms were analyzed in 574 European subjects (controls: n=382; CRC: n=192). PSCA C>T (rs2294008), PSCA G>A (rs2976392), MUC1 A>G (rs4072037) and PLCE1 A>G (rs2274223) SNPs were genotyped by RT-PCR.

RESULTS

The distribution of genotypes for all four SNPs was in line with the Hardy-Weinberg equilibrium (rs2294008, P=0.153; rs2976392, P=0.269; rs4072037, P=0.609; rs2274223, P=0.858). The distribution of genotypes and alleles of PSCA C>T, PSCA G>A, MUC1 A>G and PLCE1 A>G SNPs was similar among controls and CRC patient groups (P>0.05). GG genotype of MUC1 SNP was more frequent in CRC patients (24.0%) than in controls (20.2%); however, this association failed to reach significance (OR-1.45, P=0.15). Overall, in the present study SNPs of PSCA (rs2294008, rs2976392), MUC1 (rs4072037) and PLCE1 (rs2274223) genes were not associated with the presence of CRC.

CONCLUSIONS

Gene polymorphisms of PSCA, PLCE1 and MUC1 genes are not associated with the presence of CRC in European subjects.

Predictive imaging of chemotherapeutic response in a transgenic mouse model of pancreatic cancer

The underglycosylated mucin 1 tumor antigen (uMUC1) is a biomarker that forecasts the progression of adenocarcinomas. In this study, we evaluated the utility of a dual-modality molecular imaging approach based on targeting uMUC1 for monitoring chemotherapeutic response in a transgenic murine model of pancreatic cancer (KCM triple transgenic mice). An uMUC1-specific contrast agent (MN-EPPT) was synthesized for use with magnetic resonance imaging (MRI) and fluorescence optical imaging. It consisted of dextran-coated iron oxide nanoparticles conjugated to the near infrared fluorescent dye Cy5.5 and to a uMUC1-specific peptide (EPPT). KCM triple transgenic mice were given gemcitabine as chemotherapy while control animals received saline injections following the same schedule. Changes in uMUC1 levels following chemotherapy were monitored using T2-weighted MRI and optical imaging before and 24 hr after injection of the MN-EPPT. uMUC1 expression in tumors from both groups was evaluated by histology and qRT-PCR. We observed that the average delta-T2 in the gemcitabine-treated group was significantly reduced compared to the control group indicating lower accumulation of MN-EPPT, and correspondingly, a lower level of uMUC1 expression. In vivo optical imaging confirmed the MRI findings. Fluorescence microscopy of pancreatic tumor sections showed a lower level of uMUC1 expression in the gemcitabine-treated group compared to the control, which was confirmed by qRT-PCR. Our data proved that changes in uMUC1 expression after gemcitabine chemotherapy could be evaluated using MN-EPPT-enhanced in vivo MR and optical imaging. These results suggest that the uMUC1-targeted imaging approach could provide a useful tool for the predictive assessment of therapeutic response.

Anti-MUC1 Antibody in Nipple Aspirate Fluids Correlates with Tumor Aggressiveness in Breast Cancer: A Feasibility Study

Antibodies against MUC1 are found in circulation of breast cancer (BC) patients. We hypothesized that anti-MUC1 antibodies might be present in even a higher concentration in nipple aspirate fluid (NAF) and could be used to predict aggressiveness of BC. Serum and NAF samples were collected from high risk lesions, BC, and healthy contralateral breasts. ELISA was used to measure the amount of IgG, IgM, and IgA against a tumor-specific MUC1 peptide derived from the extracellular tandem repeat domain of MUC1. Tumor characteristics were recorded prospectively; 120 NAF samples were obtained from a total of 77 women in the study. There was no significant difference of anti-MUC1 antibody levels compared to BC with other lesions. Anti-MUC1 IgG level in NAF was higher in triple negative tumors (P = 0.02); serum anti-MUC1 IgG levels were significantly higher in patients with ER (−) tumor and recurrent disease (P = 0.01); NAF anti-MUC1 IgA levels were significantly higher in patients with LVI and Her2-neu (+) tumors (P < 0.05). These results show that NAF could be a reliable biomarker to predict tumor aggressiveness in BC. A larger study will be needed to confirm these data and to investigate the potential of anti-MUC1 antibodies in NAF and serum to predict disease outcome.

The Role of Glycosylation in Breast Cancer Metastasis and Cancer Control

Glycosylation and its correlation to the formation of remote metastasis in breast cancer had been an important scientific topic in the last 25 years. With the development of new analytical techniques, new insights were gained on the mechanisms underlying metastasis formation and the role of aberrant glycosylation within. Mucin-1 and Galectin were recognized as key players in glycosylation. Interestingly, aberrant carbohydrate structures seem to support the development of brain metastasis in breast cancer patients, as changes in glycosylation structures facilitate an overcoming of blood–brain barrier. Changes in the gene expression of glycosyltransferases are the leading cause for a modification of carbohydrate chains, so that also altered gene expression plays a role for glycosylation. In consequence, glycosylation and changes within can be useful for cancer diagnosis, determination of tumor stage, and prognosis, but can as well be targets for therapeutic strategies. Thus, further research on this topic would worthwhile for cancer combating.

The GALNT9, BNC1 and CCDC8 genes are frequently epigenetically dysregulated in breast tumours that metastasise to the brain

Background

Tumour metastasis to the brain is a common and deadly development in certain cancers; 18–30 % of breast tumours metastasise to the brain. The contribution that gene silencing through epigenetic mechanisms plays in these metastatic tumours is not well understood.

Results

We have carried out a bioinformatic screen of genome-wide breast tumour methylation data available at The Cancer Genome Atlas (TCGA) and a broad literature review to identify candidate genes that may contribute to breast to brain metastasis (BBM). This analysis identified 82 candidates. We investigated the methylation status of these genes using Combined Bisulfite and Restriction Analysis (CoBRA) and identified 21 genes frequently methylated in BBM. We have identified three genes, GALNT9, CCDC8 and BNC1, that were frequently methylated (55, 73 and 71 %, respectively) and silenced in BBM and infrequently methylated in primary breast tumours. CCDC8 was commonly methylated in brain metastases and their associated primary tumours whereas GALNT9 and BNC1 were methylated and silenced only in brain metastases, but not in the associated primary breast tumours from individual patients. This suggests differing roles for these genes in the evolution of metastatic tumours; CCDC8 methylation occurs at an early stage of metastatic evolution whereas methylation of GANLT9 and BNC1 occurs at a later stage of tumour evolution. Knockdown of these genes by RNAi resulted in a significant increase in the migratory and invasive potential of breast cancer cell lines.

Conclusions

These findings indicate that GALNT9 (an initiator of O-glycosylation), CCDC8 (a regulator of microtubule dynamics) and BNC1 (a transcription factor with a broad range of targets) may play a role in the progression of primary breast tumours to brain metastases. These genes may be useful as prognostic markers and their products may provide novel therapeutic targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0089-x) contains supplementary material, which is available to authorized users.

Label-free in vivo molecular imaging of underglycosylated mucin-1 expression in tumour cells

Alterations in mucin expression and glycosylation are associated with cancer development. Underglycosylated mucin-1 (uMUC1) is overexpressed in most malignant adenocarcinomas of epithelial origin (for example, colon, breast and ovarian cancer). Its counterpart MUC1 is a large polymer rich in glycans containing multiple exchangeable OH protons, which is readily detectable by chemical exchange saturation transfer (CEST) MRI. We show here that deglycosylation of MUC1 results in >75% reduction in CEST signal. Three uMUC1⁺ human malignant cancer cell lines overexpressing uMUC1 (BT20, HT29 and LS174T) show a significantly lower CEST signal compared with the benign human epithelial cell line MCF10A and the uMUC1⁻ tumour cell line U87. Furthermore, we demonstrate that in vivo CEST MRI is able to make a distinction between LS174T and U87 tumour cells implanted in the mouse brain. These results suggest that the mucCEST MRI signal can be used as a label-free surrogate marker to non-invasively assess mucin glycosylation and tumour malignancy.

Overexpression of underglycosylated MUC1 (uMUC1) is found in most malignant adenocarcinomas of epithelial origin. Here the authors use chemical exchange saturation transfer (CEST) MRI to detect uMUC1 and to distinguish between malignant and nonmalignant tumours.

Selected reaction monitoring to differentiate and relatively quantitate isomers of sulfated and unsulfated core 1 O-glycans from salivary MUC7 protein in rheumatoid arthritis

Rheumatoid arthritis is a common and debilitating systemic inflammatory condition affecting up to 1% of the world's population. This study aimed to investigate the immunological significance of O-glycans in chronic arthritis at a local and systemic level. O-Glycans released from synovial glycoproteins during acute and chronic arthritic conditions were compared and immune-reactive glycans identified. The sulfated core 1 O-glycan (Galβ1-3GalNAcol) was immune reactive, showing a different isomeric profile in the two conditions. From acute reactive arthritis, three isomers could be sequenced, but in patients with chronic rheumatoid arthritis, only a single 3-Gal sulfate-linked isomer could be identified. The systemic significance of this glycan epitope was investigated using the salivary mucin MUC7 in patients with rheumatoid arthritis and normal controls. To analyze this low abundance glycan, a selected reaction monitoring (SRM) method was developed to differentiate and relatively quantitate the core 1 O-glycan and the sulfated core 1 O-glycan Gal- and GalNAc-linked isomers. The acquisition of highly sensitive full scan linear ion trap MS/MS spectra in addition to quantitative SRM data allowed the 3- and 6-linked Gal isomers to be differentiated. The method was used to relatively quantitate the core 1 glycans from MUC7 to identify any systemic changes in this carbohydrate epitope. A statistically significant increase in sulfation was identified in salivary MUC7 from rheumatoid arthritis patients. This suggests a potential role for this epitope in chronic inflammation. This study was able to develop an SRM approach to specifically identify and relatively quantitate sulfated core 1 isomers and the unsulfated structure. The expansion of this method may afford an avenue for the high throughput investigation of O-glycans.