Summary report on the ISOBM TD-4 Workshop: analysis of 56 monoclonal antibodies against the MUC1 mucin. San Diego, Calif., November 17-23, 1996

External quality assessment-based tumor marker harmonization simulation; insights in achievable harmonization for CA 15-3 and CEA

OBJECTIVES

CA 15-3 and CEA are tumor markers used in routine clinical care for breast cancer and colorectal cancer, among others. Current measurement procedures (MP) for these tumor markers are considered to be insufficiently harmonized. This study investigated the achievable harmonization for CA 15-3 and CEA by using an in silico simulation of external quality assessment (EQA) data from multiple EQA programs using patient-pool based samples.

METHODS

CA 15-3 and CEA data from SKML (2021), UK NEQAS (2020-2021) and KEQAS (2020-2021) were used. A harmonization protocol was defined in which MPs that were considered equivalent were used to value assign EQA samples, and recalibration was only required if the MP had a bias of >5 % with value assigned EQA. Harmonization status was assessed by determining the mean level of agreement and residual variation by CV (%).

RESULTS

Only MPs from Abbott, Beckman, Roche and Siemens were available in all EQA programs. For CA 15-3, recalibration was proposed for Beckman MP only and for CEA, recalibration was proposed for Siemens MP only. When the harmonization procedures were applied, for CA 15-3 the pre-harmonization mean bias range per MP was reduced from -29.28 to 9.86 %, into -0.09-0.12 % after harmonization. For CEA, the mean bias range per MP was reduced from -23.78 to 2.00 % pre-harmonization to -3.13-1.42 % post-harmonization.

CONCLUSIONS

The present study suggests that a significant improvement in the harmonization status of CA 15-3 and CEA may be achieved by recalibration of a limited number of MPs.

Longitudinal evaluation of external quality assessment results for CA 15-3, CA 19-9, and CA 125

Background

Tumor markers are established laboratory tools that help to diagnose, estimate prognosis, and monitor the course of cancer. For meaningful decision-making in patient care, it is essential that methods and analytical platforms demonstrate high sensitivity, specificity, precision, and comparability. Regular participation at external quality assessment (EQA) schemes is mandatory for laboratories. Here, a longitudinal evaluation of EQA data was performed to assess the performance of tumor marker assays over time.

Methods

Longitudinal data of the cancer antigens (CA) 15-3 (n = 5,492), CA 19-9 (n = 6,802), and CA 125 (n = 5,362) from 14 INSTAND EQAs conducted between 2019 and 2023 were evaluated. A median of 197, 244 and 191 laboratories participated at the EQAs for CA 15-3, CA 19-9 and CA 125, respectively. Data evaluation encompasses intra- and inter-manufacturer specific variations over time, assay precision, and adherence to the EQA limits of ±24% for CA 15-3, ±27% for CA 19-9 and ±36% for CA 125.

Results

The study showed median manufacturer-dependent differences of up to 107% for CA 15-3, 99% for CA 125, and even 549% for CA 19-9 between the highest and the lowest methods over the studied period. Regarding the normalized median of all methods, the values of the most deviant methods were 0.42 for CA 15-3, 7.61 for CA 19-9, and 1.82 for CA 125. Intra-manufacturer variability was generally low, with median coefficients of variation (CV) below 10%. As the methods were evaluated according to method-specific consensus values, most participants passed the EQAs within the acceptance criteria. When the criteria were consistently set at 24%, the central 90% of participants passed the EQAs in 78.6%-100% for CA 15-3 (with exception of AX), 89.3%-100% for CA 125, and 64.3%-100% for CA 19-9.

Conclusion

While intra-method precision of most analytical platforms is acceptable for all three tumor markers, considerable inter-method variability was observed over the whole studied period demonstrating the necessity for better standardization and harmonization of the methods, development of international reference materials, and comprehensive commutability studies with patient samples.

Lung cancer biomarkers: Raising the clinical value of the classical and the new ones

Blood-based diagnostics for lung cancer support the diagnosis, estimation of prognosis, prediction, and monitoring of therapy response in lung cancer patients. The clinical utility of serum tumor markers has considerably increased due to developments in serum protein tumor markers analytics and clinical biomarker studies, the exploration of preanalytical and influencing conditions, the interpretation of biomarker combinations and individual biomarker kinetics, as well as the implementation of biostatistical models. In addition, circulating tumor DNA (ctDNA) and other liquid biopsy markers are playing an increasingly prominent role in the molecular tumor characterization and the monitoring of tumor evolution over time. Thus, modern lung cancer biomarkers may considerably contribute to an individualized companion diagnostics and provide a sensitive guidance for patients throughout the course of their disease. In this special edition on Tumor Markers in Lung Cancer, experts summarize recent developments in clinical laboratory diagnostics of lung cancer and give an outlook on future challenges and opportunities.

A novel humanized MUC1 antibody-drug conjugate for the treatment of trastuzumab-resistant breast cancer

Mucin 1 (MUC1) has been regarded as an ideal target for cancer treatment, since it is overexpressed in a variety of different cancers including the majority of breast cancer. However, there are still no approved monoclonal antibody drugs targeting MUC1. In this study, we generated a humanized MUC1 (HzMUC1) antibody from our previously developed MUC1 mouse monoclonal antibody that only recognizes MUC1 on the surface of tumor cells. Furthermore, an antibody-drug conjugate (ADC) was generated by conjugating HzMUC1 with monomethyl auristatin (MMAE), and the efficacy of HzMUC1-MMAE on the MUC1-positive HER2+ breast cancer in vitro and in 'Xenograft' model was tested. Results from western blot analysis and immunoprecipitation revealed that the HzMUC1 antibody did not recognize cell-free MUC1-N in sera from breast cancer patients. Confocal microscopy analysis showed that HzMUC1 antibody bound to MUC1 on the surface of breast cancer cells. Results from mapping experiments suggested that HzMUC1 may recognize an epitope present in the interaction region between MUC1-N and MUC1-C. Results from colony formation assay and flow cytometry demonstrated that HzMUC1-MMAE significantly inhibited cell growth by inducing G2/M cell cycle arrest and apoptosis in trastuzumab-resistant HER2-positive breast cancer cells. Meanwhile, HzMUC1-MMAE significantly reduced the growth of HCC1954 xenograft tumors by inhibiting cell proliferation and enhancing cell death. In conclusion, our results indicate that HzMUC1-ADC is a novel therapeutic drug that can overcome trastuzumab resistance of breast cancer. HzMUC1-ADC should also be an effective therapeutic drug for the treatment of different MUC1-positive cancers in clinic.

Structure-based Design of Anti-cancer Vaccines: The Significance of Antigen Presentation to Boost the Immune Response

Immunotherapy, alone or in combination with other therapies, is widely used against cancer. Glycoprotein Mucin 1 (MUC1), which is overexpressed and aberrantly glycosylated in tumor cells, is one of the most promising candidates to engineer new cancer vaccines. In this context, the development of stable antigens that can elicit a robust immune response is mandatory. Here, we describe the design and in vivo biological evaluation of three vaccine candidates based on MUC1 glycopeptides that comprise unnatural elements in their structure. By placing the Tn antigen (GalNAcα-O-Ser/Thr) at the center of the design, the chemical modifications include changes to the peptide backbone, glycosidic linkage, and at the carbohydrate level. Significantly, the three vaccines elicit robust immune responses in mice and produce antibodies that can be recognized by several human cancer cells. In all cases, a link was stablished between the conformational changes induced by the new elements in the antigen presentation and the immune response induced in mice. According to our data, the development of effective MUC1-based vaccines should use surrogates that mimic the conformational space of aberrantly glycosylated MUC1 glycopeptides found in tumors.

Mucin Binding to Moraxella catarrhalis During Airway Inflammation is Dependent on Sialic Acid

Chronic obstructive pulmonary disease (COPD) is associated with colonization by bacterial pathogens and repeated airway infections, leading to exacerbations and impaired lung function. The highly glycosylated mucins in the mucus lining the airways are an important part of the host defense against pathogens. However, mucus accumulation can contribute to COPD pathology. Here, we examined whether inflammation is associated with glycosylation changes that affect interactions between airway mucins and pathogens. We isolated mucins from lower airway samples (LAS, n=4-9) from long-term smokers with and without COPD and from never-smokers. The most abundant terminal glycan moiety was N-acetylneuraminic acid (Neu5Ac) among smokers with and without COPD and N-acetyl-hexoseamine among never-smokers. Moraxella catarrhalis bound to MUC5 mucins from smokers with and without COPD. M. catarrhalis binding correlated with inflammatory parameters and Neu5Ac content. M. catarrhalis binding was abolished by enzymatic removal of Neu5Ac. Furthermore, M. catarrhalis bound to α2-6 sialyl-lactose suggesting that α2-6 sialic acid contributes to M. catarrhalis binding to mucins. Further, we detected more M. catarrhalis binding to mucins from patients with pneumonia than to those from control subjects (n=8-13) and this binding correlated with C-reactive protein and Neu5Ac levels. These results suggest a key role of inflammation induced Neu5Ac in adhesion of M. catarrhalis to airway mucins. Inflammation induced ability of MUC5 mucins to bind M. catarrhalis is likely a host defense mechanism in the healthy lung, although it cannot be excluded that impaired mucociliary clearance limits the effectiveness of this defense in COPD patients.

Nonspecific nuclear uptake of anti-MUC1 aptamers by dead cells: the role of cell viability monitoring in aptamer targeting of membrane-bound protein cancer biomarkers

Most aptamers targeting cell-expressed antigens are intended for in vivo application, however, these sequences are commonly generated in vitro against synthetic oligopeptide epitopes or recombinant proteins. As these in vitro analogues frequently do not mimic the in vivo target within an endogenous environment, the evolved aptamers are often prone to nonspecific binding. The presence of dead cells and cellular debris further complicate aptamer targeting, due to their high nonspecific affinities to single-stranded DNA. Despite these known limitations, assessment of cell viability and/or the removal of dead cells is rarely applied as part of the methodology during in vivo testing of aptamer binding. Furthermore, the extent and route(s) by which dead cells uptake existing aptamers remains to be determined in the literature. For this purpose, the previously reported aptamer sequences 5TR1, 5TR4, 5TRG2 and S22 - enriched against the MUC1 tumour marker of the mucin glycoprotein family - were used as model sequences to evaluate the influence of cell viability and the presence of nontarget cell-expressed protein on aptamer binding to the MUC1 expressing human cancer cell lines MCF-7, Hs578T, SW480, and SW620. From fluorescence microscopy analysis, all tested aptamers demonstrated extensive nonspecific uptake within the nuclei of dead cells with compromised membrane integrities. Using fluorescent-activated cell sorting (FACS), the inclusion of excess double-stranded DNA as a blocking agent showed no effect on nonspecific aptamer uptake by dead cells. Further nonspecific binding to cell-membrane bound and intracellular protein was evident for each aptamer sequence, as assessed by southwestern blotting and FACS. These factors likely contributed to the ∼120-fold greater binding response of the 5TR1 aptamer to dead MCF-7 cells over equivalent live cell populations. The identification of dead cells and cellular debris using viability stains and the subsequent exclusion of these cells from FACS analysis was identified as an essential requirement for the evaluation of aptamer binding specificity to live cell populations of the cancer cell lines MCF-7, Hs578T and SW480. The research findings stress the importance of dead cell uptake and more comprehensive cell viability screening to validate novel aptamer sequences for diagnostic and therapeutic application.

Amplified Detection of Breast Cancer Autoantibodies Using MUC1-Based Tn Antigen Mimics

In many human carcinomas, mucin-1 (MUC1) is overexpressed and aberrantly glycosylated, resulting in the exposure of previously hidden antigens. This generates new patient antibody profiles that can be used in cancer diagnosis. In the present study, we focused on the MUC1-associated Tn antigen (α-O-GalNAc-Ser/Thr) and substituted the GalNAc monosaccharide by a glycomimic to identify MUC1-based glycopeptides with increased antigenicity. Two different glycopeptide libraries presenting the natural Tn antigen or the sp²-iminosugar analogue were synthesized and evaluated with anti-MUC1 monoclonal antibodies in a microarray platform. The most promising candidates were tested with healthy and breast cancer sera aiming for potential autoantibody-based biomarkers. The suitability of sp²-iminosugar glycopeptides to detect anti-MUC1 antibodies was demonstrated, and serological experiments showed stage I breast cancer autoantibodies binding with a specific unnatural glycopeptide with almost no healthy serum interaction. These results will promote further studies on their capabilities as early cancer biomarkers.

A straightforward approach to antibodies recognising cancer specific glycopeptidic neoepitopes

Aberrantly truncated immature O-glycosylation in proteins occurs in essentially all types of epithelial cancer cells, which was demonstrated to be a common feature of most adenocarcinomas and strongly associated with cancer proliferation and metastasis. Although extensive efforts have been made toward the development of anticancer antibodies targeting MUC1, one of the most studied mucins having cancer-relevant immature O-glycans, no anti-MUC1 antibody recognises carbohydrates and the proximal MUC1 peptide region, concurrently. Here we present a general strategy that allows for the creation of antibodies interacting specifically with glycopeptidic neoepitopes by using homogeneous synthetic MUC1 glycopeptides designed for the streamlined process of immunization, antibody screening, three-dimensional structure analysis, epitope mapping and biochemical analysis. The X-ray crystal structure of the anti-MUC1 monoclonal antibody SN-101 complexed with the antigenic glycopeptide provides for the first time evidence that SN-101 recognises specifically the essential epitope by forming multiple hydrogen bonds both with the proximal peptide and GalNAc linked to the threonine residue, concurrently. Remarkably, the structure of the MUC1 glycopeptide in complex with SN-101 is identical to its solution NMR structure, an extended conformation induced by site-specific glycosylation. We demonstrate that this method accelerates dramatically the development of a new class of designated antibodies targeting a variety of "dynamic neoepitopes" elaborated by disease-specific O-glycosylation in the immunodominant mucin domains and mucin-like sequences found in intrinsically disordered regions of many proteins.

Products of Chemoenzymatic Synthesis Representing MUC1 Tandem Repeat Unit with T-, ST- or STn-antigen Revealed Distinct Specificities of Anti-MUC1 Antibodies

Anti-mucin1 (MUC1) antibodies have long been used clinically in cancer diagnosis and therapy and specific bindings of some of them are known to be dependent on the differential glycosylation of MUC1. However, a systematic comparison of the binding specificities of anti-MUC1 antibodies was not previously conducted. Here, a total of 20 glycopeptides including the tandem repeat unit of MUC1, APPAHGVTSAPDTRPAPGSTAPPAHGV with GalNAc (Tn-antigen), Galβ1-3GalNAc (T-antigen), NeuAcα2-3Galβ1-3GalNAc (sialyl-T-antigen), or NeuAcα2-6GalNAc (sialyl-Tn-antigen) at each threonine or serine residue were prepared by a combination of chemical glycopeptide synthesis and enzymatic extension of carbohydrate chains. These glycopeptides were tested by the enzyme-linked immunosorbent assay (ELISA) for their capacity to bind 13 monoclonal antibodies (mAbs) known to be specific for MUC1. The results indicated that anti-MUC1 mAbs have diverse specificities but can be classified into a few characteristic groups based on their binding pattern toward glycopeptides in some cases having a specific glycan at unique glycosylation sites. Because the clinical significance of some of these antibodies was already established, the structural features identified by these antibodies as revealed in the present study should provide useful information relevant to their further clinical use and the biological understanding of MUC1.

Modulating MUC1 Function on T Cells

Immunotherapy is a promising approach to treating cancer. Mucin1 (MUC1), an epithelial glycoprotein, is hypo-glycosylated and overexpressed on epithelial cancers. This renders it a promising target for potential immunotherapeutic approaches. However, MUC1 has also been identified on T cells, which might complicate its potential as a target for immunotherapies.

Targeting cell-bound MUC1 on myelomonocytic, monocytic leukemias and phenotypically defined leukemic stem cells with anti-SEA module antibodies

Cell surface molecules aberrantly expressed or overexpressed by myeloid leukemic cells represent potential disease-specific therapeutic targets for antibodies. MUC1 is a polymorphic glycoprotein, the cleavage of which yields two unequal chains: a large extracellular α subunit containing a tandem repeat array bound in a strong noncovalent interaction to a smaller β subunit containing the transmembrane and cytoplasmic domains. Because the α-chain can be released from the cell-bound domains of MUC1, agents directed against the α-chain will not effectively target MUC1⁺ cells. The MUC1 SEA (a highly conserved protein module so called from its initial identification in a sea urchin sperm protein, in enterokinase, and in agrin) domain formed by the binding of the α and β chains  represents a stable structure fixed to the cell surface at all times. DMB-5F3, a partially humanized murine anti-MUC1 SEA domain monoclonal antibody, was used to examine MUC1 expression in acute myeloid leukemia (AML) and was found to bind acute myelomonocytic and monocytic leukemia (AML-M4 and AML-M5) cell lines. We also examined monocytic neoplasms freshly obtained from patients including chronic myelomonocytic leukemia and juvenile myelomonocytic leukemia, which were found to uniformly express MUC1. CD34⁺/lin^-/CD38^- or CD38⁺ presumed leukemic stem cell populations from CD34⁺ AML and CD34^-CD38^- or CD38⁺ populations from CD34^- AML were also found to express MUC1, although at low percentages. Based on these studies, we generated an anti-MUC1 immunotoxin to directly gauge the cytotoxic efficacy of targeting AML-bound MUC1. Using single-chain DMB-5F3 fused to recombinant gelonin toxin, the degree of AML cytotoxicity was found to correlate with MUC1 expression. Our data support the use of an anti-MUC1 SEA module-drug conjugates to selectively target and inhibit MUC1-expressing myelomonocytic leukemic cells.

Neuraminidase 1-mediated desialylation of the mucin 1 ectodomain releases a decoy receptor that protects against Pseudomonas aeruginosa lung infection

Pseudomonas aeruginosa (Pa) expresses an adhesin, flagellin, that engages the mucin 1 (MUC1) ectodomain (ED) expressed on airway epithelia, increasing association of MUC1-ED with neuraminidase 1 (NEU1) and MUC1-ED desialylation. The MUC1-ED desialylation unmasks both cryptic binding sites for Pa and a protease recognition site, permitting its proteolytic release as a hyperadhesive decoy receptor for Pa. We found here that intranasal administration of Pa strain K (PAK) to BALB/c mice increases MUC1-ED shedding into the bronchoalveolar compartment. MUC1-ED levels increased as early as 12 h, peaked at 24-48 h with a 7.8-fold increase, and decreased by 72 h. The a-type flagellin-expressing PAK strain and the b-type flagellin-expressing PAO1 strain stimulated comparable levels of MUC1-ED shedding. A flagellin-deficient PAK mutant provoked dramatically reduced MUC1-ED shedding compared with the WT strain, and purified flagellin recapitulated the WT effect. In lung tissues, Pa increased association of NEU1 and protective protein/cathepsin A with MUC1-ED in reciprocal co-immunoprecipitation assays and stimulated MUC1-ED desialylation. NEU1-selective sialidase inhibition protected against Pa-induced MUC1-ED desialylation and shedding. In Pa-challenged mice, MUC1-ED-enriched bronchoalveolar lavage fluid (BALF) inhibited flagellin binding and Pa adhesion to human airway epithelia by up to 44% and flagellin-driven motility by >30%. Finally, Pa co-administration with recombinant human MUC1-ED dramatically diminished lung and BALF bacterial burden, proinflammatory cytokine levels, and pulmonary leukostasis and increased 5-day survival from 0% to 75%. We conclude that Pa flagellin provokes NEU1-mediated airway shedding of MUC1-ED, which functions as a decoy receptor protecting against lethal Pa lung infection.

Clinical associations of mucin 1 in human lung cancer and precancerous lesions

Mucin 1 (MUC1) is a cell membrane glycoprotein overexpressed in non-small cell lung cancer (NSCLC) and has been implicated in carcinogenesis of premalignant lung lesions. Thus, MUC1 has been a target of interest for vaccine strategies for lung cancer treatment and prevention. Here, we assessed MUC1 expression by immunohistochemistry using tumor samples from patients with biopsy-proven NSCLC. Levels of expression in areas of dysplasia, metaplasia, adenocarcinoma in situ, and carcinoma within the same tissue sample were characterized independently on a scale of 0-3 for paired comparison. We also assessed clinical data for correlations with MUC1 expression. Our analysis included 16 samples from patients with squamous lesions and 19 from patients with adenocarcinoma lesions. Among squamous lesions, MUC1 expression score was significantly increased in dysplastic compared with metaplastic areas (mean difference = 0.83, 95% confidence interval [CI], 0.21-infinity; P = 0.021). MUC1 expression was also increased among areas of squamous cell carcinoma versus dysplastic areas (mean difference = 0.44, 95% CI, -0.006-infinity; P = 0.052). In the adenocarcinoma lesions, MUC1 expression was increased in adenocarcinoma versus adenocarcinoma in situ, although not significantly (mean difference = 0.20, 95% CI, -0.055-infinity; P = 0.094). The increase in MUC1 expression with the progression of premalignant lung lesions to invasive carcinoma in patients with NSCLC supports MUC1 as a possible therapeutic target for the prevention and treatment of lung cancer.

Epitopes of MUC1 Tandem Repeats in Cancer as Revealed by Antibody Crystallography: Toward Glycopeptide Signature-Guided Therapy

Abnormally O-glycosylated MUC1 tandem repeat glycopeptide epitopes expressed by multiple types of cancer have long been attractive targets for therapy in the race against genetic mutations of tumor cells. Glycopeptide signature-guided therapy might be a more promising avenue than mutation signature-guided therapy. Three O-glycosylated peptide motifs, PDTR, GSTA, and GVTS, exist in a tandem repeat HGVTSAPDTRPAPGSTAPPA, containing five O-glycosylation sites. The exact peptide and sugar residues involved in antibody binding are poorly defined. Co-crystal structures of glycopeptides and respective monoclonal antibodies are very few. Here we review 3 groups of monoclonal antibodies: antibodies which only bind to peptide portion, antibodies which only bind to sugar portion, and antibodies which bind to both peptide and sugar portions. The antigenicity of peptide and sugar portions of glyco-MUC1 tandem repeat were analyzed according to available biochemical and structural data, especially the GSTA and GVTS motifs independent from the most studied PDTR. Tn is focused as a peptide-modifying residue in vaccine design, to induce glycopeptide-binding antibodies with cross reactivity to Tn-related tumor glycans, but not glycans of healthy cells. The unique requirement for the designs of antibody in antibody-drug conjugate, bi-specific antibodies, and chimeric antigen receptors are also discussed.

Human MUC1 Mucin: A Multifaceted Glycoprotein

Human MUC1 mucin, a membrane-bound glycoprotein, is a major component of the ductal cell surface of normal glandular cells. MUC1 is overexpressed and aberrantly glycosylated in carcinoma cells. The role MUC1 plays in cancer progression represents two sides of one coin: on the one hand, loss of polarity and overexpression of MUC1 in cancer cells interferes with cell adhesion and shields the tumor cell from immune recognition by the cellular arm of the immune system, thus favoring metastases; on the other hand, MUC1, in essence a self-antigen, is displaced and altered in malignancy and induces immune responses. Tumor-associated MUC1 has short carbohydrate sidechains and exposed epitopes on its peptide core; it gains access to the circulation and comes into contact with the immune system provoking humoral and cellular immune responses. Natural antibodies to MUC1 present in the circulation of cancer patients may be beneficial to the patient by restricting tumor growth and dissemination: early stage breast cancer patients with a humoral response to MUC1 have a better disease-specific survival. Several MUC1 peptide vaccines, differing in vectors, carrier proteins and adjuvants, have been tested in phase I clinical trials. They are capable of inducing predominantly humoral responses to the antigen, but evidence that these immune responses may be effective against the tumor in humans is still scarce.

Cross-reactivity between MUC1 antigen and MCA: false elevation of serum CA 15-3 level in pregnant and lactating women by Ma695-Ma552-based assay

PURPOSE

Cancer antigen 153 (CA 15-3) is one of the most commonly used biomarkers of breast cancer. However, elevated CA 15-3 is reported in pregnant and lactating women more frequently on Beckman DxI 800 immunoassay system (Ma695-Ma552 antibody pair) than on Abbott ARCHITECT system (115D8-DF3 antibody pair) in laboratory methodological evaluation. We conducted this study in order to figure out the reason behind this phenomenon.

METHODS

Serum CA 15-3 concentration was analyzed in 426 subjects, including 180 patients with breast cancer, 121 patients with benign breast disease, and 125 healthy volunteers (45 pregnant and 80 non-pregnant women). CA 15-3 assay was further validated using another cohort of 112 pregnant or postpartum women. Immunological cross reaction was analyzed by Western blotting and immunoprecipitation.

RESULTS

The serum CA 15-3 level was abnormally higher in almost 95% of the pregnant and lactating women detected using Ma695-Ma552 antibody pair (median: 71.4 U/mL) than that detected using 115D8-DF3 antibody pair (median: 16.5 U/mL). Western blotting and immunoprecipitation indicated that such a significant difference was mainly due to the cross reaction between monoclonal antibody Ma552 and mucin-like carcinoma-associated antigen (MCA).

CONCLUSIONS

The CA 15-3 assay using 115D8-DF3 antibody pair is more suitable for monitoring therapy in pregnancy-associated breast cancer.

Analysis of sialyl-Lewis x on MUC5AC and MUC1 mucins in pancreatic cancer tissues

Pancreatic adenocarcinoma (PDAC) lacks efficient biomarkers. Mucins are glycoproteins that can carry aberrant glycosylation in cancer. Our objective was to identify cancer-related glycan epitopes on MUC1 and MUC5AC mucins in PDAC as potential biomarkers. We have analysed the tumour-associated carbohydrate antigens sialyl-Lewis x (SLe^x) and sialyl-Tn (STn) on MUC1 and MUC5AC in PDAC tissues. The selected cohort for this study consisted of twenty-one PDAC tissues positive for SLe^x antigen and three normal pancreas specimens as controls. STn expression was shown in 76% of the PDAC tissues. MUC1 and MUC5AC were detected in 90% of PDAC tissues. We performed in situ proximity ligation assay combining antibodies against mucins and glycan epitopes to identify specific mucin glycoforms. MUC1-SLe^x and MUC5AC-SLe^x were found in 68% and 84% respectively, of the mucin expressing PDAC tissues, while STn hardly colocalized with any of the evaluated mucins. Further analysis by Western blot of MUC5AC and SLe^x in eight PDAC tissue lysates showed that six out of eight cases were positive for both markers. Moreover, immunoprecipitation of MUC5AC from positive PDAC tissues and subsequent SLe^x immunodetection confirmed the presence of SLe^x on MUC5AC. Altogether, MUC5AC-SLe^x glycoform is present in PDAC and can be regarded as potential biomarker.

Generation of Novel Anti-MUC1 Monoclonal Antibodies with Designed Carbohydrate Specificities Using MUC1 Glycopeptide Library

Numerous anti-mucin 1 (anti-MUC1) antibodies that recognize O-glycan core structures have already been developed. However, most of them show low specificities toward O-glycan structures and/or low affinity toward a monovalent epitope. In this study, using an MUC1 glycopeptide library, we established two novel anti-MUC1 monoclonal antibodies (1B2 and 12D10) with designed carbohydrate specificities. Compared with previously reported anti-MUC1 antibodies, 1B2 and 12D10 showed quite different features regarding their specificities, affinities, and reactivity profiles to various cell lines. Both antibodies recognized specific O-glycan structures at the PDT*R motif (the asterisk represents an O-glycosylation site). 1B2 recognized O-glycans with an unsubstituted O-6 position of the GalNAc residue (Tn, T, and 23ST), whereas 12D10 recognized Neu5Ac at the same position (STn, 26ST, and dST). Neither of them bound to glycopeptides with core 2 O-glycans that have GlcNAc at the O-6 position of the GalNAc residue. Furthermore, 1B2 and 12D10 showed a strong binding to not only native MUC1 but also 20-mer glycopeptide with a monovalent epitope. These anti-MUC1 antibodies should thus become powerful tools for biological studies on MUC1 O-glycan structures. Furthermore, the strategy of using glycopeptide libraries should enable the development of novel antibodies with predesigned O-glycan specificities.

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.

Apical membrane expression of distinct sulfated glycans represents a novel marker of cholangiolocellular carcinoma

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver neoplasm, followed by hepatocellular carcinoma. ICC can be further subclassified as (i) perihilar and (ii) peripheral types, the latter histologically resembling small-sized intrahepatic bile ducts, such as interlobular bile ducts, cholangioles/ductules and the canals of Hering. Cholangiolocellular carcinoma (CoCC), now classified by the World Health Organization as a subtype of combined hepatocellular-cholangiocarcinoma, is currently regarded as a subtype of peripheral-type ICC. The present study was undertaken to determine whether sulfated glycans recognized by the MECA-79 monoclonal antibody could serve as a CoCC marker. Using immunohistochemistry, we show that MECA-79 sulfated glycans are preferentially expressed at the apical membrane of cholangiocytes found in small-sized intrahepatic bile ducts in normal liver and in canalicular structures formed in CoCC. We also report that apical membrane MECA-79 sulfated glycan expression colocalizes with that of mucin 1 (MUC1) core proteins. We also present immunoblotting of Chinese hamster ovary cells overexpressing FLAG-tagged MUC1 to show that MUC1 serves as a MECA-79 scaffold. Furthermore, we report that SSP-25 human ICC cells overexpressing N-acetylglucosamine-6-O-sulfotransferase 2 (GlcNAc6ST-2), but not GlcNAc6ST-1, exhibit membrane expression of MECA-79 sulfated glycans, suggesting that GlcNAc6ST-2 catalyzes MECA-79 epitope biosynthesis in cholangiocytes. Moreover, both wild-type and GlcNAc6ST-1 knockout mice exhibit apical membrane MECA-79 expression in small-sized intrahepatic bile ducts, namely interlobular bile ducts, whereas MECA-79 expression was completely absent in comparable tissues from GlcNAc6ST-1 and GlcNAc6ST-2 double knockout mice. These data collectively indicate that apical membrane localization of MUC1 proteins decorated with GlcNAc6ST-2-dependent MECA-79 sulfated glycans may mark cholangiocytes with cholangiolar/ductular differentiation and could serve as a useful CoCC marker.

Antibodies elicited by the first non-viral prophylactic cancer vaccine show tumor-specificity and immunotherapeutic potential

MUC1 is a shared tumor antigen expressed on >80% of human cancers. We completed the first prophylactic cancer vaccine clinical trial based on a non-viral antigen, MUC1, in healthy individuals at-risk for colon cancer. This trial provided a unique source of potentially effective and safe immunotherapeutic drugs, fully-human antibodies affinity-matured in a healthy host to a tumor antigen. We purified, cloned, and characterized 13 IgGs specific for several tumor-associated MUC1 epitopes with a wide range of binding affinities. These antibodies bind hypoglycosylated MUC1 on human cancer cell lines and tumor tissues but show no reactivity against fully-glycosylated MUC1 on normal cells and tissues. We found that several antibodies activate complement-mediated cytotoxicity and that T cells carrying chimeric antigen receptors with the antibody variable regions kill MUC1(+) target cells, express activation markers, and produce interferon gamma. Fully-human and tumor-specific, these antibodies are candidates for further testing and development as immunotherapeutic drugs.

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.

Epitope recognition in the human-pig comparison model on fixed and embedded material

The conditions and the specificity by which an antibody binds to its target protein in routinely fixed and embedded tissues are unknown. Direct methods, such as staining in a knock-out animal or in vitro peptide scanning of the epitope, are costly and impractical. We aimed to elucidate antibody specificity and binding conditions using tissue staining and public genomic and immunological databases by comparing human and pig—the farmed mammal evolutionarily closest to humans besides apes. We used a database of 146 anti-human antibodies and found that antibodies tolerate partially conserved amino acid substitutions but not changes in target accessibility, as defined by epitope prediction algorithms. Some epitopes are sensitive to fixation and embedding in a species-specific fashion. We also find that half of the antibodies stain porcine tissue epitopes that have 60% to 100% similarity to human tissue at the amino acid sequence level. The reason why the remaining antibodies fail to stain the tissues remains elusive. Because of its similarity with the human, pig tissue offers a convenient tissue for quality control in immunohistochemistry, within and across laboratories, and an interesting model to investigate antibody specificity.

Assessment of a panel of tumor markers for the differential diagnosis of benign and malignant effusions by well-based reverse phase protein array

Background

The differential diagnosis of benign and malignant effusion is often hampered by low cell content or insufficiently preserved tumor cells. In this study, we evaluated the combined diagnostic value of six tumor markers measured by well-based reverse-phase protein array (RPPA) for diagnosis of malignant effusion.

Methods

A total of 114 patients (46 with malignant effusions, 32 with probable malignant effusions, and 36 with benign effusions) were enrolled. Expressional levels of MUC1, EMA, Pan-CK, HSP90, TGF-β and CA125 were determined by well-based RPPA.

Results

Median relative expression of MUC1, Pan-CK and EMA were significantly higher in malignant effusion than those in probable malignant or benign (p < 0.001, p = 0.003, p < 0.001, respectively), whereas the level of TGF-β in malignant effusions were significantly lower than that in the other groups (p = 0.005). For predicting malignancy, EMA presented the best areas under the curve of 0.728 followed by MUC1 of 0.701. The sensitivity of 52.0% for MUC1 and 48.0% for EMA were not better than cytology. However, sensitivity, negative predictive value, and accuracy of the tumor marker panel were better than cytology by 14.7%, 7.5%, and 6.1%, respectively.

Conclusions

Tumor marker panel measured by well-based RPPA showed values in the differential diagnosis between benign and malignant effusions. Further large scale studies need to be performed to evaluate the utility of this panel of markers.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1433424467160224

Electronic supplementary material

The online version of this article (doi:10.1186/s13000-015-0290-4) contains supplementary material, which is available to authorized users.

Increased N-glycosylation of Asn⁸⁸ in serum pancreatic ribonuclease 1 is a novel diagnostic marker for pancreatic cancer

Alterations of carbohydrate structures in cancer cells are the most promising targets for developing clinical diagnostic reagents. Pancreatic cancer is one of the most difficult cancers to diagnose because it lacks definitive symptoms. Two antibodies were raised against human pancreatic ribonuclease 1 that bind to the enzyme containing unglycosylated Asn⁸⁸, but not when its Asn⁸⁸ is N-glycosylated. Differential studies using these antibodies in immunoassays and Western blot analyses showed a significant increase in the serum levels of pancreatic ribonuclease 1 containing N-glycosylated Asn⁸⁸ in pancreatic cancer patients compared with normal human subjects. Focusing on the increase in an N-glycosylated Asn residue of serum pancreatic ribonuclease 1, specifically Asn⁸⁸, affords a new diagnostic marker for pancreatic cancer. This is the first report of a diagnostic cancer marker that takes advantage of the presence or absence of N-glycosylation at a specific Asn residue of a glycoprotein.

Fast epitope mapping for the anti-MUC1 monoclonal antibody by combining a one-bead-one-glycopeptide library and a microarray platform

Anti-MUC1 monoclonal antibodies (mAbs) are powerful tools that can be used to recognize cancer-related MUC1 molecules, the O-glycosylation status of which is believed to affect binding affinity. We demonstrate the feasibility of using a rapid screening methodology to elucidate those effects. The approach involves i) "one-bead-one-compound"-based preparation of bilayer resins carrying glycopeptides on the shell and mass-tag tripeptides coding O-glycan patterns in the core, ii) on-resin screening with an anti-MUC1 mAb, iii) separating positive resins by utilizing secondary antibody conjugation with magnetic beads, and (iv) decoding the mass-tag that is detached from the positive resins pool by using mass spectrometric analysis. We tested a small library consisting of 27 MUC1 glycopeptides with different O-glycosylations against anti-MUC1 mAb clone VU-3C6. Qualitative mass-tag analysis showed that increasing the number of glycans leads to an increase in the binding affinity. Six glycopeptides selected from the library were validated by using a microarray-based assay. Our screening provides valuable information on O-glycosylations of epitopes leading to high affinity with mAb.

Human prominin-1 (CD133) is detected in both neoplastic and non-neoplastic salivary gland diseases and released into saliva in a ubiquitinated form

Prominin-1 (CD133) is physiologically expressed at the apical membranes of secretory (serous and mucous) and duct cells of major salivary glands. We investigated its expression in various human salivary gland lesions using two distinct anti-prominin-1 monoclonal antibodies (80B258 and AC133) applied on paraffin-embedded sections and characterized its occurrence in saliva. The 80B258 epitope was extensively expressed in adenoid cystic carcinoma, in lesser extent in acinic cell carcinoma and pleomorphic adenoma, and rarely in mucoepidermoid carcinoma. The 80B258 immunoreactivity was predominately detected at the apical membrane of tumor cells showing acinar or intercalated duct cell differentiation, which lined duct- or cyst-like structures, and in luminal secretions. It was observed on the whole cell membrane in non-luminal structures present in the vicinity of thin-walled blood vessels and hemorrhagic areas in adenoid cystic carcinoma. Of note, AC133 labeled only a subset of 80B258–positive structures. In peritumoral salivary gland tissues as well as in obstructive sialadenitis, an up-regulation of prominin-1 (both 80B258 and AC133 immunoreactivities) was observed in intercalated duct cells. In most tissues, prominin-1 was partially co-expressed with two cancer markers: carcinoembryonic antigen (CEA) and mucin-1 (MUC1). Differential centrifugation of saliva followed by immunoblotting indicated that all three markers were released in association with small membrane vesicles. Immuno-isolated prominin-1–positive vesicles contained CEA and MUC1, but also exosome-related proteins CD63, flotillin-1, flotillin-2 and the adaptor protein syntenin-1. The latter protein was shown to interact with prominin-1 as demonstrated by its co-immunoisolation. A fraction of saliva-associated prominin-1 appeared to be ubiquitinated. Collectively, our findings bring new insights into the biochemistry and trafficking of prominin-1 as well as its immunohistochemical profile in certain types of salivary gland tumors and inflammatory diseases.

Sensitivity of CA 15-3, CEA and serum HER2 in the early detection of recurrence of breast cancer

BACKGROUND

The aim of this project was to investigate the sensitivity of CA 15-3, CEA and HER2 in the early diagnosis of metastatic breast cancer.

METHODS

Serial serum values of CA 15-3, CEA and HER2 were determined in 107 patients with recurrence after breast cancer. Fifteen of the patients had primary disseminated disease, nine patients only developed local recurrence during the follow-up period and the remaining 83 developed distant metastases.

RESULTS

In the group of patients with distant metastatic disease (n=83), elevated serum levels of CA 15-3 (>32.4 U/mL), CEA (>2.5 µg/L for non-smokers and >10 µg/L for smokers) and HER2 (>15 µg/L) were found in 49.4%, 38.6% and 32.5%, respectively, at the time of diagnosis of recurrence. CA 15-3 was significantly better than HER2 (p=0.027). The most sensitive combination was obtained using CA 15-3/CEA (60.2%) or CA 15-3/HER2 (57.8%). Combining all three tumour markers raised the sensitivity to 63.9%. In the subgroup of patients with tissue HER2+ tumours, the sensitivity of HER2 increased to 55.6%. The best combination in this group was CEA/HER2 (66.7%). In the subgroup of patients with tissue HER2- tumours, CA 15-3 was significantly better. The best combination was CA 15-3/HER2 or CA 15-3/CEA with a sensitivity of 55.8% and 59.6%, respectively.

CONCLUSIONS

The combination of several tumour markers enhances the sensitivity for detection of metastatic breast cancer. We recommend HER2 or the combination of CEA and HER2 in tissue HER2+ and CA 15-3 or the combination of CA 15-3 and CEA in tissue HER2-.

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.

Multicentric and multifocal versus unifocal breast cancer: differences in the expression of E-cadherin suggest differences in tumor biology

Background

The aim of this study was to evaluate the expression of the cell adhesion-related glycoproteins MUC-1, β-catenin and E-cadherin in multicentric/multifocal breast cancer in comparison to unifocal disease in order to identify potential differences in the biology of these tumor types.

Methods

A retrospective analysis was performed on the expression of MUC1, β-catenin and E-cadherin by immunohistochemistry on tumor tissues of a series of 112 breast cancer patients (total collective) treated in Munich between 2000 and 2002. By matched-pair analysis, 46 patients were entered into two comparable groups of 23 patients after categorizing them as having multicentric/multifocal or unifocal breast cancer. Matching criteria were tumor size, histology grade and lymph node status; based on these criteria, patients were distributed equally between the two groups (p = 1.000 each). Data were analyzed with the Kruskal-Wallis and the Mann–Whitney tests.

Results

In the matched groups, we found a significantly down-regulated expression of E-cadherin in multicentric/multifocal breast cancer compared to unifocal disease (p = 0.024). The total collective showed even higher significance with a value of p < 0.0001. In contrast, no significant differences were observed in the expression of β-catenin between multicentric/multifocal and unifocal tumors (p = 0.636 and p = 0.914, respectively). When comparing the expression of MUC1, E-cadherin and β-catenin within the unifocal group, we found a significant positive correlation between E-cadherin and β-catenin (p = 0.003). In the multicentric/multifocal group we observed, in contrast to the unifocal group, a significant decrease of MUC1 expression with increased grading (p = 0.027).

Conclusion

This study demonstrates that multicentric/multifocal and unifocal breast cancers with identical TNM-staging clearly differ in the expression level of E-cadherin. We suggest that the down-regulation of E-cadherin in multicentric/multifocal breast cancer is causally connected with the worse prognosis of this tumor type.

Gastrointestinal cell lines form polarized epithelia with an adherent mucus layer when cultured in semi-wet interfaces with mechanical stimulation

Mucin glycoproteins are secreted in large quantities by mucosal epithelia and cell surface mucins are a prominent feature of the glycocalyx of all mucosal epithelia. Currently, studies investigating the gastrointestinal mucosal barrier use either animal experiments or non-in vivo like cell cultures. Many pathogens cause different pathology in mice compared to humans and the in vitro cell cultures used are suboptimal because they are very different from an in vivo mucosal surface, are often not polarized, lack important components of the glycocalyx, and often lack the mucus layer. Although gastrointestinal cell lines exist that produce mucins or polarize, human cell line models that reproducibly create the combination of a polarized epithelial cell layer, functional tight junctions and an adherent mucus layer have been missing until now. We trialed a range of treatments to induce polarization, 3D-organization, tight junctions, mucin production, mucus secretion, and formation of an adherent mucus layer that can be carried out using standard equipment. These treatments were tested on cell lines of intestinal (Caco-2, LS513, HT29, T84, LS174T, HT29 MTX-P8 and HT29 MTX-E12) and gastric (MKN7, MKN45, AGS, NCI-N87 and its hTERT Clone5 and Clone6) origins using Ussing chamber methodology and (immuno)histology. Semi-wet interface culture in combination with mechanical stimulation and DAPT caused HT29 MTX-P8, HT29 MTX-E12 and LS513 cells to polarize, form functional tight junctions, a three-dimensional architecture resembling colonic crypts, and produce an adherent mucus layer. Caco-2 and T84 cells also polarized, formed functional tight junctions and produced a thin adherent mucus layer after this treatment, but with less consistency. In conclusion, culture methods affect cell lines differently, and testing a matrix of methods vs. cell lines may be important to develop better in vitro models. The methods developed herein create in vitro mucosal surfaces suitable for studies of host-pathogen interactions at the mucosal surface.

Evaluation of Mucin-1 protein and mRNA expression as prognostic and predictive markers after neoadjuvant chemotherapy for breast cancer

BACKGROUND

Mucin-1 (MUC1) is a promising antigen for the development of tumor vaccines. We evaluated the frequency of MUC1 expression and its impact on therapy response and survival after neoadjuvant chemotherapy for breast cancer.

PATIENTS AND METHODS

Pre-treatment core biopsies of patients from the GeparTrio neoadjuvant trial (NCT 00544765) were evaluated for MUC1 by immunohistochemistry (IHC; N = 691) and quantitative RT-PCR (qRT-PCR; N = 286) from formalin-fixed paraffin-embedded (FFPE) samples.

RESULTS

MUC1 protein and mRNA was detectable in the majority of cases and was associated with hormone-receptor-positive status (P < 0.001). High MUC1 protein and mRNA expression were associated with lower probability of pathologic complete response (P = 0.017 and P < 0.001) and with longer patient survival (P = 0.03 and P < 0.001). In multivariable analysis, MUC1 protein and mRNA expression were independently predictive (P = 0.001 and P < 0.001). MUC1 protein and mRNA expression were independently prognostic for overall survival (P = 0.029 and P = 0.015).

CONCLUSIONS

MUC1 is frequently expressed in breast cancer and detectable on mRNA and protein level from FFPE tissue. It provides independent predictive information for therapy response and survival after neoadjuvant chemotherapy. In clinical immunotherapy trials, MUC1 expression may serve as a predictive marker.

Glycoprotein disease markers and single protein-omics

Glycoproteins are well represented among biomarkers for inflammatory and cancer diseases. Secreted and membrane-associated glycoproteins make excellent targets for noninvasive detection. In this review, we discuss clinically applicable markers of cancer diseases and methods for their analysis. High throughput discovery continues to supply marker candidates with unusual glycan structures, altered glycoprotein abundance, or distribution of site-specific glycoforms. Improved analytical methods are needed to unlock the potential of these discoveries in validated clinical assays. A new generation of targeted quantitative assays is expected to advance the use of glycoproteins in early detection of diseases, molecular disease classification, and monitoring of therapeutic interventions.

Microarray Glycoprofiling of CA125 improves differential diagnosis of ovarian cancer

The CA125 biomarker assay plays an important role in the diagnosis and management of primary invasive epithelial ovarian/tubal cancer (iEOC). However, a fundamental problem with CA125 is that it is not cancer-specific and may be elevated in benign gynecological conditions such as benign ovarian neoplasms and endometriosis. Aberrant O-glycosylation is an inherent and specific property of cancer cells and could potentially aid in differentiating cancer from these benign conditions, thereby improving specificity of the assay. We report on the development of a novel microarray-based platform for profiling specific aberrant glycoforms, such as Neu5Acα2,6GalNAc (STn) and GalNAc (Tn), present on CA125 (MUC16) and CA15-3 (MUC1). In a blinded cohort study of patients with an elevated CA125 levels (30-500 kU/L) and a pelvic mass from the UK Ovarian Cancer Population Study (UKOPS), we measured STn-CA125, ST-CA125 and STn-CA15-3. The combined glycoform profile was able to distinguish benign ovarian neoplasms from invasive epithelial ovarian/tubule cancer (iEOCs) with a specificity of 61.1% at 90% sensitivity. The findings suggest that microarray glycoprofiling could improve differential diagnosis and significantly reduce the number of patients elected for further testing. The approach warrants further investigation in other cancers.

Mucin-1 and its relation to grade, stage and survival in ovarian carcinoma patients

BACKGROUND

Mucin-1 is known to be over-expressed by various human carcinomas and is shed into the circulation where it can be detected in patient's serum by specific anti-Mucin-1 antibodies, such as the tumour marker assays CA 15-3 and CA 27.29. The prognostic value of Mucin-1 expression in ovarian carcinoma remains uncertain. One aim of this study was to compare the concentrations of Mucin-1 in a cohort of patients with either benign or malignant ovarian tumours detected by CA 15-3 and CA 27.29. Another aim of this study was to evaluate Mucin-1 expression by immunohistochemistry in a different cohort of ovarian carcinoma patients with respect to grade, stage and survival.

METHODS

Patients diagnosed with and treated for ovarian tumours were included in the study. Patient characteristics, histology including histological subtype, tumour stage, grading and follow-up data were available from patient records. Serum Mucin-1 concentrations were measured with ELISA technology detecting CA 15-3 and CA 27.29, Mucin-1 tissue expression was determined by immunohistochemistry using the VU4H5 and VU3C6 anti-Mucin-1 antibodies. Statistical analysis was performed by using SPSS 18.0.

RESULTS

Serum samples of 118 patients with ovarian tumours were obtained to determine levels of Mucin-1. Median CA 15-3 and CA 27.29 concentrations were significantly higher in patients with malignant disease (p< 0.001) than in patients with benign disease.Paraffin-embedded tissue of 154 patients with ovarian carcinoma was available to determine Mucin-1 expression. The majority of patients presented with advanced stage disease at primary diagnosis. Median follow-up time was 11.39 years. Immunohistochemistry results for VU4H5 showed significant differences with respect to tumour grade, FIGO stage and overall survival. Patients with negative expression had a mean overall survival of 9.33 years compared to 6.27 years for patients with positive Mucin-1 expression.

CONCLUSIONS

This study found significantly elevated Mucin-1 serum concentrations in ovarian carcinoma patients as compared to those women suffering from benign ovarian diseases. However, it needs to be noted that Mucin-1 concentrations in carcinoma patients showed a rather high variability. Results from immunohistochemistry indicate that Mucin-1 has a prognostic relevance in ovarian carcinomas when evaluating the expression by VU4H5 antibody.

Correlation study of Carcino Embryonic Antigen & Cancer Antigen 15.3 in pretreated female breast cancer patients

Carcino Embryonic Antigen (CEA) and Cancer Antigen 15.3 (CA15.3) are the most common tumor markers in breast cancer patients. Measurement of circulating tumor markers is a non-invasive quantitative method. Serum levels of CEA and CA 15.3 were studied in female breast cancer patients prior to treatment. To evaluate the utility of these markers, 207 Breast carcinoma patients belonging to all the stages were considered. Healthy age matched 75 female individuals formed the control group. The serum levels of CEA and CA 15.3 were analyzed by Enzyme Linked Immunosorbent Assay (ELISA). Results were taken and compared with stages, tumor size, node and grade. The serum CA 15.3 levels were significant in all the study parameters whereas serum CEA levels showed no significant changes with any of the parameters. Measurement of serum CA 15.3 levels showed significant correlation (24.8%) with advanced stages and larger tumor sizes, whereas serum CEA levels did not show any significant correlation in breast cancer patients prior to treatment.

Serum tumour markers as a diagnostic and prognostic tool in Libyan breast cancer

Results from studies on efficacy of carcinoembryonic antigen (CEA), carbohydrate antigen 15.3 (CA 15.3) and thymidine kinase (TK1) as diagnostic and prognostic tools for primary breast cancer (BC) have presented conflicting results, and usefulness of these markers for clinical use in BC remains unclear. The aim of this study is to evaluate potential of concentration of the sera CEA, CA15.3 and TK1 peptides' use as markers in the diagnosis and prognosis of breast lesions of Libyan patients. Serum tumour markers were studied in 20 healthy subjects, 30 patient with benign lesion diseases and 50 patients with histologically confirmed BC diagnosed at the National Cancer Institute (NCI), Misurata, Libya during the period 2005-2009. The concentrations of the BC patients' cutoff points used for diagnostic and prognostic sensitivity were 8.82 ng/ml, 35.57 U/ml and 32.57 U/mg/protein for CEA, CA15.3 and TK1, respectively. Increased CEA (>8.82 ng/ml), CA 15.3 (>35.57 U/ml) and TK1 (>32.57 U/mg/protein) concentrations were found in 62 %, 70 % and 78 % of the BC patients, respectively. For all three tumour markers, increased concentrations correlated increased tumour size and nodal involvement. Significantly higher serum TK1 levels were found in patients with advanced disease (p < 0.0001) and TK1 levels also correlated with disease-specific survival (DSS, p < 0.07). The combined data set of the three markers' data from three markers increased the diagnostic sensitivity to 90 %. The serum marker analysis for CEA, CA 15.3, and S-TK1 concentrations is shown to be a useful tool for identification of malignant cases in our BC population and for the prognostic evaluation of patients with primary BC. Increased concentrations of the markers were also observed to be higher in patients with advanced tumours and indicative of the development of distant metastasis.

Mucin-based targeted pancreatic cancer therapy

The prognosis of pancreatic cancer (PC) patients is very poor with a five-year survival of less than 5%. One of the major challenges in developing new therapies for PC is the lack of expression of specific markers by pancreatic tumor cells. Mucins are heavily Oglycosylated proteins characterized by the presence of short stretches of amino acid sequences repeated several times in tandem. The expression of several mucins including MUC1, MUC4, MUC5AC, and MUC16 is strongly upregulated in PC. Recent studies have also demonstrated a link between the aberrant expression and differential overexpression of mucin glycoproteins to the initiation, progression, and poor prognosis of the disease. These studies have led to increasing recognition of mucins as potential diagnostic markers and therapeutic targets in PC. In this focused review we present an overview of the therapies targeting mucins in PC, including immunotherapy (i.e. vaccines, antibodies, and radioimmunoconjugates), gene therapy, and other novel therapeutic strategies.

Aberrantly glycosylated MUC1 is expressed on the surface of breast cancer cells and a target for antibody-dependent cell-mediated cytotoxicity

Protein glycosylation often changes during cancer development, resulting in the expression of cancer-associated carbohydrate antigens. In particular mucins such as MUC1 are subject to these changes. We previously identified an immunodominant Tn-MUC1 (GalNAc-α-MUC1) cancer-specific epitope not covered by immunological tolerance in MUC1 humanized mice and man. The objective of this study was to determine if mouse antibodies to this Tn-MUC1 epitope induce antibody-dependent cellular cytotoxicity (ADCC) pivotal for their potential use in cancer immunotherapy. Binding affinity of mAb 5E5 directed to Tn-MUC1 was investigated using BiaCore. The availability of Tn-MUC1 on the surface of breast cancer cells was evaluated by immunohistochemistry, confocal microscopy, and flow cytometry, followed by in vitro assessment of antibody-dependent cellular cytotoxicity by mAb 5E5. Biacore analysis demonstrated high affinity binding (KD = 1.7 nM) of mAb 5E5 to its target, Tn-MUC1. Immunolabelling with mAb 5E5 revealed surface expression of the Tn-MUC1 epitope in breast cancer tissue and cell lines, and mAb 5E5 induced ADCC in two human breast cancer cell lines, MCF7 and T47D. Aberrantly glycosylated MUC1 is expressed on the surface of breast cancer cells and a target for antibody-dependent cell-mediated cytotoxicity suggesting that antibodies targeting glycopeptide epitopes on mucins are strong candidates for cancer-specific immunotherapies.

Epitope reactions can be gauged by relative antibody discriminating specificity (RADS) values supported by deletion, substitution and cysteine bridge formation analyses: potential uses in pathogenesis studies

Background

Epitope-mapping of infectious agents is essential for pathogenesis studies. Since polyclonal antibodies (PAbs) and monoclonal antibodies (MAbs) are always polyspecific and can react with multiple epitopes, it is important to distinguish between specific and non-specific reactions. Relative antibody discriminating specificity (RADS) values, obtained from their relative ELISA reactions with L-amino acid peptides prepared in the natural versus reverse orientations (x-fold absorbance natural/absorbance reverse = RADS value) may be valuable for this purpose.

PAbs generated against the dengue type-2 virus (DENV-2) nonstructural-1 (NS1) glycoprotein candidate vaccine also reacted with both DENV envelope (E) glycoproteins and blood-clotting proteins. New xKGSx/xSGKx amino acid motifs were identified on DENV-2 glycoproteins, HIV-1 gp41 and factor IXa. Their potential roles in DENV and HIV-1 antibody-enhanced replication (AER) and auto-immunity were assessed.

In this study, a) RADS values were determined for MAbs and PAbs, generated in congeneic (H2: class II) mice against DENV NS1 glycoprotein epitopes, to account for their cross-reaction patterns, and b) MAb 1G5.3 reactions with xKGSx/xSGKx motifs present in the DENV-4 NS1, E and HIV-1 glycoproteins and factor IXa were assessed after the introduction of amino acid substitutions, deletions, or intra-/inter-cysteine (C-C) bridges.

Results

MAbs 1H7.4, 5H4.3, 3D1.4 and 1G5.3 had high (4.23- to 16.83-fold) RADS values against single epitopes on the DENV-2 NS1 glycoprotein, and MAb 3D1.4 defined the DENV complex-conserved LX1 epitope. In contrast, MAbs 1G5.4-A1-C3 and 1C6.3 had low (0.47- to 1.67-fold) RADS values against multiple epitopes. PAb DENV complex-reactions occurred through moderately-high (2.77- and 3.11-fold) RADS values against the LX1 epitope. MAb 1G5.3 reacted with xSGKx motifs present in DENV-4 NS1 and E glycoproteins, HIV-1 gp41 and factor IXa, while natural C-C bridge formations or certain amino acid substitutions increased its binding activity.

Conclusions

These results: i) were readily obtained using a standard 96-well ELISA format, ii) showed the LX1 epitope to be the immuno-dominant DENV complex determinant in the NS1 glycoprotein, iii) supported an antigenic co-evolution of the DENV NS1 and E glycoproteins, and iv) identified methods that made it possible to determine the role of anti-DENV PAb reactions in viral pathogenesis.

Using the allergic immune system to target cancer: activity of IgE antibodies specific for human CD20 and MUC1

Monoclonal antibodies are widely used in the treatment of many B cell lymphomas and certain solid tumors. All currently approved therapeutic monoclonal antibodies are of the immunoglobulin G (IgG) isotype. We hypothesized that tumor-specific monoclonal antibodies of the IgE isotype may serve as effective cancer therapeutics. To test this hypothesis, we produced mouse-human chimeric IgE antibodies specific for the human B cell antigen CD20 and the epithelial antigen MUC1. We demonstrate here that anti-hCD20 IgE antibodies have in vitro cytotoxic activity when used with purified allergic effector cells derived from umbilical cord blood. At an effector-tumor ratio of 2:1, mast cells and tumor-specific IgE induced a 2.5-fold increase in tumor cell death, as compared to control IgE. Similar results were observed when eosinophils were used as effector cells. In an in vivo murine model of breast carcinoma, administration of anti-hMUC1 IgE reduced the growth of MUC1(+) tumors by 25-30 % in hFcεRI transgenic mice. In contrast, local production of IgE and cytokines chemotactic for macrophages, eosinophils and mast cells led to complete tumor eradication. These results suggest that allergic effector cells activated by IgE and cell surface antigens have the capacity to induce tumor cell death in vitro and in vivo. The use of chimeric antibodies and hFcεRI transgenic mice will greatly enhance investigations in the nascent field of allergo-oncology.

Clinical utility of serum tumor markers and circulating tumor cell assays in the treatment of breast cancer

OPINION STATEMENT

Though serum tumor markers and circulating tumor cells (CTCs) have been available to the oncologist for many years, their place in the management of breast cancer remains unclear. Due to issues with sensitivity and specificity, tumor markers are unreliable for the detection of metastases in early stage breast cancer. For patients with metastatic breast cancer without measurable disease (e.g., bone-only disease, pleural effusions, or ascites), it is reasonable to obtain baseline values of serum tumor markers and attempt to correlate them with the first set of scans. In patients with elevated markers at baseline whose tumor marker levels decrease in correlation with an improvement in clinical symptoms, it may be reasonable to use them in conjunction with imaging to help determine whether there is progression of disease. CTCs have been found to hold strong prognostic value for breast cancer in both the early stage and metastatic settings. No large prospective studies to date, however, have shown any predictive value for CTCs and their clinical utility is therefore limited. Whether changing treatment in response to an increase in CTCs without radiologic progression results in improvements in quality of life or survival remains to be seen. CTCs hold great promise in the management of breast cancer and future studies will help delineate their role more appropriately.

A metalloproteinase secreted by Streptococcus pneumoniae removes membrane mucin MUC16 from the epithelial glycocalyx barrier

The majority of bacterial infections occur across wet-surfaced mucosal epithelia, including those that cover the eye, respiratory tract, gastrointestinal tract and genitourinary tract. The apical surface of all these mucosal epithelia is covered by a heavily glycosylated glycocalyx, a major component of which are membrane-associated mucins (MAMs). MAMs form a barrier that serves as one of the first lines of defense against invading bacteria. While opportunistic bacteria rely on pre-existing defects or wounds to gain entry to epithelia, non opportunistic bacteria, especially the epidemic disease-causing ones, gain access to epithelial cells without evidence of predisposing injury. The molecular mechanisms employed by these non opportunistic pathogens to breach the MAM barrier remain unknown. To test the hypothesis that disease-causing non opportunistic bacteria gain access to the epithelium by removal of MAMs, corneal, conjunctival, and tracheobronchial epithelial cells, cultured to differentiate to express the MAMs, MUCs 1, 4, and 16, were exposed to a non encapsulated, non typeable strain of Streptococcus pneumoniae (SP168), which causes epidemic conjunctivitis. The ability of strain SP168 to induce MAM ectodomain release from epithelia was compared to that of other strains of S. pneumoniae, as well as the opportunistic pathogen Staphylococcus aureus. The experiments reported herein demonstrate that the epidemic disease-causing S. pneumoniae species secretes a metalloproteinase, ZmpC, which selectively induces ectodomain shedding of the MAM MUC16. Furthermore, ZmpC-induced removal of MUC16 from the epithelium leads to loss of the glycocalyx barrier function and enhanced internalization of the bacterium. These data suggest that removal of MAMs by bacterial enzymes may be an important virulence mechanism employed by disease-causing non opportunistic bacteria to gain access to epithelial cells to cause infection.