Autoantibodies to aberrantly glycosylated MUC1 in early stage breast cancer are associated with a better prognosis

Abstract

IntroductionDetection of serum biomarkers for early diagnosis of breast cancer remains an important goal. Changes in the structure of O-linked glycans occur in all breast cancers resulting in the expression of glycoproteins that are antigenically distinct. Indeed, the serum assay widely used for monitoring disease progression in breast cancer (CA15.3), detects a glycoprotein (MUC1), but elevated levels of the antigen cannot be detected in early stage patients. However, since the immune system acts to amplify the antigenic signal, antibodies can be detected in sera long before the antigen. We have exploited the change in O-glycosylation to measure autoantibody responses to cancer-associated glycoforms of MUC1 in sera from early stage breast cancer patients.MethodsWe used a microarray platform of 60mer MUC1 glycopeptides, to confirm the presence of autoantibodies to cancer associated glycoforms of MUC1 in a proportion of early breast cancer patients (54/198). Five positive sera were selected for detailed definition of the reactive epitopes using on chip glycosylation technology and a panel of glycopeptides based on a single MUC1 tandem repeat carrying specific glycans at specific sites. Based on these results, larger amounts of an extended repertoire of defined MUC1 glycopeptides were synthesised, printed on microarrays, and screened with sera from a large cohort of breast cancer patients (n = 395), patients with benign breast disease (n = 108) and healthy controls (n = 99). All sera were collected in the 1970s and 1980s and complete clinical follow-up of breast cancer patients is available.ResultsThe presence and level of autoantibodies was significantly higher in the sera from cancer patients compared with the controls, and a highly significant correlation with age was observed. High levels of a subset of autoantibodies to the core3MUC1 (GlcNAcβ1-3GalNAc-MUC1) and STnMUC1 (NeuAcα2,6GalNAc-MUC1) glycoforms were significantly associated with reduced incidence and increased time to metastasis.ConclusionsAutoantibodies to specific cancer associated glycoforms of MUC1 are found more frequently and at higher levels in early stage breast cancer patients than in women with benign breast disease or healthy women. Association of strong antibody response with reduced rate and delay in metastases suggests that autoantibodies can affect disease progression.

Microvesicle Cargo of Tumor-Associated MUC1 to Dendritic Cells Allows Cross-presentation and Specific Carbohydrate Processing

“…Two distinct recombinant MUC1 glycoproteins, both tumor associated, were employed to test this hypothesis: the highly sialylated rST-MUC1, mostly carrying ST-O-linked glycan (85%) and the rTn-MUC1 carrying only Tn-glycans. rST-MUC1 exerts immunosuppressing effects on dendritic cell differentiation (32), promotes tumor growth (33), and no IgG specific response against the ST-MUC1 glycoform was detected in patients with cancer (34). On the other hand, Tn-MUC1 is immunogenic in mouse models (17,20) and is a target of a specific IgG immune response in patients with cancer (5).…”

Engineering Mammalian Mucin-type O-Glycosylation in Plants

“…Our interest in engineering O-glycosylation from scratch stems from our previous identification of immunodominant aberrant O-glycopeptide epitopes in the cancer-associated MUC1 mucin, which are not covered by immunological tolerance (41,61,62). Vaccination with MUC1 glycopeptides with the truncated GalNAc-Ser/Thr O-glycoform produced by GalNAc-T2 and -T4 in combination produce IgG antibodies with cancer-specific reactivity (61), and spontaneous IgG antibodies to the same epitope are found in many cancer patients at time of diagnosis (3,63). Recombinant production of such vaccines will require a host cell that produces similar truncated O-glycans, and glycoengineered plants as reported here may provide such a system.…”

Immune recognition of tumor-associated mucin MUC1 is achieved by a fully synthetic aberrantly glycosylated MUC1 tripartite vaccine

“…Humoral responses to MUC1 have been observed in benign diseases and carcinoma patients and the presence of circulating antibodies against MUC1 at the time of cancer diagnosis has been correlated with a favorable disease outcome in breast cancer patients (6,7). The MUC1-derived peptide sequences RPAPGS, PPAHGVT, and PDTRP have been identified as the most frequent minimal epitopes (8,9).…”