Silvia von Mensdorff-Pouilly

Reactivity of natural and induced human antibodies to MUC1 mucin with MUC1 peptides and n‐acetylgalactosamine (GalNAc) peptides

Antibodies (Abs) to MUC1 occur naturally in both healthy subjects and cancer patients and can be induced by MUC1 peptide vaccination. We compared the specificity of natural and induced MUC1 Abs with the objective of defining an effective MUC1 vaccine for active immunotherapy of adenocarcinoma patients. Serum samples, selected out of a screened population of 492 subjects for their high levels of IgG and/or IgM MUC1 Abs, were obtained from 55 control subjects and from 26 breast cancer patients before primary treatment, as well as from 19 breast cancer patients immunized with MUC1 peptides coupled to keyhole limpet hemocyanin (KLH) and mixed with QS‐21. The samples were tested with enzyme‐linked immunoassays for reactivity with (1) overlapping hepta‐ and 20‐mer peptides spanning the MUC1 tandem repeat sequence; (2) two modified 60‐mer peptides with substitutions in the PDTR (PDTA) or in the STAPPA (STAAAA) sequence of each tandem repeat; and (3) four 60‐mer glycopeptides with each 1, 2, 3 and 5 mol N‐acetylgalactosamine (GalNAc) per repeat. More than one minimal epitopic sequence could be defined, indicating that Abs directed to more than one region of the MUC1 peptide core can coexist in one and the same subject. The most frequent minimal epitopic sequence of natural MUC1 IgG and IgM Abs was RPAPGS, followed by PPAHGVT and PDTRP. MUC1 peptide vaccination induced high titers of IgM and IgG Abs predominantly directed, respectively, to the PDTRPAP and the STAPPAHGV sequences of the tandem repeat. Natural MUC1 Abs from breast cancer patients reacted more strongly with the N‐acetylgalactosamine (GalNAc) peptides than with the naked 60‐mer peptide, while reactivity with the GalNAc‐peptides was significantly reduced (2‐tailed p < 0.0001) in the MUC1 IgG and IgM Abs induced by MUC1 peptide vaccination. Whereas in cancer patients glycans appear to participate in epitope conformation, the epitope(s) recognized by MUC1 Abs induced by peptide vaccination are already masked by minimal glycosylation. Therefore, our results indicate that a MUC1 glycopeptide would be a better vaccine than a naked peptide. Int. J. Cancer 86:702–712, 2000.

Antibody-dependent cell-mediated cytotoxicity can be induced by MUC1 peptide vaccination of breast cancer patients

Human polymorphic epithelial mucin (PEM, MUC1) is a high molecular weight transmembrane glycoprotein expressed on the apical cell surface of glandular epithelium and is over‐expressed and hypo‐glycosylated in adenocarcinomas. The extracellular part of the molecule consists mainly of a variable number of 20 amino acid repeats that contain cryptic epitopes exposed in malignancy. The objective of our study was to determine whether humanized MUC1 MAbs and Abs induced by vaccination of breast cancer patients with MUC1 peptides can effect an antibody‐dependent cell‐mediated cytotoxicity (ADCC). An in vitro assay has been set up in which the breast tumor cell line ZR‐75‐1 is used as target and PBMC of healthy donors as effector cells. Different target and effector cells, as well as various MUC1 MAbs were tested to optimize the efficacy of the in vitro assay. The humanized MAb HuHMFG‐1, which recognizes the PDTR sequence in the MUC1 tandem repeat, induced a strong cell‐mediated cytotoxicity. Nine MUC1‐expressing tumor cell lines, including 3 bone marrow‐derived cell lines, as well as 2 MUC1‐transfected cell lines were susceptible to different extent to MUC1 Ab‐dependent killing. Large variations in the killing capacity of PBMC from healthy donors were found. The NK cells were the essential effector cells for the MUC1 Ab‐dependent killing. Plasma samples with induced high levels of MUC1 Ab were obtained from breast cancer patients repeatedly immunized with a KLH‐conjugated 33‐mer or 106‐mer MUC1 tandem repeat. Pre‐ and post‐vaccinated plasma samples of these patients were compared in the ADCC assay and it could be clearly demonstrated that the induced MUC1 Abs can effect tumor cell killing. MUC1 Ab‐dependent cell‐mediated tumor cell killing may occur in vivo and the ADCC assay can be applied to monitor MUC1 vaccination trials.

An Enzyme-Linked Immunosorbent Assay for the Measurement of Circulating Antibodies to Polymorphic Epithelial Mucin (MUC1)

Introduction: About one-third of breast and ovarian carcinoma patients have circulating antibodies reactive with polymorphic epithelial mucin (MUC1), either free or bound to immune complexes. While the presence of these immune complexes has prognostic significance in breast cancer patients, the significance of free MUC1 antibodies is less clear. The objective of this study was to develop a reliable assay for the accurate determination of circulating free antibodies to MUC1. Material and Methods: We developed an enzyme-linked immunosorbent assay (ELISA) (PEM.CIg) employing a 60 mer peptide (a triple tandem repeat sequence of the MUC1 peptide core) conjugated to bovine serum albumin and peroxidase-labeled antihuman immunoglobulin G or M antibodies. The assay was standardized and its analytical performance evaluated. A total of 492 serum samples were obtained from 40 healthy men, from 201 healthy women (including 55 women without a history of pregnancy and 45 pregnant women), and (before primary treatment) from 62 benign breast tumor patients and 190 breast cancer patients. MUC1 serum levels were determined with commercial CA 15-3 tests. Results: Circulating antibodies to MUC1 are present both in healthy subjects and in breast cancer patients. The within- and between-assay coefficients of variation were, respectively, 2 and 12% for the IgG determinations and 1.2 and 3% for the IgM determinations. Correlation coefficients for serially diluted serum samples ranged from 0.9998 to 0.9920 for IgG and from 0.9996 to 0.9818 for IgM determinations. The reactivity of serum samples was partially blocked by the addition of various MUC1 peptides and by MUC1 mucin. The inhibiting effect of modified 60 mer peptides suggests the presence of antibodies directed to more than one epitope. Conclusions: The PEM. CIg assay is a reliable ELISA for measuring free MUC1 antibodies in serum. We are in the process of relating the results obtained in the breast cancer group to disease outcome to evaluate its prognostic significance. In addition, the assay may become a useful tool for vaccine therapy monitoring.

Polypeptide GalNAc-transferases, ST6GalNAc-transferase I, and ST3Gal-transferase I expression in gastric carcinoma cell lines.

Mucin O-glycosylation in cancer is characterized by aberrant expression of immature carbohydrate structures leading to exposure of simple mucin-type carbohydrate antigens and peptide epitopes. Glycosyltransferases controlling the initial steps of mucin O-glycosylation are responsible for the altered glycosylation observed in cancer. We studied the expression in gastric cell lines of six UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (GalNAc-T1, T2, T3, T4, T6, T11) that catalyze the initial key step in the regulation of mucin O-glycosylation, the transfer of GalNAc from UDP-GalNAc to serine and threonine residues. We also studied the expression of ST6GalNAc-I, the enzyme responsible for the synthesis of Sialyl-Tn antigen (NeuAcα2,6GalNAc) and the ST3Gal-I, the enzyme responsible for the synthesis of Sialyl-T antigen (NeuAcα2,3Galβ1,3GalNAc). This study was done using specific monoclonal antibodies, enzymatic assays, and RT-PCR. Our results showed that GalNAc-T1, -T2, and -T3 have an ubiquitous expression in all gastric cell lines, whereas GalNAc-T4, -T6, and -T11 show a restricted expression pattern. The immunoreactivity with MAb VU-2-G7 suggests that, apart from GalNAc-T4, another GalNAc transferase is involved in the glycosylation of the Thr in the PDTR region of the MUC1 tandem repeat. The expression of ST3Gal-I correlates with the expression of the Sialyl-T antigen in gastric cell lines and in the control cell lines studied. The expression of ST6GalNAc-I is low in gastric cell lines, in accordance with the low/absent expression of the Sialyl-Tn antigen.

Cancer specific Mucin-1 glycoforms are expressed on multiple myeloma

Present therapies cannot cure the large majority of patients with multiple myeloma (MM) and therefore new treatment strategies are imperative. This study analysed the different glycosylation profiles of Mucin‐1 (MUC1) on MM and acute myeloid leukaemia (AML) cells using a series of anti‐MUC1 antibodies. Seventy‐three per cent of the MM patients had plasma cells that expressed the fully glycosylated forms of MUC1. In contrast to controls, normal bone marrow cells and AML cells, the differentiation‐dependent and cancer‐associated glycoforms of MUC1 were present on 59% and 36% MM tumour cells respectively. This indicated that aberrantly glycosylated MUC1 is a potential immunotherapeutic target in MM patients.

Isolation of MUC1-primed B lymphocytes from tumour-draining lymph nodes by immunomagnetic beads

Abstract The humoral immune response against a tumour-associated antigen, polymorphic epithelial mucin (PEM, MUC1) in cancer patients was studied by isolating specific B cells primed for the antigen. Human B lymphocytes from tumour-draining lymph nodes, obtained from 12 patients with epithelial cancers, were immunoselected with magnetic beads coated with a 60mer synthetic peptide corresponding to three tandem repeats of the protein core of the MUC1 antigen. Short-term cultures of B cells were established utilizing interleukin-10 (IL-10), IL-4 and monoclonal antibody anti-CD40, and were maintained for a maximum of 3␣weeks. B cell culture supernatants contained human anti-MUC1 antibodies, as detected by enzyme-linked immunosorbent assay, in 6/12 of the patients tested. Five of these patients, all with early-stage cancer, also had high levels of circulating anti-MUC1 IgM antibodies in the serum. A significant correlation was found (two-tailed P = 0.041) between the presence of circulating anti-MUC1 antibodies and the ability to isolate PEM-specific B cells from tumour-draining lymph nodes. The technique proposed provides a useful method for the analysis of natural immunity against defined tumour antigens.

Autoantibodies to p53 in ovarian cancer patients and healthy women: a comparison between whole p53 protein and 18-mer peptides for screening purposes

Autoantibodies against complete p53 protein and 18-mer peptides of p53 in ovarian cancer patients and healthy women were examined. Sera from 9% (4/46) of ovarian cancer patients but none (0/51) of healthy women recognized complete p53 protein. The antibodies were mainly of the IgG1 isotype. Two patients had also IgG2 antibodies. Sera from 28% (13/46) of cancer patients and 21% (11/52) of healthy women contained either IgM, or IgM plus IgG2 antibodies against 18-mer p53 peptides. Screening against complete p53 protein instead of peptides seems necessary for identifying patients with tumor-related antibodies. IgG2 antibodies against p53 suggest p53-specific CD4+ T helper 1 cell activity in some of the ovarian cancer patients.

Low prevalence of (pre) malignant lesions in the breast and high prevalence in the ovary and Fallopian tube in women at hereditary high risk of breast and ovarian cancer.

To analyse the prevalence of (pre) malignant lesions occurring in breast and adnexal tissue at prophylactic surgery in women at hereditary high risk of breast and/or ovarian cancers. Tissue was obtained from 85 women who underwent prophylactic bilateral salpingo‐oophorectomy (pBSO) and from 59 women who underwent prophylactic mastectomy (pM). Control tissue samples were obtained from women undergoing breast reduction surgery (N = 99) or adnexal surgery for benign reasons (N = 72). In women with a BRCA1/2 mutation, the prevalence of a (pre) malignant adnexal lesion was 50% (95% CI 26–74) if older than 40 years and 14% (95% CI 0–58) if younger. The prevalences of (pre) malignant breast lesions in women older than 40 years, with and without a BRCA1/2 mutation, were 0% (95% CI 0–16) and 47% (95% CI 21–73), respectively. No association was found between (pre) malignant lesions in breast and adnexal tissue occurring in 28 women who underwent surgery on both organs (R = 0.155, p = 0.432), but the prevalence of lesions was significantly higher in adnexal tissue than in the breast (p = 0.023). Compared to controls, women at hereditary high risk had a higher chance of (pre) malignant lesions in the breast and an even higher chance of such lesions in the adnexal tissue. There was no indication for concomitant presence of such lesions in both organs at the time of prophylactic surgery. The high frequency of (pre) malignant lesions in the adnexal tissue stresses further the importance of pBSO from the age of 40 onwards in women at hereditary high risk.

Serum CA-125 in Relation to Adnexal Dysplasia and Cancer in Women at Hereditary High Risk of Ovarian Cancer

PURPOSE Serum CA-125 level is commonly used as indicator for ovarian cancer recurrence. However, its value for the prediction of neoplastic lesions is unknown. The aim of this study was to investigate whether CA-125 concentrations are indicative of adnexal dysplasia and cancer in women at hereditary high risk of ovarian/tubal cancer. PATIENTS AND METHODS CA-125 was obtained from 424 women at hereditary high risk of ovarian/tubal cancer attending the VU University Medical Center (Amsterdam, the Netherlands) between 1993 and 2005. Serum samples obtained at the second-to-last (n = 64) and last (n = 98) visit before surgery were tested in women who underwent adnexal surgery for diagnostic (n = 9) or prophylactic (n = 89) reasons. Serum samples obtained from 370 age-matched healthy women were used as controls. RESULTS Both the absolute value (P < .0001) and the serial change (P < .0001) of CA-125 were predictive for ovarian cancer (n = 8). For adnexal dysplasia (n = 23), the absolute value of CA-125 (P = .003) was predictive, but the serial change in CA-125 was not (P = .32). The odds ratio for adnexal dysplasia versus nondysplasia in the highest tertile (CA-125 levels 14 U/mL) compared with the lowest tertile (CA-125 < 10 U/mL) was 6 (95% CI, 1.32 to 36.66). CONCLUSION In patients at hereditary high risk for adnexal cancer, both the absolute value of serum CA-125 and the change in serial CA-125 are predictors for ovarian cancer. Remarkably, the absolute value of CA-125 is also predictive for adnexal dysplasia. CA-125 values should, therefore, be taken into account in the decision toward prophylactic bilateral salpingo-oophorectomy.

Lobulitis is a frequent finding in prophylactically removed breast tissue from women at hereditary high risk of breast cancer

The aim of this study was to investigate closely the nature of premalignant lesions that occur in prophylactically removed breast tissue from patients at hereditary high risk of breast cancer. Breast tissues obtained from 41 patients who underwent prophylactic mastectomy (pM) because of a hereditary high risk of breast cancer and control tissues from 82 age‐matched healthy controls who underwent breast reduction surgery were screened for premalignant lesions. Premalignant and malignant lesions were more frequent (p = 0.0016) in pM samples (5/41) than in controls (1/82). Interestingly, lobulitis, defined as more than 100 lymphocytes and/or plasma cells per lobule in more than one section in morphologically normal lobules, was encountered in 21 of 41 (51%) pM patients, in contrast to only 8 of 82 (10%) controls (p < 0.0001). Preliminary observations indicate a predominance of T‐cells in these infiltrates, in agreement with the already known frequent presence of lymphocytic infiltration in hereditary ductal in situ and infiltrating ductal/medullary carcinomas. This novel finding implies an immune reaction to an as yet unidentified antigen frequently present in women at hereditary high risk of breast cancer, possibly as part of an early carcinogenic event. Copyright