Tumor MUC1 expression as well as levels of MUC1, MUC1 circulating immune complexes (MUC1-CIC) and free antibodies against MUC1 (IgG and IgM-MUC1) were evaluated in 70 breast cancer patients with different stages of disease. Controls included: 135 serum samples from healthy women, normal mammary tissue samples (n = 7) and benign breast disease specimens (n = 6). In all assays, pre- and post-vaccination serum samples from breast cancer patients belonging to a vaccination protocol developed at the Memorial Sloan Kettering Cancer Center (New York, USA) were included as controls. Serum MUC1 was measured through Cancer Associated Serum Antigen test and CA15-3 test. Employing ELISA, MUC1-CIC-IgG/M were measured with either C595 or SM3 monoclonal antibodies (MAb) as catchers and also free antibodies against MUC1 (IgG and IgM) using 100mer peptide as catcher. Employing multivariate statistical analysis, results were correlated with age, tumor type, stage of disease and grade of differentiation. By quantitative immunohistochemistry using three anti-MUC1 core protein MAbs (C595, HMFG2 and SM3), tumor MUC1 was detected in 60/70 (86%) breast cancer specimens which reacted with at least one of these MAbs. High MUCI serum levels were detected in 14/67 (21%); IgG and IgM anti-MUC1 antibodies were found elevated in 32 and 14%, respectively, while IgG-MUC1-CIC-measured with C595 in 42% and IgM-MUC1-CIC in 54%; finally, SM3 was positive in 43 and 18%, respectively. Results of these studies demonstrate that in a group of breast cancer patients, MUC1 was detected both in tissue specimens as well as free in serum samples; furthermore, MUC1 can also circulate complexed with IgG and IgM antibodies; thus an accurate measurement should include free and complexed forms. On the other hand, immunohistochemical studies on breast cancer tissues may contribute to reveal different MUC1 glycoforms.

An immunohistochemical analysis was employed to determine the expression of carbohydrate antigens associated to mucins in normal epithelia. Tissue samples were obtained as biopsies from normal breast (18), colon (35) and oral cavity mucosa (8). The following carbohydrate epitopes were studied: sialyl-Lewis x, Lewis x, Lewis y, Tn hapten, sialyl-Tn and Thomsen-Friedenreich antigen. Mucins were also studied employing antibodies against MUC1, MUC2, MUC4, MUC5AC, MUC6 and also normal colonic glycolipid. Statistical analysis was performed and Kendall correlations were obtained. Lewis x showed an apical pattern mainly at plasma membrane, although cytoplasmic staining was also found in most samples. TF, Tn and sTn haptens were detected in few specimens, while sLewis x was found in oral mucosa and breast tissue. Also, normal breast expressed MUC1 at a high percentage, whereas MUC4 was observed in a small number of samples. Colon specimens mainly expressed MUC2 and MUC1, while most oral mucosa samples expressed MUC4 and MUC1. A positive correlation between MUC1VNTR and TF epitope (r=0.396) was found in breast samples, while in colon specimens MUC2 and colonic glycolipid versus Lewis x were statistically significantly correlated (r=0.28 and r=0.29, respectively). As a conclusion, a defined carbohydrate epitope expression is not exclusive of normal tissue or a determined localization, and it is possible to assume that different glycoproteins and glycolipids may be carriers of carbohydrate antigens depending on the tissue localization considered.

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The aim was to compare the expression of MUC1 and carbohydrate antigens in 124 tissue samples; 42 fibroadenoma (FA), 23 nonproliferative benign diseases (NPF), 25 usual epithelial hyperplasia (UEH), 7 atypical ductal hyperplasia (ADH), and 27 breast normal tissues. An immunohistochemical approach was adopted, using the following antibodies: reactive with MUC1 variable number of tandem repeats (C595, HMFG2, and SM3 monoclonal antibodies), anti-MUC1-cytoplasmic tail polyclonal antibody (CT33), and anti-carbohydrate antigens (sialyl Lewis x, Lewis x, Lewis y, Tn, and Thomsen-Friedenreich epitopes). Positive area of reaction, intensity, and pattern of expression were considered. A reactivity index was calculated as intensity (I) x 100+percentage of positive area (A). Statistical analysis comprised frequency analysis, P < 0.05, analysis of variance, and multiple correlation with principal component analysis. All samples expressed MUC1, detected by at least one anti-MUC1 antibody whereas Lewis x was the carbohydrate antigen most frequently found in all groups whereas variable number of tandem repeats MUC1 and Lewis x showed the highest correlation: 93% of normal samples, 62.5% of NPF, 87% of FA, 85% of UEH, and finally 80% of ADH. Although principal component analysis using reactivity indexes explained only 39% of data variability, normal samples appeared grouped and separated from benign breast diseases, which remained spread. Thomsen-Friedenreich was the only antigen that showed an increased tendency for positive expression and intensity from NPF through FA, UEH to ADH, whereas it was not detected in normals. With respect to the pattern of expression, an apical pattern was predominantly found in all the groups.