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Aberrant carbohydrate expression frequently occurs in breast cancer and may endow cells with metastatic potential. Here we first studied the relationship between expression of Vicia villosa agglutinin (lectin) (VVA)-binding carbohydrates and aggressive breast cancer. We then investigated the molecular characteristics of these glycoproteins and compared them with those of glycoproteins recognized by the mouse anti-Tn monoclonal antibody (MAb) HB-Tn1. Histochemical studies of samples from 322 cases of invasive ductal carcinoma demonstrated that VVA-binding carbohydrate expression correlated with tumor stage, lymphatic invasion, and lymph node metastasis (p=0.0385, p=0.0019, and p=0.0430. respectively). Western blotting analysis of frozen materials from 39 cases, under denaturing and reducing conditions, revealed that the major cancer cell-specific VVA-binding proteins were molecules of about 30, 33, and >200 kDa. Cases expressing the ∼33 kDa molecule had significant lymphatic invasion more frequently than did cases not expressing this molecule (p=0.0076). Binding of VVA to the ∼30 and ∼33 kDa molecules was completely lost by preincubation of VVA with 1 mM Tn antigen (N-acetylgalactosamine α1-O-serine). The VVA-binding molecules appeared to react with VU-3C6 anti-MUC1 MAb. Expression of HB-Tn1 in breast cancer cells showed significant correlation with expression of VVA-binding carbohydrate(s) (p<0.0001) but HB-Tn1 reactivity was not clearly related to breast cancer aggressiveness. Because anti-Tn MAbs bound to Tn antigen clusters, we concluded that atypical MUC1 bearing the noncluster form of Tn antigen is implicated in aggressive growth of primary breast cancer cells, particularly in lymphatic metastasis. [ABSTRACT FROM AUTHOR]

Summary MUC1 is a transmembrane molecule characterized by a repeated sequence of 20 amino acid (TAP PAHGVTSAPDTRPAPGS). Abnormal overexpression of MUC1 in cancer cells is thought to contribute to their aggressive growth, but molecular mechanisms associated with this effect are still unclear. Our current study aimed to clarify whether MUC1 expression as recognized by VU-3C6 anti-MUC1 mouse IgG monoclonal antibody (MAb) with a dominant epitope of 12 amino acids: GVTSAPDTRPAP, correlated with aggressive properties of human breast cancer. Immunohistochemical studies of 309 samples of formalin-fixed and paraffin-embedded materials showed no statistical correlation between MUC1 expression and clinicopathological parameters, as well as several breast cancer aggressiveness-related markers. Expression or nonexpression of MUC1 in 50 frozen samples, as determined by Western blotting, demonstrated no correlation with aggressive properties of breast cancer. However, samples with one MUC1-positive band more often had lymphatic vessel invasion and lymph node metastasis than those with more than two or three MUC1-positive bands (p<0.014 and p<0.043, respectively). Because VU-3C6 MAb recognizes MUC1 with short branches of O-glycosylated core carbohydrates, we used immunohistological methods to examine Tn antigen (precursor antigen: GalNAcα-O-Ser/Thr), Thomsen–Friedenreich (T) antigen, and sialyl-Tn antigen (STn) antigen. We found a strong correlation between expression of MUC1 and Tn antigen (p<0.0006), and samples with Tn antigen expression had more lymphatic metastasis than those with no such expression (p<0.08). We concluded that the lack of polymorphic MUC1 expression with Tn antigen is one characteristic related to aggressive breast cancer. [ABSTRACT FROM AUTHOR]