MUC1 is a breast cancer-associated transmembrane glycoprotein, of which the extracellular domain is formed by the repeating 20-amino acid sequence N-PDTRPAPGSTAPPAHGVTSA-C (Luo et al., 2000; Brossart et al., 1999; Engelmann et al., 2001). This evidence concerns the gene MUC1 and breast cancer.