Cell surface mucins, such as MUC1 and MUC16, are so consistently upregulated in epithelial cancers that they are considered reliable biomarkers of the disease. (Bast et al., 2009; Rahn et al., 2001) Despite their importance for diagnosis and prognosis, the mechanisms by which mucins might promote malignancy remain largely speculative. (Kufe, 2009a) To date, the majority of studies exploring the role of mucins in determining tumor phenotype have focused on the signaling function of these molecules, which resides within their short cytoplasmic tail. Here, MUC1 is linked to neoplasm.