MUC1 and neoplasm: But MUC1 overexpression also reduces adhesion of circulating tumour cells to the blood vascular endothelium, a metastatic step that is required for extravasation and establishment of a metastatic colony.20 On the other hand, interaction of MUC1 on circulating tumour cells with galectins induces MUC1 cell surface polarization to reveal the smaller cell surface adhesion molecules, causing increased cancer cell–endothelial adhesion20,21 and allowing increased formation of tumour emboli.19