Updated project metadata. How disseminated tumor cells (DTCs) engage specific stromal components in distant organs for survival and outgrowth is a critical but poorly understood step of the metastatic cascade. Previous studies have demonstrated the importance of the epithelial-mesenchymal transition (EMT) in promoting the cancer stem cell properties needed for metastasis initiation, while the reverse process of mesenchymal-epithelial transition (MET) is required for metastatic outgrowth. Here we report that this paradoxical requirement for simultaneous induction of both MET and cancer stem cell traits in DTCs is provided by bone vascular niche E-selectin. Using cell surface alkoxyamine-biotinylation and label-free LC-MS/MS, Glg1 was identified as a top candidate Fut3/Fut6-dependent E-selectin ligand. We functionally validated their involvement in the formation of bone metastasis. These findings provide unique insights into the functional role of E-selectin as a component of the vascular niche criticalfor metastatic colonization in bone.