text_1: CD44v6 is not associated with constitutive and reprogrammed cancer stem cells driving cancer metastasis.
text_2: Cytokines hepatocyte growth factor (HGF), osteopontin (OPN), and stromal-derived factor 1α (SDF-1), secreted from tumor associated cells, increase CD44v6 expression in CR-CSCs by activating the Wnt/β-catenin pathway, which promotes migration and metastasis.