Unlike the standard CD44 (CD44s), variant CD44 isoforms (CD44v) contain exons with specific post-translational modifications allowing binding of tumor-promoting cytokines like osteopontin (OPN), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) (19–23). Here, SPP1 is linked to neoplasm.